[WinEH] Allocate the registration node before the catch objects

[majnemer]

Summary

The CatchObjOffset is relative to the end of the EH registration node
for 32-bit x86 WinEH targets. A special sentinel value, 0, is used to
indicate that no catch object should be initialized.

This means that a catch object allocated immediately before the
registration node would be assigned a CatchObjOffset of 0, leading the
runtime to believe that a catch object should not be initialized.

To handle this, allocate the registration node prior to any other frame
object. This will ensure that catch objects will not be allocated
before the registration node.

This fixes PR26757.

[rnk]

lgtm

lib/CodeGen/PrologEpilogInserter.cpp

712

Not really this CL's problem, but we really should make something like enum { FI_Invalid = INT_MAX }; and standardize on it.

lib/CodeGen/AsmPrinter/WinException.cpp

for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
       OS.EmitLabel(HandlerMapXData);
       for (const WinEHHandlerType &HT : TBME.HandlerArray) {
         // Get the frame escape label with the offset of the catch object. If
         // the index is INT_MAX, then there is no catch object, and we should
         // emit an offset of zero, indicating that no copy will occur.
         const MCExpr *FrameAllocOffsetRef = nullptr;
         if (HT.CatchObj.FrameIndex != INT_MAX) {
           int Offset = getFrameIndexOffset(HT.CatchObj.FrameIndex, FuncInfo);
+          assert(Offset != 0 && "Illegal offset for catch object!");
           FrameAllocOffsetRef = MCConstantExpr::create(Offset, Asm->OutContext);
         } else {
           FrameAllocOffsetRef = MCConstantExpr::create(0, Asm->OutContext);
         }
 
         MCSymbol *HandlerSym =
             getMCSymbolForMBB(Asm, HT.Handler.dyn_cast<MachineBasicBlock *>());
 

lib/CodeGen/PrologEpilogInserter.cpp

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)
+      continue;
     if (ProtectedObjs.count(i))
       continue;
 
     // Add the objects that we need to allocate to our working set.
     ObjectsToAllocate.push_back(i);
   }
+
+  // Allocate the EH registration node first if one is present.
+  if (EHRegNodeFrameIndex != INT_MAX)
+    AdjustStackOffset(MFI, EHRegNodeFrameIndex, StackGrowsDown, Offset,
+                      MaxAlign, Skew);
+
   // Give the targets a chance to order the objects the way they like it.
   if (Fn.getTarget().getOptLevel() != CodeGenOpt::None &&
       Fn.getTarget().Options.StackSymbolOrdering)
     TFI.orderFrameObjects(Fn, ObjectsToAllocate);
   
   // Now walk the objects and actually assign base offsets to them.
   for (auto &Object : ObjectsToAllocate)
     AdjustStackOffset(MFI, Object, StackGrowsDown, Offset, MaxAlign, Skew);

test/CodeGen/X86/cleanuppad-inalloca.ll

 ;   ESP must be restored via EBP due to "dynamic" alloca.
 ; CHECK: leal -{{[0-9]+}}(%ebp), %esp
 ; CHECK: popl %ebp
 ; CHECK: retl
 
 ; CHECK: "?dtor$2@?0?passes_two@4HA":
 ; CHECK: pushl %ebp
 ; CHECK: subl $8, %esp
-; CHECK: addl $16, %ebp
+; CHECK: addl $12, %ebp
 ; CHECK: {{movl|leal}} -{{[0-9]+}}(%ebp), %ecx
 ; CHECK: calll "??1A@@QAE@XZ"
 ; CHECK: addl $8, %esp
 ; CHECK: retl
 
 declare void @takes_two(<{ %struct.A, %struct.A }>* inalloca) #0
 
 declare x86_thiscallcc %struct.A* @"\01??0A@@QAE@XZ"(%struct.A* returned) #0
 
 declare i32 @__CxxFrameHandler3(...)
 
 declare x86_thiscallcc void @"\01??1A@@QAE@XZ"(%struct.A*) #0
 
 attributes #0 = { "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }

test/CodeGen/X86/pr26757.ll

+; RUN: llc < %s | FileCheck %s
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i386-pc-windows-msvc"
+
+declare void @throw()
+
+define void @test1() personality i32 (...)* @__CxxFrameHandler3 {
+  %e = alloca i8, align 4
+  invoke void @throw()
+          to label %.noexc unwind label %catch.dispatch
+
+.noexc:
+  unreachable
+
+catch.object.Exception:
+  %cp = catchpad within %cs [i8* null, i32 0, i8* %e]
+  catchret from %cp to label %catchhandler
+
+catch.dispatch:
+  %cs = catchswitch within none [label %catch.object.Exception] unwind to caller
+
+catchhandler:
+  call void @use(i8* %e)
+  ret void
+}
+
+; CHECK-LABEL: $handlerMap$0$test1:
+; CHECK:      .long 0
+; CHECK-NEXT: .long 0
+; CHECK-NEXT: .long -20
+
+declare void @use(i8*)
+
+declare i32 @__CxxFrameHandler3(...)