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Accessing dl_hwcap from libm

From: Steve Munroe <sjmunroe at us dot ibm dot com>
To: libc-hacker at sources dot redhat dot com
Cc: Mark Brown <bmark at us dot ibm dot com>
Date: Tue, 11 May 2004 21:20:33 -0500
Subject: Accessing dl_hwcap from libm

For powerpc32 I can't assume that the fsqrt instruction is implemented.
Currently it is implemented on ALL PPC64 hardware. So I would
like to use the AT_HWCAP to detect this and conditionally use fsqrt.

Looking at i386/fpu/fesetround I see that dl_hwcap is used to check for
SSE.

        if ((GLRO(dl_hwcap) & HWCAP_I386_XMM) != 0)

But when I try something similar on powerpc w_sqrt I get:

../sysdeps/powerpc/fpu/w_sqrtf.c:37: undefined reference to
`_rtld_global_ro'

It seems that fesetround (and similar functions) are included in libc,
not libm. So is it fundamental that access to dl_dwcap (_rtld_global_ro)
is restricted to libc, or can access be extended to libm?

Steven J. Munroe
Linux on Power Toolchain Architect
IBM Corporation, Linux Technology Center

Follow-Ups:
- Re: Accessing dl_hwcap from libm
  - From: Ulrich Drepper

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