PPC and comparison reversal with -ffast-math

[Franz Sirl]

Hi Geoff,

the testcase (derived from xmms) below aborts in validate_condition_mode if 
compiled with -O2 -ffast-math. This is because can_reverse_comparison in 
jump.c is allowed to revert LT to GE if flag_fast_math is set. Now the 
question is, is it safe for your code to disable this abort if flag_fast_math 
is set? In other words, is this a pure sanity check or does the CCMode code 
in rs6000.c rely on that?

Franz.


[fsirl@enzo:/cvsx/gccmnp/gcc]$ gcc -O2 -ffast-math vis-bug.i
vis-bug.c: In function `vis_timeout_func':
vis-bug.c:12: Internal compiler error in validate_condition_mode, at 
config/rs6000/rs6000.c:3243

typedef struct
{
  float vs_data[75], vs_peak[75], vs_peak_speed[75];
  int vs_refresh_delay;
  int vs_doublesize;
} Vis;
 
void vis_timeout_func(Vis * vis)
{
  if (vis->vs_peak[0] < 0.0)
    vis->vs_peak[0] = 0.0;
}