[llvm] [ARM] CMSE security mitigation on function arguments and returned values (PR #89944)

[via llvm-commits]

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@@ -4617,6 +4636,15 @@ SDValue ARMTargetLowering::LowerFormalArguments(
           (VA.getValVT() == MVT::f16 || VA.getValVT() == MVT::bf16))
         ArgValue = MoveToHPR(dl, DAG, VA.getLocVT(), VA.getValVT(), ArgValue);
 
+      // On CMSE Entry Functions, formal integer arguments whose bitwidth is
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ostannard wrote:

If it's dead can it be removed? I'm concerned that, if there is a case where it does get executed, then it could cause this truncate-extend pair to be removed, and we'd have the security vulnerability again.

https://github.com/llvm/llvm-project/pull/89944