tint: Implement const-eval of modf

Bug: tint:1581
Change-Id: I53151ebf43601cd6afcdd2ec91d0ff9c4e650ef3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/111241
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/tint/intrinsics.def

@@ -504,8 +504,8 @@ fn log2<N: num, T: f32_f16>(vec<N, T>) -> vec<N, T>
 fn mix<T: f32_f16>(T, T, T) -> T
 fn mix<N: num, T: f32_f16>(vec<N, T>, vec<N, T>, vec<N, T>) -> vec<N, T>
 fn mix<N: num, T: f32_f16>(vec<N, T>, vec<N, T>, T) -> vec<N, T>
-fn modf<T: f32_f16>(T) -> __modf_result<T>
+@const fn modf<T: f32_f16>(@test_value(-1.5) T) -> __modf_result<T>
-fn modf<N: num, T: f32_f16>(vec<N, T>) -> __modf_result_vec<N, T>
+@const fn modf<N: num, T: f32_f16>(@test_value(-1.5) vec<N, T>) -> __modf_result_vec<N, T>
 fn normalize<N: num, T: f32_f16>(vec<N, T>) -> vec<N, T>
 @const fn pack2x16float(vec2<f32>) -> u32
 @const fn pack2x16snorm(vec2<f32>) -> u32

src/tint/resolver/const_eval.cc

@@ -2266,6 +2266,40 @@ ConstEval::Result ConstEval::min(const sem::Type* ty,
     return TransformElements(builder, ty, transform, args[0], args[1]);
 }
 
+ConstEval::Result ConstEval::modf(const sem::Type* ty,
+                                  utils::VectorRef<const sem::Constant*> args,
+                                  const Source& source) {
+    auto transform_fract = [&](const sem::Constant* c) {
+        auto create = [&](auto e) {
+            return CreateElement(builder, source, c->Type(),
+                                 decltype(e)(e.value - std::trunc(e.value)));
+        };
+        return Dispatch_fa_f32_f16(create, c);
+    };
+    auto transform_whole = [&](const sem::Constant* c) {
+        auto create = [&](auto e) {
+            return CreateElement(builder, source, c->Type(), decltype(e)(std::trunc(e.value)));
+        };
+        return Dispatch_fa_f32_f16(create, c);
+    };
+
+    utils::Vector<const sem::Constant*, 2> fields;
+
+    if (auto fract = TransformElements(builder, args[0]->Type(), transform_fract, args[0])) {
+        fields.Push(fract.Get());
+    } else {
+        return utils::Failure;
+    }
+
+    if (auto whole = TransformElements(builder, args[0]->Type(), transform_whole, args[0])) {
+        fields.Push(whole.Get());
+    } else {
+        return utils::Failure;
+    }
+
+    return CreateComposite(builder, ty, std::move(fields));
+}
+
 ConstEval::Result ConstEval::pack2x16float(const sem::Type* ty,
                                            utils::VectorRef<const sem::Constant*> args,
                                            const Source& source) {

src/tint/resolver/const_eval.h

@@ -628,6 +628,15 @@ class ConstEval {
                utils::VectorRef<const sem::Constant*> args,
                const Source& source);
 
+    /// modf builtin
+    /// @param ty the expression type
+    /// @param args the input arguments
+    /// @param source the source location
+    /// @return the result value, or null if the value cannot be calculated
+    Result modf(const sem::Type* ty,
+                utils::VectorRef<const sem::Constant*> args,
+                const Source& source);
+
     /// pack2x16float builtin
     /// @param ty the expression type
     /// @param args the input arguments

src/tint/resolver/const_eval_builtin_test.cc

@@ -98,6 +98,11 @@ static Case C(std::initializer_list<Types> args, Types result) {
     return Case{utils::Vector<Types, 8>{args}, utils::Vector<Types, 2>{std::move(result)}};
 }
 
+/// Creates a Case with Values for args and result
+static Case C(std::initializer_list<Types> args, std::initializer_list<Types> results) {
+    return Case{utils::Vector<Types, 8>{args}, utils::Vector<Types, 2>{results}};
+}
+
 /// Convenience overload that creates a Case with just scalars
 static Case C(std::initializer_list<ScalarTypes> sargs, ScalarTypes sresult) {
     utils::Vector<Types, 8> args;
@@ -109,6 +114,20 @@ static Case C(std::initializer_list<ScalarTypes> sargs, ScalarTypes sresult) {
     return Case{std::move(args), utils::Vector<Types, 2>{std::move(result)}};
 }
 
+/// Creates a Case with Values for args and result
+static Case C(std::initializer_list<ScalarTypes> sargs,
+              std::initializer_list<ScalarTypes> sresults) {
+    utils::Vector<Types, 8> args;
+    for (auto& sa : sargs) {
+        std::visit([&](auto&& v) { return args.Push(Val(v)); }, sa);
+    }
+    utils::Vector<Types, 2> results;
+    for (auto& sa : sresults) {
+        std::visit([&](auto&& v) { return results.Push(Val(v)); }, sa);
+    }
+    return Case{std::move(args), std::move(results)};
+}
+
 /// Creates a Case with Values for args and expected error
 static Case E(std::initializer_list<Types> args, std::string err) {
     return Case{utils::Vector<Types, 8>{args}, std::move(err)};
@@ -1290,6 +1309,38 @@ INSTANTIATE_TEST_SUITE_P(  //
                                               MinCases<AFloat>(),
                                               MinCases<f32>(),
                                               MinCases<f16>()))));
+template <typename T>
+std::vector<Case> ModfCases() {
+    return {
+        // Scalar tests
+        //  in     fract    whole
+        C({T(0.0)}, {T(0.0), T(0.0)}),              //
+        C({T(1.0)}, {T(0.0), T(1.0)}),              //
+        C({T(2.0)}, {T(0.0), T(2.0)}),              //
+        C({T(1.5)}, {T(0.5), T(1.0)}),              //
+        C({T(4.25)}, {T(0.25), T(4.0)}),            //
+        C({T(-1.0)}, {T(0.0), T(-1.0)}),            //
+        C({T(-2.0)}, {T(0.0), T(-2.0)}),            //
+        C({T(-1.5)}, {T(-0.5), T(-1.0)}),           //
+        C({T(-4.25)}, {T(-0.25), T(-4.0)}),         //
+        C({T::Lowest()}, {T(0.0), T::Lowest()}),    //
+        C({T::Highest()}, {T(0.0), T::Highest()}),  //
+
+        // Vector tests
+        //         in                 fract                    whole
+        C({Vec(T(0.0), T(0.0))}, {Vec(T(0.0), T(0.0)), Vec(T(0.0), T(0.0))}),
+        C({Vec(T(1.0), T(2.0))}, {Vec(T(0.0), T(0.0)), Vec(T(1), T(2))}),
+        C({Vec(T(-2.0), T(1.0))}, {Vec(T(0.0), T(0.0)), Vec(T(-2), T(1))}),
+        C({Vec(T(1.5), T(-2.25))}, {Vec(T(0.5), T(-0.25)), Vec(T(1.0), T(-2.0))}),
+        C({Vec(T::Lowest(), T::Highest())}, {Vec(T(0.0), T(0.0)), Vec(T::Lowest(), T::Highest())}),
+    };
+}
+INSTANTIATE_TEST_SUITE_P(  //
+    Modf,
+    ResolverConstEvalBuiltinTest,
+    testing::Combine(testing::Values(sem::BuiltinType::kModf),
+                     testing::ValuesIn(Concat(ModfCases<f32>(),  //
+                                              ModfCases<f16>()))));
 
 std::vector<Case> Pack4x8snormCases() {
     return {

src/tint/resolver/intrinsic_table.inl

@@ -12851,7 +12851,7 @@ constexpr OverloadInfo kOverloads[] = {
     /* parameters */ &kParameters[878],
     /* return matcher indices */ &kMatcherIndices[106],
     /* flags */ OverloadFlags(OverloadFlag::kIsBuiltin, OverloadFlag::kSupportsVertexPipeline, OverloadFlag::kSupportsFragmentPipeline, OverloadFlag::kSupportsComputePipeline),
-    /* const eval */ nullptr,
+    /* const eval */ &ConstEval::modf,
   },
   {
     /* [378] */
@@ -12863,7 +12863,7 @@ constexpr OverloadInfo kOverloads[] = {
     /* parameters */ &kParameters[879],
     /* return matcher indices */ &kMatcherIndices[45],
     /* flags */ OverloadFlags(OverloadFlag::kIsBuiltin, OverloadFlag::kSupportsVertexPipeline, OverloadFlag::kSupportsFragmentPipeline, OverloadFlag::kSupportsComputePipeline),
-    /* const eval */ nullptr,
+    /* const eval */ &ConstEval::modf,
   },
   {
     /* [379] */
@@ -14351,8 +14351,8 @@ constexpr IntrinsicInfo kBuiltins[] = {
   },
   {
     /* [53] */
-    /* fn modf<T : f32_f16>(T) -> __modf_result<T> */
+    /* fn modf<T : f32_f16>(@test_value(-1.5) T) -> __modf_result<T> */
-    /* fn modf<N : num, T : f32_f16>(vec<N, T>) -> __modf_result_vec<N, T> */
+    /* fn modf<N : num, T : f32_f16>(@test_value(-1.5) vec<N, T>) -> __modf_result_vec<N, T> */
     /* num overloads */ 2,
     /* overloads */ &kOverloads[377],
   },

src/tint/resolver/validator.cc

@@ -530,9 +530,13 @@ bool Validator::AddressSpaceLayout(const sem::Variable* var,
     }
 
     if (auto* str = var->Type()->UnwrapRef()->As<sem::Struct>()) {
-        if (!AddressSpaceLayout(str, var->AddressSpace(), str->Declaration()->source, layouts)) {
+        // Check the structure has a declaration. Builtins like modf() and frexp() return untypeable
-            AddNote("see declaration of variable", var->Declaration()->source);
+        // structures, and so they have no declaration. Just skip validation for these.
-            return false;
+        if (auto* str_decl = str->Declaration()) {
+            if (!AddressSpaceLayout(str, var->AddressSpace(), str_decl->source, layouts)) {
+                AddNote("see declaration of variable", var->Declaration()->source);
+                return false;
+            }
         }
     } else {
         Source source = var->Declaration()->source;

src/tint/writer/glsl/generator_impl.cc

@@ -939,9 +939,7 @@ bool GeneratorImpl::EmitWorkgroupAtomicCall(std::ostream& out,
             return true;
         }
         case sem::BuiltinType::kAtomicCompareExchangeWeak: {
-            // Emit the builtin return type unique to this overload. This does not
+            if (!EmitStructType(&helpers_, builtin->ReturnType()->As<sem::Struct>())) {
-            // exist in the AST, so it will not be generated in Generate().
-            if (!EmitStructTypeOnce(&helpers_, builtin->ReturnType()->As<sem::Struct>())) {
                 return false;
             }
 
@@ -2373,10 +2371,12 @@ bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constan
             return true;
         },
         [&](const sem::Struct* s) {
-            if (!EmitType(out, s, ast::AddressSpace::kNone, ast::Access::kUndefined, "")) {
+            if (!EmitStructType(&helpers_, s)) {
                 return false;
             }
 
+            out << StructName(s);
+
             ScopedParen sp(out);
 
             for (size_t i = 0; i < s->Members().size(); i++) {
@@ -2998,6 +2998,11 @@ bool GeneratorImpl::EmitTypeAndName(std::ostream& out,
 }
 
 bool GeneratorImpl::EmitStructType(TextBuffer* b, const sem::Struct* str) {
+    auto it = emitted_structs_.emplace(str);
+    if (!it.second) {
+        return true;
+    }
+
     auto address_space_uses = str->AddressSpaceUsage();
     line(b) << "struct " << StructName(str) << " {";
     EmitStructMembers(b, str);
@@ -3007,14 +3012,6 @@ bool GeneratorImpl::EmitStructType(TextBuffer* b, const sem::Struct* str) {
     return true;
 }
 
-bool GeneratorImpl::EmitStructTypeOnce(TextBuffer* buffer, const sem::Struct* str) {
-    auto it = emitted_structs_.emplace(str);
-    if (!it.second) {
-        return true;
-    }
-    return EmitStructType(buffer, str);
-}
-
 bool GeneratorImpl::EmitStructMembers(TextBuffer* b, const sem::Struct* str) {
     ScopedIndent si(b);
     for (auto* mem : str->Members()) {

src/tint/writer/glsl/generator_impl.h

@@ -430,17 +430,12 @@ class GeneratorImpl : public TextGenerator {
                          ast::AddressSpace address_space,
                          ast::Access access,
                          const std::string& name);
-    /// Handles generating a structure declaration
+    /// Handles generating a structure declaration. If the structure has already been emitted, then
+    /// this function will simply return `true` without emitting anything.
     /// @param buffer the text buffer that the type declaration will be written to
     /// @param ty the struct to generate
     /// @returns true if the struct is emitted
     bool EmitStructType(TextBuffer* buffer, const sem::Struct* ty);
-    /// Handles generating a structure declaration only the first time called. Subsequent calls are
-    /// a no-op and return true.
-    /// @param buffer the text buffer that the type declaration will be written to
-    /// @param ty the struct to generate
-    /// @returns true if the struct is emitted
-    bool EmitStructTypeOnce(TextBuffer* buffer, const sem::Struct* ty);
     /// Handles generating the members of a structure
     /// @param buffer the text buffer that the struct members will be written to
     /// @param ty the struct to generate

src/tint/writer/glsl/generator_impl_builtin_test.cc

@@ -416,9 +416,9 @@ TEST_F(GlslGeneratorImplTest_Builtin, FMA_f16) {
     EXPECT_EQ(out.str(), "((a) * (b) + (c))");
 }
 
