[PATCH] D149325: [DAG] Do not call computeKnownBits from isKnownToBeAPowerOfTwo
Jay Foad via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 27 01:36:51 PDT 2023
foad created this revision.
foad added reviewers: craig.topper, RKSimon, spatel.
Herald added subscribers: StephenFan, hiraditya.
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The only way known bits could help identify a known power of two is if
it knows exactly which power of two it is, i.e. if it is a known
constant. But in that case the value should have been simplified to a
constant already. So save some compile time by not calling
computeKnownBits.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D149325
Files:
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4022,10 +4022,7 @@
// More could be done here, though the above checks are enough
// to handle some common cases.
-
- // Fall back to computeKnownBits to catch other known cases.
- KnownBits Known = computeKnownBits(Val);
- return (Known.countMaxPopulation() == 1) && (Known.countMinPopulation() == 1);
+ return false;
}
unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, unsigned Depth) const {
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