[WinEH] Make llvm.x86.seh.restoreframe work for stack realignment prologues

The incoming EBP value points to the end of a local stack allocation, so
we can use that to restore ESI, the base pointer. Once we do that, we
can use local stack allocations. If we know we need stack realignment,
spill the original frame pointer in the prologue and reload it after
restoring ESI.

llvm-svn: 241648

1 files changed, 15 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 85c5b649913..87ace1ec94f 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -90,7 +90,7 @@ bool X86FrameLowering::hasFP(const MachineFunction &MF) const {
   return (MF.getTarget().Options.DisableFramePointerElim(MF) ||
           TRI->needsStackRealignment(MF) ||
           MFI->hasVarSizedObjects() ||
-          MFI->isFrameAddressTaken() || MFI->hasInlineAsmWithSPAdjust() ||
+          MFI->isFrameAddressTaken() || MFI->hasOpaqueSPAdjustment() ||
           MF.getInfo<X86MachineFunctionInfo>()->getForceFramePointer() ||
           MMI.callsUnwindInit() || MMI.callsEHReturn() ||
           MFI->hasStackMap() || MFI->hasPatchPoint());
@@ -967,13 +967,26 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
       .addReg(StackPtr)
       .setMIFlag(MachineInstr::FrameSetup);
     if (X86FI->getRestoreBasePointer()) {
-      // Stash value of base pointer.  Saving RSP instead of EBP shortens dependence chain.
+      // Stash value of base pointer.  Saving RSP instead of EBP shortens
+      // dependence chain. Used by SjLj EH.
       unsigned Opm = Uses64BitFramePtr ? X86::MOV64mr : X86::MOV32mr;
       addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opm)),
                    FramePtr, true, X86FI->getRestoreBasePointerOffset())
         .addReg(StackPtr)
         .setMIFlag(MachineInstr::FrameSetup);
     }
+
+    if (X86FI->getHasSEHFramePtrSave()) {
+      // Stash the value of the frame pointer relative to the base pointer for
+      // Win32 EH. This supports Win32 EH, which does the inverse of the above:
+      // it recovers the frame pointer from the base pointer rather than the
+      // other way around.
+      unsigned Opm = Uses64BitFramePtr ? X86::MOV64mr : X86::MOV32mr;
+      addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opm)), BasePtr, true,
+                   getFrameIndexOffset(MF, X86FI->getSEHFramePtrSaveIndex()))
+          .addReg(FramePtr)
+          .setMIFlag(MachineInstr::FrameSetup);
+    }
   }
 
   if (((!HasFP && NumBytes) || PushedRegs) && NeedsDwarfCFI) {