-TEST_F(GlslGeneratorImplTest_Builtin, Modf_Scalar_f32) {
+TEST_F(GlslGeneratorImplTest_Builtin, Runtime_Modf_Scalar_f32) {
-    auto* call = Call("modf", 1_f);
+    WrapInFunction(Decl(Let("f", Expr(1.5_f))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -438,7 +438,8 @@ modf_result tint_modf(float param_0) {
 
 
 void test_function() {
-  tint_modf(1.0f);
+  float f = 1.5f;
+  modf_result v = tint_modf(f);
 }
 
 layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
@@ -449,11 +450,11 @@ void main() {
 )");
 }
 
-TEST_F(GlslGeneratorImplTest_Builtin, Modf_Scalar_f16) {
+TEST_F(GlslGeneratorImplTest_Builtin, Runtime_Modf_Scalar_f16) {
     Enable(ast::Extension::kF16);
 
-    auto* call = Call("modf", 1_h);
+    WrapInFunction(Decl(Let("f", Expr(1.5_h))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -474,7 +475,8 @@ modf_result_f16 tint_modf(float16_t param_0) {
 
 
 void test_function() {
-  tint_modf(1.0hf);
+  float16_t f = 1.5hf;
+  modf_result_f16 v = tint_modf(f);
 }
 
 layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
@@ -485,9 +487,9 @@ void main() {
 )");
 }
 
-TEST_F(GlslGeneratorImplTest_Builtin, Modf_Vector_f32) {
+TEST_F(GlslGeneratorImplTest_Builtin, Runtime_Modf_Vector_f32) {
-    auto* call = Call("modf", vec3<f32>());
+    WrapInFunction(Decl(Let("f", vec3<f32>(1.5_f, 2.5_f, 3.5_f))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -507,7 +509,8 @@ modf_result_vec3 tint_modf(vec3 param_0) {
 
 
 void test_function() {
-  tint_modf(vec3(0.0f));
+  vec3 f = vec3(1.5f, 2.5f, 3.5f);
+  modf_result_vec3 v = tint_modf(f);
 }
 
 layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
@@ -518,11 +521,11 @@ void main() {
 )");
 }
 
-TEST_F(GlslGeneratorImplTest_Builtin, Modf_Vector_f16) {
+TEST_F(GlslGeneratorImplTest_Builtin, Runtime_Modf_Vector_f16) {
     Enable(ast::Extension::kF16);
 
-    auto* call = Call("modf", vec3<f16>());
+    WrapInFunction(Decl(Let("f", vec3<f16>(1.5_h, 2.5_h, 3.5_h))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -543,7 +546,118 @@ modf_result_vec3_f16 tint_modf(f16vec3 param_0) {
 
 
 void test_function() {
-  tint_modf(f16vec3(0.0hf));
+  f16vec3 f = f16vec3(1.5hf, 2.5hf, 3.5hf);
+  modf_result_vec3_f16 v = tint_modf(f);
+}
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void main() {
+  test_function();
+  return;
+}
+)");
+}
+
+TEST_F(GlslGeneratorImplTest_Builtin, Const_Modf_Scalar_f32) {
+    WrapInFunction(Decl(Let("v", Call("modf", 1.5_f))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#version 310 es
+
+struct modf_result {
+  float fract;
+  float whole;
+};
+
+
+void test_function() {
+  modf_result v = modf_result(0.5f, 1.0f);
+}
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void main() {
+  test_function();
+  return;
+}
+)");
+}
+
+TEST_F(GlslGeneratorImplTest_Builtin, Const_Modf_Scalar_f16) {
+    Enable(ast::Extension::kF16);
+
+    WrapInFunction(Decl(Let("v", Call("modf", 1.5_h))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#version 310 es
+#extension GL_AMD_gpu_shader_half_float : require
+
+struct modf_result_f16 {
+  float16_t fract;
+  float16_t whole;
+};
+
+
+void test_function() {
+  modf_result_f16 v = modf_result_f16(0.5hf, 1.0hf);
+}
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void main() {
+  test_function();
+  return;
+}
+)");
+}
+
+TEST_F(GlslGeneratorImplTest_Builtin, Const_Modf_Vector_f32) {
+    WrapInFunction(Decl(Let("v", Call("modf", vec3<f32>(1.5_f, 2.5_f, 3.5_f)))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#version 310 es
+
+struct modf_result_vec3 {
+  vec3 fract;
+  vec3 whole;
+};
+
+
+void test_function() {
+  modf_result_vec3 v = modf_result_vec3(vec3(0.5f), vec3(1.0f, 2.0f, 3.0f));
+}
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void main() {
+  test_function();
+  return;
+}
+)");
+}
+
+TEST_F(GlslGeneratorImplTest_Builtin, Const_Modf_Vector_f16) {
+    Enable(ast::Extension::kF16);
+
+    WrapInFunction(Decl(Let("v", Call("modf", vec3<f16>(1.5_h, 2.5_h, 3.5_h)))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#version 310 es
+#extension GL_AMD_gpu_shader_half_float : require
+
+struct modf_result_vec3_f16 {
+  f16vec3 fract;
+  f16vec3 whole;
+};
+
+
+void test_function() {
+  modf_result_vec3_f16 v = modf_result_vec3_f16(f16vec3(0.5hf), f16vec3(1.0hf, 2.0hf, 3.0hf));
 }
 
 layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;

src/tint/writer/hlsl/generator_impl.cc

@@ -1651,9 +1651,7 @@ bool GeneratorImpl::EmitWorkgroupAtomicCall(std::ostream& out,
             return true;
         }
         case sem::BuiltinType::kAtomicCompareExchangeWeak: {
-            // Emit the builtin return type unique to this overload. This does not
+            if (!EmitStructType(&helpers_, builtin->ReturnType()->As<sem::Struct>())) {
-            // exist in the AST, so it will not be generated in Generate().
-            if (!EmitStructTypeOnce(&helpers_, builtin->ReturnType()->As<sem::Struct>())) {
                 return false;
             }
 
@@ -2506,7 +2504,7 @@ bool GeneratorImpl::EmitCase(const ast::SwitchStatement* s, size_t case_idx) {
             out << "default";
         } else {
             out << "case ";
-            if (!EmitConstant(out, selector->Value())) {
+            if (!EmitConstant(out, selector->Value(), /* is_variable_initializer */ false)) {
                 return false;
             }
         }
@@ -2552,7 +2550,13 @@ bool GeneratorImpl::EmitDiscard(const ast::DiscardStatement*) {
 bool GeneratorImpl::EmitExpression(std::ostream& out, const ast::Expression* expr) {
     if (auto* sem = builder_.Sem().Get(expr)) {
         if (auto* constant = sem->ConstantValue()) {
-            return EmitConstant(out, constant);
+            bool is_variable_initializer = false;
+            if (auto* stmt = sem->Stmt()) {
+                if (auto* decl = As<ast::VariableDeclStatement>(stmt->Declaration())) {
+                    is_variable_initializer = decl->variable->initializer == expr;
+                }
+            }
+            return EmitConstant(out, constant, is_variable_initializer);
         }
     }
     return Switch(
@@ -3042,7 +3046,9 @@ bool GeneratorImpl::EmitEntryPointFunction(const ast::Function* func) {
     return true;
 }
 
-bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constant) {
+bool GeneratorImpl::EmitConstant(std::ostream& out,
+                                 const sem::Constant* constant,
+                                 bool is_variable_initializer) {
     return Switch(
         constant->Type(),  //
         [&](const sem::Bool*) {
@@ -3072,7 +3078,7 @@ bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constan
             if (constant->AllEqual()) {
                 {
                     ScopedParen sp(out);
-                    if (!EmitConstant(out, constant->Index(0))) {
+                    if (!EmitConstant(out, constant->Index(0), is_variable_initializer)) {
                         return false;
                     }
                 }
@@ -3093,7 +3099,7 @@ bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constan
                 if (i > 0) {
                     out << ", ";
                 }
-                if (!EmitConstant(out, constant->Index(i))) {
+                if (!EmitConstant(out, constant->Index(i), is_variable_initializer)) {
                     return false;
                 }
             }
@@ -3110,7 +3116,7 @@ bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constan
                 if (i > 0) {
                     out << ", ";
                 }
-                if (!EmitConstant(out, constant->Index(i))) {
+                if (!EmitConstant(out, constant->Index(i), is_variable_initializer)) {
                     return false;
                 }
             }
@@ -3139,7 +3145,7 @@ bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constan
                 if (i > 0) {
                     out << ", ";
                 }
-                if (!EmitConstant(out, constant->Index(i))) {
+                if (!EmitConstant(out, constant->Index(i), is_variable_initializer)) {
                     return false;
                 }
             }
@@ -3147,25 +3153,45 @@ bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constan
             return true;
         },
         [&](const sem::Struct* s) {
+            if (!EmitStructType(&helpers_, s)) {
+                return false;
+            }
+
             if (constant->AllZero()) {
-                out << "(";
+                out << "(" << StructName(s) << ")0";
-                if (!EmitType(out, s, ast::AddressSpace::kNone, ast::Access::kUndefined, "")) {
-                    return false;
-                }
-                out << ")0";
                 return true;
             }
 
-            out << "{";
+            auto emit_member_values = [&](std::ostream& o) {
-            TINT_DEFER(out << "}");
+                o << "{";
-
+                for (size_t i = 0; i < s->Members().size(); i++) {
-            for (size_t i = 0; i < s->Members().size(); i++) {
+                    if (i > 0) {
-                if (i > 0) {
+                        o << ", ";
-                    out << ", ";
+                    }
+                    if (!EmitConstant(o, constant->Index(i), is_variable_initializer)) {
+                        return false;
+                    }
                 }
-                if (!EmitConstant(out, constant->Index(i))) {
+                o << "}";
+                return true;
+            };
+
+            if (is_variable_initializer) {
+                if (!emit_member_values(out)) {
                     return false;
                 }
+            } else {
+                // HLSL requires structure initializers to be assigned directly to a variable.
+                auto name = UniqueIdentifier("c");
+                {
+                    auto decl = line();
+                    decl << "const " << StructName(s) << " " << name << " = ";
+                    if (!emit_member_values(decl)) {
+                        return false;
+                    }
+                    decl << ";";
+                }
+                out << name;
             }
 
             return true;
@@ -3891,6 +3917,11 @@ bool GeneratorImpl::EmitTypeAndName(std::ostream& out,
 }
 
 bool GeneratorImpl::EmitStructType(TextBuffer* b, const sem::Struct* str) {
+    auto it = emitted_structs_.emplace(str);
+    if (!it.second) {
+        return true;
+    }
+
     line(b) << "struct " << StructName(str) << " {";
     {
         ScopedIndent si(b);
@@ -3967,14 +3998,6 @@ bool GeneratorImpl::EmitStructType(TextBuffer* b, const sem::Struct* str) {
     return true;
 }
 
-bool GeneratorImpl::EmitStructTypeOnce(TextBuffer* buffer, const sem::Struct* str) {
-    auto it = emitted_structs_.emplace(str);
-    if (!it.second) {
-        return true;
-    }
-    return EmitStructType(buffer, str);
-}
-
 bool GeneratorImpl::EmitUnaryOp(std::ostream& out, const ast::UnaryOpExpression* expr) {
     switch (expr->op) {
         case ast::UnaryOp::kIndirection:

src/tint/writer/hlsl/generator_impl.h

@@ -348,8 +348,12 @@ class GeneratorImpl : public TextGenerator {
     /// Handles a constant value
     /// @param out the output stream
     /// @param constant the constant value to emit
+    /// @param is_variable_initializer true if the constant is used as the RHS of a variable
+    /// initializer
     /// @returns true if the constant value was successfully emitted
-    bool EmitConstant(std::ostream& out, const sem::Constant* constant);
+    bool EmitConstant(std::ostream& out,
+                      const sem::Constant* constant,
+                      bool is_variable_initializer);
     /// Handles a literal
     /// @param out the output stream
     /// @param lit the literal to emit
@@ -420,17 +424,12 @@ class GeneratorImpl : public TextGenerator {
                          ast::AddressSpace address_space,
                          ast::Access access,
                          const std::string& name);
-    /// Handles generating a structure declaration
+    /// Handles generating a structure declaration. If the structure has already been emitted, then
+    /// this function will simply return `true` without emitting anything.
     /// @param buffer the text buffer that the type declaration will be written to
     /// @param ty the struct to generate
     /// @returns true if the struct is emitted
     bool EmitStructType(TextBuffer* buffer, const sem::Struct* ty);
-    /// Handles generating a structure declaration only the first time called. Subsequent calls are
-    /// a no-op and return true.
-    /// @param buffer the text buffer that the type declaration will be written to
-    /// @param ty the struct to generate
-    /// @returns true if the struct is emitted
-    bool EmitStructTypeOnce(TextBuffer* buffer, const sem::Struct* ty);
     /// Handles a unary op expression
     /// @param out the output of the expression stream
     /// @param expr the expression to emit

src/tint/writer/hlsl/generator_impl_builtin_test.cc

@@ -381,9 +381,9 @@ TEST_F(HlslGeneratorImplTest_Builtin, Select_Vector) {
     EXPECT_EQ(out.str(), "(bool2(true, false) ? b : a)");
 }
 
