[Bug tree-optimization/85416] Massive performance regression when switching on "-march=native"

[martin@mpa-garching.mpg.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85416

--- Comment #9 from Martin Reinecke <martin@mpa-garching.mpg.de> ---
Sure!

martin@martin-Latitude-E7450 ~/tmp $ gcc -O3 testcase2.c -lm
martin@martin-Latitude-E7450 ~/tmp $ perf stat ./a.out

 Performance counter stats for './a.out':

       1109,985866      task-clock (msec)         #    0,999 CPUs utilized      
                 2      context-switches          #    0,002 K/sec              
                 0      cpu-migrations            #    0,000 K/sec              
             2.000      page-faults               #    0,002 M/sec              
     3.155.388.780      cycles                    #    2,843 GHz                
     6.717.336.961      instructions              #    2,13  insn per cycle     
       979.526.022      branches                  #  882,467 M/sec              
            38.112      branch-misses             #    0,00% of all branches    

       1,110639187 seconds time elapsed

martin@martin-Latitude-E7450 ~/tmp $ gcc -O3 testcase2.c -march=native -lm
martin@martin-Latitude-E7450 ~/tmp $ perf stat ./a.out

 Performance counter stats for './a.out':

       7724,004864      task-clock (msec)         #    1,000 CPUs utilized      
                86      context-switches          #    0,011 K/sec              
                 1      cpu-migrations            #    0,000 K/sec              
             2.004      page-faults               #    0,259 K/sec              
    22.129.645.853      cycles                    #    2,865 GHz                
     6.723.657.441      instructions              #    0,30  insn per cycle     
       980.761.202      branches                  #  126,976 M/sec              
           171.813      branch-misses             #    0,02% of all branches    

       7,726058359 seconds time elapsed