Fix a problem exposed by PR3354: simplifycfg was making a potentially
trapping instruction be executed unconditionally.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62541 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index b0feadf..4abc2eb 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1423,11 +1423,21 @@
if ((!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
Cond->getParent() != BB || &BB->front() != Cond || !Cond->hasOneUse())
return false;
-
+
// Make sure the instruction after the condition is the cond branch.
BasicBlock::iterator CondIt = Cond; ++CondIt;
if (&*CondIt != BI)
return false;
+
+ // Cond is known to be a compare or binary operator. Check to make sure that
+ // neither operand is a potentially-trapping constant expression.
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(0)))
+ if (CE->canTrap())
+ return false;
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(1)))
+ if (CE->canTrap())
+ return false;
+
// Finally, don't infinitely unroll conditional loops.
BasicBlock *TrueDest = BI->getSuccessor(0);
@@ -1438,6 +1448,7 @@
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
BasicBlock *PredBlock = *PI;
BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
+
// Check that we have two conditional branches. If there is a PHI node in
// the common successor, verify that the same value flows in from both
// blocks.
@@ -1459,6 +1470,8 @@
else
continue;
+ DOUT << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB;
+
// If we need to invert the condition in the pred block to match, do so now.
if (InvertPredCond) {
Value *NewCond =