spirv-reader: support textureSampleCompareLevel

- Translates from OpImageSampleDrefExplicitLod, but the Lod must
  be a constant 0, or the reader issues an error.
  The requirement for Lod 0 is a constraint from Metal, inherited
  by WGSL.

Fixed: tint:425, tint:482
Change-Id: I8fdf10dbd9c5ac3e24398519a28202c84677c38d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51803
Commit-Queue: David Neto <dneto@google.com>
Auto-Submit: David Neto <dneto@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/reader/spirv/function.cc

@@ -3262,16 +3262,10 @@ bool FunctionEmitter::EmitStatement(const spvtools::opt::Instruction& inst) {
       // Handle exceptional cases
       switch (GetSkipReason(ptr_id)) {
         case SkipReason::kPointSizeBuiltinPointer:
-          if (const auto* c = constant_mgr_->FindDeclaredConstant(value_id)) {
+          if (IsFloatOne(value_id)) {
-            // If we're writing a constant 1.0, then skip the write.  That's all
-            // that WebGPU handles.
-            auto* ct = c->type();
-            if (ct->AsFloat() && (ct->AsFloat()->width() == 32) &&
-                (c->GetFloat() == 1.0f)) {
             // Don't store to PointSize
             return true;
           }
-          }
           return Fail() << "cannot store a value other than constant 1.0 to "
                            "PointSize builtin: "
                         << inst.PrettyPrint();
@@ -4843,6 +4837,17 @@ bool FunctionEmitter::EmitImageAccess(const spvtools::opt::Instruction& inst) {
     if (use_level_of_detail_suffix) {
       builtin_name += "Level";
     }
+    if (is_dref_sample) {
+      // Metal only supports Lod = 0 for comparison sampling without
+      // derivatives.
+      if (!IsFloatZero(inst.GetSingleWordInOperand(arg_index))) {
+        return Fail() << "WGSL comparison sampling without derivatives "
+                         "requires level-of-detail 0.0"
+                      << inst.PrettyPrint();
+      }
+      // Don't generate the Lod argument.
+    } else {
+      // Generate the Lod argument.
       TypedExpression lod = MakeOperand(inst, arg_index);
       // When sampling from a depth texture, the Lod operand must be an I32.
       if (texture_type->Is<DepthTexture>()) {
@@ -4850,6 +4855,8 @@ bool FunctionEmitter::EmitImageAccess(const spvtools::opt::Instruction& inst) {
         lod = ToI32(lod);
       }
       params.push_back(lod.expr);
+    }
+
     image_operands_mask ^= SpvImageOperandsLodMask;
     arg_index++;
   } else if ((opcode == SpvOpImageFetch) &&
@@ -5466,6 +5473,28 @@ TypedExpression FunctionEmitter::Dereference(TypedExpression expr) {
   };
 }
 
+bool FunctionEmitter::IsFloatZero(uint32_t value_id) {
+  if (const auto* c = constant_mgr_->FindDeclaredConstant(value_id)) {
+    if (const auto* float_const = c->AsFloatConstant()) {
+      return 0.0f == float_const->GetFloatValue();
+    }
+    if (c->AsNullConstant()) {
+      // Valid SPIR-V requires it to be a float value anyway.
+      return true;
+    }
+  }
+  return false;
+}
+
+bool FunctionEmitter::IsFloatOne(uint32_t value_id) {
+  if (const auto* c = constant_mgr_->FindDeclaredConstant(value_id)) {
+    if (const auto* float_const = c->AsFloatConstant()) {
+      return 1.0f == float_const->GetFloatValue();
+    }
+  }
+  return false;
+}
+
 FunctionEmitter::FunctionDeclaration::FunctionDeclaration() = default;
 FunctionEmitter::FunctionDeclaration::~FunctionDeclaration() = default;
 

src/reader/spirv/function.h

@@ -851,6 +851,11 @@ class FunctionEmitter {
   /// @returns the value itself, or converted to signed integral
   TypedExpression ToSignedIfUnsigned(TypedExpression value);
 
+  /// Returns true if the given SPIR-V id represents a constant float 0.
+  bool IsFloatZero(uint32_t value_id);
+  /// Returns true if the given SPIR-V id represents a constant float 1.
+  bool IsFloatOne(uint32_t value_id);
+
  private:
   /// FunctionDeclaration contains the parsed information for a function header.
   struct FunctionDeclaration {

src/reader/spirv/parser_impl_handle_test.cc

@@ -90,6 +90,7 @@ std::string CommonBasicTypes() {
     %v4float = OpTypeVector %float 4
 
