909196 – dev-lang/python[lto] compiles in single thread, ignores -flto cflags with -flto-partition=one

Bug 909196 - dev-lang/python[lto] compiles in single thread, ignores -flto cflags with -flto-partition=one

Summary: dev-lang/python[lto] compiles in single thread, ignores -flto cflags with -fl...

Status:	UNCONFIRMED

Alias:	None

Product:	Gentoo Linux
Classification:	Unclassified
Component:	Current packages (show other bugs)
Hardware:	All Linux

Importance:	Normal normal
Assignee:	Python Gentoo Team

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Depends on:
Blocks:	lto
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Reported:	2023-06-26 16:03 UTC by om3i
Modified:	2024-11-09 15:29 UTC (History)
CC List:	1 user (show)

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Runtime testing required:	---

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Description om3i 2023-06-26 16:03:54 UTC

To be more specific, the linker plugin only performs half of the compilation in a single thread. This is because configure.ac overrides the user-specified flags:
-flto=12 -flto-compression-level=0
with these flags:
LTOFLAGS="-flto ... -flto-partition=none"
I understand that single-threaded lto may produce better optimization, but I don't think it's worth the trade-off.

Reproducible: Always

Comment 1 Sam James archtester

2023-06-26 16:13:32 UTC

This is more nuanced than it appears, in that the reason we do USE=lto for the configure argument is because for years, the configure test was broken.

This has finally been fixed in autoconf-archive via https://github.com/autoconf-archive/autoconf-archive/pull/279, but it's not yet in a release.

Comment 2 Sam James archtester

2024-06-16 06:30:10 UTC

Eli and I have discussed this a few times in -python, really, there's on reason for it to be passing -flto-partition=none. It's been there since the LTO configure arg was added upstream...