[X86] Don't give catch objects a displacement of zero

Catch objects with a displacement of zero do not initialize a catch
object.  The displacement is relative to %rsp at the end of the
function's prologue for x86_64 targets.

If we place an object at the top-of-stack, we will end up wit a
displacement of zero resulting in our catch object remaining
uninitialized.

Address this by creating our catch objects as fixed objects.  We will
ensure that the UnwindHelp object is created after the catch objects so
that no catch object will have a displacement of zero.

Differential Revision: http://reviews.llvm.org/D17823

llvm-svn: 262546

1 files changed, 17 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 378204f6c0c..de56259f744 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -2839,14 +2839,30 @@ void X86FrameLowering::processFunctionBeforeFrameFinalized(
   // were no fixed objects, use offset -SlotSize, which is immediately after the
   // return address. Fixed objects have negative frame indices.
   MachineFrameInfo *MFI = MF.getFrameInfo();
+  WinEHFuncInfo &EHInfo = *MF.getWinEHFuncInfo();
   int64_t MinFixedObjOffset = -SlotSize;
   for (int I = MFI->getObjectIndexBegin(); I < 0; ++I)
     MinFixedObjOffset = std::min(MinFixedObjOffset, MFI->getObjectOffset(I));
 
+  for (WinEHTryBlockMapEntry &TBME : EHInfo.TryBlockMap) {
+    for (WinEHHandlerType &H : TBME.HandlerArray) {
+      int FrameIndex = H.CatchObj.FrameIndex;
+      if (FrameIndex != INT_MAX) {
+        // Ensure alignment.
+        unsigned Align = MFI->getObjectAlignment(FrameIndex);
+        MinFixedObjOffset -= std::abs(MinFixedObjOffset) % Align;
+        MinFixedObjOffset -= MFI->getObjectSize(FrameIndex);
+        MFI->setObjectOffset(FrameIndex, MinFixedObjOffset);
+      }
+    }
+  }
+
+  // Ensure alignment.
+  MinFixedObjOffset -= std::abs(MinFixedObjOffset) % 8;
   int64_t UnwindHelpOffset = MinFixedObjOffset - SlotSize;
   int UnwindHelpFI =
       MFI->CreateFixedObject(SlotSize, UnwindHelpOffset, /*Immutable=*/false);
-  MF.getWinEHFuncInfo()->UnwindHelpFrameIdx = UnwindHelpFI;
+  EHInfo.UnwindHelpFrameIdx = UnwindHelpFI;
 
   // Store -2 into UnwindHelp on function entry. We have to scan forwards past
   // other frame setup instructions.