Add support for generating SPIR-V shaders for OpenGL

* Only a couple of these are needed - ones we might link with user shaders in a
  program

renderdoc/data/glsl/fixedcol.frag

@@ -36,8 +36,15 @@ IO_LOCATION(0) out vec4 color_out;
 
 #endif
 
-#ifndef VULKAN    // OpenGL can't use SPIR-V patching
-uniform vec4 RENDERDOC_Fixed_Color;
+#ifndef VULKAN    // Vulkan uses SPIR-V patching
+
+// if we're compiling for GL SPIR-V, give the uniform an explicit location
+#ifdef GL_SPIRV
+layout(location = 99)
+#endif
+
+    uniform vec4 RENDERDOC_Fixed_Color;
+
 #endif
 
 void main(void)

renderdoc/data/glsl/glsl_globals.h

@@ -38,6 +38,16 @@
 
 #else    // ifdef VULKAN
 
+// GL SPIR-V compilation uses a mixture
+#ifdef GL_SPIRV
+
+#define BINDING(b) layout(binding = b, std140)
+#define IO_LOCATION(l) layout(location = l)
+#define VERTEX_ID gl_VertexID
+#define INSTANCE_ID gl_InstanceID
+
+#else
+
 // drop I/O location specifiers and bindings on GL, we don't use separate programs so I/O variables
 // can be matched by name, and we don't want to require GL_ARB_shading_language_420pack so we can't
 // specify bindings in shaders.
@@ -46,6 +56,8 @@
 #define VERTEX_ID gl_VertexID
 #define INSTANCE_ID gl_InstanceID
 
+#endif
+
 #endif    // ifdef VULKAN
 
 #define INST_NAME(name) name

renderdoc/data/glsl/quadwrite.frag

@@ -42,7 +42,16 @@
 // descriptor set will be patched from 0 to whichever descriptor set we're using in code
 layout(set = 0, binding = 0, r32ui) uniform coherent uimage2DArray overdrawImage;
 #else    // OPENGL and OPENGL_ES
-layout(r32ui) uniform coherent uimage2DArray overdrawImage;
+
+// if we're compiling for GL SPIR-V, give the image an explicit binding
+#ifdef GL_SPIRV
+layout(binding = 0, r32ui)
+#else
+layout(r32ui)
+#endif
+
+    uniform coherent uimage2DArray overdrawImage;
+
 #endif
 layout(early_fragment_tests) in;
 

renderdoc/data/glsl_shaders.cpp

@@ -125,6 +125,8 @@ std::string GenerateGLSLShader(const std::string &shader, ShaderType type, int v
 
   if(type == eShaderVulkan)
     flags = EShMessages(flags | EShMsgSpvRules | EShMsgVulkanRules);
+  else if(type == eShaderGLSPIRV)
+    flags = EShMessages(flags | EShMsgSpvRules);
 
   std::string ret;
 

renderdoc/data/glsl_shaders.h

@@ -26,7 +26,8 @@ enum ShaderType
 {
   eShaderGLSL,
   eShaderGLSLES,
-  eShaderVulkan
+  eShaderVulkan,
+  eShaderGLSPIRV,
 };
 
 #include <string>