[CodeGen] Fix PrologEpilogInserter to avoid duplicate allocation of SEH structs

[etienneb]

Summary

When stack-protection is activated and WinEH exceptions is used,
the EHRegNode (exception handling registration) is allocated twice on the stack.

This was not breaking anything except loosing space on the stack.

D:\src\llvm\examples>llc exc2.ll  -debug-only=pei
alloc FI(0) at SP[-24]
alloc FI(1) at SP[-48]   <<-- Allocated
alloc FI(1) at SP[-72]   <<-- Allocated twice!?
alloc FI(2) at SP[-76]
alloc FI(4) at SP[-80]
alloc FI(3) at SP[-84]

[majnemer]

LGTM

lib/CodeGen/PrologEpilogInserter.cpp

for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
       MFI->setObjectOffset(Entry.first, FIOffset);
     }
     // Allocate the local block
     Offset += MFI->getLocalFrameSize();
 
     MaxAlign = std::max(Align, MaxAlign);
   }
 
+  // Retrieve the Exception Handler registration node.
+  int EHRegNodeFrameIndex = INT_MAX;
+  if (const WinEHFuncInfo *FuncInfo = Fn.getWinEHFuncInfo())
+    EHRegNodeFrameIndex = FuncInfo->EHRegNodeFrameIndex;
+
   // Make sure that the stack protector comes before the local variables on the
   // stack.
   SmallSet<int, 16> ProtectedObjs;
   if (MFI->getStackProtectorIndex() >= 0) {
     StackObjSet LargeArrayObjs;
     StackObjSet SmallArrayObjs;
     StackObjSet AddrOfObjs;
 
     AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
                       Offset, MaxAlign, Skew);
 
     // Assign large stack objects first.
     for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
       if (MFI->isObjectPreAllocated(i) &&
           MFI->getUseLocalStackAllocationBlock())
         continue;
       if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
         continue;
       if (RS && RS->isScavengingFrameIndex((int)i))
         continue;
       if (MFI->isDeadObjectIndex(i))
         continue;
-      if (MFI->getStackProtectorIndex() == (int)i)
+      if (MFI->getStackProtectorIndex() == (int)i ||
+          EHRegNodeFrameIndex == (int)i)
         continue;
 
       switch (SP->getSSPLayout(MFI->getObjectAllocation(i))) {
       case StackProtector::SSPLK_None:
         continue;
       case StackProtector::SSPLK_SmallArray:
         SmallArrayObjs.insert(i);
         continue;
if (MFI->getStackProtectorIndex() >= 0) {
     AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
                           Offset, MaxAlign, Skew);
     AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown,
                           Offset, MaxAlign, Skew);
   }
 
   SmallVector<int, 8> ObjectsToAllocate;
 
-  int EHRegNodeFrameIndex = INT_MAX;
-  if (const WinEHFuncInfo *FuncInfo = Fn.getWinEHFuncInfo())
-    EHRegNodeFrameIndex = FuncInfo->EHRegNodeFrameIndex;
-
   // Then prepare to assign frame offsets to stack objects that are not used to
   // spill callee saved registers.
   for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
     if (MFI->isObjectPreAllocated(i) &&
         MFI->getUseLocalStackAllocationBlock())
       continue;
     if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
       continue;
     if (RS && RS->isScavengingFrameIndex((int)i))
       continue;
     if (MFI->isDeadObjectIndex(i))
       continue;
-    if (MFI->getStackProtectorIndex() == (int)i)
-      continue;
-    if (EHRegNodeFrameIndex == (int)i)
+    if (MFI->getStackProtectorIndex() == (int)i ||
+        EHRegNodeFrameIndex == (int)i)
       continue;
     if (ProtectedObjs.count(i))
       continue;
 
     // Add the objects that we need to allocate to our working set.
     ObjectsToAllocate.push_back(i);
   }