commit cb5c7bd9ebfa004751a1b8815a281f51de2083dc
author Erik Pilkington <erik.pilkington@gmail.com> Wed Apr 10 23:42:11 2019 +0000
committer Erik Pilkington <erik.pilkington@gmail.com> Wed Apr 10 23:42:11 2019 +0000
tree afab549d77bf0b2dac02196a236c12667eea244d
parent 2f46de8c0b253e40ea84bb99e6a77079abd86daa

Fix a hang when lowering __builtin_dynamic_object_size

If the ObjectSizeOffsetEvaluator fails to fold the object size call, then it may
litter some unused instructions in the function. When done repeatably in
InstCombine, this results in an infinite loop. Fix this by tracking the set of
instructions that were inserted, then removing them on failure.

rdar://49172227

Differential revision: https://reviews.llvm.org/D60298

llvm-svn: 358146

llvm/lib/Analysis/MemoryBuiltins.cpp

diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp
index 56332bb..0825426 100644
--- a/llvm/lib/Analysis/MemoryBuiltins.cpp
+++ b/llvm/lib/Analysis/MemoryBuiltins.cpp
@@ -765,7 +765,10 @@
 ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
     const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
     ObjectSizeOpts EvalOpts)
-    : DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)),
+    : DL(DL), TLI(TLI), Context(Context),
+      Builder(Context, TargetFolder(DL),
+              IRBuilderCallbackInserter(
+                  [&](Instruction *I) { InsertedInstructions.insert(I); })),
       EvalOpts(EvalOpts) {
   // IntTy and Zero must be set for each compute() since the address space may
   // be different for later objects.
@@ -788,9 +791,16 @@
       if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
         CacheMap.erase(CacheIt);
     }
+
+    // Erase any instructions we inserted as part of the traversal.
+    for (Instruction *I : InsertedInstructions) {
+      I->replaceAllUsesWith(UndefValue::get(I->getType()));
+      I->eraseFromParent();
+    }
   }
 
   SeenVals.clear();
+  InsertedInstructions.clear();
   return Result;
 }
 
@@ -934,24 +944,28 @@
     if (!bothKnown(EdgeData)) {
       OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
       OffsetPHI->eraseFromParent();
+      InsertedInstructions.erase(OffsetPHI);
       SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
       SizePHI->eraseFromParent();
+      InsertedInstructions.erase(SizePHI);
       return unknown();
     }
     SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
     OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
   }
 
-  Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp;
-  if ((Tmp = SizePHI->hasConstantValue())) {
+  Value *Size = SizePHI, *Offset = OffsetPHI;
+  if (Value *Tmp = SizePHI->hasConstantValue()) {
     Size = Tmp;
     SizePHI->replaceAllUsesWith(Size);
     SizePHI->eraseFromParent();
+    InsertedInstructions.erase(SizePHI);
   }
-  if ((Tmp = OffsetPHI->hasConstantValue())) {
+  if (Value *Tmp = OffsetPHI->hasConstantValue()) {
     Offset = Tmp;
     OffsetPHI->replaceAllUsesWith(Offset);
     OffsetPHI->eraseFromParent();
+    InsertedInstructions.erase(OffsetPHI);
   }
   return std::make_pair(Size, Offset);
 }