Initialize work group size variables

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@1b8a007

Author: bader

llvm-spirv/lib/SPIRV/SPIRVWriter.cpp

@@ -4511,15 +4511,15 @@ bool LLVMToSPIRVBase::transExecutionMode() {
         break;
       case spv::ExecutionModeLocalSize:
       case spv::ExecutionModeLocalSizeHint: {
-        unsigned X, Y, Z;
+        unsigned X = 0, Y = 0, Z = 0;
         N.get(X).get(Y).get(Z);
         BF->addExecutionMode(BM->add(new SPIRVExecutionMode(
             BF, static_cast<ExecutionMode>(EMode), X, Y, Z)));
       } break;
       case spv::ExecutionModeMaxWorkgroupSizeINTEL: {
         if (BM->isAllowedToUseExtension(
                 ExtensionID::SPV_INTEL_kernel_attributes)) {
-          unsigned X, Y, Z;
+          unsigned X = 0, Y = 0, Z = 0;
           N.get(X).get(Y).get(Z);
           BF->addExecutionMode(BM->add(new SPIRVExecutionMode(
               BF, static_cast<ExecutionMode>(EMode), X, Y, Z)));