[PING] Inline C99 math functions
Commit Message
> Wilco Dijkstra wrote:
> Add inlining of the C99 math functions isinf/isnan/signbit/isfinite/isnormal/fpclassify using
> GCC built-ins when available. Since going through the PLT is expensive for these small
> functions, inlining results in major speedups (about 7x on Cortex-A57 for isinf). The GCC
> built-ins are not correct if signalling NaN support is required, and thus are turned off in
> that case (see GCC bug 66462). The test-snan.c tests sNaNs and so must be explicitly built
> with -fsignaling-nans.
>
> As a result of this many target overrides and the various __isnan/__finite inlines in
> math_private.h are no longer required. If agreed we could remove all this code and only keep
> the generic definition of isinf/etc which will use the builtin.
>
> Tested on AArch64. OK for commit?
>
> ChangeLog:
> 2015-06-15 Wilco Dijkstra <wdijkstr@arm.com>
>
> * math/Makefile: Build test-snan.c with -fsignaling-nans.
> * math/math.h (fpclassify): Use __builtin_fpclassify when
> available. (signbit): Use __builtin_signbit(f/l).
> (isfinite): Use__builtin_isfinite. (isnormal): Use
> __builtin_isnormal. (isnan): Use __builtin_isnan.
> (isinf): Use __builtin_isinf_sign.
As suggested __fpclassify is not inlined when optimizing for size, and a benchmark
has been created (json output for x64 attached showing the large gains due to inlining).
OK for commit?
---
math/Makefile | 1 +
math/math.h | 51 ++++++++++++++++++++++++++++++---------------------
2 files changed, 31 insertions(+), 21 deletions(-)
Comments
On 07/13/2015 11:11 AM, Wilco Dijkstra wrote:
>> Wilco Dijkstra wrote:
>> Add inlining of the C99 math functions isinf/isnan/signbit/isfinite/isnormal/fpclassify using
>> GCC built-ins when available. Since going through the PLT is expensive for these small
>> functions, inlining results in major speedups (about 7x on Cortex-A57 for isinf). The GCC
>> built-ins are not correct if signalling NaN support is required, and thus are turned off in
>> that case (see GCC bug 66462). The test-snan.c tests sNaNs and so must be explicitly built
>> with -fsignaling-nans.
>>
>> As a result of this many target overrides and the various __isnan/__finite inlines in
>> math_private.h are no longer required. If agreed we could remove all this code and only keep
>> the generic definition of isinf/etc which will use the builtin.
>>
>> Tested on AArch64. OK for commit?
>>
>> ChangeLog:
>> 2015-06-15 Wilco Dijkstra <wdijkstr@arm.com>
>>
>> * math/Makefile: Build test-snan.c with -fsignaling-nans.
>> * math/math.h (fpclassify): Use __builtin_fpclassify when
>> available. (signbit): Use __builtin_signbit(f/l).
>> (isfinite): Use__builtin_isfinite. (isnormal): Use
>> __builtin_isnormal. (isnan): Use __builtin_isnan.
>> (isinf): Use __builtin_isinf_sign.
>
> As suggested __fpclassify is not inlined when optimizing for size, and a benchmark
> has been created (json output for x64 attached showing the large gains due to inlining).
>
> OK for commit?
This looks good to me for 2.23, it is not OK for 2.22.
Please wait until after 2.23 opens and until after you commit the benchmark.
Cheers,
Carlos.
