Vulkan: Output SPIR-V ids from compiler

In this change, the shader interface variables are given SPIR-V ids by
the compiler before SPIR-V generation.  Those ids are made available
through the ShaderVariable interface.

The transformer does not yet rely on this information.  A follow up
change will rework the backend's name->info map and the transformer to
directly use ids instead of names.

Bug: angleproject:7220
Change-Id: Ic0a62681d4bcf3ed171c39c3ecd83e438ea068c8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4600609
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Roman Lavrov <romanl@google.com>
Reviewed-by: Yuxin Hu <yuxinhu@google.com>

include/GLSLANG/ShaderLang.h

@@ -26,7 +26,7 @@
 
 // Version number for shader translation API.
 // It is incremented every time the API changes.
-#define ANGLE_SH_VERSION 334
+#define ANGLE_SH_VERSION 335
 
 enum ShShaderSpec
 {
@@ -1027,10 +1027,15 @@ enum ReservedIds
 
     // Pre-rotation and Z-correction support
     kIdTransformPositionFunction,
+    kIdOutputPerVertexVar,
 
     // Transform feedback support
     kIdXfbEmulationGetOffsetsFunction,
     kIdXfbEmulationCaptureFunction,
+    kIdXfbEmulationBufferVarZero,
+    kIdXfbEmulationBufferVarOne,
+    kIdXfbEmulationBufferVarTwo,
+    kIdXfbEmulationBufferVarThree,
 
     // Multisampling support
     kIdSampleID,
@@ -1039,12 +1044,14 @@ enum ReservedIds
     // ANGLE internal shader variables, which are not produced as ShaderVariables.
     // kIdShaderVariablesBegin marks the beginning of these ids.  variableId -> info maps in the
     // backend can use |variableId - kIdShaderVariablesBegin| as key into a flat array.
+    //
+    // Note that for blocks, only the block id is in this section as that is the id used in the
+    // variableId -> info maps.
     kIdShaderVariablesBegin,
 
     // gl_PerVertex
     kIdInputPerVertexBlock = kIdShaderVariablesBegin,
     kIdOutputPerVertexBlock,
-    kIdOutputPerVertexVar,
     // The driver and default uniform blocks
     kIdDriverUniformsBlock,
     kIdDefaultUniformsBlock,
@@ -1055,10 +1062,6 @@ enum ReservedIds
     kIdXfbEmulationBufferBlockOne,
     kIdXfbEmulationBufferBlockTwo,
     kIdXfbEmulationBufferBlockThree,
-    kIdXfbEmulationBufferVarZero,
-    kIdXfbEmulationBufferVarOne,
-    kIdXfbEmulationBufferVarTwo,
-    kIdXfbEmulationBufferVarThree,
     // Additional varying added to hold untransformed gl_Position for transform feedback capture
     kIdXfbExtensionPosition,
 

include/GLSLANG/ShaderVars.h

@@ -240,6 +240,11 @@ struct ShaderVariable
     // If the variable is a sampler that has ever been statically used with texelFetch
     bool texelFetchStaticUse;
 
+    // Id of the variable in the shader.  Currently used by the SPIR-V output to communicate the
+    // SPIR-V id of the variable.  This value is only set for variables that the SPIR-V transformer
+    // needs to know about, i.e. active variables, excluding non-zero array elements etc.
+    uint32_t id;
+
   protected:
     bool isSameVariableAtLinkTime(const ShaderVariable &other,
                                   bool matchPrecision,
@@ -296,6 +301,9 @@ struct InterfaceBlock
     bool isReadOnly;
     BlockType blockType;
     std::vector<ShaderVariable> fields;
+
+    // Id of the interface block in the shader.  Similar to |ShaderVariable::id|.
+    uint32_t id;
 };
 
 struct WorkGroupSize