Fix ASAN stack-use-after-scope in SpirvEmitter::processGetAttributeAt… (#5975)

…Vertex

arg1ConstExpr->getValue() returns an APInt by value, and we were calling
getRawData() on the returned temporary, making the pointer dangle after
the statement executed, and the APInt temporary was destroyed. Fixed by
keeping the returned APInt on the stack.

tools/clang/lib/SPIRV/SpirvEmitter.cpp

@@ -11983,7 +11983,7 @@ SpirvEmitter::processGetAttributeAtVertex(const CallExpr *expr) {
   // arg1 : vertexId
   const auto *arg1BaseExpr = doExpr(expr->getArg(1)->IgnoreParenLValueCasts());
   const auto *arg1ConstExpr = dyn_cast<SpirvConstantInteger>(arg1BaseExpr);
-  const auto *vertexId = arg1ConstExpr->getValue().getRawData();
+  const auto vertexId = arg1ConstExpr->getValue();
 
   // arg0 : <NoInterpolation> decorated input
   // Tip  : for input with boolean type, we need to ignore implicit cast first,
@@ -12000,8 +12000,8 @@ SpirvEmitter::processGetAttributeAtVertex(const CallExpr *expr) {
   }
   // Change to access chain instr
   SpirvInstruction *accessChainPtr = paramDeclInstr;
-  SpirvConstant *vtxId = spvBuilder.getConstantInt(astContext.UnsignedIntTy,
-                                                   llvm::APInt(32, *vertexId));
+  SpirvConstant *vtxId = spvBuilder.getConstantInt(
+      astContext.UnsignedIntTy, llvm::APInt(32, *(vertexId.getRawData())));
   if (isa<SpirvAccessChain>(accessChainPtr)) {
     auto *accessInstr = dyn_cast<SpirvAccessChain>(accessChainPtr);
     accessInstr->insertIndex(vtxId, accessInstr->getIndexes().size());