> ---
> math/Makefile | 1 +
> math/math.h | 51 ++++++++++++++++++++++++++++++---------------------
> 2 files changed, 31 insertions(+), 21 deletions(-)
>
> diff --git a/math/Makefile b/math/Makefile
> index 9a3cf32..f78d75b 100644
> --- a/math/Makefile
> +++ b/math/Makefile
> @@ -155,6 +155,7 @@ CFLAGS-test-tgmath.c = -fno-builtin
> CFLAGS-test-tgmath2.c = -fno-builtin
> CFLAGS-test-tgmath-ret.c = -fno-builtin
> CFLAGS-test-powl.c = -fno-builtin
> +CFLAGS-test-snan.c = -fsignaling-nans
> CPPFLAGS-test-ifloat.c = -U__LIBC_INTERNAL_MATH_INLINES -D__FAST_MATH__ \
> -DTEST_FAST_MATH -fno-builtin
> CPPFLAGS-test-idouble.c = -U__LIBC_INTERNAL_MATH_INLINES -D__FAST_MATH__ \
> diff --git a/math/math.h b/math/math.h
> index 22f0989..1721118 100644
> --- a/math/math.h
> +++ b/math/math.h
> @@ -215,8 +215,15 @@ enum
> FP_NORMAL
> };
>
> +/* GCC bug 66462 means we cannot use the math builtins with -fsignaling-nan,
> + so disable builtins if this is enabled. When fixed in a newer GCC,
> + the __SUPPORT_SNAN__ check may be skipped for those versions. */
> +
> /* Return number of classification appropriate for X. */
> -# ifdef __NO_LONG_DOUBLE_MATH
> +# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__ && !defined __OPTIMIZE_SIZE__
> +# define fpclassify(x) __builtin_fpclassify (FP_NAN, FP_INFINITE, \
> + FP_NORMAL, FP_SUBNORMAL, FP_ZERO, x)
> +# elif defined __NO_LONG_DOUBLE_MATH
> # define fpclassify(x) \
> (sizeof (x) == sizeof (float) ? __fpclassifyf (x) : __fpclassify (x))
> # else
> @@ -229,32 +236,26 @@ enum
>
> /* Return nonzero value if sign of X is negative. */
> # if __GNUC_PREREQ (4,0)
> -# ifdef __NO_LONG_DOUBLE_MATH
> -# define signbit(x) \
> - (sizeof (x) == sizeof (float) \
> - ? __builtin_signbitf (x) : __builtin_signbit (x))
> -# else
> -# define signbit(x) \
> - (sizeof (x) == sizeof (float) \
> - ? __builtin_signbitf (x) \
> - : sizeof (x) == sizeof (double) \
> +# define signbit(x) \
> + (sizeof (x) == sizeof (float) \
> + ? __builtin_signbitf (x) \
> + : sizeof (x) == sizeof (double) \
> ? __builtin_signbit (x) : __builtin_signbitl (x))
> -# endif
> -# else
> -# ifdef __NO_LONG_DOUBLE_MATH
> -# define signbit(x) \
> +# elif defined __NO_LONG_DOUBLE_MATH
> +# define signbit(x) \
> (sizeof (x) == sizeof (float) ? __signbitf (x) : __signbit (x))
> -# else
> -# define signbit(x) \
> +# else
> +# define signbit(x) \
> (sizeof (x) == sizeof (float) \
> ? __signbitf (x) \
> : sizeof (x) == sizeof (double) \
> ? __signbit (x) : __signbitl (x))
> -# endif
> # endif
>
> /* Return nonzero value if X is not +-Inf or NaN. */
> -# ifdef __NO_LONG_DOUBLE_MATH
> +# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
> +# define isfinite(x) __builtin_isfinite (x)
> +# elif defined __NO_LONG_DOUBLE_MATH
> # define isfinite(x) \
> (sizeof (x) == sizeof (float) ? __finitef (x) : __finite (x))
> # else
> @@ -266,11 +267,17 @@ enum
> # endif
>
> /* Return nonzero value if X is neither zero, subnormal, Inf, nor NaN. */
> -# define isnormal(x) (fpclassify (x) == FP_NORMAL)
> +# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
> +# define isnormal(x) __builtin_isnormal (x)
> +# else
> +# define isnormal(x) (fpclassify (x) == FP_NORMAL)
> +# endif
>
> /* Return nonzero value if X is a NaN. We could use `fpclassify' but
> we already have this functions `__isnan' and it is faster. */
> -# ifdef __NO_LONG_DOUBLE_MATH
> +# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
> +# define isnan(x) __builtin_isnan (x)
> +# elif defined __NO_LONG_DOUBLE_MATH
> # define isnan(x) \
> (sizeof (x) == sizeof (float) ? __isnanf (x) : __isnan (x))
> # else
> @@ -282,7 +289,9 @@ enum
> # endif
>
> /* Return nonzero value if X is positive or negative infinity. */
> -# ifdef __NO_LONG_DOUBLE_MATH
> +# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
> +# define isinf(x) __builtin_isinf_sign (x)
> +# elif defined __NO_LONG_DOUBLE_MATH
> # define isinf(x) \
> (sizeof (x) == sizeof (float) ? __isinff (x) : __isinf (x))
> # else
>
On Mon, 13 Jul 2015, Wilco Dijkstra wrote:
> > Wilco Dijkstra wrote:
> > Add inlining of the C99 math functions isinf/isnan/signbit/isfinite/isnormal/fpclassify using
> > GCC built-ins when available. Since going through the PLT is expensive for these small
> > functions, inlining results in major speedups (about 7x on Cortex-A57 for isinf). The GCC
> > built-ins are not correct if signalling NaN support is required, and thus are turned off in
> > that case (see GCC bug 66462). The test-snan.c tests sNaNs and so must be explicitly built
> > with -fsignaling-nans.
