[llvm] Refactored llvm::UpgradeIntrinsicCall() function in lib/IR/AutoUpgrade.cpp with lookup table based on #30382 (PR #128611)

[Matt Arsenault via llvm-commits]

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@@ -4348,41 +4352,51 @@ void llvm::UpgradeIntrinsicCall(CallBase *CI, Function *NewFn) {
     assert(Name.starts_with("llvm.") && "Intrinsic doesn't start with 'llvm.'");
     Name = Name.substr(5);
 
-    bool IsX86 = Name.consume_front("x86.");
-    bool IsNVVM = Name.consume_front("nvvm.");
-    bool IsAArch64 = Name.consume_front("aarch64.");
-    bool IsARM = Name.consume_front("arm.");
-    bool IsAMDGCN = Name.consume_front("amdgcn.");
-    bool IsDbg = Name.consume_front("dbg.");
-    Value *Rep = nullptr;
+    const std::string prefix_x86 = "x86.";
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arsenm wrote:

Don't use std::string, these can be StringRef 

https://github.com/llvm/llvm-project/pull/128611