spirv: Support initializers on uniforms

If a uniform has an initializer it will now be given as the optional
initializer operand to the OpVariable instruction.

Fixes: KhronosGroup#1259

SPIRV/GlslangToSpv.cpp

@@ -2650,7 +2650,18 @@ spv::Id TGlslangToSpvTraverser::createSpvVariable(const glslang::TIntermSymbol*
     if (glslang::IsAnonymous(name))
         name = "";
 
-    return builder.createVariable(storageClass, spvType, name);
+    spv::Id initializer = spv::NoResult;
+
+    if (node->getType().getQualifier().storage == glslang::EvqUniform &&
+        !node->getConstArray().empty()) {
+            int nextConst = 0;
+            initializer = createSpvConstantFromConstUnionArray(node->getType(),
+                                                               node->getConstArray(),
+                                                               nextConst,
+                                                               false /* specConst */);
+    }
+
+    return builder.createVariable(storageClass, spvType, name, initializer);
 }
 
 // Return type Id of the sampled type.

SPIRV/SpvBuilder.cpp

@@ -1183,7 +1183,7 @@ void Builder::makeDiscard()
 }
 
 // Comments in header
-Id Builder::createVariable(StorageClass storageClass, Id type, const char* name)
+Id Builder::createVariable(StorageClass storageClass, Id type, const char* name, Id initializer)
 {
     Id pointerType = makePointer(storageClass, type);
     Instruction* inst = new Instruction(getUniqueId(), pointerType, OpVariable);
@@ -1204,6 +1204,9 @@ Id Builder::createVariable(StorageClass storageClass, Id type, const char* name)
     if (name)
         addName(inst->getResultId(), name);
 
+    if (initializer != NoResult)
+        inst->addIdOperand(initializer);
+
     return inst->getResultId();
 }
 

SPIRV/SpvBuilder.h

@@ -268,7 +268,7 @@ class Builder {
     void makeDiscard();
 
     // Create a global or function local or IO variable.
-    Id createVariable(StorageClass, Id type, const char* name = 0);
+    Id createVariable(StorageClass, Id type, const char* name = 0, Id initializer = NoResult);
 
     // Create an intermediate with an undefined value.
     Id createUndefined(Id type);