[Bug middle-end/23181] [4.1 Regression] Slowdown of the bresenham line drawing by roughly 20%

[hubicka at gcc dot gnu dot org]

------- Comment #10 from hubicka at gcc dot gnu dot org  2005-10-31 20:55 -------
Jeff, you missed the propagation DOM makes that hurts register allocation
indpeendently on whether code sinking does or does not it's job.
In reality code sinking (that appeared in GCC after I reported the bug)
improves the code as we create conditional move:
hubicka@kampanus:/aux/hubicka/gcc/build/gcc$ ./xgcc -B ./ -O2 ~/nodom.c ; time
./a.out ; time ./a.out

real    0m0.698s
user    0m0.695s
sys     0m0.001s

real    0m0.698s
user    0m0.698s
sys     0m0.000s
hubicka@kampanus:/aux/hubicka/gcc/build/gcc$ ./xgcc -B ./ -O2 ~/nodom.c
-fno-tree-sink; time ./a.out ; time ./a.out

real    0m0.762s
user    0m0.760s
sys     0m0.001s

real    0m0.763s
user    0m0.761s
sys     0m0.001s
hubicka@kampanus:/aux/hubicka/gcc/build/gcc$ ./xgcc -B ./ -O2 ~/nodom.c
-fno-tree-dominator-opts -fno-tree-sink; time ./a.out ;
time ./a.out

real    0m0.740s
user    0m0.736s
sys     0m0.001s

real    0m0.737s
user    0m0.736s
sys     0m0.002s
hubicka@kampanus:/aux/hubicka/gcc/build/gcc$ ./xgcc -B ./ -O2 ~/nodom.c
-fno-tree-dominator-opts; time ./a.out ; time ./a.out

real    0m0.574s
user    0m0.573s
sys     0m0.001s

real    0m0.580s
user    0m0.574s
sys     0m0.002s


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23181