writer/hlsl: Ignore struct member offset attribute

These are generated by the SPIR-V reader. Structures used by the
storage and uniform storage classes are handled separately, so we can
safely ignore this attribute for the other storage classes which are
not shared with the host.

Fixed: tint:1027
Change-Id: I8df4b41c687922a97f3b0ed97804cecc17d8997a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/59240
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/writer/hlsl/generator_impl.cc

@@ -3089,9 +3089,11 @@ bool GeneratorImpl::EmitStructType(const sem::Struct* str) {
           // See discussion here: https://github.com/gpuweb/gpuweb/issues/893
           pre += "precise ";
         } else if (!deco->IsAnyOf<ast::StructMemberAlignDecoration,
+                                  ast::StructMemberOffsetDecoration,
                                   ast::StructMemberSizeDecoration>()) {
           TINT_ICE(Writer, diagnostics_)
               << "unhandled struct member attribute: " << deco->name();
+          return false;
         }
       }
 

src/writer/hlsl/generator_impl_type_test.cc

@@ -236,6 +236,26 @@ TEST_F(HlslGeneratorImplTest_Type, EmitType_Struct_NameCollision) {
 )"));
 }
 
+TEST_F(HlslGeneratorImplTest_Type, EmitType_Struct_WithOffsetAttributes) {
+  auto* s = Structure("S",
+                      {
+                          Member("a", ty.i32(), {MemberOffset(0)}),
+                          Member("b", ty.f32(), {MemberOffset(8)}),
+                      },
+                      {create<ast::StructBlockDecoration>()});
+  Global("g", ty.Of(s), ast::StorageClass::kPrivate);
+
+  GeneratorImpl& gen = Build();
+
+  auto* sem_s = program->TypeOf(s)->As<sem::Struct>();
+  ASSERT_TRUE(gen.EmitStructType(sem_s)) << gen.error();
+  EXPECT_EQ(gen.result(), R"(struct S {
+  int a;
+  float b;
+};
+)");
+}
+
 TEST_F(HlslGeneratorImplTest_Type, EmitType_U32) {
   auto* u32 = create<sem::U32>();