commit e69bdb8619c716d506d69a0bebedf24ca3254bc7
author Reid Kleckner <reid@kleckner.net> Tue Jul 07 23:45:58 2015 +0000
committer Reid Kleckner <reid@kleckner.net> Tue Jul 07 23:45:58 2015 +0000
tree 208b2da9cf004c469e45af14454bcdf4726d862b
parent 84936e0b431efb85e404390b21f7f3b8951e9cad

[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

llvm/lib/Target/X86/X86FrameLowering.cpp

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 85c5b64..87ace1e 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -90,7 +90,7 @@
   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 @@
       .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) {