Accessing dl_hwcap from libm

Accessing dl_hwcap from libm

[Steve Munroe]

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

Re: Accessing dl_hwcap from libm

[Ulrich Drepper]

Steve Munroe wrote:
> So is it fundamental that access to dl_dwcap (_rtld_global_ro)
> is restricted to libc, or can access be extended to libm?

_rtld_global_ro is defined in ld.so and exported from there.  If you
cannot use it something is wrong with ld.so, the way libm is built, or
your binutils.

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