[Bug lto/90500] ICE error in copy_forbiden
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90500 Guobing changed: What|Removed |Added CC||neochen.life at aliyun dot com --- Comment #9 from Guobing --- After applied this patch, I get below errors during compiling with GCC9, while I expect it should be pass as the same as GCC8. ../sysdeps/ieee754/dbl-64/s_tanh.c:97:247: error: clones for ‘target_clones’ attribute cannot be created ../sysdeps/ieee754/dbl-64/s_tanh.c:97:247: note: ‘target_clones’ cannot be combined with ‘alias’ attribute ../sysdeps/ieee754/dbl-64/s_tanh.c:97:135: error: clones for ‘target_clones’ attribute cannot be created ../sysdeps/ieee754/dbl-64/s_tanh.c:97:135: note: ‘target_clones’ cannot be combined with ‘alias’ attribute ../sysdeps/ieee754/dbl-64/s_tanh.c:97:26: error: clones for ‘target_clones’ attribute cannot be created ../sysdeps/ieee754/dbl-64/s_tanh.c:97:26: note: ‘target_clones’ cannot be combined with ‘alias’ attribute
[Bug lto/90500] ICE error in copy_forbiden
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90500
--- Comment #11 from Guobing ---
(In reply to Martin Liška from comment #10)
> (In reply to Guobing from comment #8)
> > Hi, I am the original reporter of this bug. This problem seems not happen on
> > GCC8 while do on GCC9. We try to use FMV (target_clone) for some of the
> > GlibC libm functions which leads us to this issue. From the Patch below,
> > seems this fix the GCC9 crash issue but still not allow target_clone to be
> > used together with alias. But this is allowed in GCC8 as we can compile and
> > run well under GCC8. So could you help to make the behavior the same as GCC8
> > or tell us a way to walkaround it?
>
> Well, maybe that was allowed in GCC8, but it was not intentional. Please
> describe me your use case and we can come up to a solution that will use
> target_clone (or target attribute)?
The background is that, we want to try optimize libm with avx2/avx512, and
found that not all the libm math functions will have benefit when we generally
use 'arch=haswell' or 'arch=skylake-avx512' to compile libm. So we picked those
'good' libm math functions to add FMV attribute like target_clone("default",
"arch=haswell", "arch=skylake-avx512") to get performance benefit. The alias is
used in libm code by default. I have no idea why these two are conflicting that
not allowed by GCC9.
[Bug lto/90500] ICE error in copy_forbiden
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90500
--- Comment #13 from Guobing ---
(In reply to Martin Liška from comment #12)
> > The background is that, we want to try optimize libm with avx2/avx512, and
> > found that not all the libm math functions will have benefit when we
> > generally use 'arch=haswell' or 'arch=skylake-avx512' to compile libm. So we
> > picked those 'good' libm math functions to add FMV attribute like
> > target_clone("default", "arch=haswell", "arch=skylake-avx512") to get
> > performance benefit. The alias is used in libm code by default. I have no
> > idea why these two are conflicting that not allowed by GCC9.
>
> That makes sense. Based on the test-case you provided, you just want:
>
> __attribute__((target_clones("default", "arch=haswell",
> "arch=skylake-avx512")))
> double
> __tanh (double x)
> {
> double t, z;
> int32_t jx, ix, lx;
>
>
> do { ieee_double_shape_type ew_u; ew_u.value = (x); (jx) = ew_u.parts.msw;
> (lx) = ew_u.parts.lsw; } while (0);
> ix = jx & 0x7fff;
> ...
> }
>
> extern __typeof (__tanh) tanh __attribute__ ((weak, alias ("__tanh"))); //
> __attribute__ ((__copy__ (__tanh)));
>
> You don't want to use __copy__ attribute because it's responsible for
> copying of target_clone attribute to the alias.
> And it does not make sense to create clones of an alias.
The copy is from alias used by libm by default (Below I paste the src code), I
cannot remove this copy seems. How can I then to use FMV for this function?
__attribute__((target_clones("default", "arch=haswell", "arch=broadwell"
,"arch=skylake", "arch=skylake-avx512")))
double
__tanh (double x)
{
double t, z;
int32_t jx, ix, lx;
/* High word of |x|. */
EXTRACT_WORDS (jx, lx, x);
ix = jx & 0x7fff;
/* x is INF or NaN */
if (ix >= 0x7ff0)
{
if (jx >= 0)
return one / x + one; /* tanh(+-inf)=+-1 */
else
return one / x - one; /* tanh(NaN) = NaN */
}
/* |x| < 22 */
if (ix < 0x4036) /* |x|<22 */
{
if ((ix | lx) == 0)
return x; /* x == +-0 */
if (ix < 0x3c80) /* |x|<2**-55 */
{
math_check_force_underflow (x);
return x * (one + x); /* tanh(small) = small */
}
if (ix >= 0x3ff0) /* |x|>=1 */
{
t = __expm1 (two * fabs (x));
z = one - two / (t + two);
}
else
{
t = __expm1 (-two * fabs (x));
z = -t / (t + two);
}
/* |x| > 22, return +-1 */
}
else
{
z = one - tiny; /* raised inexact flag */
}
return (jx >= 0) ? z : -z;
}
libm_alias_double (__tanh, tanh)
[Bug lto/90500] ICE error in copy_forbiden
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90500
--- Comment #15 from Guobing Chen ---
(In reply to Martin Liška from comment #14)
> (In reply to Guobing Chen from comment #13)
> > (In reply to Martin Liška from comment #12)
> > > > The background is that, we want to try optimize libm with avx2/avx512,
> > > > and
> > > > found that not all the libm math functions will have benefit when we
> > > > generally use 'arch=haswell' or 'arch=skylake-avx512' to compile libm.
> > > > So we
> > > > picked those 'good' libm math functions to add FMV attribute like
> > > > target_clone("default", "arch=haswell", "arch=skylake-avx512") to get
> > > > performance benefit. The alias is used in libm code by default. I have
> > > > no
> > > > idea why these two are conflicting that not allowed by GCC9.
> > >
> > > That makes sense. Based on the test-case you provided, you just want:
> > >
> > > __attribute__((target_clones("default", "arch=haswell",
> > > "arch=skylake-avx512")))
> > > double
> > > __tanh (double x)
> > > {
> > > double t, z;
> > > int32_t jx, ix, lx;
> > >
> > >
> > > do { ieee_double_shape_type ew_u; ew_u.value = (x); (jx) =
> > > ew_u.parts.msw;
> > > (lx) = ew_u.parts.lsw; } while (0);
> > > ix = jx & 0x7fff;
> > > ...
> > > }
> > >
> > > extern __typeof (__tanh) tanh __attribute__ ((weak, alias ("__tanh"))); //
> > > __attribute__ ((__copy__ (__tanh)));
> > >
> > > You don't want to use __copy__ attribute because it's responsible for
> > > copying of target_clone attribute to the alias.
> > > And it does not make sense to create clones of an alias.
> >
> > The copy is from alias used by libm by default (Below I paste the src code),
> > I cannot remove this copy seems. How can I then to use FMV for this
> > function?
> >
>
> Then you'll have to make one libm_alias_double_no_copy that will do the same
> except setting the copy attribute.
I am not quite familiar with libm, will this change the its bevhavior or other
side effect?
