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Re: [PATCH], Define __FP_FAST_FMAF128 on PowerPC ISA 3.0
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Michael Meissner <meissner at linux dot vnet dot ibm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Segher Boessenkool <segher at kernel dot crashing dot org>, David Edelsohn <dje dot gcc at gmail dot com>, Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Date: Thu, 28 Sep 2017 00:40:24 +0000
- Subject: Re: [PATCH], Define __FP_FAST_FMAF128 on PowerPC ISA 3.0
- Authentication-results: sourceware.org; auth=none
- References: <20170927221818.GA20589@ibm-tiger.the-meissners.org>
On Wed, 27 Sep 2017, Michael Meissner wrote:
> The glibc team has requested we define the standard macro (__FP_FAST_FMAF128)
> for PowerPC code when we have the IEEE 128-bit floating point hardware
> instructions enabled.
It's not a standard macro. TS 18661-3 has FP_FAST_FMAF128 as an optional
math.h macro (but glibc doesn't define it anywhere at present).
> This patch does this in the PowerPC backend. As I look at the whole issue, at
> some point we should do this more in the machine independent portion of the
> compiler. I have some initial patches to do this in the c-family files, but at
> the present time, the patches are not complete, and I need to think about it
> more.
I think a machine-independent definition (for _FloatN / _FloatNx types in
general) should go along with machine-independent fmafN / fmafNx built-in
functions; when the built-in function is machine-specific, it's natural
for the macro to be as well.
But in any case, the new macro should be documented in cpp.texi alongside
the existing __FP_FAST_FMA* macros (probably in the generic
__FP_FAST_FMAF@var{n} and __FP_FAST_FMAF@var{n}X form).
--
Joseph S. Myers
joseph@codesourcery.com