[LegalizeDAG] Return after replacing ISD::POISON with ISD::UNDEF. #173173
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We already replaced the node, we shouldn't run the rest of the code that still uses the old node.
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@llvm/pr-subscribers-llvm-selectiondag Author: Craig Topper (topperc) ChangesWe already replaced the node, we shouldn't run the rest of the code that still uses the old node. Full diff: https://github.com/llvm/llvm-project/pull/173173.diff 1 Files Affected:
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index fc3e9ff0d6238..73f59b4064144 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -993,18 +993,18 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
TargetLowering::LegalizeAction Action = TargetLowering::Legal;
bool SimpleFinishLegalizing = true;
switch (Node->getOpcode()) {
- // TODO: Currently, POISON is being lowered to UNDEF here. However, there is
- // an open concern that this transformation may not be ideal, as targets
- // should ideally handle POISON directly. Changing this behavior would require
- // adding support for POISON in TableGen, which is a large change.
- // Additionally, many existing test cases rely on the current behavior (e.g.,
- // llvm/test/CodeGen/PowerPC/vec_shuffle.ll). A broader discussion and
- // incremental changes might be needed to properly
- // support POISON without breaking existing targets and tests.
case ISD::POISON: {
+ // TODO: Currently, POISON is being lowered to UNDEF here. However, there is
+ // an open concern that this transformation may not be ideal, as targets
+ // should ideally handle POISON directly. Changing this behavior would
+ // require adding support for POISON in TableGen, which is a large change.
+ // Additionally, many existing test cases rely on the current behavior
+ // (e.g., llvm/test/CodeGen/PowerPC/vec_shuffle.ll). A broader discussion
+ // and incremental changes might be needed to properly support POISON
+ // without breaking existing targets and tests.
SDValue UndefNode = DAG.getUNDEF(Node->getValueType(0));
ReplaceNode(Node, UndefNode.getNode());
- break;
+ return;
}
case ISD::INTRINSIC_W_CHAIN:
case ISD::INTRINSIC_WO_CHAIN:
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arsenm
approved these changes
Dec 21, 2025
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/141/builds/13893 Here is the relevant piece of the build log for the reference |
Collaborator
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/24/builds/15885 Here is the relevant piece of the build log for the reference |
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/43180 Here is the relevant piece of the build log for the reference |
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We already replaced the node, we shouldn't run the rest of the code that still uses the old node.