diff options
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 23812d795f5f..91fd2d843f44 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -16717,7 +16717,8 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) { // Fold freeze(op(x, ...)) -> op(freeze(x), ...). // Try to push freeze through instructions that propagate but don't produce // poison as far as possible. If an operand of freeze follows three - // conditions 1) one-use, and 2) does not produce poison then push + // conditions 1) one-use, 2) does not produce poison, and 3) has all but one + // guaranteed-non-poison operands (or is a BUILD_VECTOR or similar) then push // the freeze through to the operands that are not guaranteed non-poison. // NOTE: we will strip poison-generating flags, so ignore them here. if (DAG.canCreateUndefOrPoison(N0, /*PoisonOnly*/ false, @@ -16725,6 +16726,18 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) { N0->getNumValues() != 1 || !N0->hasOneUse()) return SDValue(); + // TOOD: we should always allow multiple operands, however this increases the + // likelihood of infinite loops due to the ReplaceAllUsesOfValueWith call + // below causing later nodes that share frozen operands to fold again and no + // longer being able to confirm other operands are not poison due to recursion + // depth limits on isGuaranteedNotToBeUndefOrPoison. + bool AllowMultipleMaybePoisonOperands = + N0.getOpcode() == ISD::SELECT_CC || N0.getOpcode() == ISD::SETCC || + N0.getOpcode() == ISD::BUILD_VECTOR || + N0.getOpcode() == ISD::BUILD_PAIR || + N0.getOpcode() == ISD::VECTOR_SHUFFLE || + N0.getOpcode() == ISD::CONCAT_VECTORS || N0.getOpcode() == ISD::FMUL; + // Avoid turning a BUILD_VECTOR that can be recognized as "all zeros", "all // ones" or "constant" into something that depends on FrozenUndef. We can // instead pick undef values to keep those properties, while at the same time @@ -16757,6 +16770,10 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) { MaybePoisonOperandNumbers.push_back(OpNo); if (!HadMaybePoisonOperands) continue; + if (IsNewMaybePoisonOperand && !AllowMultipleMaybePoisonOperands) { + // Multiple maybe-poison ops when not allowed - bail out. + return SDValue(); + } } // NOTE: the whole op may be not guaranteed to not be undef or poison because // it could create undef or poison due to it's poison-generating flags. |