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Differential D89054

[WIP][IR] Make `llvm.assume` `readnone`
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Authored by jdoerfert on Oct 8 2020, 9:20 AM.

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Summary

Note: This is not a full commit. No tests were changed. Used for discussion

The llvm.assume intrinsic was historically not readnone because
control dependences need to be preserved. However, the intrinsic can
nowadays be represented as what it is, potentially UB if the condition
is false (or an operand bundle is violated). No effect but potentially
UB is readnone (in contrast to speculatable). While here we add
nosync and nofree to llvm.assume.

Diff Detail

Repository: rG LLVM Github Monorepo

Unit TestsFailed
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	Time	Test
	30 ms	linux > LLVM.Analysis/ValueTracking::assume.ll
	40 ms	linux > LLVM.Analysis/ValueTracking::numsignbits-from-assume.ll
	60 ms	linux > LLVM.Transforms/Attributor::lvi-after-jumpthreading.ll
	80 ms	linux > LLVM.Transforms/Attributor::nofree.ll
	110 ms	linux > LLVM.Transforms/Attributor::nonnull.ll
		View Full Test Results (90 Failed)

Event Timeline

jdoerfert created this revision.Oct 8 2020, 9:20 AM

Herald added a project: Restricted Project. · View Herald TranscriptOct 8 2020, 9:20 AM

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jdoerfert requested review of this revision.Oct 8 2020, 9:20 AM

jdoerfert removed a reviewer: llvm-commits.Oct 8 2020, 9:20 AM

jdoerfert edited the summary of this revision. (Show Details)

jdoerfert mentioned this in D89050: Add support for !noundef metatdata on loads.

jdoerfert added a subscriber: llvm-commits.

Harbormaster completed remote builds in B74455: Diff 296993.Oct 8 2020, 9:54 AM

This looks like a very reasonable change to me, but I can't say that I understand the full consequences :)

I think this approach makes sense.

This change makes a lot of sense, but i don't understand all the consequences either.

I will (try to) do some testing with this and report back.

jdoerfert added a subscriber: hfinkel.Oct 12 2020, 8:21 AM

sstefan1 added a subscriber: sstefan1.Oct 12 2020, 8:57 AM

jdoerfert mentioned this in D93734: [LoopDeletion] Insert an early exit from dead path in loop.Dec 22 2020, 3:55 PM

jdoerfert mentioned this in D93974: [ValueTracking] Safe assumption context for args.Jan 14 2021, 8:41 AM

nikic mentioned this in D99022: [IR] Mark assume/annotation as InaccessibleMemOnly.Mar 20 2021, 10:26 AM

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llvm/

include/

llvm/

IR/

8 lines

Diff 296993

llvm/include/llvm/IR/Intrinsics.td

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