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[CVP] Eliminate urem when LHS < RHS

Authored by caojoshua on Nov 19 2022, 11:31 AM.

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caojoshua created this revision.Nov 19 2022, 11:31 AM
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caojoshua added a comment.EditedNov 19 2022, 11:42 AM

Most arithmetic optimizations that use ConstantRange data defer logic to
ConstantRange::binaryOp. ConstantRange::binaryOp can determine that
[0, 12) % [13, ...) -> [0, 12). If X is the LHS, the urem is just X, but
ConstantRange::binaryOp does not know that.

We can do this in either SCCP or CVP. I don't think we can do this in InstCombine or InstSimplify because they don't have ConstantRange data.

caojoshua edited the summary of this revision. (Show Details)Nov 19 2022, 11:48 AM
caojoshua added a reviewer: majnemer.

Check for vector type

caojoshua published this revision for review.Nov 19 2022, 12:12 PM
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nikic added inline comments.Dec 8 2022, 6:51 AM

Already checked in processUDivOrURem.


I'd suggest writing this as CR1.icmp(ICmpInst::ICMP_ULT, CR2).


Already checked in processUDivOrURem

caojoshua updated this revision to Diff 481554.Dec 9 2022, 1:22 AM

Change redundant ifs into asserts. Change constant range check to use CR1.icmp(icmp_ult, CR2).

nikic added inline comments.Dec 9 2022, 1:24 AM

Rerun please. It looks like you either manually wrote these or edited them.

caojoshua updated this revision to Diff 481831.Dec 9 2022, 10:28 PM
caojoshua marked 3 inline comments as done.

update test with

This revision is now accepted and ready to land.Dec 10 2022, 12:43 AM
caojoshua marked an inline comment as done.Dec 10 2022, 10:53 AM

Can I get help merging this? I'm not a committer. I have the patch in

This revision was landed with ongoing or failed builds.Dec 13 2022, 2:43 AM
Closed by commit rGcca01df29130: [CVP] Eliminate urem when LHS < RHS (authored by caojoshua, committed by nikic). · Explain Why
This revision was automatically updated to reflect the committed changes.