[llvm] 4e30f81 - [DAG] visitFREEZE - remove isGuaranteedNotToBeUndefOrPoison assertion (#146490)
via llvm-commits
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Tue Jul 1 03:17:45 PDT 2025
Author: Simon Pilgrim
Date: 2025-07-01T11:17:41+01:00
New Revision: 4e30f8101e4bcdc05b2a4a8c26f51a0d4f20b265
URL: https://github.com/llvm/llvm-project/commit/4e30f8101e4bcdc05b2a4a8c26f51a0d4f20b265
DIFF: https://github.com/llvm/llvm-project/commit/4e30f8101e4bcdc05b2a4a8c26f51a0d4f20b265.diff
LOG: [DAG] visitFREEZE - remove isGuaranteedNotToBeUndefOrPoison assertion (#146490)
Although nice to have to prove the freeze can be moved, this can fail
immediately after freeze(op(...)) -> op(freeze(),freeze(),...) creation
if any of the new freeze nodes now prevents value tracking from seeing
through to the source values (e.g. shift amounts/element indices are in
bounds etc.).
This will allow us to remove the isGuaranteedNotToBeUndefOrPoison checks
inside canCreateUndefOrPoison that were discussed on #146361
Added:
Modified:
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 8554db0a1220c..c43677f8b925c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -16714,28 +16714,25 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
Op = DAG.getFreeze(Op);
}
- SDValue R;
- if (auto *SVN = dyn_cast<ShuffleVectorSDNode>(N0)) {
- // Special case handling for ShuffleVectorSDNode nodes.
- R = DAG.getVectorShuffle(N0.getValueType(), SDLoc(N0), Ops[0], Ops[1],
- SVN->getMask());
- } else {
- // NOTE: this strips poison generating flags.
- // Folding freeze(op(x, ...)) -> op(freeze(x), ...) does not require nnan,
- // ninf, nsz, or fast.
- // However, contract, reassoc, afn, and arcp should be preserved,
- // as these fast-math flags do not introduce poison values.
- SDNodeFlags SrcFlags = N0->getFlags();
- SDNodeFlags SafeFlags;
- SafeFlags.setAllowContract(SrcFlags.hasAllowContract());
- SafeFlags.setAllowReassociation(SrcFlags.hasAllowReassociation());
- SafeFlags.setApproximateFuncs(SrcFlags.hasApproximateFuncs());
- SafeFlags.setAllowReciprocal(SrcFlags.hasAllowReciprocal());
- R = DAG.getNode(N0.getOpcode(), SDLoc(N0), N0->getVTList(), Ops, SafeFlags);
- }
- assert(DAG.isGuaranteedNotToBeUndefOrPoison(R, /*PoisonOnly*/ false) &&
- "Can't create node that may be undef/poison!");
- return R;
+ SDLoc DL(N0);
+
+ // Special case handling for ShuffleVectorSDNode nodes.
+ if (auto *SVN = dyn_cast<ShuffleVectorSDNode>(N0))
+ return DAG.getVectorShuffle(N0.getValueType(), DL, Ops[0], Ops[1],
+ SVN->getMask());
+
+ // NOTE: this strips poison generating flags.
+ // Folding freeze(op(x, ...)) -> op(freeze(x), ...) does not require nnan,
+ // ninf, nsz, or fast.
+ // However, contract, reassoc, afn, and arcp should be preserved,
+ // as these fast-math flags do not introduce poison values.
+ SDNodeFlags SrcFlags = N0->getFlags();
+ SDNodeFlags SafeFlags;
+ SafeFlags.setAllowContract(SrcFlags.hasAllowContract());
+ SafeFlags.setAllowReassociation(SrcFlags.hasAllowReassociation());
+ SafeFlags.setApproximateFuncs(SrcFlags.hasApproximateFuncs());
+ SafeFlags.setAllowReciprocal(SrcFlags.hasAllowReciprocal());
+ return DAG.getNode(N0.getOpcode(), DL, N0->getVTList(), Ops, SafeFlags);
}
/// We know that BV is a build_vector node with Constant, ConstantFP or Undef
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