Bug 2346439

Summary:	DotNet9.0 fails to build with clang-20 on ppc64le
Product:	[Fedora] Fedora	Reporter:	Tom Stellard <tstellar>
Component:	clang	Assignee:	Tom Stellard <tstellar>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	rawhide	CC:	airlied, bugproxy, fedora-llvm-team, jchecahi, kkleine, npopov, omajid+public, omajid, sergesanspaille, siddharth.kde, suraj.ghimire7, tbaeder, tstaudt, tstellar, tuliom
Target Milestone:	---	Flags:	tstellar: mirror+
Target Release:	---
Hardware:	ppc64le
OS:	Linux
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Fixed In Version:		Doc Type:	If docs needed, set a value
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Clone Of:		Environment:
Last Closed:	2025-03-21 23:13:35 UTC	Type:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Tom Stellard 2025-02-19 01:55:00 UTC

This was a regression from clang-19 to clang-20 introduced by this upstream PR: https://github.com/llvm/llvm-project/pull/111553 (More details in the PR comments).

I think we should consider reverting this patch in our clang-20 builds if it's not fixed upstream before the clang-20 upstream release.


Reproducible: Always

Comment 1 Omair Majid 2025-02-20 00:03:42 UTC

This is the same issue reported at https://github.com/dotnet/source-build/issues/4902, right?

Comment 2 Nikita Popov 2025-02-20 08:17:01 UTC

Yes, it's the same issue. Ideally this would be fixed *both* in LLVM and DotNot. LLVM should accept it, but at the same time this is clearly just a typo in the DotNot assembly (it's one use of %R3 in a long list of %r3's).

Comment 3 Tulio Magno Quites Machado Filho 2025-02-20 12:55:37 UTC

(In reply to Nikita Popov from comment #2)
> Ideally this would be fixed *both* in LLVM and DotNot.

Nikita, why is it ideal to change DotNet too?
This code is valid in other assemblers.
I have the impression the change of behavior was unintentional.

Comment 4 Nikita Popov 2025-02-20 13:17:23 UTC

> Nikita, why is it ideal to change DotNet too?

See https://github.com/dotnet/runtime/blob/da4f0a33ecec67908327138bfa0f153c3821fa78/src/coreclr/pal/src/arch/ppc64le/context2.S#L140.

There is one use of %R3 among ~150 uses of %r3. It's a typo, not an intentional style choice.

Comment 5 Tulio Magno Quites Machado Filho 2025-02-20 13:28:53 UTC

(In reply to Nikita Popov from comment #4)
> There is one use of %R3 among ~150 uses of %r3. It's a typo, not an
> intentional style choice.

It may break DotNet's coding style, but this is still valid code AFAIK.
Projects with a coding style where GPRs are higher case are also valid.
LLVM is missing a test to guarantee this regression won't happen again.

Comment 6 Tom Stellard 2025-03-17 20:29:33 UTC

This should be fixed now that clang-20 has landed in Fedora, so I think we can close this issue.