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Differential D111241

[APInt] Fix isAllOnes and extractBits for zero width values.
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Authored by lattner on Oct 6 2021, 9:53 AM.

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rGad37a45a2e13: [APInt] Fix isAllOnes and extractBits for zero width values.

Summary

isAllOnes() should return true for zero bit values because
there are no zeros in it.

Thanks to Jay Foad for pointing this out.

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Repository: rG LLVM Github Monorepo

Event Timeline

lattner created this revision.Oct 6 2021, 9:53 AM

Herald added subscribers: dexonsmith, hiraditya. · View Herald TranscriptOct 6 2021, 9:53 AM

lattner requested review of this revision.Oct 6 2021, 9:53 AM

Herald added a project: Restricted Project. · View Herald TranscriptOct 6 2021, 9:53 AM

Herald added a subscriber: llvm-commits. · View Herald Transcript

lattner added a reviewer: foad.Oct 6 2021, 9:54 AM

lattner mentioned this in D109555: [APInt] Enable APInt to support zero bit integers..

Harbormaster completed remote builds in B127324: Diff 377580.Oct 6 2021, 11:15 AM

This makes me happy!

llvm/unittests/ADT/APIntTest.cpp
2994	'true' would be better than '1U', but isn't there an EXPECT_TRUE for this?

This revision is now accepted and ready to land.Oct 6 2021, 11:56 AM

use EXPECT_TRUE as Jay points out

This revision was landed with ongoing or failed builds.Oct 6 2021, 12:38 PM

Closed by commit rGad37a45a2e13: [APInt] Fix isAllOnes and extractBits for zero width values. (authored by lattner). · Explain Why

This revision was automatically updated to reflect the committed changes.

lattner added a commit: rGad37a45a2e13: [APInt] Fix isAllOnes and extractBits for zero width values..

Jay happiness++

Harbormaster completed remote builds in B127363: Diff 377642.Oct 6 2021, 2:01 PM

Did this get an audit for existing users? It can be argued in both ways. E.g. "".isdigit() in Python is False, because there is no digit contained and that's pretty much the same use case.

In D111241#3058363, @joerg wrote:

Did this get an audit for existing users? It can be argued in both ways. E.g. "".isdigit() in Python is False, because there is no digit contained and that's pretty much the same use case.

AFAIK there are no in-tree users to audit: zero-width APInts were only introduced very recently, and I don't think they're used in-tree except for unit tests.

Right, they are only being used in the CIRCT incubator project afaik, and it is fine.

nikic mentioned this in D151788: [APInt] Support zero-width extract in extractBitsAsZExtValue().Wed, May 31, 1:17 AM

nikic mentioned this in rG42e98c6ae875: [APInt] Support zero-width extract in extractBitsAsZExtValue().Wed, May 31, 8:14 AM

Revision Contents
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llvm/

include/

llvm/

ADT/

12 lines

lib/

Support/

1 line

unittests/

ADT/

2 lines

Diff 377643

llvm/include/llvm/ADT/APInt.h

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llvm/lib/Support/APInt.cpp

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llvm/unittests/ADT/APIntTest.cpp

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