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Re: [RFC] [BZ15384] Enchance finite and isfinite.
- From: David Miller <davem at davemloft dot net>
- To: neleai at seznam dot cz
- Cc: marc dot glisse at inria dot fr, libc-alpha at sourceware dot org
- Date: Fri, 26 Apr 2013 03:03:00 -0400 (EDT)
- Subject: Re: [RFC] [BZ15384] Enchance finite and isfinite.
- References: <20130421145745 dot GA15025 at domone dot kolej dot mff dot cuni dot cz> <alpine dot DEB dot 2 dot 02 dot 1304212033480 dot 19747 at laptop-mg dot saclay dot inria dot fr> <20130426061732 dot GA6475 at domone dot kolej dot mff dot cuni dot cz>
From: Ondřej Bílka <neleai@seznam.cz>
Date: Fri, 26 Apr 2013 08:17:32 +0200
> Following should generic version be tried on other archs. I could get
> 20% speedup on sparc on this benchmark.
>
> run with
> for i in `seq 0 7`; do echo finite$i; gcc finite_bench.c -O3 -Wall -W -fno-builtin-finite -Dfinite=finite$i; for j in `seq 1 8`; do /usr/bin/time -f "%U" ./a.out; done; done
That'll only be faster on sparc 32-bit where floating point
values are passed in integer registers.
For 64-bit, where floating point values are passed in floating point
registers, the assembler in glibc will always be faster because GCC
isn't smart enough to avoid allocating a register window when a stack
slot is needed to move values between float and integer registers.
Also, the sparc 64-bit multiarch variants make use of the VIS3
float-int move instructions when available.