> >
> > As a result of this many target overrides and the various __isnan/__finite inlines in
> > math_private.h are no longer required. If agreed we could remove all this code and only keep
> > the generic definition of isinf/etc which will use the builtin.
> >
> > Tested on AArch64. OK for commit?
> >
> > ChangeLog:
> > 2015-06-15 Wilco Dijkstra <wdijkstr@arm.com>
> >
> > * math/Makefile: Build test-snan.c with -fsignaling-nans.
> > * math/math.h (fpclassify): Use __builtin_fpclassify when
> > available. (signbit): Use __builtin_signbit(f/l).
> > (isfinite): Use__builtin_isfinite. (isnormal): Use
> > __builtin_isnormal. (isnan): Use __builtin_isnan.
> > (isinf): Use __builtin_isinf_sign.
>
> As suggested __fpclassify is not inlined when optimizing for size, and a benchmark
> has been created (json output for x64 attached showing the large gains due to inlining).
I don't see an updated ChangeLog entry (with the [BZ #N] notation I
requested). Please include the ChangeLog entry with each patch
submission.
> Joseph Myers wrote:
> On Mon, 13 Jul 2015, Wilco Dijkstra wrote:
>
> > > Wilco Dijkstra wrote:
> > > Add inlining of the C99 math functions isinf/isnan/signbit/isfinite/isnormal/fpclassify
> using
> > > GCC built-ins when available. Since going through the PLT is expensive for these small
> > > functions, inlining results in major speedups (about 7x on Cortex-A57 for isinf). The GCC
> > > built-ins are not correct if signalling NaN support is required, and thus are turned off
> in
> > > that case (see GCC bug 66462). The test-snan.c tests sNaNs and so must be explicitly built
> > > with -fsignaling-nans.
> > >
> > > As a result of this many target overrides and the various __isnan/__finite inlines in
> > > math_private.h are no longer required. If agreed we could remove all this code and only
> keep
> > > the generic definition of isinf/etc which will use the builtin.
> > >
> > > Tested on AArch64. OK for commit?
> > >
> > > ChangeLog:
> > > 2015-06-15 Wilco Dijkstra <wdijkstr@arm.com>
> > >
> > > * math/Makefile: Build test-snan.c with -fsignaling-nans.
> > > * math/math.h (fpclassify): Use __builtin_fpclassify when
> > > available. (signbit): Use __builtin_signbit(f/l).
> > > (isfinite): Use__builtin_isfinite. (isnormal): Use
> > > __builtin_isnormal. (isnan): Use __builtin_isnan.
> > > (isinf): Use __builtin_isinf_sign.
> >
> > As suggested __fpclassify is not inlined when optimizing for size, and a benchmark
> > has been created (json output for x64 attached showing the large gains due to inlining).
>
> I don't see an updated ChangeLog entry (with the [BZ #N] notation I
> requested). Please include the ChangeLog entry with each patch
> submission.
It was still in the quotes. Something like this?
2015-07-xx Wilco Dijkstra <wdijkstr@arm.com>
* math/Makefile: Build test-snan.c with -fsignaling-nans.
* math/math.h (fpclassify): Use __builtin_fpclassify when
available. (signbit): Use __builtin_signbit(f/l).
(isfinite): Use__builtin_isfinite. (isnormal): Use
__builtin_isnormal. (isnan): Use __builtin_isnan - fixes [BZ #17441].
(isinf): Use __builtin_isinf_sign - fixes [BZ #15367].
On Wed, 22 Jul 2015, Wilco Dijkstra wrote:
> > I don't see an updated ChangeLog entry (with the [BZ #N] notation I
> > requested). Please include the ChangeLog entry with each patch
> > submission.
>
> It was still in the quotes. Something like this?
>
> 2015-07-xx Wilco Dijkstra <wdijkstr@arm.com>
>
> * math/Makefile: Build test-snan.c with -fsignaling-nans.
> * math/math.h (fpclassify): Use __builtin_fpclassify when
> available. (signbit): Use __builtin_signbit(f/l).
> (isfinite): Use__builtin_isfinite. (isnormal): Use
> __builtin_isnormal. (isnan): Use __builtin_isnan - fixes [BZ #17441].
> (isinf): Use __builtin_isinf_sign - fixes [BZ #15367].
That's not the style used (and your line breaks are all wrong).
