[Bug libgcj/23495] java.lang.String.equals is suboptimal

["greenrd at greenrd dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Additional Comments From greenrd at greenrd dot org  2005-08-28 23:25 -------
memcmp (which is compiled for i686 in fedora because it is part of glibc) is
actually less efficient than the current code on my athlon! I was so surprised,
I ran the memcmp benchmark again, and the results differed by no more than +/-2%.

Here are the wallclock times in ms, followed by the advantage of block compare
over the current code. n is the length of the strings tested.

n   | Current | block compare | memcmp | Advantage of block compare
-------------------------------------------------------------------
10  | 10717   | 9236          | 11957  | 16%
30  | 16427   | 14618         | 19884  | 12%
50  | 22181   | 17539         | 27550  | 26%
70  | 28052   | 20978         | 35243  | 34%
90  | 32966   | 24695         | 42815  | 33%
110 | 42975   | 28453         | 55036  | 51%

All these tests were done on x86 with the same -O, -g and -f flags as make
bootstrap uses by default, using LD_PRELOAD to "hot-replace" the code, and
without the assertion enabled in the benchmark.

The advantage of block compare rises to 54% for n=10 and 81% for n=110 if
-march=athlon-xp is used (to compile both the original code and my block compare
code).

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23495