-TEST_F(HlslGeneratorImplTest_Builtin, Modf_Scalar_f32) {
+TEST_F(HlslGeneratorImplTest_Builtin, Runtime_Modf_Scalar_f32) {
-    auto* call = Call("modf", 1_f);
+    WrapInFunction(Decl(Let("f", Expr(1.5_f))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -400,17 +400,18 @@ modf_result tint_modf(float param_0) {
 
 [numthreads(1, 1, 1)]
 void test_function() {
-  tint_modf(1.0f);
+  const float f = 1.5f;
+  const modf_result v = tint_modf(f);
   return;
 }
 )");
 }
 
-TEST_F(HlslGeneratorImplTest_Builtin, Modf_Scalar_f16) {
+TEST_F(HlslGeneratorImplTest_Builtin, Runtime_Modf_Scalar_f16) {
     Enable(ast::Extension::kF16);
 
-    auto* call = Call("modf", 1_h);
+    WrapInFunction(Decl(Let("f", Expr(1.5_h))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -427,15 +428,16 @@ modf_result_f16 tint_modf(float16_t param_0) {
 
 [numthreads(1, 1, 1)]
 void test_function() {
-  tint_modf(float16_t(1.0h));
+  const float16_t f = float16_t(1.5h);
+  const modf_result_f16 v = tint_modf(f);
   return;
 }
 )");
 }
 
-TEST_F(HlslGeneratorImplTest_Builtin, Modf_Vector_f32) {
+TEST_F(HlslGeneratorImplTest_Builtin, Runtime_Modf_Vector_f32) {
-    auto* call = Call("modf", vec3<f32>());
+    WrapInFunction(Decl(Let("f", vec3<f32>(1.5_f, 2.5_f, 3.5_f))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -452,17 +454,18 @@ modf_result_vec3 tint_modf(float3 param_0) {
 
 [numthreads(1, 1, 1)]
 void test_function() {
-  tint_modf((0.0f).xxx);
+  const float3 f = float3(1.5f, 2.5f, 3.5f);
+  const modf_result_vec3 v = tint_modf(f);
   return;
 }
 )");
 }
 
-TEST_F(HlslGeneratorImplTest_Builtin, Modf_Vector_f16) {
+TEST_F(HlslGeneratorImplTest_Builtin, Runtime_Modf_Vector_f16) {
     Enable(ast::Extension::kF16);
 
-    auto* call = Call("modf", vec3<f16>());
+    WrapInFunction(Decl(Let("f", vec3<f16>(1.5_h, 2.5_h, 3.5_h))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -479,7 +482,110 @@ modf_result_vec3_f16 tint_modf(vector<float16_t, 3> param_0) {
 
 [numthreads(1, 1, 1)]
 void test_function() {
-  tint_modf((float16_t(0.0h)).xxx);
+  const vector<float16_t, 3> f = vector<float16_t, 3>(float16_t(1.5h), float16_t(2.5h), float16_t(3.5h));
+  const modf_result_vec3_f16 v = tint_modf(f);
+  return;
+}
+)");
+}
+
+TEST_F(HlslGeneratorImplTest_Builtin, Const_Modf_Scalar_f32) {
+    WrapInFunction(Decl(Let("v", Call("modf", 1.5_f))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(struct modf_result {
+  float fract;
+  float whole;
+};
+[numthreads(1, 1, 1)]
+void test_function() {
+  const modf_result v = {0.5f, 1.0f};
+  return;
+}
+)");
+}
+
+TEST_F(HlslGeneratorImplTest_Builtin, Const_Modf_Scalar_f16) {
+    Enable(ast::Extension::kF16);
+
+    WrapInFunction(Decl(Let("v", Call("modf", 1.5_h))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(struct modf_result_f16 {
+  float16_t fract;
+  float16_t whole;
+};
+[numthreads(1, 1, 1)]
+void test_function() {
+  const modf_result_f16 v = {float16_t(0.5h), float16_t(1.0h)};
+  return;
+}
+)");
+}
+
+TEST_F(HlslGeneratorImplTest_Builtin, Const_Modf_Vector_f32) {
+    WrapInFunction(Decl(Let("v", Call("modf", vec3<f32>(1.5_f, 2.5_f, 3.5_f)))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(struct modf_result_vec3 {
+  float3 fract;
+  float3 whole;
+};
+[numthreads(1, 1, 1)]
+void test_function() {
+  const modf_result_vec3 v = {(0.5f).xxx, float3(1.0f, 2.0f, 3.0f)};
+  return;
+}
+)");
+}
+
+TEST_F(HlslGeneratorImplTest_Builtin, Const_Modf_Vector_f16) {
+    Enable(ast::Extension::kF16);
+
+    WrapInFunction(Decl(Let("v", Call("modf", vec3<f16>(1.5_h, 2.5_h, 3.5_h)))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(struct modf_result_vec3_f16 {
+  vector<float16_t, 3> fract;
+  vector<float16_t, 3> whole;
+};
+[numthreads(1, 1, 1)]
+void test_function() {
+  const modf_result_vec3_f16 v = {(float16_t(0.5h)).xxx, vector<float16_t, 3>(float16_t(1.0h), float16_t(2.0h), float16_t(3.0h))};
+  return;
+}
+)");
+}
+
+TEST_F(HlslGeneratorImplTest_Builtin, NonInitializer_Modf_Vector_f32) {
+    WrapInFunction(
+        // Declare a variable with the result of a modf call.
+        // This is required to infer the 'var' type.
+        Decl(Var("v", Call("modf", vec3<f32>(1.5_f, 2.5_f, 3.5_f)))),
+        // Now assign 'v' again with another modf call.
+        // This requires generating a temporary variable for the struct initializer.
+        Assign("v", Call("modf", vec3<f32>(4.5_f, 5.5_f, 6.5_f))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(struct modf_result_vec3 {
+  float3 fract;
+  float3 whole;
+};
+[numthreads(1, 1, 1)]
+void test_function() {
+  modf_result_vec3 v = {(0.5f).xxx, float3(1.0f, 2.0f, 3.0f)};
+  const modf_result_vec3 c = {(0.5f).xxx, float3(4.0f, 5.0f, 6.0f)};
+  v = c;
   return;
 }
 )");

src/tint/writer/msl/generator_impl.cc

@@ -907,9 +907,7 @@ bool GeneratorImpl::EmitAtomicCall(std::ostream& out,
 
             auto func = utils::GetOrCreate(
                 atomicCompareExchangeWeak_, ACEWKeyType{{sc, str}}, [&]() -> std::string {
-                    // Emit the builtin return type unique to this overload. This does not
+                    if (!EmitStructType(&helpers_, builtin->ReturnType()->As<sem::Struct>())) {
-                    // exist in the AST, so it will not be generated in Generate().
-                    if (!EmitStructTypeOnce(&helpers_, builtin->ReturnType()->As<sem::Struct>())) {
                         return "";
                     }
 
@@ -1748,7 +1746,11 @@ bool GeneratorImpl::EmitConstant(std::ostream& out, const sem::Constant* constan
             return true;
         },
         [&](const sem::Struct* s) {
-            out << program_->Symbols().NameFor(s->Name()) << "{";
+            if (!EmitStructType(&helpers_, s)) {
+                return false;
+            }
+
+            out << StructName(s) << "{";
             TINT_DEFER(out << "}");
 
             if (constant->AllZero()) {
@@ -2747,6 +2749,11 @@ bool GeneratorImpl::EmitAddressSpace(std::ostream& out, ast::AddressSpace sc) {
 }
 
 bool GeneratorImpl::EmitStructType(TextBuffer* b, const sem::Struct* str) {
+    auto it = emitted_structs_.emplace(str);
+    if (!it.second) {
+        return true;
+    }
+
     line(b) << "struct " << StructName(str) << " {";
 
     bool is_host_shareable = str->IsHostShareable();
@@ -2903,14 +2910,6 @@ bool GeneratorImpl::EmitStructType(TextBuffer* b, const sem::Struct* str) {
     return true;
 }
 
-bool GeneratorImpl::EmitStructTypeOnce(TextBuffer* buffer, const sem::Struct* str) {
-    auto it = emitted_structs_.emplace(str);
-    if (!it.second) {
-        return true;
-    }
-    return EmitStructType(buffer, str);
-}
-
 bool GeneratorImpl::EmitUnaryOp(std::ostream& out, const ast::UnaryOpExpression* expr) {
     // Handle `-e` when `e` is signed, so that we ensure that if `e` is the
     // largest negative value, it returns `e`.

src/tint/writer/msl/generator_impl.h

@@ -328,17 +328,12 @@ class GeneratorImpl : public TextGenerator {
     /// @param sc the address space to generate
     /// @returns true if the address space is emitted
     bool EmitAddressSpace(std::ostream& out, ast::AddressSpace sc);
-    /// Handles generating a struct declaration
+    /// Handles generating a struct declaration. If the structure has already been emitted, then
+    /// this function will simply return `true` without emitting anything.
     /// @param buffer the text buffer that the type declaration will be written to
     /// @param str the struct to generate
     /// @returns true if the struct is emitted
     bool EmitStructType(TextBuffer* buffer, const sem::Struct* str);
-    /// Handles generating a structure declaration only the first time called. Subsequent calls are
-    /// a no-op and return true.
-    /// @param buffer the text buffer that the type declaration will be written to
-    /// @param ty the struct to generate
-    /// @returns true if the struct is emitted
-    bool EmitStructTypeOnce(TextBuffer* buffer, const sem::Struct* ty);
     /// Handles a unary op expression
     /// @param out the output of the expression stream
     /// @param expr the expression to emit

src/tint/writer/msl/generator_impl_builtin_test.cc

@@ -405,9 +405,9 @@ TEST_F(MslGeneratorImplTest, WorkgroupBarrier) {
     EXPECT_EQ(out.str(), "threadgroup_barrier(mem_flags::mem_threadgroup)");
 }
 
-TEST_F(MslGeneratorImplTest, Modf_Scalar_f32) {
+TEST_F(MslGeneratorImplTest, Runtime_Modf_Scalar_f32) {
-    auto* call = Call("modf", 1_f);
+    WrapInFunction(Decl(Let("f", Expr(1.5_f))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -427,18 +427,19 @@ modf_result tint_modf(float param_0) {
 }
 
 kernel void test_function() {
-  tint_modf(1.0f);
+  float const f = 1.5f;
+  modf_result const v = tint_modf(f);
   return;
 }
 
 )");
 }
 
-TEST_F(MslGeneratorImplTest, Modf_Scalar_f16) {
+TEST_F(MslGeneratorImplTest, Runtime_Modf_Scalar_f16) {
     Enable(ast::Extension::kF16);
 
-    auto* call = Call("modf", 1_h);
+    WrapInFunction(Decl(Let("f", Expr(1.5_h))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -458,16 +459,17 @@ modf_result_f16 tint_modf(half param_0) {
 }
 
 kernel void test_function() {
-  tint_modf(1.0h);
+  half const f = 1.5h;
+  modf_result_f16 const v = tint_modf(f);
   return;
 }
 
 )");
 }
 
-TEST_F(MslGeneratorImplTest, Modf_Vector_f32) {
+TEST_F(MslGeneratorImplTest, Runtime_Modf_Vector_f32) {
-    auto* call = Call("modf", vec3<f32>());
+    WrapInFunction(Decl(Let("f", vec3<f32>(1.5_f, 2.5_f, 3.5_f))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -487,18 +489,19 @@ modf_result_vec3 tint_modf(float3 param_0) {
 }
 
 kernel void test_function() {
-  tint_modf(float3(0.0f));
+  float3 const f = float3(1.5f, 2.5f, 3.5f);
+  modf_result_vec3 const v = tint_modf(f);
   return;
 }
 
 )");
 }
 
-TEST_F(MslGeneratorImplTest, Modf_Vector_f16) {
+TEST_F(MslGeneratorImplTest, Runtime_Modf_Vector_f16) {
     Enable(ast::Extension::kF16);
 
-    auto* call = Call("modf", vec3<f16>());
+    WrapInFunction(Decl(Let("f", vec3<f16>(1.5_h, 2.5_h, 3.5_h))),  //
-    WrapInFunction(CallStmt(call));
+                   Decl(Let("v", Call("modf", "f"))));
 
     GeneratorImpl& gen = SanitizeAndBuild();
 
