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Re: gcc 3.2.1 optimizer degradation (strlen, -O2)
> 11-Jan-2003 17:52 Eli Zaretskii wrote:
>>> From: "Leonid Pauzner" <uue@pauzner.dnttm.ru>
>>> Date: Sat, 11 Jan 2003 15:49:13 +0300 (MSK)
>>>
>>> It turns out that the libc strlen() function (compiled with -O2)
>>> became nearly 2 times slower when I switched from gcc 2.95.3 to gcc 3.2.1
>>> on a Pentium machine.
>> Are you sure you get the library strlen? IIRC, GCC provides its own
>> inline versions of some functions, and I think strlen is one of them.
>> Examining the code (use the -S switch to GCC to produce it) should
>> show you whether my guess was true.
[I was wrong in my previous post, lost -O2]
You are right.
2.95 do inline strlen(), while 3.2.1 is not.
Nevertheless I got the following results in my test:
gcc321 -O2
strlen.c 20 sec
strlen2.c 17 sec
(library?) 14 sec
gcc295 -O2
strlen.c 16 sec (main.c was compiled without -O)
strlen2.c 11 sec (main.c was compiled without -O)
(builtin) 8 sec
So the difference exists but not that dramatic.