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Differential D146149

[InstCombine] Canonicalize icmp eq pow2 more thoroughly
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Authored by nikic on Wed, Mar 15, 9:11 AM.

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Reviewers
spatel
RKSimon
goldstein.w.n
Commits
rG61d2f3a71e61: [InstCombine] Canonicalize icmp eq pow2 more thoroughly
Summary

We currently already canonicalize icmp eq (%x & Pow2), Pow2 to icmp ne (%x & Pow2), 0. This patch generalizes the fold based on known bits.

In particular, this allows us to handle comparisons against !range !{i64 0, i64 2} loads, which addresses an optimization regression in Rust caused by https://github.com/llvm/llvm-project/commit/8df376db7282b955e7990cb8887ee9dcd3565040.

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Event Timeline

nikic created this revision.Wed, Mar 15, 9:11 AM
Herald added a project: Restricted Project. · View Herald TranscriptWed, Mar 15, 9:11 AM
Herald added subscribers: StephenFan, JDevlieghere, hiraditya. · View Herald Transcript
nikic requested review of this revision.Wed, Mar 15, 9:11 AM
Herald added a project: Restricted Project. · View Herald TranscriptWed, Mar 15, 9:11 AM
Herald added a subscriber: llvm-commits. · View Herald Transcript
Harbormaster completed remote builds in B219661: Diff 505522.Wed, Mar 15, 10:50 AM
goldstein.w.n accepted this revision.Wed, Mar 15, 2:02 PM

LGTM.

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
5765

nit: "is" -> "is known to be".
also maybe "Pow2" -> "C_Pow2" so its a little clearer to you are refering to the exact same value.

This revision is now accepted and ready to land.Wed, Mar 15, 2:02 PM
Closed by commit rG61d2f3a71e61: [InstCombine] Canonicalize icmp eq pow2 more thoroughly (authored by nikic). · Explain WhyThu, Mar 16, 1:45 AM
This revision was automatically updated to reflect the committed changes.
nikic added a commit: rG61d2f3a71e61: [InstCombine] Canonicalize icmp eq pow2 more thoroughly.
StephenFan mentioned this in D146609: [InstCombine] Fold xor of icmps of power of 2.Tue, Mar 21, 11:45 PM

Revision Contents
Changeset List

PathSize
llvm/
lib/
Transforms/
InstCombine/
16 lines
test/
Transforms/
InstCombine/
2 lines
4 lines
4 lines
2 lines
7 lines

Diff 505724

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llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

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llvm/test/Transforms/InstCombine/div.ll

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llvm/test/Transforms/InstCombine/icmp-range.ll

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llvm/test/Transforms/InstCombine/icmp-shl-nsw.ll

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llvm/test/Transforms/InstCombine/icmp-shr-lt-gt.ll

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llvm/test/Transforms/InstCombine/zext.ll

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