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Re: Patch for IA64 performance (inline division)

Steve Ellcey wrote:

I would like to propose turning on -finline-float-divide-max-throughput
by default on IA64.  I have tested it on HP-UX and Linux with no
regressions and I also ran the 4 C floating point spec programs on HP-UX
in 64 bit mode to test the performance difference.

The largest performance improvement was in which had a 35%
improvement with -O2 and 20% with -O3.  The other tests improved from 0%
to 4% with the exception of 188.ammp which slowed down by 1.2% at -O2
(but improved by 0.5% at -O3).  I also tried the min-latency version of
inlining, it was not as good as the max-throughput version except on
188.amp where it slowed things down a little less at -O2 and sped up a
little more at -O3.

The size increase for using inline division ranged from 1.4% to 15%,
(1.4% 177.mesa, 7.6%, 6.4% 183.equake, 15% 188.ammp).

As a side note, the HP IA64 compiler always generates inline code for
floating point division.

I guess that nobody cares about code size for Itanium. It is not an embeded platform. But perfomance is real issue for Itanium gcc. Also gcc generates code 2 times smaller than Intel compiler does.

So I think the patch is reasonable.


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