     %float_null = OpConstantNull %float
+    %float_0 = OpConstant %float 0
     %float_1 = OpConstant %float 1
     %float_2 = OpConstant %float 2
     %float_3 = OpConstant %float 3
@@ -932,8 +933,6 @@ TEST_P(SpvParserHandleTest_RegisterHandleUsage_SampledImage, Variable) {
     p->DeliberatelyInvalidSpirv();
   }
   if (inst.find("ImageSampleDrefExplicitLod") != std::string::npos) {
-    // WGSL does not support querying image level of detail.
-    // So don't emit them as part of a "passing" corpus.
     p->SkipDumpingPending("crbug.com/tint/425");  // gpuweb issue #1319
   }
 }
@@ -2259,6 +2258,253 @@ INSTANTIATE_TEST_SUITE_P(
             )
           })"}));
 
+INSTANTIATE_TEST_SUITE_P(
+    ImageSampleDrefExplicitLod,
+    SpvParserHandleTest_SampledImageAccessTest,
+    // Lod must be float constant 0 due to a Metal constraint.
+    // Another test checks cases where the Lod is not float constant 0.
+    ::testing::Values(
+        // 2D
+        ImageAccessCase{"%float 2D 1 0 0 1 Unknown",
+                        "%result = OpImageSampleDrefExplicitLod "
+                        "%float %sampled_image %coords12 %depth Lod %float_0",
+                        R"(
+  Variable{
+    Decorations{
+      GroupDecoration{0}
+      BindingDecoration{0}
+    }
+    x_10
+    none
+    __sampler_comparison
+  }
+  Variable{
+    Decorations{
+      GroupDecoration{2}
+      BindingDecoration{1}
+    }
+    x_20
+    none
+    __depth_texture_2d
+  })",
+                        R"(
+          Call[not set]{
+            Identifier[not set]{textureSampleCompareLevel}
+            (
+              Identifier[not set]{x_20}
+              Identifier[not set]{x_10}
+              Identifier[not set]{coords12}
+              ScalarConstructor[not set]{0.200000}
+            )
+          })"},
+        // 2D array
+        ImageAccessCase{"%float 2D 1 1 0 1 Unknown",
+                        "%result = OpImageSampleDrefExplicitLod "
+                        "%float %sampled_image %coords123 %depth Lod %float_0",
+                        R"(
+  Variable{
+    Decorations{
+      GroupDecoration{0}
+      BindingDecoration{0}
+    }
+    x_10
+    none
+    __sampler_comparison
+  }
+  Variable{
+    Decorations{
+      GroupDecoration{2}
+      BindingDecoration{1}
+    }
+    x_20
+    none
+    __depth_texture_2d_array
+  })",
+                        R"(
+          Call[not set]{
+            Identifier[not set]{textureSampleCompareLevel}
+            (
+              Identifier[not set]{x_20}
+              Identifier[not set]{x_10}
+              MemberAccessor[not set]{
+                Identifier[not set]{coords123}
+                Identifier[not set]{xy}
+              }
+              TypeConstructor[not set]{
+                __i32
+                MemberAccessor[not set]{
+                  Identifier[not set]{coords123}
+                  Identifier[not set]{z}
+                }
+              }
+              ScalarConstructor[not set]{0.200000}
+            )
+          })"},
+        // 2D, ConstOffset
+        ImageAccessCase{"%float 2D 1 0 0 1 Unknown",
+                        "%result = OpImageSampleDrefExplicitLod %float "
+                        "%sampled_image %coords12 %depth Lod|ConstOffset "
+                        "%float_0 %offsets2d",
+                        R"(
+  Variable{
+    Decorations{
+      GroupDecoration{0}
+      BindingDecoration{0}
+    }
+    x_10
+    none
+    __sampler_comparison
+  }
+  Variable{
+    Decorations{
+      GroupDecoration{2}
+      BindingDecoration{1}
+    }
+    x_20
+    none
+    __depth_texture_2d
+  })",
+                        R"(
+          Call[not set]{
+            Identifier[not set]{textureSampleCompareLevel}
+            (
+              Identifier[not set]{x_20}
+              Identifier[not set]{x_10}
+              Identifier[not set]{coords12}
+              ScalarConstructor[not set]{0.200000}
+              TypeConstructor[not set]{
+                __vec_2__i32
+                ScalarConstructor[not set]{3}
+                ScalarConstructor[not set]{4}
+              }
+            )
+          })"},
+        // 2D array, ConstOffset
+        ImageAccessCase{"%float 2D 1 1 0 1 Unknown",
+                        "%result = OpImageSampleDrefExplicitLod %float "
+                        "%sampled_image %coords123 %depth Lod|ConstOffset "
+                        "%float_0 %offsets2d",
+                        R"(
+  Variable{
+    Decorations{
+      GroupDecoration{0}
+      BindingDecoration{0}
+    }
+    x_10
+    none
+    __sampler_comparison
+  }
+  Variable{
+    Decorations{
+      GroupDecoration{2}
+      BindingDecoration{1}
+    }
+    x_20
+    none
+    __depth_texture_2d_array
+  })",
+                        R"(
+          Call[not set]{
+            Identifier[not set]{textureSampleCompareLevel}
+            (
+              Identifier[not set]{x_20}
+              Identifier[not set]{x_10}
+              MemberAccessor[not set]{
+                Identifier[not set]{coords123}
+                Identifier[not set]{xy}
+              }
+              TypeConstructor[not set]{
+                __i32
+                MemberAccessor[not set]{
+                  Identifier[not set]{coords123}
+                  Identifier[not set]{z}
+                }
+              }
+              ScalarConstructor[not set]{0.200000}
+              TypeConstructor[not set]{
+                __vec_2__i32
+                ScalarConstructor[not set]{3}
+                ScalarConstructor[not set]{4}
+              }
+            )
+          })"},
+        // Cube
+        ImageAccessCase{"%float Cube 1 0 0 1 Unknown",
+                        "%result = OpImageSampleDrefExplicitLod "
+                        "%float %sampled_image %coords123 %depth Lod %float_0",
+                        R"(
+  Variable{
+    Decorations{
+      GroupDecoration{0}
+      BindingDecoration{0}
+    }
+    x_10
+    none
+    __sampler_comparison
+  }
+  Variable{
+    Decorations{
+      GroupDecoration{2}
+      BindingDecoration{1}
+    }
+    x_20
+    none
+    __depth_texture_cube
+  })",
+                        R"(
+          Call[not set]{
+            Identifier[not set]{textureSampleCompareLevel}
+            (
+              Identifier[not set]{x_20}
+              Identifier[not set]{x_10}
+              Identifier[not set]{coords123}
+              ScalarConstructor[not set]{0.200000}
+            )
+          })"},
+        // Cube array
+        ImageAccessCase{"%float Cube 1 1 0 1 Unknown",
+                        "%result = OpImageSampleDrefExplicitLod "
+                        "%float %sampled_image %coords1234 %depth Lod %float_0",
+                        R"(
+  Variable{
+    Decorations{
+      GroupDecoration{0}
+      BindingDecoration{0}
+    }
+    x_10
+    none
+    __sampler_comparison
+  }
+  Variable{
+    Decorations{
+      GroupDecoration{2}
+      BindingDecoration{1}
+    }
+    x_20
+    none
+    __depth_texture_cube_array
+  })",
+                        R"(
+          Call[not set]{
+            Identifier[not set]{textureSampleCompareLevel}
+            (
+              Identifier[not set]{x_20}
+              Identifier[not set]{x_10}
+              MemberAccessor[not set]{
+                Identifier[not set]{coords1234}
+                Identifier[not set]{xyz}
+              }
+              TypeConstructor[not set]{
+                __i32
+                MemberAccessor[not set]{
+                  Identifier[not set]{coords1234}
+                  Identifier[not set]{w}
+                }
+              }
+              ScalarConstructor[not set]{0.200000}
+            )
+          })"}));
+
 INSTANTIATE_TEST_SUITE_P(
     ImageSampleExplicitLod_UsingLod,
     SpvParserHandleTest_SampledImageAccessTest,
@@ -3156,7 +3402,7 @@ TEST_F(SpvParserHandleTest, ImageWrite_TooFewSrcTexelComponents_1_vs_4) {
   EXPECT_FALSE(p->BuildAndParseInternalModule());
   EXPECT_THAT(p->error(),
               Eq("texel has too few components for storage texture: 1 provided "
-                 "but 4 required, in: OpImageWrite %53 %3 %2"))
+                 "but 4 required, in: OpImageWrite %54 %3 %2"))
       << p->error();
 }
 
