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Re: lib/50887: __clzdi2 implementation in compile_rt incompatible with gcc
The following reply was made to PR lib/50887; it has been noted by GNATS.
From: Martin Husemann <martin%duskware.de@localhost>
To: Joerg Sonnenberger <joerg%britannica.bec.de@localhost>
Subject: Re: lib/50887: __clzdi2 implementation in compile_rt incompatible with gcc
Date: Fri, 4 Mar 2016 12:47:50 +0100
On Thu, Mar 03, 2016 at 11:17:26AM +0100, Joerg Sonnenberger wrote:
> I can't find any sensible reason for the GCC behavior. Even when using
> the table version, it is better to only four lookups instead of eight,
> so this is really something where GCC should be fixed to match its own
> builtin definition.
I asked Eric Botcazou and he said:
That's the default behavior for clz and clrsb though: no libgcc routine for
subword operation and fallback to the word-sized routine if no instruction.
so we would have to fix quite a few gcc targets and have issues feeding
this change back upstream (I suppose).
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