@@ -518,7 +521,100 @@ modf_result_vec3_f16 tint_modf(half3 param_0) {
 }
 
 kernel void test_function() {
-  tint_modf(half3(0.0h));
+  half3 const f = half3(1.5h, 2.5h, 3.5h);
+  modf_result_vec3_f16 const v = tint_modf(f);
+  return;
+}
+
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Const_Modf_Scalar_f32) {
+    WrapInFunction(Decl(Let("v", Call("modf", 1.5_f))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#include <metal_stdlib>
+
+using namespace metal;
+
+struct modf_result {
+  float fract;
+  float whole;
+};
+kernel void test_function() {
+  modf_result const v = modf_result{.fract=0.5f, .whole=1.0f};
+  return;
+}
+
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Const_Modf_Scalar_f16) {
+    Enable(ast::Extension::kF16);
+
+    WrapInFunction(Decl(Let("v", Call("modf", 1.5_h))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#include <metal_stdlib>
+
+using namespace metal;
+
+struct modf_result_f16 {
+  half fract;
+  half whole;
+};
+kernel void test_function() {
+  modf_result_f16 const v = modf_result_f16{.fract=0.5h, .whole=1.0h};
+  return;
+}
+
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Const_Modf_Vector_f32) {
+    WrapInFunction(Decl(Let("v", Call("modf", vec3<f32>(1.5_f, 2.5_f, 3.5_f)))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#include <metal_stdlib>
+
+using namespace metal;
+
+struct modf_result_vec3 {
+  float3 fract;
+  float3 whole;
+};
+kernel void test_function() {
+  modf_result_vec3 const v = modf_result_vec3{.fract=float3(0.5f), .whole=float3(1.0f, 2.0f, 3.0f)};
+  return;
+}
+
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Const_Modf_Vector_f16) {
+    Enable(ast::Extension::kF16);
+
+    WrapInFunction(Decl(Let("v", Call("modf", vec3<f16>(1.5_h, 2.5_h, 3.5_h)))));
+
+    GeneratorImpl& gen = SanitizeAndBuild();
+
+    ASSERT_TRUE(gen.Generate()) << gen.error();
+    EXPECT_EQ(gen.result(), R"(#include <metal_stdlib>
+
+using namespace metal;
+
+struct modf_result_vec3_f16 {
+  half3 fract;
+  half3 whole;
+};
+kernel void test_function() {
+  modf_result_vec3_f16 const v = modf_result_vec3_f16{.fract=half3(0.5h), .whole=half3(1.0h, 2.0h, 3.0h)};
   return;
 }
 

src/tint/writer/spirv/builder_builtin_test.cc

@@ -1630,7 +1630,7 @@ OpFunctionEnd
     EXPECT_EQ(got, expect);
 }
 
-TEST_F(BuiltinBuilderTest, Call_Modf_f32) {
+TEST_F(BuiltinBuilderTest, Runtime_Call_Modf_f32) {
     auto* vec = Var("vec", vec2<f32>(1_f, 2_f));
     auto* expr = Call("modf", vec);
     Func("a_func", utils::Empty, ty.void_(),
@@ -1682,7 +1682,7 @@ OpFunctionEnd
     Validate(b);
 }
 
-TEST_F(BuiltinBuilderTest, Call_Modf_f16) {
+TEST_F(BuiltinBuilderTest, Runtime_Call_Modf_f16) {
     Enable(ast::Extension::kF16);
 
     auto* vec = Var("vec", vec2<f16>(1_h, 2_h));
@@ -1740,6 +1740,100 @@ OpFunctionEnd
     Validate(b);
 }
 
+TEST_F(BuiltinBuilderTest, Const_Call_Modf_f32) {
+    auto* expr = Call("modf", vec2<f32>(1_f, 2_f));
+    Func("a_func", utils::Empty, ty.void_(),
+         utils::Vector{
+             CallStmt(expr),
+         },
+         utils::Vector{
+             Stage(ast::PipelineStage::kFragment),
+         });
+
+    spirv::Builder& b = Build();
+
+    ASSERT_TRUE(b.Build()) << b.error();
+    auto got = DumpBuilder(b);
+    auto* expect = R"(OpCapability Shader
+%9 = OpExtInstImport "GLSL.std.450"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %3 "a_func"
+OpExecutionMode %3 OriginUpperLeft
+OpName %3 "a_func"
+OpName %6 "__modf_result_vec2"
+OpMemberName %6 0 "fract"
+OpMemberName %6 1 "whole"
+OpMemberDecorate %6 0 Offset 0
+OpMemberDecorate %6 1 Offset 8
+%2 = OpTypeVoid
+%1 = OpTypeFunction %2
+%8 = OpTypeFloat 32
+%7 = OpTypeVector %8 2
+%6 = OpTypeStruct %7 %7
+%10 = OpConstant %8 1
+%11 = OpConstant %8 2
+%12 = OpConstantComposite %7 %10 %11
+%3 = OpFunction %2 None %1
+%4 = OpLabel
+%5 = OpExtInst %6 %9 ModfStruct %12
+OpReturn
+OpFunctionEnd
+)";
+    EXPECT_EQ(expect, got);
+
+    Validate(b);
+}
+
+TEST_F(BuiltinBuilderTest, Const_Call_Modf_f16) {
+    Enable(ast::Extension::kF16);
+
+    auto* expr = Call("modf", vec2<f16>(1_h, 2_h));
+    Func("a_func", utils::Empty, ty.void_(),
+         utils::Vector{
+             CallStmt(expr),
+         },
+         utils::Vector{
+             Stage(ast::PipelineStage::kFragment),
+         });
+
+    spirv::Builder& b = Build();
+
+    ASSERT_TRUE(b.Build()) << b.error();
+    auto got = DumpBuilder(b);
+    auto* expect = R"(OpCapability Shader
+OpCapability Float16
+OpCapability UniformAndStorageBuffer16BitAccess
+OpCapability StorageBuffer16BitAccess
+OpCapability StorageInputOutput16
+%9 = OpExtInstImport "GLSL.std.450"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %3 "a_func"
+OpExecutionMode %3 OriginUpperLeft
+OpName %3 "a_func"
+OpName %6 "__modf_result_vec2_f16"
+OpMemberName %6 0 "fract"
+OpMemberName %6 1 "whole"
+OpMemberDecorate %6 0 Offset 0
+OpMemberDecorate %6 1 Offset 4
+%2 = OpTypeVoid
+%1 = OpTypeFunction %2
+%8 = OpTypeFloat 16
+%7 = OpTypeVector %8 2
+%6 = OpTypeStruct %7 %7
+%10 = OpConstant %8 0x1p+0
+%11 = OpConstant %8 0x1p+1
+%12 = OpConstantComposite %7 %10 %11
+%3 = OpFunction %2 None %1
+%4 = OpLabel
+%5 = OpExtInst %6 %9 ModfStruct %12
+OpReturn
+OpFunctionEnd
+)";
+    EXPECT_EQ(expect, got);
+
+    Validate(b);
+}
+
 TEST_F(BuiltinBuilderTest, Call_Frexp_f32) {
     auto* vec = Var("vec", vec2<f32>(1_f, 2_f));
     auto* expr = Call("frexp", vec);

test/tint/bug/chromium/1236161.wgsl.expected.dxc.hlsl

@@ -1,18 +1,8 @@
-struct modf_result {
-  float fract;
-  float whole;
-};
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 [numthreads(1, 1, 1)]
 void unused_entry_point() {
   return;
 }
 
 void i() {
-  const float s = tint_modf(1.0f).whole;
+  const float s = 1.0f;
 }

test/tint/bug/chromium/1236161.wgsl.expected.fxc.hlsl

@@ -1,18 +1,8 @@
-struct modf_result {
-  float fract;
-  float whole;
-};
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 [numthreads(1, 1, 1)]
 void unused_entry_point() {
   return;
 }
 
 void i() {
-  const float s = tint_modf(1.0f).whole;
+  const float s = 1.0f;
 }

test/tint/bug/chromium/1236161.wgsl.expected.glsl

@@ -1,22 +1,10 @@
 #version 310 es
 
-struct modf_result {
-  float fract;
-  float whole;
-};
-
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
-
 layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
 void unused_entry_point() {
   return;
 }
 void i() {
-  float s = tint_modf(1.0f).whole;
+  float s = 1.0f;
 }
 

test/tint/bug/chromium/1236161.wgsl.expected.msl

@@ -1,18 +1,7 @@
 #include <metal_stdlib>
 
 using namespace metal;
-
-struct modf_result {
-  float fract;
-  float whole;
-};
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void i() {
-  float const s = tint_modf(1.0f).whole;
+  float const s = 1.0f;
 }
 

test/tint/bug/chromium/1236161.wgsl.expected.spvasm

@@ -1,24 +1,17 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 13
+; Bound: 9
 ; Schema: 0
                OpCapability Shader
-         %10 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint GLCompute %unused_entry_point "unused_entry_point"
                OpExecutionMode %unused_entry_point LocalSize 1 1 1
                OpName %unused_entry_point "unused_entry_point"
                OpName %tint_symbol "tint_symbol"
-               OpName %__modf_result "__modf_result"
-               OpMemberName %__modf_result 0 "fract"
-               OpMemberName %__modf_result 1 "whole"
-               OpMemberDecorate %__modf_result 0 Offset 0
-               OpMemberDecorate %__modf_result 1 Offset 4
        %void = OpTypeVoid
           %1 = OpTypeFunction %void
       %float = OpTypeFloat 32
-%__modf_result = OpTypeStruct %float %float
     %float_1 = OpConstant %float 1
 %unused_entry_point = OpFunction %void None %1
           %4 = OpLabel
@@ -26,7 +19,5 @@
                OpFunctionEnd
 %tint_symbol = OpFunction %void None %1
           %6 = OpLabel
-          %7 = OpExtInst %__modf_result %10 ModfStruct %float_1
-         %12 = OpCompositeExtract %float %7 1
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/2d50da.wgsl

@@ -23,7 +23,7 @@
 
 // fn modf(vec<2, f32>) -> __modf_result_vec<2, f32>
 fn modf_2d50da() {
-  var res = modf(vec2<f32>(1.f));
+  var res = modf(vec2<f32>(-1.5f));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/2d50da.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec2 {
   float2 fract;
   float2 whole;
 };
-modf_result_vec2 tint_modf(float2 param_0) {
-  modf_result_vec2 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_2d50da() {
-  modf_result_vec2 res = tint_modf((1.0f).xx);
+  modf_result_vec2 res = {(-0.5f).xx, (-1.0f).xx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/2d50da.wgsl.expected.fxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec2 {
   float2 fract;
   float2 whole;
 };
-modf_result_vec2 tint_modf(float2 param_0) {
-  modf_result_vec2 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_2d50da() {
-  modf_result_vec2 res = tint_modf((1.0f).xx);
+  modf_result_vec2 res = {(-0.5f).xx, (-1.0f).xx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/2d50da.wgsl.expected.glsl

@@ -5,15 +5,9 @@ struct modf_result_vec2 {
   vec2 whole;
 };
 
-modf_result_vec2 tint_modf(vec2 param_0) {
-  modf_result_vec2 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_2d50da() {
-  modf_result_vec2 res = tint_modf(vec2(1.0f));
+  modf_result_vec2 res = modf_result_vec2(vec2(-0.5f), vec2(-1.0f));
 }
 
 vec4 vertex_main() {
@@ -37,15 +31,9 @@ struct modf_result_vec2 {
   vec2 whole;
 };
 
-modf_result_vec2 tint_modf(vec2 param_0) {
-  modf_result_vec2 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_2d50da() {
-  modf_result_vec2 res = tint_modf(vec2(1.0f));
+  modf_result_vec2 res = modf_result_vec2(vec2(-0.5f), vec2(-1.0f));
 }
 
 void fragment_main() {
@@ -63,15 +51,9 @@ struct modf_result_vec2 {
   vec2 whole;
 };
 
-modf_result_vec2 tint_modf(vec2 param_0) {
-  modf_result_vec2 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_2d50da() {
-  modf_result_vec2 res = tint_modf(vec2(1.0f));
+  modf_result_vec2 res = modf_result_vec2(vec2(-0.5f), vec2(-1.0f));
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/2d50da.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result_vec2 {
   float2 fract;
   float2 whole;
 };
-modf_result_vec2 tint_modf(float2 param_0) {
-  modf_result_vec2 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_2d50da() {
-  modf_result_vec2 res = tint_modf(float2(1.0f));
+  modf_result_vec2 res = modf_result_vec2{.fract=float2(-0.5f), .whole=float2(-1.0f)};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/2d50da.wgsl.expected.spvasm

@@ -1,10 +1,9 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 35
+; Bound: 37
 ; Schema: 0
                OpCapability Shader
-         %16 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -38,37 +37,40 @@
           %9 = OpTypeFunction %void
     %v2float = OpTypeVector %float 2
 %__modf_result_vec2 = OpTypeStruct %v2float %v2float
-    %float_1 = OpConstant %float 1
+ %float_n0_5 = OpConstant %float -0.5
-         %18 = OpConstantComposite %v2float %float_1 %float_1
+         %16 = OpConstantComposite %v2float %float_n0_5 %float_n0_5
+   %float_n1 = OpConstant %float -1
+         %18 = OpConstantComposite %v2float %float_n1 %float_n1
+         %19 = OpConstantComposite %__modf_result_vec2 %16 %18
 %_ptr_Function___modf_result_vec2 = OpTypePointer Function %__modf_result_vec2
-         %21 = OpConstantNull %__modf_result_vec2
+         %22 = OpConstantNull %__modf_result_vec2
-         %22 = OpTypeFunction %v4float
+         %23 = OpTypeFunction %v4float
+    %float_1 = OpConstant %float 1
 %modf_2d50da = OpFunction %void None %9
          %12 = OpLabel
-        %res = OpVariable %_ptr_Function___modf_result_vec2 Function %21
+        %res = OpVariable %_ptr_Function___modf_result_vec2 Function %22
-         %13 = OpExtInst %__modf_result_vec2 %16 ModfStruct %18
+               OpStore %res %19
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
-%vertex_main_inner = OpFunction %v4float None %22
+%vertex_main_inner = OpFunction %v4float None %23
-         %24 = OpLabel
+         %25 = OpLabel
-         %25 = OpFunctionCall %void %modf_2d50da
+         %26 = OpFunctionCall %void %modf_2d50da
                OpReturnValue %5
                OpFunctionEnd
 %vertex_main = OpFunction %void None %9
-         %27 = OpLabel
+         %28 = OpLabel
-         %28 = OpFunctionCall %v4float %vertex_main_inner
+         %29 = OpFunctionCall %v4float %vertex_main_inner
-               OpStore %value %28
+               OpStore %value %29
                OpStore %vertex_point_size %float_1
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %30 = OpLabel
+         %32 = OpLabel
-         %31 = OpFunctionCall %void %modf_2d50da
+         %33 = OpFunctionCall %void %modf_2d50da
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %33 = OpLabel
+         %35 = OpLabel
-         %34 = OpFunctionCall %void %modf_2d50da
+         %36 = OpFunctionCall %void %modf_2d50da
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/2d50da.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 fn modf_2d50da() {
-  var res = modf(vec2<f32>(1.0f));
+  var res = modf(vec2<f32>(-(1.5f)));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/45005f.wgsl

