diff options
| -rw-r--r-- | lib/Transforms/Scalar/JumpThreading.cpp | 25 | ||||
| -rw-r--r-- | test/Transforms/JumpThreading/crash.ll | 27 |
2 files changed, 52 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp index 3a65c98195..a7b4d157fc 100644 --- a/lib/Transforms/Scalar/JumpThreading.cpp +++ b/lib/Transforms/Scalar/JumpThreading.cpp @@ -1123,6 +1123,11 @@ bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) { isa<ConstantInt>(BO->getOperand(1))) return false; + // If the first instruction in BB isn't a phi, we won't be able to infer + // anything special about any particular predecessor. + if (!isa<PHINode>(BB->front())) + return false; + // If we have a xor as the branch input to this block, and we know that the // LHS or RHS of the xor in any predecessor is true/false, then we can clone // the condition into the predecessor and fix that value to true, saving some @@ -1180,6 +1185,26 @@ bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) { BlocksToFoldInto.push_back(XorOpValues[i].second); } + // If we inferred a value for all of the predecessors, then duplication won't + // help us. However, we can just replace the LHS or RHS with the constant. + if (BlocksToFoldInto.size() == + cast<PHINode>(BB->front()).getNumIncomingValues()) { + if (SplitVal == 0) { + // If all preds provide undef, just nuke the xor, because it is undef too. + BO->replaceAllUsesWith(UndefValue::get(BO->getType())); + BO->eraseFromParent(); + } else if (SplitVal->isZero()) { + // If all preds provide 0, replace the xor with the other input. + BO->replaceAllUsesWith(BO->getOperand(isLHS)); + BO->eraseFromParent(); + } else { + // If all preds provide 1, set the computed value to 1. + BO->setOperand(!isLHS, SplitVal); + } + + return true; + } + // Try to duplicate BB into PredBB. return DuplicateCondBranchOnPHIIntoPred(BB, BlocksToFoldInto); } diff --git a/test/Transforms/JumpThreading/crash.ll b/test/Transforms/JumpThreading/crash.ll index c0ef078ed2..ff980ffcc6 100644 --- a/test/Transforms/JumpThreading/crash.ll +++ b/test/Transforms/JumpThreading/crash.ll @@ -259,3 +259,30 @@ for.cond: ; preds = %for.body, %lor.end for.body: ; preds = %for.cond br label %for.cond } + +; PR6119 +define i32 @test9(i32 %action) nounwind { +entry: + switch i32 %action, label %lor.rhs [ + i32 1, label %if.then + i32 0, label %lor.end + ] + +if.then: ; preds = %for.cond, %lor.end, %entry + ret i32 undef + +lor.rhs: ; preds = %entry + br label %lor.end + +lor.end: ; preds = %lor.rhs, %entry + %0 = phi i1 [ undef, %lor.rhs ], [ true, %entry ] ; <i1> [#uses=1] + %cmp103 = xor i1 undef, %0 ; <i1> [#uses=1] + br i1 %cmp103, label %for.cond, label %if.then + +for.cond: ; preds = %for.body, %lor.end + br i1 undef, label %if.then, label %for.body + +for.body: ; preds = %for.cond + br label %for.cond +} + |