Implement vector initialization from single scalar (aka "splat")

Updated spir-v and HSLS backends to emit valid constructors.

Bug: tint:656
Change-Id: I53356945563b633239b12c0f4e207f160dbc23d8
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53780
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@chromium.org>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>

src/resolver/resolver.cc

@@ -1895,10 +1895,10 @@ bool Resolver::ValidateVectorConstructor(
     }
   }
 
-  // A correct vector constructor must either be a zero-value expression
-  // or the number of components of all constructor arguments must add up
-  // to the vector cardinality.
-  if (value_cardinality_sum > 0 && value_cardinality_sum != vec_type->size()) {
+  // A correct vector constructor must either be a zero-value expression,
+  // a single-value initializer (splat) expression, or the number of components
+  // of all constructor arguments must add up to the vector cardinality.
+  if (value_cardinality_sum > 1 && value_cardinality_sum != vec_type->size()) {
     if (values.empty()) {
       TINT_ICE(diagnostics_)
           << "constructor arguments expected to be non-empty!";

src/resolver/validation_test.cc

@@ -776,18 +776,6 @@ TEST_F(ResolverValidationTest,
       "12:34 error: attempted to construct 'vec2<f32>' with 4 component(s)");
 }
 
-TEST_F(ResolverValidationTest,
-       Expr_Constructor_Vec2_Error_TooFewArgumentsScalar) {
-  auto* tc = vec2<f32>(create<ast::ScalarConstructorExpression>(
-      Source{{12, 34}}, Literal(1.0f)));
-  WrapInFunction(tc);
-
-  EXPECT_FALSE(r()->Resolve());
-  EXPECT_EQ(
-      r()->error(),
-      "12:34 error: attempted to construct 'vec2<f32>' with 1 component(s)");
-}
-
 TEST_F(ResolverValidationTest,
        Expr_Constructor_Vec2_Error_TooManyArgumentsScalar) {
   auto* tc = vec2<f32>(
@@ -1632,16 +1620,16 @@ TEST_F(ResolverValidationTest,
 
 TEST_F(ResolverValidationTest,
        Expr_Constructor_NestedVectorConstructors_InnerError) {
-  auto* tc = vec4<f32>(
-      vec3<f32>(1.0f, vec2<f32>(create<ast::ScalarConstructorExpression>(
-                          Source{{12, 34}}, Literal(1.0f)))),
-      1.0f);
+  auto* tc = vec4<f32>(vec4<f32>(1.0f, 1.0f,
+                                 vec3<f32>(Expr(Source{{12, 34}}, 1.0f),
+                                           Expr(Source{{12, 34}}, 1.0f))),
+                       1.0f);
   WrapInFunction(tc);
 
   EXPECT_FALSE(r()->Resolve());
   EXPECT_EQ(
       r()->error(),
-      "12:34 error: attempted to construct 'vec2<f32>' with 1 component(s)");
+      "12:34 error: attempted to construct 'vec3<f32>' with 2 component(s)");
 }
 
 TEST_F(ResolverValidationTest,

src/sem/type.cc

@@ -119,6 +119,10 @@ bool Type::is_numeric_vector() const {
       [](const Vector* v) { return v->type()->is_numeric_scalar(); });
 }
 
+bool Type::is_scalar_vector() const {
+  return Is<Vector>([](const Vector* v) { return v->type()->is_scalar(); });
+}
+
 bool Type::is_numeric_scalar_or_vector() const {
   return is_numeric_scalar() || is_numeric_vector();
 }

src/sem/type.h

@@ -85,6 +85,8 @@ class Type : public Castable<Type, Node> {
   bool is_bool_scalar_or_vector() const;
   /// @returns true if this type is a numeric vector
   bool is_numeric_vector() const;
+  /// @returns true if this type is a vector of scalar type
+  bool is_scalar_vector() const;
   /// @returns true if this type is a numeric scale or vector
   bool is_numeric_scalar_or_vector() const;
   /// @returns true if this type is a handle type

src/writer/hlsl/generator_impl.cc

@@ -1377,6 +1377,12 @@ bool GeneratorImpl::EmitTypeConstructor(std::ostream& pre,
 
   bool brackets = type->IsAnyOf<sem::Array, sem::Struct>();
 
+  // For single-value vector initializers, swizzle the scalar to the right
+  // vector dimension using .x
+  const bool is_single_value_vector_init =
+      type->is_scalar_vector() && expr->values().size() == 1 &&
+      TypeOf(expr->values()[0])->is_scalar();
+
   if (brackets) {
     out << "{";
   } else {
@@ -1387,6 +1393,10 @@ bool GeneratorImpl::EmitTypeConstructor(std::ostream& pre,
     out << "(";
   }
 