@@ -25,7 +25,7 @@ enable f16;
 
 // fn modf(vec<3, f16>) -> __modf_result_vec<3, f16>
 fn modf_45005f() {
-  var res = modf(vec3<f16>(1.h));
+  var res = modf(vec3<f16>(-1.5h));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/45005f.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec3_f16 {
   vector<float16_t, 3> fract;
   vector<float16_t, 3> whole;
 };
-modf_result_vec3_f16 tint_modf(vector<float16_t, 3> param_0) {
-  modf_result_vec3_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_45005f() {
-  modf_result_vec3_f16 res = tint_modf((float16_t(1.0h)).xxx);
+  modf_result_vec3_f16 res = {(float16_t(-0.5h)).xxx, (float16_t(-1.0h)).xxx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/45005f.wgsl.expected.glsl

@@ -6,15 +6,9 @@ struct modf_result_vec3_f16 {
   f16vec3 whole;
 };
 
-modf_result_vec3_f16 tint_modf(f16vec3 param_0) {
-  modf_result_vec3_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_45005f() {
-  modf_result_vec3_f16 res = tint_modf(f16vec3(1.0hf));
+  modf_result_vec3_f16 res = modf_result_vec3_f16(f16vec3(-0.5hf), f16vec3(-1.0hf));
 }
 
 vec4 vertex_main() {
@@ -39,15 +33,9 @@ struct modf_result_vec3_f16 {
   f16vec3 whole;
 };
 
-modf_result_vec3_f16 tint_modf(f16vec3 param_0) {
-  modf_result_vec3_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_45005f() {
-  modf_result_vec3_f16 res = tint_modf(f16vec3(1.0hf));
+  modf_result_vec3_f16 res = modf_result_vec3_f16(f16vec3(-0.5hf), f16vec3(-1.0hf));
 }
 
 void fragment_main() {
@@ -66,15 +54,9 @@ struct modf_result_vec3_f16 {
   f16vec3 whole;
 };
 
-modf_result_vec3_f16 tint_modf(f16vec3 param_0) {
-  modf_result_vec3_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_45005f() {
-  modf_result_vec3_f16 res = tint_modf(f16vec3(1.0hf));
+  modf_result_vec3_f16 res = modf_result_vec3_f16(f16vec3(-0.5hf), f16vec3(-1.0hf));
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/45005f.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result_vec3_f16 {
   half3 fract;
   half3 whole;
 };
-modf_result_vec3_f16 tint_modf(half3 param_0) {
-  modf_result_vec3_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_45005f() {
-  modf_result_vec3_f16 res = tint_modf(half3(1.0h));
+  modf_result_vec3_f16 res = modf_result_vec3_f16{.fract=half3(-0.5h), .whole=half3(-1.0h)};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/45005f.wgsl.expected.spvasm

@@ -1,14 +1,13 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 37
+; Bound: 38
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
                OpCapability UniformAndStorageBuffer16BitAccess
                OpCapability StorageBuffer16BitAccess
                OpCapability StorageInputOutput16
-         %17 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -43,38 +42,40 @@
        %half = OpTypeFloat 16
      %v3half = OpTypeVector %half 3
 %__modf_result_vec3_f16 = OpTypeStruct %v3half %v3half
-%half_0x1p_0 = OpConstant %half 0x1p+0
+%half_n0x1pn1 = OpConstant %half -0x1p-1
-         %19 = OpConstantComposite %v3half %half_0x1p_0 %half_0x1p_0 %half_0x1p_0
+         %17 = OpConstantComposite %v3half %half_n0x1pn1 %half_n0x1pn1 %half_n0x1pn1
+%half_n0x1p_0 = OpConstant %half -0x1p+0
+         %19 = OpConstantComposite %v3half %half_n0x1p_0 %half_n0x1p_0 %half_n0x1p_0
+         %20 = OpConstantComposite %__modf_result_vec3_f16 %17 %19
 %_ptr_Function___modf_result_vec3_f16 = OpTypePointer Function %__modf_result_vec3_f16
-         %22 = OpConstantNull %__modf_result_vec3_f16
+         %23 = OpConstantNull %__modf_result_vec3_f16
-         %23 = OpTypeFunction %v4float
+         %24 = OpTypeFunction %v4float
     %float_1 = OpConstant %float 1
 %modf_45005f = OpFunction %void None %9
          %12 = OpLabel
-        %res = OpVariable %_ptr_Function___modf_result_vec3_f16 Function %22
+        %res = OpVariable %_ptr_Function___modf_result_vec3_f16 Function %23
-         %13 = OpExtInst %__modf_result_vec3_f16 %17 ModfStruct %19
+               OpStore %res %20
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
-%vertex_main_inner = OpFunction %v4float None %23
+%vertex_main_inner = OpFunction %v4float None %24
-         %25 = OpLabel
+         %26 = OpLabel
-         %26 = OpFunctionCall %void %modf_45005f
+         %27 = OpFunctionCall %void %modf_45005f
                OpReturnValue %5
                OpFunctionEnd
 %vertex_main = OpFunction %void None %9
-         %28 = OpLabel
+         %29 = OpLabel
-         %29 = OpFunctionCall %v4float %vertex_main_inner
+         %30 = OpFunctionCall %v4float %vertex_main_inner
-               OpStore %value %29
+               OpStore %value %30
                OpStore %vertex_point_size %float_1
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %32 = OpLabel
+         %33 = OpLabel
-         %33 = OpFunctionCall %void %modf_45005f
+         %34 = OpFunctionCall %void %modf_45005f
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %35 = OpLabel
+         %36 = OpLabel
-         %36 = OpFunctionCall %void %modf_45005f
+         %37 = OpFunctionCall %void %modf_45005f
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/45005f.wgsl.expected.wgsl

@@ -1,7 +1,7 @@
 enable f16;
 
 fn modf_45005f() {
-  var res = modf(vec3<f16>(1.0h));
+  var res = modf(vec3<f16>(-(1.5h)));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/4bfced.wgsl

@@ -23,7 +23,7 @@
 
 // fn modf(vec<4, f32>) -> __modf_result_vec<4, f32>
 fn modf_4bfced() {
-  var res = modf(vec4<f32>(1.f));
+  var res = modf(vec4<f32>(-1.5f));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/4bfced.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec4 {
   float4 fract;
   float4 whole;
 };
-modf_result_vec4 tint_modf(float4 param_0) {
-  modf_result_vec4 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_4bfced() {
-  modf_result_vec4 res = tint_modf((1.0f).xxxx);
+  modf_result_vec4 res = {(-0.5f).xxxx, (-1.0f).xxxx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/4bfced.wgsl.expected.fxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec4 {
   float4 fract;
   float4 whole;
 };
-modf_result_vec4 tint_modf(float4 param_0) {
-  modf_result_vec4 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_4bfced() {
-  modf_result_vec4 res = tint_modf((1.0f).xxxx);
+  modf_result_vec4 res = {(-0.5f).xxxx, (-1.0f).xxxx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/4bfced.wgsl.expected.glsl

@@ -5,15 +5,9 @@ struct modf_result_vec4 {
   vec4 whole;
 };
 
-modf_result_vec4 tint_modf(vec4 param_0) {
-  modf_result_vec4 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_4bfced() {
-  modf_result_vec4 res = tint_modf(vec4(1.0f));
+  modf_result_vec4 res = modf_result_vec4(vec4(-0.5f), vec4(-1.0f));
 }
 
 vec4 vertex_main() {
@@ -37,15 +31,9 @@ struct modf_result_vec4 {
   vec4 whole;
 };
 
-modf_result_vec4 tint_modf(vec4 param_0) {
-  modf_result_vec4 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_4bfced() {
-  modf_result_vec4 res = tint_modf(vec4(1.0f));
+  modf_result_vec4 res = modf_result_vec4(vec4(-0.5f), vec4(-1.0f));
 }
 
 void fragment_main() {
@@ -63,15 +51,9 @@ struct modf_result_vec4 {
   vec4 whole;
 };
 
-modf_result_vec4 tint_modf(vec4 param_0) {
-  modf_result_vec4 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_4bfced() {
-  modf_result_vec4 res = tint_modf(vec4(1.0f));
+  modf_result_vec4 res = modf_result_vec4(vec4(-0.5f), vec4(-1.0f));
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/4bfced.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result_vec4 {
   float4 fract;
   float4 whole;
 };
-modf_result_vec4 tint_modf(float4 param_0) {
-  modf_result_vec4 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_4bfced() {
-  modf_result_vec4 res = tint_modf(float4(1.0f));
+  modf_result_vec4 res = modf_result_vec4{.fract=float4(-0.5f), .whole=float4(-1.0f)};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/4bfced.wgsl.expected.spvasm

@@ -1,10 +1,9 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 34
+; Bound: 36
 ; Schema: 0
                OpCapability Shader
-         %15 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -37,37 +36,40 @@
        %void = OpTypeVoid
           %9 = OpTypeFunction %void
 %__modf_result_vec4 = OpTypeStruct %v4float %v4float
-    %float_1 = OpConstant %float 1
+ %float_n0_5 = OpConstant %float -0.5
-         %17 = OpConstantComposite %v4float %float_1 %float_1 %float_1 %float_1
+         %15 = OpConstantComposite %v4float %float_n0_5 %float_n0_5 %float_n0_5 %float_n0_5
+   %float_n1 = OpConstant %float -1
+         %17 = OpConstantComposite %v4float %float_n1 %float_n1 %float_n1 %float_n1
+         %18 = OpConstantComposite %__modf_result_vec4 %15 %17
 %_ptr_Function___modf_result_vec4 = OpTypePointer Function %__modf_result_vec4
-         %20 = OpConstantNull %__modf_result_vec4
+         %21 = OpConstantNull %__modf_result_vec4
-         %21 = OpTypeFunction %v4float
+         %22 = OpTypeFunction %v4float
+    %float_1 = OpConstant %float 1
 %modf_4bfced = OpFunction %void None %9
          %12 = OpLabel
-        %res = OpVariable %_ptr_Function___modf_result_vec4 Function %20
+        %res = OpVariable %_ptr_Function___modf_result_vec4 Function %21
-         %13 = OpExtInst %__modf_result_vec4 %15 ModfStruct %17
+               OpStore %res %18
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
-%vertex_main_inner = OpFunction %v4float None %21
+%vertex_main_inner = OpFunction %v4float None %22
-         %23 = OpLabel
+         %24 = OpLabel
-         %24 = OpFunctionCall %void %modf_4bfced
+         %25 = OpFunctionCall %void %modf_4bfced
                OpReturnValue %5
                OpFunctionEnd
 %vertex_main = OpFunction %void None %9
-         %26 = OpLabel
+         %27 = OpLabel
-         %27 = OpFunctionCall %v4float %vertex_main_inner
+         %28 = OpFunctionCall %v4float %vertex_main_inner
-               OpStore %value %27
+               OpStore %value %28
                OpStore %vertex_point_size %float_1
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %29 = OpLabel
+         %31 = OpLabel
-         %30 = OpFunctionCall %void %modf_4bfced
+         %32 = OpFunctionCall %void %modf_4bfced
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %32 = OpLabel
+         %34 = OpLabel
-         %33 = OpFunctionCall %void %modf_4bfced
+         %35 = OpFunctionCall %void %modf_4bfced
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/4bfced.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 fn modf_4bfced() {
-  var res = modf(vec4<f32>(1.0f));
+  var res = modf(vec4<f32>(-(1.5f)));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/5ea256.wgsl

@@ -23,7 +23,7 @@
 
 // fn modf(vec<3, f32>) -> __modf_result_vec<3, f32>
 fn modf_5ea256() {
-  var res = modf(vec3<f32>(1.f));
+  var res = modf(vec3<f32>(-1.5f));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/5ea256.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec3 {
   float3 fract;
   float3 whole;
 };
-modf_result_vec3 tint_modf(float3 param_0) {
-  modf_result_vec3 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_5ea256() {
-  modf_result_vec3 res = tint_modf((1.0f).xxx);
+  modf_result_vec3 res = {(-0.5f).xxx, (-1.0f).xxx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/5ea256.wgsl.expected.fxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec3 {
   float3 fract;
   float3 whole;
 };
-modf_result_vec3 tint_modf(float3 param_0) {
-  modf_result_vec3 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_5ea256() {
-  modf_result_vec3 res = tint_modf((1.0f).xxx);
+  modf_result_vec3 res = {(-0.5f).xxx, (-1.0f).xxx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/5ea256.wgsl.expected.glsl

