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Date: Wed, 26 Jun 2024 11:25:47 -0400
From: Rich Felker <>
To: Thorsten Glaser <>
Subject: Re: roundf() (and round(), and ...)

On Wed, Jun 26, 2024 at 03:43:27AM +0000, Thorsten Glaser wrote:
> Markus Wichmann dixit:
> >memcpy() is special, in that GCC reserves the right to create calls to
> >it (and memmove(), memcmp(), and memset()) even in freestanding mode. It
> >doesn't do that for any other builtin.
> But not to replace code that implements a memcpy, only to implement
> things like struct copying.

FWIW "struct copying" (with __may_alias__ attribute) is, or would be,
a reasonable way to write a portable "efficiently copy blocks of the
middle at a time" part of memcpy -- outsourcing the strategy for doing
so to the compiler's logic for what insn patterns are efficient.

Unfortunately you can't because it will just emit a call to memcpy on
many archs.


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