[clang] [llvm] [CodeGen][i386] Move -mregparm storage earlier and fix Runtime calls (PR #89707)

[Eli Friedman via llvm-commits]

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@@ -4781,6 +4782,7 @@ CodeGenModule::CreateRuntimeFunction(llvm::FunctionType *FTy, StringRef Name,
         }
       }
       setDSOLocal(F);
+      markRegisterParameterAttributes(F);
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efriedma-quic wrote:

This really shouldn't work this way: we should go through CodeGenModule::SetLLVMFunctionAttributes to get all the correct attributes for a function.  Unfortunately, that's a bit complicated in this context because you need to construct a CGFunctionInfo, and none of the callers currently do that.  Which might be more work than you really want...  CC @JonPsson1 @jdoerfert @jhuber6

https://github.com/llvm/llvm-project/pull/89707