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

[Pan Tao via llvm-commits]

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@@ -29242,6 +29242,24 @@ bool AArch64TargetLowering::useLoadStackGuardNode(const Module &M) const {
   return true;
 }
 
+bool AArch64TargetLowering::useStackGuardMixCookie() const {
+  // Currently only MSVC CRTs XOR the frame pointer into the stack guard value.
+  return Subtarget->getTargetTriple().isOSMSVCRT() &&
+         !getTargetMachine().Options.EnableGlobalISel;
+}
+
+SDValue AArch64TargetLowering::emitStackGuardMixCookie(SelectionDAG &DAG,
+                                                       SDValue Val,
+                                                       const SDLoc &DL,
+                                                       bool FailureBB) const {
+  if (FailureBB) {
+    return DAG.getNode(
+        ISD::ADD, DL, Val.getValueType(),
+        DAG.getRegister(getStackPointerRegisterToSaveRestore(), MVT::i64), Val);
----------------
PanTao2 wrote:

When running llvm/test/CodeGen/AArch64/stack-protector-target.ll, the SDValue returned by DAG.getRegister (getRegister(getStackPointerRegisterToSaveRestore(), MVT:: i64) is "t4: i64 = Register $physreg8".
DAG.getRegister wraps Register as SDValue, while DAG.getCopyFromReg (used in previous version) uses DAG.getRegister and adds a move (copy) instruction.

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