+  if (is_single_value_vector_init) {
+    out << "(";
+  }
+
   bool first = true;
   for (auto* e : expr->values()) {
     if (!first) {
@@ -1399,6 +1409,10 @@ bool GeneratorImpl::EmitTypeConstructor(std::ostream& pre,
     }
   }
 
+  if (is_single_value_vector_init) {
+    out << ")." << std::string(type->As<sem::Vector>()->size(), 'x');
+  }
+
   out << (brackets ? "}" : ")");
   return true;
 }

src/writer/hlsl/generator_impl_constructor_test.cc

@@ -135,6 +135,54 @@ TEST_F(HlslGeneratorImplTest_Constructor, EmitConstructor_Type_Vec_Empty) {
   Validate();
 }
 
+TEST_F(HlslGeneratorImplTest_Constructor,
+       EmitConstructor_Type_Vec_SingleScalar_Float) {
+  WrapInFunction(vec3<f32>(2.0f));
+
+  GeneratorImpl& gen = Build();
+
+  ASSERT_TRUE(gen.Generate(out)) << gen.error();
+  EXPECT_THAT(result(), HasSubstr("float3((2.0f).xxx)"));
+
+  Validate();
+}
+
+TEST_F(HlslGeneratorImplTest_Constructor,
+       EmitConstructor_Type_Vec_SingleScalar_Bool) {
+  WrapInFunction(vec3<bool>(true));
+
+  GeneratorImpl& gen = Build();
+
+  ASSERT_TRUE(gen.Generate(out)) << gen.error();
+  EXPECT_THAT(result(), HasSubstr("bool3((true).xxx)"));
+
+  Validate();
+}
+
+TEST_F(HlslGeneratorImplTest_Constructor,
+       EmitConstructor_Type_Vec_SingleScalar_Int) {
+  WrapInFunction(vec3<i32>(2));
+
+  GeneratorImpl& gen = Build();
+
+  ASSERT_TRUE(gen.Generate(out)) << gen.error();
+  EXPECT_THAT(result(), HasSubstr("int3((2).xxx)"));
+
+  Validate();
+}
+
+TEST_F(HlslGeneratorImplTest_Constructor,
+       EmitConstructor_Type_Vec_SingleScalar_UInt) {
+  WrapInFunction(vec3<u32>(2u));
+
+  GeneratorImpl& gen = Build();
+
+  ASSERT_TRUE(gen.Generate(out)) << gen.error();
+  EXPECT_THAT(result(), HasSubstr("uint3((2u).xxx)"));
+
+  Validate();
+}
+
 TEST_F(HlslGeneratorImplTest_Constructor, EmitConstructor_Type_Mat) {
   WrapInFunction(
       mat2x3<f32>(vec3<f32>(1.f, 2.f, 3.f), vec3<f32>(3.f, 4.f, 5.f)));

src/writer/spirv/builder.cc

@@ -1430,6 +1430,16 @@ uint32_t Builder::GenerateTypeConstructorExpression(
     }
   }
 
+  // For a single-value vector initializer, splat the initializer value.
+  auto* const init_result_type = TypeOf(init)->UnwrapRef();
+  if (values.size() == 1 && init_result_type->is_scalar_vector() &&
+      TypeOf(values[0])->is_scalar()) {
+    size_t vec_size = init_result_type->As<sem::Vector>()->size();
+    for (size_t i = 0; i < (vec_size - 1); ++i) {
+      ops.push_back(ops[0]);
+    }
+  }
+
   auto str = out.str();
   auto val = type_constructor_to_id_.find(str);
   if (val != type_constructor_to_id_.end()) {

src/writer/spirv/builder_constructor_expression_test.cc

@@ -241,6 +241,38 @@ TEST_F(SpvBuilderConstructorTest, Type_F32_With_F32) {
   EXPECT_EQ(DumpInstructions(b.functions()[0].instructions()), R"()");
 }
 
+TEST_F(SpvBuilderConstructorTest, Type_Vec2_With_Bool) {
+  auto* cast = vec2<bool>(true);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateExpression(cast), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeBool
+%1 = OpTypeVector %2 2
+%3 = OpConstantTrue %2
+%4 = OpConstantComposite %1 %3 %3
+)");
+}
+
+TEST_F(SpvBuilderConstructorTest, Type_Vec2_With_F32) {
+  auto* cast = vec2<f32>(2.0f);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateExpression(cast), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 2
+%3 = OpConstant %2 2
+%4 = OpConstantComposite %1 %3 %3
+)");
+}
+
 TEST_F(SpvBuilderConstructorTest, Type_Vec2_With_F32_F32) {
   auto* cast = vec2<f32>(2.0f, 2.0f);
   WrapInFunction(cast);
@@ -275,6 +307,38 @@ TEST_F(SpvBuilderConstructorTest, Type_Vec2_With_Vec2) {
   EXPECT_EQ(DumpInstructions(b.functions()[0].instructions()), R"()");
 }
 
