XOR the frame pointer with the stack cookie when protecting the stack

Summary: This strengthens the guard and matches MSVC.

Reviewers: hans, etienneb

Subscribers: hiraditya, JDevlieghere, vlad.tsyrklevich, llvm-commits

Differential Revision: https://reviews.llvm.org/D40622

llvm-svn: 319490

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 45246421bab..a298d0a7823 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -1685,6 +1685,19 @@ bool X86TargetLowering::useLoadStackGuardNode() const {
   return Subtarget.isTargetMachO() && Subtarget.is64Bit();
 }
 
+bool X86TargetLowering::useStackGuardXorFP() const {
+  // Currently only MSVC CRTs XOR the frame pointer into the stack guard value.
+  return Subtarget.getTargetTriple().isOSMSVCRT();
+}
+
+SDValue X86TargetLowering::emitStackGuardXorFP(SelectionDAG &DAG, SDValue Val,
+                                               const SDLoc &DL) const {
+  EVT PtrTy = getPointerTy(DAG.getDataLayout());
+  unsigned XorOp = Subtarget.is64Bit() ? X86::XOR64_FP : X86::XOR32_FP;
+  MachineSDNode *Node = DAG.getMachineNode(XorOp, DL, PtrTy, Val);
+  return SDValue(Node, 0);
+}
+
 TargetLoweringBase::LegalizeTypeAction
 X86TargetLowering::getPreferredVectorAction(EVT VT) const {
   if (ExperimentalVectorWideningLegalization &&