Expose setting relaxed Vulkan rules from glslang

.gitignore

@@ -18,3 +18,4 @@ third_party/tint
 android_test/libs
 android_test/include
 .DS_Store
+.vscode/

libshaderc/include/shaderc/shaderc.h

@@ -489,6 +489,12 @@ SHADERC_EXPORT void shaderc_compile_options_set_hlsl_functionality1(
 SHADERC_EXPORT void shaderc_compile_options_set_hlsl_16bit_types(
     shaderc_compile_options_t options, bool enable);
 
+// Enables or disables relaxed Vulkan rules.
+//
+// This allows most OpenGL shaders to compile under Vulkan semantics.
+SHADERC_EXPORT void shaderc_compile_options_set_vulkan_rules_relaxed(
+    shaderc_compile_options_t options, bool enable);
+
 // Sets whether the compiler should invert position.Y output in vertex shader.
 SHADERC_EXPORT void shaderc_compile_options_set_invert_y(
     shaderc_compile_options_t options, bool enable);

libshaderc/include/shaderc/shaderc.hpp

@@ -353,6 +353,13 @@ class CompileOptions {
     shaderc_compile_options_set_hlsl_16bit_types(options_, enable);
   }
 
+  // Enables or disables relaxed Vulkan rules.
+  //
+  // This allows most OpenGL shaders to compile under Vulkan semantics.
+  void SetVulkanRulesRelaxed(bool enable) {
+    shaderc_compile_options_set_vulkan_rules_relaxed(options_, enable);
+  }
+
   // Sets whether the compiler should invert position.Y output in vertex shader.
   void SetInvertY(bool enable) {
     shaderc_compile_options_set_invert_y(options_, enable);

libshaderc/src/shaderc.cc

@@ -564,6 +564,11 @@ void shaderc_compile_options_set_hlsl_16bit_types(
   options->compiler.EnableHlsl16BitTypes(enable);
 }
 
+void shaderc_compile_options_set_vulkan_rules_relaxed(
+    shaderc_compile_options_t options, bool enable) {
+  options->compiler.SetVulkanRulesRelaxed(enable);
+}
+
 void shaderc_compile_options_set_invert_y(
     shaderc_compile_options_t options, bool enable) {
   options->compiler.EnableInvertY(enable);

libshaderc_util/include/libshaderc_util/compiler.h

@@ -233,6 +233,11 @@ class Compiler {
   // Enables or disables HLSL 16-bit types.
   void EnableHlsl16BitTypes(bool enable);
 
+  // Enables or disables relaxed Vulkan rules.
+  //
+  // This allows most OpenGL shaders to compile under Vulkan semantics.
+  void SetVulkanRulesRelaxed(bool enable);
+
   // Enables or disables invert position.Y output in vertex shader.
   void EnableInvertY(bool enable);
 
@@ -545,6 +550,10 @@ class Compiler {
   // True if the compiler should support 16-bit HLSL types.
   bool hlsl_16bit_types_enabled_;
 
+  // True if the compiler should relax Vulkan rules to allow OGL shaders to
+  // compile.
+  bool vulkan_rules_relaxed_ = false;
+
   // True if the compiler should invert position.Y output in vertex shader.
   bool invert_y_enabled_;
 

libshaderc_util/src/compiler.cc

@@ -294,6 +294,22 @@ std::tuple<bool, std::vector<uint32_t>, size_t> Compiler::Compile(
   if (hlsl_functionality1_enabled_) {
     shader.setEnvTargetHlslFunctionality1();
   }
+  if (vulkan_rules_relaxed_) {
+    glslang::EShSource language = glslang::EShSourceNone;
+    switch(source_language_) {
+      case SourceLanguage::GLSL:
+        language = glslang::EShSourceGlsl;
+        break;
+      case SourceLanguage::HLSL:
+        language = glslang::EShSourceHlsl;
+        break;
+    }
+    // This option will only be used if the Vulkan client is used.
+    // If new versions of GL_KHR_vulkan_glsl come out, it would make sense to
+    // let callers specify which version to use. For now, just use 100.
+    shader.setEnvInput(language, used_shader_stage, glslang::EShClientVulkan, 100);
+    shader.setEnvInputVulkanRulesRelaxed();
+  }
   shader.setInvertY(invert_y_enabled_);
   shader.setNanMinMaxClamp(nan_clamp_);
 
@@ -452,6 +468,10 @@ void Compiler::EnableHlslFunctionality1(bool enable) {
   hlsl_functionality1_enabled_ = enable;
 }
 
+void Compiler::SetVulkanRulesRelaxed(bool enable) {
+  vulkan_rules_relaxed_ = enable;
+}
+
 void Compiler::EnableHlsl16BitTypes(bool enable) {
   hlsl_16bit_types_enabled_ = enable;
 }

libshaderc_util/src/compiler_test.cc

@@ -106,6 +106,18 @@ const char kGlslVertShaderExplicitLocation[] =
          gl_Position = my_mat * my_vec;
        })";
 
+// A GLSL fragment shader with the location defined for its non-opaque uniform
+// variable.
+const char kGlslFragShaderOpaqueUniforms[] =
+    R"(#version 320 es
+       precision lowp float;
+
+       layout(location = 0) out vec4 oColor;
+       layout(location = 0) uniform float a;
+       void main(void) {
+         oColor = vec4(1.0, 0.0, 0.0, a);
+       })";
+
 // A GLSL vertex shader without the location defined for its non-opaque uniform
 // variable.
 const char kGlslVertShaderNoExplicitLocation[] =
@@ -813,6 +825,18 @@ TEST_F(CompilerTest, HlslFunctionality1Enabled) {
       << disassembly;
 }
 
+TEST_F(CompilerTest, RelaxedVulkanRulesEnabled) {
+  compiler_.SetSourceLanguage(Compiler::SourceLanguage::GLSL);
+  compiler_.SetAutoBindUniforms(true);  // Uniform variable needs a binding
+  compiler_.SetVulkanRulesRelaxed(true);
+  const auto words =
+      SimpleCompilationBinary(kGlslFragShaderOpaqueUniforms, EShLangFragment);
+  const auto disassembly = Disassemble(words);
+  EXPECT_THAT(disassembly,
+              HasSubstr("OpMemberName %gl_DefaultUniformBlock 0 \"a\""))
+      << disassembly;
+}
+
 TEST_F(CompilerTest, ClampMapsToFClampByDefault) {
   const auto words =
       SimpleCompilationBinary(kGlslShaderWithClamp, EShLangFragment);