On 2024-07-03 17:59, Jeff Law wrote:
On 7/3/24 3:59 AM, Sébastien Michelland wrote:
libgcc's fp-bit.c is quite slow and most modern/developed architectures
have switched to using the soft-fp library. This patch does so for
free-standing/unknown-OS SH3/SH4 builds, using soft-fp's default
parameters
for the most part, most notably no exceptions.
A quick run of Whetstone (built with OpenLibm) on an SH4 machine shows
about x3 speedup (~320 -> 1050 Kwhets/s).
I'm sending this as RFC because I'm quite unsure about testing. I built
the compiler and ran the benchmark, but I don't know if GCC has a test
for soft-fp correctness and whether I can run that in my non-hosted
environment. Any advice?
Cheers,
Sébastien
libgcc/ChangeLog:
* config.host: Use soft-fp library for non-hosted SH3/SH4
instead of fpdbit.
* config/sh/sfp-machine.h: New.
I'd really like to hear from Oleg on this, though given we're using the
soft-fp library on other targets it seems reasonable at a high level.
As far as testing, the GCC testsuite has some FP components which would
implicitly test soft fp on any target that doesn't have hardware
floating point.
Thank you. I went this route, following the guide [1] and the
instructions for cross-compiling [2] before hitting "Newlib does not
support CPU sh3eb" which I should have seen coming.
There are plenty of random ports lying around but just grabbing one
doesn't feel right (and I don't have a canonical one to go to as I
usually run a custom libc for... mostly bad reasons).
Deferring maybe again to the few SH users... how do you usually do it?
Sébastien
[1] https://gcc.gnu.org/install/test.html
[2] https://gcc.gnu.org/simtest-howto.html
