[FFmpeg-devel] FASTDIV macro
Sat Aug 15 22:47:05 CEST 2009
>>> How do we know which is faster?
> Of the benchmarks we've seen so far (ARM, PPC, x86), all have
> benefited significantly from the table method, although only PPC is
> lacking an asm version. IMHO we should enable CONFIG_FASTDIV by
> default (possibly dependent on !CONFIG_SMALL), and deal with anything
> where it is slower if we ever find such a machine.
I reduced TESTS_COUNT from 10 to 2.
68040 at 25MHz (GCC 4.4.1 -m68040 -O3 -fomit-frame-pointer):
normaldiv(-1896828497) : time=65.793s
fastdiv_c(-1896828497) : time=66.521s
68060 at 50MHz (GCC 4.4.1 -m68060 -O3 -fomit-frame-pointer):
normaldiv(-1896828497) : time=29.296s
fastdiv_c(-1896828497) : time=52.392s (here GCC uses _muldi3)
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