@@ -5,15 +5,9 @@ struct modf_result_vec3 {
   vec3 whole;
 };
 
-modf_result_vec3 tint_modf(vec3 param_0) {
-  modf_result_vec3 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_5ea256() {
-  modf_result_vec3 res = tint_modf(vec3(1.0f));
+  modf_result_vec3 res = modf_result_vec3(vec3(-0.5f), vec3(-1.0f));
 }
 
 vec4 vertex_main() {
@@ -37,15 +31,9 @@ struct modf_result_vec3 {
   vec3 whole;
 };
 
-modf_result_vec3 tint_modf(vec3 param_0) {
-  modf_result_vec3 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_5ea256() {
-  modf_result_vec3 res = tint_modf(vec3(1.0f));
+  modf_result_vec3 res = modf_result_vec3(vec3(-0.5f), vec3(-1.0f));
 }
 
 void fragment_main() {
@@ -63,15 +51,9 @@ struct modf_result_vec3 {
   vec3 whole;
 };
 
-modf_result_vec3 tint_modf(vec3 param_0) {
-  modf_result_vec3 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_5ea256() {
-  modf_result_vec3 res = tint_modf(vec3(1.0f));
+  modf_result_vec3 res = modf_result_vec3(vec3(-0.5f), vec3(-1.0f));
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/5ea256.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result_vec3 {
   float3 fract;
   float3 whole;
 };
-modf_result_vec3 tint_modf(float3 param_0) {
-  modf_result_vec3 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_5ea256() {
-  modf_result_vec3 res = tint_modf(float3(1.0f));
+  modf_result_vec3 res = modf_result_vec3{.fract=float3(-0.5f), .whole=float3(-1.0f)};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/5ea256.wgsl.expected.spvasm

@@ -1,10 +1,9 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 35
+; Bound: 37
 ; Schema: 0
                OpCapability Shader
-         %16 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -38,37 +37,40 @@
           %9 = OpTypeFunction %void
     %v3float = OpTypeVector %float 3
 %__modf_result_vec3 = OpTypeStruct %v3float %v3float
-    %float_1 = OpConstant %float 1
+ %float_n0_5 = OpConstant %float -0.5
-         %18 = OpConstantComposite %v3float %float_1 %float_1 %float_1
+         %16 = OpConstantComposite %v3float %float_n0_5 %float_n0_5 %float_n0_5
+   %float_n1 = OpConstant %float -1
+         %18 = OpConstantComposite %v3float %float_n1 %float_n1 %float_n1
+         %19 = OpConstantComposite %__modf_result_vec3 %16 %18
 %_ptr_Function___modf_result_vec3 = OpTypePointer Function %__modf_result_vec3
-         %21 = OpConstantNull %__modf_result_vec3
+         %22 = OpConstantNull %__modf_result_vec3
-         %22 = OpTypeFunction %v4float
+         %23 = OpTypeFunction %v4float
+    %float_1 = OpConstant %float 1
 %modf_5ea256 = OpFunction %void None %9
          %12 = OpLabel
-        %res = OpVariable %_ptr_Function___modf_result_vec3 Function %21
+        %res = OpVariable %_ptr_Function___modf_result_vec3 Function %22
-         %13 = OpExtInst %__modf_result_vec3 %16 ModfStruct %18
+               OpStore %res %19
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
-%vertex_main_inner = OpFunction %v4float None %22
+%vertex_main_inner = OpFunction %v4float None %23
-         %24 = OpLabel
+         %25 = OpLabel
-         %25 = OpFunctionCall %void %modf_5ea256
+         %26 = OpFunctionCall %void %modf_5ea256
                OpReturnValue %5
                OpFunctionEnd
 %vertex_main = OpFunction %void None %9
-         %27 = OpLabel
+         %28 = OpLabel
-         %28 = OpFunctionCall %v4float %vertex_main_inner
+         %29 = OpFunctionCall %v4float %vertex_main_inner
-               OpStore %value %28
+               OpStore %value %29
                OpStore %vertex_point_size %float_1
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %30 = OpLabel
+         %32 = OpLabel
-         %31 = OpFunctionCall %void %modf_5ea256
+         %33 = OpFunctionCall %void %modf_5ea256
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %33 = OpLabel
+         %35 = OpLabel
-         %34 = OpFunctionCall %void %modf_5ea256
+         %36 = OpFunctionCall %void %modf_5ea256
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/5ea256.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 fn modf_5ea256() {
-  var res = modf(vec3<f32>(1.0f));
+  var res = modf(vec3<f32>(-(1.5f)));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/8dbbbf.wgsl

@@ -25,7 +25,7 @@ enable f16;
 
 // fn modf(f16) -> __modf_result<f16>
 fn modf_8dbbbf() {
-  var res = modf(1.h);
+  var res = modf(-1.5h);
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/8dbbbf.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_f16 {
   float16_t fract;
   float16_t whole;
 };
-modf_result_f16 tint_modf(float16_t param_0) {
-  modf_result_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_8dbbbf() {
-  modf_result_f16 res = tint_modf(float16_t(1.0h));
+  modf_result_f16 res = {float16_t(-0.5h), float16_t(-1.0h)};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/8dbbbf.wgsl.expected.glsl

@@ -6,15 +6,9 @@ struct modf_result_f16 {
   float16_t whole;
 };
 
-modf_result_f16 tint_modf(float16_t param_0) {
-  modf_result_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_8dbbbf() {
-  modf_result_f16 res = tint_modf(1.0hf);
+  modf_result_f16 res = modf_result_f16(-0.5hf, -1.0hf);
 }
 
 vec4 vertex_main() {
@@ -39,15 +33,9 @@ struct modf_result_f16 {
   float16_t whole;
 };
 
-modf_result_f16 tint_modf(float16_t param_0) {
-  modf_result_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_8dbbbf() {
-  modf_result_f16 res = tint_modf(1.0hf);
+  modf_result_f16 res = modf_result_f16(-0.5hf, -1.0hf);
 }
 
 void fragment_main() {
@@ -66,15 +54,9 @@ struct modf_result_f16 {
   float16_t whole;
 };
 
-modf_result_f16 tint_modf(float16_t param_0) {
-  modf_result_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_8dbbbf() {
-  modf_result_f16 res = tint_modf(1.0hf);
+  modf_result_f16 res = modf_result_f16(-0.5hf, -1.0hf);
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/8dbbbf.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result_f16 {
   half fract;
   half whole;
 };
-modf_result_f16 tint_modf(half param_0) {
-  modf_result_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_8dbbbf() {
-  modf_result_f16 res = tint_modf(1.0h);
+  modf_result_f16 res = modf_result_f16{.fract=-0.5h, .whole=-1.0h};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/8dbbbf.wgsl.expected.spvasm

@@ -8,7 +8,6 @@
                OpCapability UniformAndStorageBuffer16BitAccess
                OpCapability StorageBuffer16BitAccess
                OpCapability StorageInputOutput16
-         %16 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -42,7 +41,9 @@
           %9 = OpTypeFunction %void
        %half = OpTypeFloat 16
 %__modf_result_f16 = OpTypeStruct %half %half
-%half_0x1p_0 = OpConstant %half 0x1p+0
+%half_n0x1pn1 = OpConstant %half -0x1p-1
+%half_n0x1p_0 = OpConstant %half -0x1p+0
+         %17 = OpConstantComposite %__modf_result_f16 %half_n0x1pn1 %half_n0x1p_0
 %_ptr_Function___modf_result_f16 = OpTypePointer Function %__modf_result_f16
          %20 = OpConstantNull %__modf_result_f16
          %21 = OpTypeFunction %v4float
@@ -50,8 +51,7 @@
 %modf_8dbbbf = OpFunction %void None %9
          %12 = OpLabel
         %res = OpVariable %_ptr_Function___modf_result_f16 Function %20
-         %13 = OpExtInst %__modf_result_f16 %16 ModfStruct %half_0x1p_0
+               OpStore %res %17
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
 %vertex_main_inner = OpFunction %v4float None %21

test/tint/builtins/gen/literal/modf/8dbbbf.wgsl.expected.wgsl

@@ -1,7 +1,7 @@
 enable f16;
 
 fn modf_8dbbbf() {
-  var res = modf(1.0h);
+  var res = modf(-(1.5h));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/995934.wgsl

@@ -25,7 +25,7 @@ enable f16;
 
 // fn modf(vec<4, f16>) -> __modf_result_vec<4, f16>
 fn modf_995934() {
-  var res = modf(vec4<f16>(1.h));
+  var res = modf(vec4<f16>(-1.5h));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/995934.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec4_f16 {
   vector<float16_t, 4> fract;
   vector<float16_t, 4> whole;
 };
-modf_result_vec4_f16 tint_modf(vector<float16_t, 4> param_0) {
-  modf_result_vec4_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_995934() {
-  modf_result_vec4_f16 res = tint_modf((float16_t(1.0h)).xxxx);
+  modf_result_vec4_f16 res = {(float16_t(-0.5h)).xxxx, (float16_t(-1.0h)).xxxx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/995934.wgsl.expected.glsl

@@ -6,15 +6,9 @@ struct modf_result_vec4_f16 {
   f16vec4 whole;
 };
 
-modf_result_vec4_f16 tint_modf(f16vec4 param_0) {
-  modf_result_vec4_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_995934() {
-  modf_result_vec4_f16 res = tint_modf(f16vec4(1.0hf));
+  modf_result_vec4_f16 res = modf_result_vec4_f16(f16vec4(-0.5hf), f16vec4(-1.0hf));
 }
 
 vec4 vertex_main() {
@@ -39,15 +33,9 @@ struct modf_result_vec4_f16 {
   f16vec4 whole;
 };
 
-modf_result_vec4_f16 tint_modf(f16vec4 param_0) {
-  modf_result_vec4_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_995934() {
-  modf_result_vec4_f16 res = tint_modf(f16vec4(1.0hf));
+  modf_result_vec4_f16 res = modf_result_vec4_f16(f16vec4(-0.5hf), f16vec4(-1.0hf));
 }
 
 void fragment_main() {
@@ -66,15 +54,9 @@ struct modf_result_vec4_f16 {
   f16vec4 whole;
 };
 
-modf_result_vec4_f16 tint_modf(f16vec4 param_0) {
-  modf_result_vec4_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_995934() {
-  modf_result_vec4_f16 res = tint_modf(f16vec4(1.0hf));
+  modf_result_vec4_f16 res = modf_result_vec4_f16(f16vec4(-0.5hf), f16vec4(-1.0hf));
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/995934.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result_vec4_f16 {
   half4 fract;
   half4 whole;
 };
-modf_result_vec4_f16 tint_modf(half4 param_0) {
-  modf_result_vec4_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_995934() {
-  modf_result_vec4_f16 res = tint_modf(half4(1.0h));
+  modf_result_vec4_f16 res = modf_result_vec4_f16{.fract=half4(-0.5h), .whole=half4(-1.0h)};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/995934.wgsl.expected.spvasm

@@ -1,14 +1,13 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 37
+; Bound: 38
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
                OpCapability UniformAndStorageBuffer16BitAccess
                OpCapability StorageBuffer16BitAccess
                OpCapability StorageInputOutput16
-         %17 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -43,38 +42,40 @@
        %half = OpTypeFloat 16
      %v4half = OpTypeVector %half 4
 %__modf_result_vec4_f16 = OpTypeStruct %v4half %v4half
-%half_0x1p_0 = OpConstant %half 0x1p+0
+%half_n0x1pn1 = OpConstant %half -0x1p-1
-         %19 = OpConstantComposite %v4half %half_0x1p_0 %half_0x1p_0 %half_0x1p_0 %half_0x1p_0
+         %17 = OpConstantComposite %v4half %half_n0x1pn1 %half_n0x1pn1 %half_n0x1pn1 %half_n0x1pn1
+%half_n0x1p_0 = OpConstant %half -0x1p+0
+         %19 = OpConstantComposite %v4half %half_n0x1p_0 %half_n0x1p_0 %half_n0x1p_0 %half_n0x1p_0
+         %20 = OpConstantComposite %__modf_result_vec4_f16 %17 %19
 %_ptr_Function___modf_result_vec4_f16 = OpTypePointer Function %__modf_result_vec4_f16
-         %22 = OpConstantNull %__modf_result_vec4_f16
+         %23 = OpConstantNull %__modf_result_vec4_f16
-         %23 = OpTypeFunction %v4float
+         %24 = OpTypeFunction %v4float
     %float_1 = OpConstant %float 1
 %modf_995934 = OpFunction %void None %9
          %12 = OpLabel
-        %res = OpVariable %_ptr_Function___modf_result_vec4_f16 Function %22
+        %res = OpVariable %_ptr_Function___modf_result_vec4_f16 Function %23
-         %13 = OpExtInst %__modf_result_vec4_f16 %17 ModfStruct %19
+               OpStore %res %20
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
-%vertex_main_inner = OpFunction %v4float None %23
+%vertex_main_inner = OpFunction %v4float None %24
-         %25 = OpLabel
+         %26 = OpLabel
-         %26 = OpFunctionCall %void %modf_995934
+         %27 = OpFunctionCall %void %modf_995934
                OpReturnValue %5
                OpFunctionEnd
 %vertex_main = OpFunction %void None %9
-         %28 = OpLabel
+         %29 = OpLabel
-         %29 = OpFunctionCall %v4float %vertex_main_inner
+         %30 = OpFunctionCall %v4float %vertex_main_inner
-               OpStore %value %29
+               OpStore %value %30
                OpStore %vertex_point_size %float_1
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %32 = OpLabel
+         %33 = OpLabel
-         %33 = OpFunctionCall %void %modf_995934
+         %34 = OpFunctionCall %void %modf_995934
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %35 = OpLabel
+         %36 = OpLabel
-         %36 = OpFunctionCall %void %modf_995934
+         %37 = OpFunctionCall %void %modf_995934
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/995934.wgsl.expected.wgsl