+TEST_F(SpvBuilderConstructorTest, Type_Vec3_With_F32) {
+  auto* cast = vec3<f32>(2.0f);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateExpression(cast), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 3
+%3 = OpConstant %2 2
+%4 = OpConstantComposite %1 %3 %3 %3
+)");
+}
+
+TEST_F(SpvBuilderConstructorTest, Type_Vec3_With_Bool) {
+  auto* cast = vec3<bool>(true);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateExpression(cast), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeBool
+%1 = OpTypeVector %2 3
+%3 = OpConstantTrue %2
+%4 = OpConstantComposite %1 %3 %3 %3
+)");
+}
+
 TEST_F(SpvBuilderConstructorTest, Type_Vec3_With_F32_F32_F32) {
   auto* cast = vec3<f32>(2.0f, 2.0f, 2.0f);
   WrapInFunction(cast);
@@ -353,6 +417,38 @@ TEST_F(SpvBuilderConstructorTest, Type_Vec3_With_Vec3) {
   EXPECT_EQ(DumpInstructions(b.functions()[0].instructions()), R"()");
 }
 
+TEST_F(SpvBuilderConstructorTest, Type_Vec4_With_Bool) {
+  auto* cast = vec4<bool>(true);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateExpression(cast), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeBool
+%1 = OpTypeVector %2 4
+%3 = OpConstantTrue %2
+%4 = OpConstantComposite %1 %3 %3 %3 %3
+)");
+}
+
+TEST_F(SpvBuilderConstructorTest, Type_Vec4_With_F32) {
+  auto* cast = vec4<f32>(2.0f);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateExpression(cast), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 4
+%3 = OpConstant %2 2
+%4 = OpConstantComposite %1 %3 %3 %3 %3
+)");
+}
+
 TEST_F(SpvBuilderConstructorTest, Type_Vec4_With_F32_F32_F32_F32) {
   auto* cast = vec4<f32>(2.0f, 2.0f, 2.0f, 2.0f);
   WrapInFunction(cast);
@@ -523,6 +619,22 @@ TEST_F(SpvBuilderConstructorTest, Type_Vec4_With_Vec4) {
   EXPECT_EQ(DumpInstructions(b.functions()[0].instructions()), R"()");
 }
 
+TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec2_With_F32) {
+  auto* cast = vec2<f32>(2.0f);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateConstructorExpression(nullptr, cast, true), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 2
+%3 = OpConstant %2 2
+%4 = OpConstantComposite %1 %3 %3
+)");
+}
+
 TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec2_With_Vec2) {
   auto* cast = vec2<f32>(vec2<f32>(2.0f, 2.0f));
   WrapInFunction(cast);
@@ -571,6 +683,22 @@ TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec4_With_Vec4) {
 )");
 }
 
+TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec3_With_F32) {
+  auto* cast = vec3<f32>(2.0f);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateConstructorExpression(nullptr, cast, true), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 3
+%3 = OpConstant %2 2
+%4 = OpConstantComposite %1 %3 %3 %3
+)");
+}
+
 TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec3_With_F32_Vec2) {
   auto* cast = vec3<f32>(2.0f, vec2<f32>(2.0f, 2.0f));
   WrapInFunction(cast);
@@ -617,6 +745,22 @@ TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec3_With_Vec2_F32) {
 )");
 }
 
+TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec4_With_F32) {
+  auto* cast = vec4<f32>(2.0f);
+  WrapInFunction(cast);
+
+  spirv::Builder& b = Build();
+
+  b.push_function(Function{});
+  EXPECT_EQ(b.GenerateConstructorExpression(nullptr, cast, true), 4u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 4
+%3 = OpConstant %2 2
+%4 = OpConstantComposite %1 %3 %3 %3 %3
+)");
+}
+
 TEST_F(SpvBuilderConstructorTest, Type_ModuleScope_Vec4_With_F32_F32_Vec2) {
   auto* cast = vec4<f32>(2.0f, 2.0f, vec2<f32>(2.0f, 2.0f));
   WrapInFunction(cast);