Bug#1129949: llvm-toolchain-21: FTBFS on ppc64el on Trixie

[Trupti]

Hi Fabian,

Thank you for the detailed analysis and for filing the upstream issue.
I'm looking into this from the ppc64el porter side and will test your
proposed fix in commit 133f997 
(https://github.com/llvm/llvm-project/pull/184995/changes/133f997099485bdd326d4941addc4082509be553)
the missing uint128.h include and parser.h fix.

Will follow up once I've confirmed results on ppc64el.

The direction of 133f997 looks correct — it completes what PR 
https://github.com/llvm/llvm-project/pull/136614
left incomplete without the ABI risk of 
-DPPC_LINUX_DEFAULT_IEEELONGDOUBLE=ON.


Thanks,
Trupti



On 2026-03-06 17:48, Fabian Grünbichler wrote:
> Source: llvm-toolchain-21
> Severity: normal
> Tags: upstream ftbfs patch
> X-Debbugs-Cc: debian-powerpc at lists.debian.org,
> debian at fabian.gruenbichler.email, doko at debian.org
> User: debian-powerpc at lists.debian.org
> Usertags: powerpcspe ppc64el
> 
> Hi!
> 
> I've been trying to backport llvm-toolchain-21 for Trixie for the past 
> few
> weeks, because it is a requirement for backporting newer rustc 
> versions.
> 
> Unfortunately the build fails with floating point related errors. Those 
> errors
> go away if I set -DPPC_LINUX_DEFAULT_IEEELONGDOUBLE=ON , but that is 
> the wrong
> thing to do on Trixie which generally lacks IEEE long double..
> 
> I've tried various things, and ended up bisecting upstream LLVM which 
> points at
> 8437b7f5584765ad4f7885500647657714930fbb. That commit allegedly got 
> fixed[0],
> but the fix seems incomplete (since it is included in 21.1.8 and that 
> is still
> broken). I've now filed an issue[1] and PR[2] upstream after verifying 
> that
> upstream main is also affected.
> 
> I'd appreciate input upstream from ppc experts, in particular whether 
> my
> proposed changes (which do fix the package build when backporting to 
> Trixie!)
> seem reasonable.
> 
> Thanks,
> Fabian
> 
> 0: https://github.com/llvm/llvm-project/issues/136596
> 1: https://github.com/llvm/llvm-project/issues/184994
> 2: https://github.com/llvm/llvm-project/issues/184995