@@ -1,7 +1,7 @@
 enable f16;
 
 fn modf_995934() {
-  var res = modf(vec4<f16>(1.0h));
+  var res = modf(vec4<f16>(-(1.5h)));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/a545b9.wgsl

@@ -25,7 +25,7 @@ enable f16;
 
 // fn modf(vec<2, f16>) -> __modf_result_vec<2, f16>
 fn modf_a545b9() {
-  var res = modf(vec2<f16>(1.h));
+  var res = modf(vec2<f16>(-1.5h));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/a545b9.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result_vec2_f16 {
   vector<float16_t, 2> fract;
   vector<float16_t, 2> whole;
 };
-modf_result_vec2_f16 tint_modf(vector<float16_t, 2> param_0) {
-  modf_result_vec2_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_a545b9() {
-  modf_result_vec2_f16 res = tint_modf((float16_t(1.0h)).xx);
+  modf_result_vec2_f16 res = {(float16_t(-0.5h)).xx, (float16_t(-1.0h)).xx};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/a545b9.wgsl.expected.glsl

@@ -6,15 +6,9 @@ struct modf_result_vec2_f16 {
   f16vec2 whole;
 };
 
-modf_result_vec2_f16 tint_modf(f16vec2 param_0) {
-  modf_result_vec2_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_a545b9() {
-  modf_result_vec2_f16 res = tint_modf(f16vec2(1.0hf));
+  modf_result_vec2_f16 res = modf_result_vec2_f16(f16vec2(-0.5hf), f16vec2(-1.0hf));
 }
 
 vec4 vertex_main() {
@@ -39,15 +33,9 @@ struct modf_result_vec2_f16 {
   f16vec2 whole;
 };
 
-modf_result_vec2_f16 tint_modf(f16vec2 param_0) {
-  modf_result_vec2_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_a545b9() {
-  modf_result_vec2_f16 res = tint_modf(f16vec2(1.0hf));
+  modf_result_vec2_f16 res = modf_result_vec2_f16(f16vec2(-0.5hf), f16vec2(-1.0hf));
 }
 
 void fragment_main() {
@@ -66,15 +54,9 @@ struct modf_result_vec2_f16 {
   f16vec2 whole;
 };
 
-modf_result_vec2_f16 tint_modf(f16vec2 param_0) {
-  modf_result_vec2_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_a545b9() {
-  modf_result_vec2_f16 res = tint_modf(f16vec2(1.0hf));
+  modf_result_vec2_f16 res = modf_result_vec2_f16(f16vec2(-0.5hf), f16vec2(-1.0hf));
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/a545b9.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result_vec2_f16 {
   half2 fract;
   half2 whole;
 };
-modf_result_vec2_f16 tint_modf(half2 param_0) {
-  modf_result_vec2_f16 result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_a545b9() {
-  modf_result_vec2_f16 res = tint_modf(half2(1.0h));
+  modf_result_vec2_f16 res = modf_result_vec2_f16{.fract=half2(-0.5h), .whole=half2(-1.0h)};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/a545b9.wgsl.expected.spvasm

@@ -1,14 +1,13 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 37
+; Bound: 38
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
                OpCapability UniformAndStorageBuffer16BitAccess
                OpCapability StorageBuffer16BitAccess
                OpCapability StorageInputOutput16
-         %17 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -43,38 +42,40 @@
        %half = OpTypeFloat 16
      %v2half = OpTypeVector %half 2
 %__modf_result_vec2_f16 = OpTypeStruct %v2half %v2half
-%half_0x1p_0 = OpConstant %half 0x1p+0
+%half_n0x1pn1 = OpConstant %half -0x1p-1
-         %19 = OpConstantComposite %v2half %half_0x1p_0 %half_0x1p_0
+         %17 = OpConstantComposite %v2half %half_n0x1pn1 %half_n0x1pn1
+%half_n0x1p_0 = OpConstant %half -0x1p+0
+         %19 = OpConstantComposite %v2half %half_n0x1p_0 %half_n0x1p_0
+         %20 = OpConstantComposite %__modf_result_vec2_f16 %17 %19
 %_ptr_Function___modf_result_vec2_f16 = OpTypePointer Function %__modf_result_vec2_f16
-         %22 = OpConstantNull %__modf_result_vec2_f16
+         %23 = OpConstantNull %__modf_result_vec2_f16
-         %23 = OpTypeFunction %v4float
+         %24 = OpTypeFunction %v4float
     %float_1 = OpConstant %float 1
 %modf_a545b9 = OpFunction %void None %9
          %12 = OpLabel
-        %res = OpVariable %_ptr_Function___modf_result_vec2_f16 Function %22
+        %res = OpVariable %_ptr_Function___modf_result_vec2_f16 Function %23
-         %13 = OpExtInst %__modf_result_vec2_f16 %17 ModfStruct %19
+               OpStore %res %20
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
-%vertex_main_inner = OpFunction %v4float None %23
+%vertex_main_inner = OpFunction %v4float None %24
-         %25 = OpLabel
+         %26 = OpLabel
-         %26 = OpFunctionCall %void %modf_a545b9
+         %27 = OpFunctionCall %void %modf_a545b9
                OpReturnValue %5
                OpFunctionEnd
 %vertex_main = OpFunction %void None %9
-         %28 = OpLabel
+         %29 = OpLabel
-         %29 = OpFunctionCall %v4float %vertex_main_inner
+         %30 = OpFunctionCall %v4float %vertex_main_inner
-               OpStore %value %29
+               OpStore %value %30
                OpStore %vertex_point_size %float_1
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %32 = OpLabel
+         %33 = OpLabel
-         %33 = OpFunctionCall %void %modf_a545b9
+         %34 = OpFunctionCall %void %modf_a545b9
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %35 = OpLabel
+         %36 = OpLabel
-         %36 = OpFunctionCall %void %modf_a545b9
+         %37 = OpFunctionCall %void %modf_a545b9
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/a545b9.wgsl.expected.wgsl

@@ -1,7 +1,7 @@
 enable f16;
 
 fn modf_a545b9() {
-  var res = modf(vec2<f16>(1.0h));
+  var res = modf(vec2<f16>(-(1.5h)));
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/bbf7f7.wgsl

@@ -23,7 +23,7 @@
 
 // fn modf(f32) -> __modf_result<f32>
 fn modf_bbf7f7() {
-  var res = modf(1.f);
+  var res = modf(-1.5f);
 }
 
 @vertex

test/tint/builtins/gen/literal/modf/bbf7f7.wgsl.expected.dxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result {
   float fract;
   float whole;
 };
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_bbf7f7() {
-  modf_result res = tint_modf(1.0f);
+  modf_result res = {-0.5f, -1.0f};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/bbf7f7.wgsl.expected.fxc.hlsl

@@ -2,14 +2,8 @@ struct modf_result {
   float fract;
   float whole;
 };
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_bbf7f7() {
-  modf_result res = tint_modf(1.0f);
+  modf_result res = {-0.5f, -1.0f};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/bbf7f7.wgsl.expected.glsl

@@ -5,15 +5,9 @@ struct modf_result {
   float whole;
 };
 
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_bbf7f7() {
-  modf_result res = tint_modf(1.0f);
+  modf_result res = modf_result(-0.5f, -1.0f);
 }
 
 vec4 vertex_main() {
@@ -37,15 +31,9 @@ struct modf_result {
   float whole;
 };
 
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_bbf7f7() {
-  modf_result res = tint_modf(1.0f);
+  modf_result res = modf_result(-0.5f, -1.0f);
 }
 
 void fragment_main() {
@@ -63,15 +51,9 @@ struct modf_result {
   float whole;
 };
 
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 
 void modf_bbf7f7() {
-  modf_result res = tint_modf(1.0f);
+  modf_result res = modf_result(-0.5f, -1.0f);
 }
 
 void compute_main() {

test/tint/builtins/gen/literal/modf/bbf7f7.wgsl.expected.msl

@@ -6,14 +6,8 @@ struct modf_result {
   float fract;
   float whole;
 };
-modf_result tint_modf(float param_0) {
-  modf_result result;
-  result.fract = modf(param_0, result.whole);
-  return result;
-}
-
 void modf_bbf7f7() {
-  modf_result res = tint_modf(1.0f);
+  modf_result res = modf_result{.fract=-0.5f, .whole=-1.0f};
 }
 
 struct tint_symbol {

test/tint/builtins/gen/literal/modf/bbf7f7.wgsl.expected.spvasm

@@ -1,10 +1,9 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 33
+; Bound: 34
 ; Schema: 0
                OpCapability Shader
-         %15 = OpExtInstImport "GLSL.std.450"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %vertex_main "vertex_main" %value %vertex_point_size
                OpEntryPoint Fragment %fragment_main "fragment_main"
@@ -37,15 +36,17 @@
        %void = OpTypeVoid
           %9 = OpTypeFunction %void
 %__modf_result = OpTypeStruct %float %float
-    %float_1 = OpConstant %float 1
+ %float_n0_5 = OpConstant %float -0.5
+   %float_n1 = OpConstant %float -1
+         %16 = OpConstantComposite %__modf_result %float_n0_5 %float_n1
 %_ptr_Function___modf_result = OpTypePointer Function %__modf_result
          %19 = OpConstantNull %__modf_result
          %20 = OpTypeFunction %v4float
+    %float_1 = OpConstant %float 1
 %modf_bbf7f7 = OpFunction %void None %9
          %12 = OpLabel
         %res = OpVariable %_ptr_Function___modf_result Function %19
-         %13 = OpExtInst %__modf_result %15 ModfStruct %float_1
+               OpStore %res %16
-               OpStore %res %13
                OpReturn
                OpFunctionEnd
 %vertex_main_inner = OpFunction %v4float None %20
@@ -61,12 +62,12 @@
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %28 = OpLabel
+         %29 = OpLabel
-         %29 = OpFunctionCall %void %modf_bbf7f7
+         %30 = OpFunctionCall %void %modf_bbf7f7
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %31 = OpLabel
+         %32 = OpLabel
-         %32 = OpFunctionCall %void %modf_bbf7f7
+         %33 = OpFunctionCall %void %modf_bbf7f7
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/literal/modf/bbf7f7.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 fn modf_bbf7f7() {
-  var res = modf(1.0f);
+  var res = modf(-(1.5f));
 }
 
 @vertex

test/tint/builtins/gen/var/modf/2d50da.wgsl

@@ -23,7 +23,7 @@
 
 // fn modf(vec<2, f32>) -> __modf_result_vec<2, f32>
 fn modf_2d50da() {
-  var arg_0 = vec2<f32>(1.f);
+  var arg_0 = vec2<f32>(-1.5f);
   var res = modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/2d50da.wgsl.expected.dxc.hlsl

@@ -9,7 +9,7 @@ modf_result_vec2 tint_modf(float2 param_0) {
 }
 
 void modf_2d50da() {
-  float2 arg_0 = (1.0f).xx;
+  float2 arg_0 = (-1.5f).xx;
   modf_result_vec2 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/2d50da.wgsl.expected.fxc.hlsl

@@ -9,7 +9,7 @@ modf_result_vec2 tint_modf(float2 param_0) {
 }
 
 void modf_2d50da() {
-  float2 arg_0 = (1.0f).xx;
+  float2 arg_0 = (-1.5f).xx;
   modf_result_vec2 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/2d50da.wgsl.expected.glsl

@@ -13,7 +13,7 @@ modf_result_vec2 tint_modf(vec2 param_0) {
 
 
 void modf_2d50da() {
-  vec2 arg_0 = vec2(1.0f);
+  vec2 arg_0 = vec2(-1.5f);
   modf_result_vec2 res = tint_modf(arg_0);
 }
 
@@ -46,7 +46,7 @@ modf_result_vec2 tint_modf(vec2 param_0) {
 
 
 void modf_2d50da() {
-  vec2 arg_0 = vec2(1.0f);
+  vec2 arg_0 = vec2(-1.5f);
   modf_result_vec2 res = tint_modf(arg_0);
 }
 
@@ -73,7 +73,7 @@ modf_result_vec2 tint_modf(vec2 param_0) {
 
 
 void modf_2d50da() {
-  vec2 arg_0 = vec2(1.0f);
+  vec2 arg_0 = vec2(-1.5f);
   modf_result_vec2 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/2d50da.wgsl.expected.msl