@@ -5365,7 +5611,7 @@ INSTANTIATE_TEST_SUITE_P(
          {"Identifier[not set]{vf12}\n"}},
         {"%float 2D 1 0 0 1 Unknown",
          "%result = OpImageSampleDrefExplicitLod %float %sampled_image %vf12 "
-         "%depth Lod %f1",
+         "%depth Lod %float_0",
          "",
          {"Identifier[not set]{vf12}\n"}},
     }));
@@ -5434,7 +5680,7 @@ INSTANTIATE_TEST_SUITE_P(
 )"}},
         {"%float 2D 1 1 0 1 Unknown",
          "%result = OpImageSampleDrefExplicitLod %float %sampled_image "
-         "%vf123 %depth Lod %f1",
+         "%vf123 %depth Lod %float_0",
          "",
          {
              R"(MemberAccessor[not set]{
@@ -5668,7 +5914,7 @@ INSTANTIATE_TEST_SUITE_P(
         {"%float 1D 0 0 0 1 Unknown",
          "%50 = OpCopyObject %float %float_1",
          "internal error: couldn't find image for "
-         "%50 = OpCopyObject %18 %44",
+         "%50 = OpCopyObject %18 %45",
          {}},
         {"%float 1D 0 0 0 1 Unknown",
          "OpStore %float_var %float_1",
@@ -5687,29 +5933,29 @@ INSTANTIATE_TEST_SUITE_P(
          "%result = OpImageSampleImplicitLod "
          // bad type for coordinate: not a number
          "%v4float %sampled_image %float_var",
-         "bad or unsupported coordinate type for image access: %72 = "
+         "bad or unsupported coordinate type for image access: %73 = "
-         "OpImageSampleImplicitLod %42 %71 %1",
+         "OpImageSampleImplicitLod %42 %72 %1",
          {}},
         {"%float 2D 0 0 0 1 Unknown",  // 2D
          "%result = OpImageSampleImplicitLod "
          // 1 component, but need 2
          "%v4float %sampled_image %f1",
          "image access required 2 coordinate components, but only 1 provided, "
-         "in: %72 = OpImageSampleImplicitLod %42 %71 %12",
+         "in: %73 = OpImageSampleImplicitLod %42 %72 %12",
          {}},
         {"%float 2D 0 1 0 1 Unknown",  // 2DArray
          "%result = OpImageSampleImplicitLod "
          // 2 component, but need 3
          "%v4float %sampled_image %vf12",
          "image access required 3 coordinate components, but only 2 provided, "
-         "in: %72 = OpImageSampleImplicitLod %42 %71 %13",
+         "in: %73 = OpImageSampleImplicitLod %42 %72 %13",
          {}},
         {"%float 3D 0 0 0 1 Unknown",  // 3D
          "%result = OpImageSampleImplicitLod "
          // 2 components, but need 3
          "%v4float %sampled_image %vf12",
          "image access required 3 coordinate components, but only 2 provided, "
-         "in: %72 = OpImageSampleImplicitLod %42 %71 %13",
+         "in: %73 = OpImageSampleImplicitLod %42 %72 %13",
          {}},
     }));
 
