From 1ef654024f490b403494265c968570ca6bd800f3 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Thu, 3 Mar 2016 00:01:25 +0000
Subject: [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
---
 .../CodeGen/SelectionDAG/FunctionLoweringInfo.cpp  | 60 ++++++++++++++--------
 1 file changed, 40 insertions(+), 20 deletions(-)

(limited to 'llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp')

diff --git a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index 08815ed787d..e5c7ade8859 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -88,6 +88,7 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
   RegInfo = &MF->getRegInfo();
   MachineModuleInfo &MMI = MF->getMMI();
   const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
+  unsigned StackAlign = TFI->getStackAlignment();
 
   // Check whether the function can return without sret-demotion.
   SmallVector<ISD::OutputArg, 4> Outs;
@@ -96,6 +97,31 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
   CanLowerReturn = TLI->CanLowerReturn(Fn->getCallingConv(), *MF,
                                        Fn->isVarArg(), Outs, Fn->getContext());
 
+  // If this personality uses funclets, we need to do a bit more work.
+  DenseMap<const AllocaInst *, int *> CatchObjects;
+  EHPersonality Personality = classifyEHPersonality(
+      Fn->hasPersonalityFn() ? Fn->getPersonalityFn() : nullptr);
+  if (isFuncletEHPersonality(Personality)) {
+    // Calculate state numbers if we haven't already.
+    WinEHFuncInfo &EHInfo = *MF->getWinEHFuncInfo();
+    if (Personality == EHPersonality::MSVC_CXX)
+      calculateWinCXXEHStateNumbers(&fn, EHInfo);
+    else if (isAsynchronousEHPersonality(Personality))
+      calculateSEHStateNumbers(&fn, EHInfo);
+    else if (Personality == EHPersonality::CoreCLR)
+      calculateClrEHStateNumbers(&fn, EHInfo);
+
+    // Map all BB references in the WinEH data to MBBs.
+    for (WinEHTryBlockMapEntry &TBME : EHInfo.TryBlockMap) {
+      for (WinEHHandlerType &H : TBME.HandlerArray) {
+        if (const AllocaInst *AI = H.CatchObj.Alloca)
+          CatchObjects.insert({AI, &H.CatchObj.FrameIndex});
+        else
+          H.CatchObj.FrameIndex = INT_MAX;
+      }
+    }
+  }
+
   // Initialize the mapping of values to registers.  This is only set up for
   // instruction values that are used outside of the block that defines
   // them.
@@ -108,7 +134,6 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
         unsigned Align =
           std::max((unsigned)MF->getDataLayout().getPrefTypeAlignment(Ty),
                    AI->getAlignment());
-        unsigned StackAlign = TFI->getStackAlignment();
 
         // Static allocas can be folded into the initial stack frame
         // adjustment. For targets that don't realign the stack, don't
@@ -120,9 +145,21 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
 
           TySize *= CUI->getZExtValue();   // Get total allocated size.
           if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
+          int FrameIndex = INT_MAX;
+          auto Iter = CatchObjects.find(AI);
+          if (Iter != CatchObjects.end() && TLI->needsFixedCatchObjects()) {
+            FrameIndex = MF->getFrameInfo()->CreateFixedObject(
+                TySize, 0, /*Immutable=*/false, /*isAliased=*/true);
+            MF->getFrameInfo()->setObjectAlignment(FrameIndex, Align);
+          } else {
+            FrameIndex =
+                MF->getFrameInfo()->CreateStackObject(TySize, Align, false, AI);
+          }
 
-          StaticAllocaMap[AI] =
-            MF->getFrameInfo()->CreateStackObject(TySize, Align, false, AI);
+          StaticAllocaMap[AI] = FrameIndex;
+          // Update the catch handler information.
+          if (Iter != CatchObjects.end())
+            *Iter->second = FrameIndex;
         } else {
           // FIXME: Overaligned static allocas should be grouped into
           // a single dynamic allocation instead of using a separate
@@ -281,31 +318,14 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
       LPads.push_back(LPI);
   }
 
-  // If this personality uses funclets, we need to do a bit more work.
-  if (!Fn->hasPersonalityFn())
-    return;
-  EHPersonality Personality = classifyEHPersonality(Fn->getPersonalityFn());
   if (!isFuncletEHPersonality(Personality))
     return;
 
-  // Calculate state numbers if we haven't already.
   WinEHFuncInfo &EHInfo = *MF->getWinEHFuncInfo();
-  if (Personality == EHPersonality::MSVC_CXX)
-    calculateWinCXXEHStateNumbers(&fn, EHInfo);
-  else if (isAsynchronousEHPersonality(Personality))
-    calculateSEHStateNumbers(&fn, EHInfo);
-  else if (Personality == EHPersonality::CoreCLR)
-    calculateClrEHStateNumbers(&fn, EHInfo);
 
   // Map all BB references in the WinEH data to MBBs.
   for (WinEHTryBlockMapEntry &TBME : EHInfo.TryBlockMap) {
     for (WinEHHandlerType &H : TBME.HandlerArray) {
-      if (H.CatchObj.Alloca) {
-        assert(StaticAllocaMap.count(H.CatchObj.Alloca));
-        H.CatchObj.FrameIndex = StaticAllocaMap[H.CatchObj.Alloca];
-      } else {
-        H.CatchObj.FrameIndex = INT_MAX;
-      }
       if (H.Handler)
         H.Handler = MBBMap[H.Handler.get<const BasicBlock *>()];
     }
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