[llvm] [llvm] Preserve existing calling conv when auto-upgrading nvvm.annota… (PR #125568)

[Matt Arsenault via llvm-commits]

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@@ -5023,8 +5023,10 @@ bool llvm::UpgradeDebugInfo(Module &M) {
 bool static upgradeSingleNVVMAnnotation(GlobalValue *GV, StringRef K,
                                         const Metadata *V) {
   if (K == "kernel") {
-    if (!mdconst::extract<ConstantInt>(V)->isZero())
-      cast<Function>(GV)->setCallingConv(CallingConv::PTX_Kernel);
+    auto *F = cast<Function>(GV);
+    if (!mdconst::extract<ConstantInt>(V)->isZero() &&
+        !F->hasKernelCallingConv())
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arsenm wrote:

Probably should check if the CC is not CCC 

https://github.com/llvm/llvm-project/pull/125568