spirv-reader: fix arity for depth texture builtins

Texture buitins on depth textures always result in scalar f32.
Corresponding operations in SPIR-V always result in vec4<f32>.

When translating to Tint AST, wrap the generated texture builtin
in a type constructor to vec4, with the builtin result as the
x component.

Fixed: tint:411
Change-Id: Idf26a1cbc7e875bc8a97bf3c0b342c0220c6d4b7
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/35900
Auto-Submit: David Neto <dneto@google.com>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

src/reader/spirv/function.cc

@@ -4145,14 +4145,31 @@ bool FunctionEmitter::EmitImageAccess(const spvtools::opt::Instruction& inst) {
     // It returns a value.
     ast::Expression* value = call_expr;
 
-    // If necessary, convert the result to the signedness of the instruction
+    // The result type, derived from the SPIR-V instruction.
-    // result type. Compare the SPIR-V image's sampled component type with the
-    // component of the result type of the SPIR-V instruction.
     auto* result_type = parser_impl_.ConvertType(inst.type_id());
     auto* result_component_type = result_type;
     if (auto* result_vector_type = result_type->As<ast::type::Vector>()) {
       result_component_type = result_vector_type->type();
     }
+
+    // Convert the arity of the result when operating on depth textures.
+    // SPIR-V operations on depth textures always result in 4-element vectors.
+    // But WGSL operations on depth textures always result in a f32 scalar.
+    // Construct a 4-element vector with the result from the builtin in the
+    // first component.
+    if (texture_type->Is<ast::type::DepthTexture>()) {
+      value = create<ast::TypeConstructorExpression>(
+          Source{},
+          result_type,  // a vec4
+          ast::ExpressionList{
+              value, parser_impl_.MakeNullValue(result_component_type),
+              parser_impl_.MakeNullValue(result_component_type),
+              parser_impl_.MakeNullValue(result_component_type)});
+    }
+
+    // If necessary, convert the result to the signedness of the instruction
+    // result type. Compare the SPIR-V image's sampled component type with the
+    // component of the result type of the SPIR-V instruction.
     auto* spirv_image_type =
         parser_impl_.GetSpirvTypeForHandleMemoryObjectDeclaration(*image);
     if (!spirv_image_type || (spirv_image_type->opcode() != SpvOpTypeImage)) {

src/reader/spirv/parser_impl_handle_test.cc

@@ -1751,6 +1751,8 @@ INSTANTIATE_TEST_SUITE_P(
         none
         __vec_4__f32
         {
+          TypeConstructor[not set]{
+            __vec_4__f32
             Call[not set]{
               Identifier[not set]{textureSample}
               (
@@ -1759,6 +1761,10 @@ INSTANTIATE_TEST_SUITE_P(
                 Identifier[not set]{coords12}
               )
             }
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+          }
         }
       }
     }
@@ -1768,6 +1774,8 @@ INSTANTIATE_TEST_SUITE_P(
         none
         __vec_4__f32
         {
+          TypeConstructor[not set]{
+            __vec_4__f32
             Call[not set]{
               Identifier[not set]{textureSampleCompare}
               (
@@ -1777,6 +1785,10 @@ INSTANTIATE_TEST_SUITE_P(
                 ScalarConstructor[not set]{0.200000}
               )
             }
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+          }
         }
       }
     })"}));
@@ -1809,6 +1821,8 @@ INSTANTIATE_TEST_SUITE_P(
     __depth_texture_2d
   })",
                         R"(
+          TypeConstructor[not set]{
+            __vec_4__f32
             Call[not set]{
               Identifier[not set]{textureSampleCompare}
               (
@@ -1817,6 +1831,10 @@ INSTANTIATE_TEST_SUITE_P(
                 Identifier[not set]{coords12}
                 ScalarConstructor[not set]{0.200000}
               )
+            }
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
           })"},
         // ImageSampleDrefImplicitLod - arrayed
         ImageAccessCase{"%float 2D 0 1 0 1 Unknown",
@@ -1842,6 +1860,8 @@ INSTANTIATE_TEST_SUITE_P(
     __depth_texture_2d_array
   })",
                         R"(
+          TypeConstructor[not set]{
+            __vec_4__f32
             Call[not set]{
               Identifier[not set]{textureSampleCompare}
               (
@@ -1860,6 +1880,10 @@ INSTANTIATE_TEST_SUITE_P(
                 }
                 ScalarConstructor[not set]{0.200000}
               )
+            }
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
           })"},
         // ImageSampleDrefImplicitLod with ConstOffset
         ImageAccessCase{
@@ -1886,6 +1910,8 @@ INSTANTIATE_TEST_SUITE_P(
     __depth_texture_2d
   })",
             R"(
+          TypeConstructor[not set]{
+            __vec_4__f32
             Call[not set]{
               Identifier[not set]{textureSampleCompare}
               (
@@ -1895,6 +1921,10 @@ INSTANTIATE_TEST_SUITE_P(
                 ScalarConstructor[not set]{0.200000}
                 Identifier[not set]{offsets2d}
               )
+            }
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
           })"},
         // ImageSampleDrefImplicitLod arrayed with ConstOffset
         ImageAccessCase{
@@ -1921,6 +1951,8 @@ INSTANTIATE_TEST_SUITE_P(
     __depth_texture_2d_array
   })",
             R"(
+          TypeConstructor[not set]{
+            __vec_4__f32
             Call[not set]{
               Identifier[not set]{textureSampleCompare}
               (
@@ -1940,6 +1972,10 @@ INSTANTIATE_TEST_SUITE_P(
                 ScalarConstructor[not set]{0.200000}
                 Identifier[not set]{offsets2d}
               )
+            }
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
           })"}));
 
 INSTANTIATE_TEST_SUITE_P(
@@ -2471,6 +2507,8 @@ INSTANTIATE_TEST_SUITE_P(
     __depth_texture_2d
   })",
          R"(
+          TypeConstructor[not set]{
+            __vec_4__f32
             Call[not set]{
               Identifier[not set]{textureSampleLevel}
               (
@@ -2482,6 +2520,10 @@ INSTANTIATE_TEST_SUITE_P(
                   Identifier[not set]{f1}
                 }
               )
+            }
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
+            ScalarConstructor[not set]{0.000000}
           })"}}));
 
 using SpvParserTest_ImageAccessTest =