[Feat] (MG_Util/ShaderCompiler): extract global UBO offset from GL plain uniforms

MobileGL/MG_Util/ShaderTranspiler/SpvcSession.h

@@ -7,9 +7,25 @@
 
 #pragma once
 
+#define SPVC_CHK_INIT \
+    auto __r = SPVC_SUCCESS;
+
+#define SPVC_CHK_RESULT(res) \
+    __r = res; \
+    if (__r != SPVC_SUCCESS) { \
+        return __r; \
+    }
+
+#define SPVC_CHK_RETURN \
+    return __r;
+
 namespace MobileGL {
 namespace MG_Util {
 namespace ShaderTranspiler {
+    struct SpvcMetadata {
+        UnorderedMap<String, unsigned> plainUniformOffsetsInUBO;
+    };
+
     class SpvcSession {
     public:
         SpvcSession() {}
@@ -29,15 +45,21 @@ namespace ShaderTranspiler {
         spvc_result CreateOptions(spvc_compiler_options *options);
         spvc_result SetOptions(spvc_compiler_options options);
         Vector<InterfaceVariable> GetShaderInterface(spvc_resource_type resource_type) const;
-        spvc_result Compile(const char** result) const;
+        spvc_result Compile(const char** result);
+        const SpvcMetadata& GetMetadata() const;
         const char* GetLastErrorString() const;
 
     private:
+        // Should be called once, and only once, for every SPIR-V binary
+        spvc_result ParseMetaData();
+
         spvc_context context = nullptr;
         spvc_parsed_ir ir = nullptr;
         spvc_compiler compiler = nullptr;
         spvc_compiler_options compiler_options = nullptr;
         spvc_resources resources = nullptr;
+
+        SpvcMetadata metadata;
     };
 }
 }