[clang] [CUDA] make kernel stub ICF-proof (PR #90155)

[Yaxun Liu via cfe-commits]

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@@ -424,6 +424,34 @@ void CGNVCUDARuntime::emitDeviceStubBodyNew(CodeGenFunction &CGF,
       CGM.CreateRuntimeFunction(FTy, LaunchKernelName);
   CGF.EmitCall(FI, CGCallee::forDirect(cudaLaunchKernelFn), ReturnValueSlot(),
                LaunchKernelArgs);
+
+  // To prevent CUDA device stub functions from being merged by ICF in MSVC
+  // environment, create an unique global variable for each kernel and write to
+  // the variable in the device stub.
+  if (CGM.getContext().getTargetInfo().getCXXABI().isMicrosoft() &&
+      !CGF.getLangOpts().HIP) {
+    llvm::Function *KernelFunction = llvm::cast<llvm::Function>(Kernel);
+    if (KernelFunction->hasComdat()) {
+      std::string KernelName = KernelFunction->getName().str();
+      std::string GlobalVarName = KernelName + ".id";
+
+      llvm::GlobalVariable *HandleVar =
+          CGM.getModule().getNamedGlobal(GlobalVarName);
+      if (!HandleVar) {
+        HandleVar = new llvm::GlobalVariable(
+            CGM.getModule(), CGM.Int8Ty,
+            /*Constant=*/false, KernelFunction->getLinkage(),
+            llvm::ConstantInt::get(CGM.Int8Ty, 0), GlobalVarName);
+        HandleVar->setDSOLocal(KernelFunction->isDSOLocal());
+        HandleVar->setVisibility(KernelFunction->getVisibility());
+        HandleVar->setComdat(CGM.getModule().getOrInsertComdat(GlobalVarName));
+      }
+
+      CGF.Builder.CreateAlignedStore(llvm::ConstantInt::get(CGM.Int8Ty, 1),
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yxsamliu wrote:

will do

https://github.com/llvm/llvm-project/pull/90155