[Bug tree-optimization/57315] LTO and/or vectorizer performance regression on salsa20 core, 4.7->4.8

[vmakarov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57315

--- Comment #4 from Vladimir Makarov <vmakarov at gcc dot gnu.org> ---
  Zack, thanks for reporting this.  Crypto algorithms are very interesting
cases for RA.  A lot of performance improvements were done for RA during
gcc-4.9 development.  Now on Intel Haswell I have

bash-4.2$ /home/cygnus/vmakarov/build/comparison/4.7-64/bin/gcc -std=c99 -O2
-march=native salsa-test.c && ./a.out
 779.132 keys/s
bash-4.2$ /home/cygnus/vmakarov/build/comparison/4.8-64/bin/gcc -std=c99 -O2
-march=native salsa-test.c && ./a.out
 778.976 keys/s
bash-4.2$ /home/cygnus/vmakarov/build1/trunk5/64r/bin/gcc -std=c99 -O2
-march=native salsa-test.c && ./a.out
1392.555 keys/s
bash-4.2$ /home/cygnus/vmakarov/build/comparison/4.7-64/bin/gcc -std=c99 -O3
-fwhole-program -march=native salsa-test.c && ./a.out
1375.610 keys/s
bash-4.2$ /home/cygnus/vmakarov/build/comparison/4.8-64/bin/gcc -std=c99 -O3
-fwhole-program -march=native salsa-test.c && ./a.out
1224.177 keys/s
bash-4.2$ /home/cygnus/vmakarov/build1/trunk5/64r/bin/gcc -std=c99 -O3
-fwhole-program -march=native salsa-test.c && ./a.out
1436.539 keys/s

Here, trunk5 is today GCC trunk.

Unfortunately, the changes in RA are too big and can not be ported to gcc-4.8.