[llvm] [aarch64] XOR the frame pointer with the stack cookie when protecting the stack (PR #161114)

[Eli Friedman via llvm-commits]

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@@ -2497,6 +2497,16 @@ bool AArch64InstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
           .addMemOperand(*MI.memoperands_begin());
     }
   }
+  // To match MSVC
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efriedma-quic wrote:

Maybe extend this comment a little to explain what exactly we're matching.

https://github.com/llvm/llvm-project/pull/161114