@@ -13,7 +13,7 @@ modf_result_vec2 tint_modf(float2 param_0) {
 }
 
 void modf_2d50da() {
-  float2 arg_0 = float2(1.0f);
+  float2 arg_0 = float2(-1.5f);
   modf_result_vec2 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/2d50da.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 39
+; Bound: 40
 ; Schema: 0
                OpCapability Shader
          %21 = OpExtInstImport "GLSL.std.450"
@@ -38,14 +38,15 @@
        %void = OpTypeVoid
           %9 = OpTypeFunction %void
     %v2float = OpTypeVector %float 2
-    %float_1 = OpConstant %float 1
+ %float_n1_5 = OpConstant %float -1.5
-         %15 = OpConstantComposite %v2float %float_1 %float_1
+         %15 = OpConstantComposite %v2float %float_n1_5 %float_n1_5
 %_ptr_Function_v2float = OpTypePointer Function %v2float
          %18 = OpConstantNull %v2float
 %__modf_result_vec2 = OpTypeStruct %v2float %v2float
 %_ptr_Function___modf_result_vec2 = OpTypePointer Function %__modf_result_vec2
          %25 = OpConstantNull %__modf_result_vec2
          %26 = OpTypeFunction %v4float
+    %float_1 = OpConstant %float 1
 %modf_2d50da = OpFunction %void None %9
          %12 = OpLabel
       %arg_0 = OpVariable %_ptr_Function_v2float Function %18
@@ -69,12 +70,12 @@
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %34 = OpLabel
+         %35 = OpLabel
-         %35 = OpFunctionCall %void %modf_2d50da
+         %36 = OpFunctionCall %void %modf_2d50da
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %37 = OpLabel
+         %38 = OpLabel
-         %38 = OpFunctionCall %void %modf_2d50da
+         %39 = OpFunctionCall %void %modf_2d50da
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/var/modf/2d50da.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 fn modf_2d50da() {
-  var arg_0 = vec2<f32>(1.0f);
+  var arg_0 = vec2<f32>(-(1.5f));
   var res = modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/45005f.wgsl

@@ -25,7 +25,7 @@ enable f16;
 
 // fn modf(vec<3, f16>) -> __modf_result_vec<3, f16>
 fn modf_45005f() {
-  var arg_0 = vec3<f16>(1.h);
+  var arg_0 = vec3<f16>(-1.5h);
   var res = modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/45005f.wgsl.expected.dxc.hlsl

@@ -9,7 +9,7 @@ modf_result_vec3_f16 tint_modf(vector<float16_t, 3> param_0) {
 }
 
 void modf_45005f() {
-  vector<float16_t, 3> arg_0 = (float16_t(1.0h)).xxx;
+  vector<float16_t, 3> arg_0 = (float16_t(-1.5h)).xxx;
   modf_result_vec3_f16 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/45005f.wgsl.expected.glsl

@@ -14,7 +14,7 @@ modf_result_vec3_f16 tint_modf(f16vec3 param_0) {
 
 
 void modf_45005f() {
-  f16vec3 arg_0 = f16vec3(1.0hf);
+  f16vec3 arg_0 = f16vec3(-1.5hf);
   modf_result_vec3_f16 res = tint_modf(arg_0);
 }
 
@@ -48,7 +48,7 @@ modf_result_vec3_f16 tint_modf(f16vec3 param_0) {
 
 
 void modf_45005f() {
-  f16vec3 arg_0 = f16vec3(1.0hf);
+  f16vec3 arg_0 = f16vec3(-1.5hf);
   modf_result_vec3_f16 res = tint_modf(arg_0);
 }
 
@@ -76,7 +76,7 @@ modf_result_vec3_f16 tint_modf(f16vec3 param_0) {
 
 
 void modf_45005f() {
-  f16vec3 arg_0 = f16vec3(1.0hf);
+  f16vec3 arg_0 = f16vec3(-1.5hf);
   modf_result_vec3_f16 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/45005f.wgsl.expected.msl

@@ -13,7 +13,7 @@ modf_result_vec3_f16 tint_modf(half3 param_0) {
 }
 
 void modf_45005f() {
-  half3 arg_0 = half3(1.0h);
+  half3 arg_0 = half3(-1.5h);
   modf_result_vec3_f16 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/45005f.wgsl.expected.spvasm

@@ -43,8 +43,8 @@
           %9 = OpTypeFunction %void
        %half = OpTypeFloat 16
      %v3half = OpTypeVector %half 3
-%half_0x1p_0 = OpConstant %half 0x1p+0
+%half_n0x1_8p_0 = OpConstant %half -0x1.8p+0
-         %16 = OpConstantComposite %v3half %half_0x1p_0 %half_0x1p_0 %half_0x1p_0
+         %16 = OpConstantComposite %v3half %half_n0x1_8p_0 %half_n0x1_8p_0 %half_n0x1_8p_0
 %_ptr_Function_v3half = OpTypePointer Function %v3half
          %19 = OpConstantNull %v3half
 %__modf_result_vec3_f16 = OpTypeStruct %v3half %v3half

test/tint/builtins/gen/var/modf/45005f.wgsl.expected.wgsl

@@ -1,7 +1,7 @@
 enable f16;
 
 fn modf_45005f() {
-  var arg_0 = vec3<f16>(1.0h);
+  var arg_0 = vec3<f16>(-(1.5h));
   var res = modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/4bfced.wgsl

@@ -23,7 +23,7 @@
 
 // fn modf(vec<4, f32>) -> __modf_result_vec<4, f32>
 fn modf_4bfced() {
-  var arg_0 = vec4<f32>(1.f);
+  var arg_0 = vec4<f32>(-1.5f);
   var res = modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/4bfced.wgsl.expected.dxc.hlsl

@@ -9,7 +9,7 @@ modf_result_vec4 tint_modf(float4 param_0) {
 }
 
 void modf_4bfced() {
-  float4 arg_0 = (1.0f).xxxx;
+  float4 arg_0 = (-1.5f).xxxx;
   modf_result_vec4 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/4bfced.wgsl.expected.fxc.hlsl

@@ -9,7 +9,7 @@ modf_result_vec4 tint_modf(float4 param_0) {
 }
 
 void modf_4bfced() {
-  float4 arg_0 = (1.0f).xxxx;
+  float4 arg_0 = (-1.5f).xxxx;
   modf_result_vec4 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/4bfced.wgsl.expected.glsl

@@ -13,7 +13,7 @@ modf_result_vec4 tint_modf(vec4 param_0) {
 
 
 void modf_4bfced() {
-  vec4 arg_0 = vec4(1.0f);
+  vec4 arg_0 = vec4(-1.5f);
   modf_result_vec4 res = tint_modf(arg_0);
 }
 
@@ -46,7 +46,7 @@ modf_result_vec4 tint_modf(vec4 param_0) {
 
 
 void modf_4bfced() {
-  vec4 arg_0 = vec4(1.0f);
+  vec4 arg_0 = vec4(-1.5f);
   modf_result_vec4 res = tint_modf(arg_0);
 }
 
@@ -73,7 +73,7 @@ modf_result_vec4 tint_modf(vec4 param_0) {
 
 
 void modf_4bfced() {
-  vec4 arg_0 = vec4(1.0f);
+  vec4 arg_0 = vec4(-1.5f);
   modf_result_vec4 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/4bfced.wgsl.expected.msl

@@ -13,7 +13,7 @@ modf_result_vec4 tint_modf(float4 param_0) {
 }
 
 void modf_4bfced() {
-  float4 arg_0 = float4(1.0f);
+  float4 arg_0 = float4(-1.5f);
   modf_result_vec4 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/4bfced.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 37
+; Bound: 38
 ; Schema: 0
                OpCapability Shader
          %19 = OpExtInstImport "GLSL.std.450"
@@ -37,13 +37,14 @@
 %vertex_point_size = OpVariable %_ptr_Output_float Output %8
        %void = OpTypeVoid
           %9 = OpTypeFunction %void
-    %float_1 = OpConstant %float 1
+ %float_n1_5 = OpConstant %float -1.5
-         %14 = OpConstantComposite %v4float %float_1 %float_1 %float_1 %float_1
+         %14 = OpConstantComposite %v4float %float_n1_5 %float_n1_5 %float_n1_5 %float_n1_5
 %_ptr_Function_v4float = OpTypePointer Function %v4float
 %__modf_result_vec4 = OpTypeStruct %v4float %v4float
 %_ptr_Function___modf_result_vec4 = OpTypePointer Function %__modf_result_vec4
          %23 = OpConstantNull %__modf_result_vec4
          %24 = OpTypeFunction %v4float
+    %float_1 = OpConstant %float 1
 %modf_4bfced = OpFunction %void None %9
          %12 = OpLabel
       %arg_0 = OpVariable %_ptr_Function_v4float Function %5
@@ -67,12 +68,12 @@
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %32 = OpLabel
+         %33 = OpLabel
-         %33 = OpFunctionCall %void %modf_4bfced
+         %34 = OpFunctionCall %void %modf_4bfced
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %35 = OpLabel
+         %36 = OpLabel
-         %36 = OpFunctionCall %void %modf_4bfced
+         %37 = OpFunctionCall %void %modf_4bfced
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/var/modf/4bfced.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 fn modf_4bfced() {
-  var arg_0 = vec4<f32>(1.0f);
+  var arg_0 = vec4<f32>(-(1.5f));
   var res = modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/5ea256.wgsl

@@ -23,7 +23,7 @@
 
 // fn modf(vec<3, f32>) -> __modf_result_vec<3, f32>
 fn modf_5ea256() {
-  var arg_0 = vec3<f32>(1.f);
+  var arg_0 = vec3<f32>(-1.5f);
   var res = modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/5ea256.wgsl.expected.dxc.hlsl

@@ -9,7 +9,7 @@ modf_result_vec3 tint_modf(float3 param_0) {
 }
 
 void modf_5ea256() {
-  float3 arg_0 = (1.0f).xxx;
+  float3 arg_0 = (-1.5f).xxx;
   modf_result_vec3 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/5ea256.wgsl.expected.fxc.hlsl

@@ -9,7 +9,7 @@ modf_result_vec3 tint_modf(float3 param_0) {
 }
 
 void modf_5ea256() {
-  float3 arg_0 = (1.0f).xxx;
+  float3 arg_0 = (-1.5f).xxx;
   modf_result_vec3 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/5ea256.wgsl.expected.glsl

@@ -13,7 +13,7 @@ modf_result_vec3 tint_modf(vec3 param_0) {
 
 
 void modf_5ea256() {
-  vec3 arg_0 = vec3(1.0f);
+  vec3 arg_0 = vec3(-1.5f);
   modf_result_vec3 res = tint_modf(arg_0);
 }
 
@@ -46,7 +46,7 @@ modf_result_vec3 tint_modf(vec3 param_0) {
 
 
 void modf_5ea256() {
-  vec3 arg_0 = vec3(1.0f);
+  vec3 arg_0 = vec3(-1.5f);
   modf_result_vec3 res = tint_modf(arg_0);
 }
 
@@ -73,7 +73,7 @@ modf_result_vec3 tint_modf(vec3 param_0) {
 
 
 void modf_5ea256() {
-  vec3 arg_0 = vec3(1.0f);
+  vec3 arg_0 = vec3(-1.5f);
   modf_result_vec3 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/5ea256.wgsl.expected.msl

@@ -13,7 +13,7 @@ modf_result_vec3 tint_modf(float3 param_0) {
 }
 
 void modf_5ea256() {
-  float3 arg_0 = float3(1.0f);
+  float3 arg_0 = float3(-1.5f);
   modf_result_vec3 res = tint_modf(arg_0);
 }
 

test/tint/builtins/gen/var/modf/5ea256.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 39
+; Bound: 40
 ; Schema: 0
                OpCapability Shader
          %21 = OpExtInstImport "GLSL.std.450"
@@ -38,14 +38,15 @@
        %void = OpTypeVoid
           %9 = OpTypeFunction %void
     %v3float = OpTypeVector %float 3
-    %float_1 = OpConstant %float 1
+ %float_n1_5 = OpConstant %float -1.5
-         %15 = OpConstantComposite %v3float %float_1 %float_1 %float_1
+         %15 = OpConstantComposite %v3float %float_n1_5 %float_n1_5 %float_n1_5
 %_ptr_Function_v3float = OpTypePointer Function %v3float
          %18 = OpConstantNull %v3float
 %__modf_result_vec3 = OpTypeStruct %v3float %v3float
 %_ptr_Function___modf_result_vec3 = OpTypePointer Function %__modf_result_vec3
          %25 = OpConstantNull %__modf_result_vec3
          %26 = OpTypeFunction %v4float
+    %float_1 = OpConstant %float 1
 %modf_5ea256 = OpFunction %void None %9
          %12 = OpLabel
       %arg_0 = OpVariable %_ptr_Function_v3float Function %18
@@ -69,12 +70,12 @@
                OpReturn
                OpFunctionEnd
 %fragment_main = OpFunction %void None %9
-         %34 = OpLabel
+         %35 = OpLabel
-         %35 = OpFunctionCall %void %modf_5ea256
+         %36 = OpFunctionCall %void %modf_5ea256
                OpReturn
                OpFunctionEnd
 %compute_main = OpFunction %void None %9
-         %37 = OpLabel
+         %38 = OpLabel
-         %38 = OpFunctionCall %void %modf_5ea256
+         %39 = OpFunctionCall %void %modf_5ea256
                OpReturn
                OpFunctionEnd

test/tint/builtins/gen/var/modf/5ea256.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 fn modf_5ea256() {
-  var arg_0 = vec3<f32>(1.0f);
+  var arg_0 = vec3<f32>(-(1.5f));
   var res = modf(arg_0);
 }