@@ -5751,12 +5997,12 @@ INSTANTIATE_TEST_SUITE_P(
         // ImageSampleDrefExplicitLod
         {"%uint 2D 0 0 0 1 Unknown",
          "%result = OpImageSampleDrefExplicitLod %uint %sampled_image %vf12 "
-         "%f1 Lod %f1",
+         "%f1 Lod %float_0",
          "sampled image must have float component type",
          {}},
         {"%int 2D 0 0 0 1 Unknown",
          "%result = OpImageSampleDrefExplicitLod %int %sampled_image %vf12 "
-         "%f1 Lod %f1",
+         "%f1 Lod %float_0",
          "sampled image must have float component type",
          {}}}));
 
@@ -5845,6 +6091,43 @@ INSTANTIATE_TEST_SUITE_P(
          "gradient: ",
          {}}}));
 
+INSTANTIATE_TEST_SUITE_P(
+    ImageSampleDrefExplicitLod_CheckForLod0,
+    // Metal requires comparison sampling with explicit Level-of-detail to use
+    // Lod 0.  The SPIR-V reader requires the operand to be parsed as a constant
+    // 0 value. SPIR-V validation requires the Lod parameter to be a floating
+    // point value for non-fetch operations. So only test float values.
+    SpvParserHandleTest_ImageCoordsTest,
+    ::testing::ValuesIn(std::vector<ImageCoordsCase>{
+        // float 0.0 works
+        {"%float 2D 1 0 0 1 Unknown",
+         "%result = OpImageSampleDrefExplicitLod %float %sampled_image %vf1234 "
+         "%depth Lod %float_0",
+         "",
+         {R"(MemberAccessor[not set]{
+  Identifier[not set]{vf1234}
+  Identifier[not set]{xy}
+}
+)"}},
+        // float null works
+        {"%float 2D 1 0 0 1 Unknown",
+         "%result = OpImageSampleDrefExplicitLod %float %sampled_image %vf1234 "
+         "%depth Lod %float_0",
+         "",
+         {R"(MemberAccessor[not set]{
+  Identifier[not set]{vf1234}
+  Identifier[not set]{xy}
+}
+)"}},
+        // float 1.0 fails.
+        {"%float 2D 1 0 0 1 Unknown",
+         "%result = OpImageSampleDrefExplicitLod %float %sampled_image %vf1234 "
+         "%depth Lod %float_1",
+         "WGSL comparison sampling without derivatives requires "
+         "level-of-detail "
+         "0.0",
+         {}}}));
+
 TEST_F(SpvParserHandleTest, CombinedImageSampler_IsError) {
   const auto assembly = Preamble() + R"(
      OpEntryPoint Fragment %100 "main"