[CodeGen] Fix some broken IR generated by -fsanitize=unsigned-integer-overflow

I think the author of the function assumed that `GetInsertBlock()`
wouldn't change from where `atomicPHI` was created, but this isn't
true when `-fsanitize=unsigned-integer-overflow` is enabled (we
generate an overflow/continuation label). Fix by keeping track of the
block we want to return to to complete the cmpxchg loop.

rdar://48406558

Differential revision: https://reviews.llvm.org/D58744

llvm-svn: 355054

1 files changed, 6 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index bdc07f17769..e831c823da7 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -2555,14 +2555,14 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
   }
 
   if (atomicPHI) {
-    llvm::BasicBlock *opBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *curBlock = Builder.GetInsertBlock();
     llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
     auto Pair = CGF.EmitAtomicCompareExchange(
         LV, RValue::get(atomicPHI), RValue::get(value), E->getExprLoc());
     llvm::Value *old = CGF.EmitToMemory(Pair.first.getScalarVal(), type);
     llvm::Value *success = Pair.second;
-    atomicPHI->addIncoming(old, opBB);
-    Builder.CreateCondBr(success, contBB, opBB);
+    atomicPHI->addIncoming(old, curBlock);
+    Builder.CreateCondBr(success, contBB, atomicPHI->getParent());
     Builder.SetInsertPoint(contBB);
     return isPre ? value : input;
   }
@@ -2909,14 +2909,14 @@ LValue ScalarExprEmitter::EmitCompoundAssignLValue(
                                 Loc, ScalarConversionOpts(CGF.SanOpts));
 
   if (atomicPHI) {
-    llvm::BasicBlock *opBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *curBlock = Builder.GetInsertBlock();
     llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
     auto Pair = CGF.EmitAtomicCompareExchange(
         LHSLV, RValue::get(atomicPHI), RValue::get(Result), E->getExprLoc());
     llvm::Value *old = CGF.EmitToMemory(Pair.first.getScalarVal(), LHSTy);
     llvm::Value *success = Pair.second;
-    atomicPHI->addIncoming(old, opBB);
-    Builder.CreateCondBr(success, contBB, opBB);
+    atomicPHI->addIncoming(old, curBlock);
+    Builder.CreateCondBr(success, contBB, atomicPHI->getParent());
     Builder.SetInsertPoint(contBB);
     return LHSLV;
   }