[llvm] [aarch64][win] Add support for import call optimization (equivalent to MSVC /d2ImportCallOptimization) (PR #121516)

[Eli Friedman via llvm-commits]

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@@ -77,6 +78,11 @@ static cl::opt<PtrauthCheckMode> PtrauthAuthChecks(
     cl::desc("Check pointer authentication auth/resign failures"),
     cl::init(Default));
 
+static cl::opt<bool> EnableImportCallOptimization(
+    "aarch64-win-import-call-optimization", cl::Hidden,
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efriedma-quic wrote:

Yes, you'll have to make the clang driver pass this down as a clang codegen option (clang/include/clang/Basic/CodeGenOptions.def), then make clang codegen add the attribute.  This sort of thing is pretty common.

https://github.com/llvm/llvm-project/pull/121516