https://gcc.gnu.org/bugzilla/show_bug.cgi?id=22326
--- Comment #17 from luoxhu at gcc dot gnu.org ---
(In reply to rsand...@gcc.gnu.org from comment #16)
> > 2) mad2.c
> >
> > float foo (double x, float y, float z)
> > {
> > return ( y * fabs (x) + z );
> > }
> >
> >
> > mad2.c.098t.cunrolli:
> >
> > foo (double x, float y, float z)
> > {
> > double _1;
> > double _2;
> > double _3;
> > double _4;
> > double _5;
> > float _9;
> >
> > <bb 2> [local count: 1073741824]:
> > _1 = (double) y_6(D);
> > _2 = ABS_EXPR <x_7(D)>;
> > _3 = _1 * _2;
> > _4 = (double) z_8(D);
> > _5 = _3 + _4;
> > _9 = (float) _5;
> > return _9;
> >
> > }
> >
> > mad2.c.099t.backprop:
> >
> > [USE] _9 in return _9;
> > [USE] _5 in _9 = (float) _5;
> > _5: convert from float to double not important
> > [DEF] Recording new information for _5 = _3 + _4;
> > _5: convert from float to double not important
> > [USE] _4 in _5 = _3 + _4;
> > _4: convert from float to double not important
> > [DEF] Recording new information for _4 = (double) z_8(D);
> > _4: convert from float to double not important
> > [USE] _3 in _5 = _3 + _4;
> > _3: convert from float to double not important
> > [DEF] Recording new information for _3 = _1 * _2;
> > _3: convert from float to double not important
> > [USE] _2 in _3 = _1 * _2;
> > _2: convert from float to double not important
> > [DEF] Recording new information for _2 = ABS_EXPR <x_7(D)>;
> > _2: convert from float to double not important
> > [USE] _1 in _3 = _1 * _2;
> > _1: convert from float to double not important
> > [DEF] Recording new information for _1 = (double) y_6(D);
> > _1: convert from float to double not important
> >
> > Deleting _4 = (double) z_8(D);
> > Deleting _1 = (double) y_6(D);
> >
> >
> > EMERGENCY DUMP:
> >
> > __attribute__((noinline))
> > foo (double x, float y, float z)
> > {
> > double _2;
> > double _3;
> > double _5;
> > float _9;
> >
> > <bb 2> [local count: 1073741824]:
> > _2 = ABS_EXPR <x_7(D)>;
> > _3 = _2 * y_6(D);
> > _5 = _3 + z_8(D);
> > _9 = (float) _5;
> > return _9;
> >
> > }
> Maybe I'm misunderstanding the point, but isn't this
> just an issue with the way that the results of the
> analysis are applied to the IL, rather than a problem
> in the analysis itself?
Yes, the optimize operations on Gimple is a bit uncertain.
Do you mean add convert from double to float at proper place
like below to avoid ICE caused by type mismatch ICE in verify_ssa?
Which one will be better, and whether it is correct for all kind
of math operations like pow/exp, etc under fast-math? If so, no
cancelling is needed again as Richi mentioned?
1) convert before ABS_EXPR:
foo (double x, float y, float z)
{
float _9;
float _11;
float _12;
float _13;
float _14;
<bb 2> [local count: 1073741824]:
_11 = (float) x_6(D);
_12 = ABS_EXPR <_11>;
_13 = y_7(D) * _12;
_14 = z_8(D) + _13;
_9 = _14;
return _9;
}
foo:
.LFB0:
.cfi_startproc
frsp 0,1
fabs 0,0
fmadds 1,2,0,3
blr
2) OR convert after ABS_EXPR:
foo (double x, float y, float z)
{
double _1;
float _9;
float _11;
float _12;
float _13;
<bb 2> [local count: 1073741824]:
_1 = ABS_EXPR <x_6(D)>;
_11 = (float) _1;
_12 = y_7(D) * _11;
_13 = z_8(D) + _12;
_9 = _13;
return _9;
}
foo:
.LFB0:
.cfi_startproc
fabs 0,1
frsp 0,0
fmadds 1,2,0,3
blr