<TAB>[BZ #N]<LF> at the start of the ChangeLog entry, after the initial
author-date line and blank line and before the lines describing changes to
each file.
"Wilco Dijkstra" <wdijkstr@arm.com> writes:
>> Wilco Dijkstra wrote:
>> Add inlining of the C99 math functions isinf/isnan/signbit/isfinite/isnormal/fpclassify using
>> GCC built-ins when available. Since going through the PLT is expensive for these small
>> functions, inlining results in major speedups (about 7x on Cortex-A57 for isinf). The GCC
>> built-ins are not correct if signalling NaN support is required, and thus are turned off in
>> that case (see GCC bug 66462). The test-snan.c tests sNaNs and so must be explicitly built
>> with -fsignaling-nans.
>>
>> As a result of this many target overrides and the various __isnan/__finite inlines in
>> math_private.h are no longer required. If agreed we could remove all this code and only keep
>> the generic definition of isinf/etc which will use the builtin.
>>
>> Tested on AArch64. OK for commit?
FAIL: elf/check-localplt
$ cat elf/check-localplt.out
Missing required PLT reference: libm.so: __signbitl
Missing required PLT reference: libc.so: __signbitl
Missing required PLT reference: libm.so: __signbitf
Missing required PLT reference: libm.so: __signbit
Missing required PLT reference: libc.so: __signbit
Andreas.
Andreas Schwab wrote:
> "Wilco Dijkstra" <wdijkstr@arm.com> writes:
>
> >> Wilco Dijkstra wrote:
> >> Add inlining of the C99 math functions
> >> isinf/isnan/signbit/isfinite/isnormal/fpclassify using GCC built-ins
> >> when available. Since going through the PLT is expensive for these
> >> small functions, inlining results in major speedups (about 7x on
> >> Cortex-A57 for isinf). The GCC built-ins are not correct if
> >> signalling NaN support is required, and thus are turned off in that
case
> (see GCC bug 66462). The test-snan.c tests sNaNs and so must be explicitly
> built with -fsignaling-nans.
> >>
> >> As a result of this many target overrides and the various
> >> __isnan/__finite inlines in math_private.h are no longer required. If
> >> agreed we could remove all this code and only keep the generic
definition
> of isinf/etc which will use the builtin.
> >>
> >> Tested on AArch64. OK for commit?
>
> FAIL: elf/check-localplt
> $ cat elf/check-localplt.out
> Missing required PLT reference: libm.so: __signbitl Missing required PLT
> reference: libc.so: __signbitl Missing required PLT reference: libm.so:
> __signbitf Missing required PLT reference: libm.so: __signbit Missing
> required PLT reference: libc.so: __signbit
I'm not exactly sure what this means - should we now remove the __signbit*
from
all the localplt.data files now that signbit is always inlined on all
targets?
Wilco
"Wilco Dijkstra" <Wilco.Dijkstra@arm.com> writes:
> I'm not exactly sure what this means - should we now remove the __signbit*
> from
> all the localplt.data files now that signbit is always inlined on all
> targets?
Yes, that is correct. The references are not supposed to reappear.
Andreas.
@@ -155,6 +155,7 @@ CFLAGS-test-tgmath.c = -fno-builtin
CFLAGS-test-tgmath2.c = -fno-builtin
CFLAGS-test-tgmath-ret.c = -fno-builtin
CFLAGS-test-powl.c = -fno-builtin
+CFLAGS-test-snan.c = -fsignaling-nans
CPPFLAGS-test-ifloat.c = -U__LIBC_INTERNAL_MATH_INLINES -D__FAST_MATH__ \
-DTEST_FAST_MATH -fno-builtin
CPPFLAGS-test-idouble.c = -U__LIBC_INTERNAL_MATH_INLINES -D__FAST_MATH__ \
@@ -215,8 +215,15 @@ enum
FP_NORMAL
};
+/* GCC bug 66462 means we cannot use the math builtins with -fsignaling-nan,
+ so disable builtins if this is enabled. When fixed in a newer GCC,
+ the __SUPPORT_SNAN__ check may be skipped for those versions. */
+
/* Return number of classification appropriate for X. */
-# ifdef __NO_LONG_DOUBLE_MATH
+# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__ && !defined __OPTIMIZE_SIZE__
+# define fpclassify(x) __builtin_fpclassify (FP_NAN, FP_INFINITE, \
+ FP_NORMAL, FP_SUBNORMAL, FP_ZERO, x)
+# elif defined __NO_LONG_DOUBLE_MATH
# define fpclassify(x) \
(sizeof (x) == sizeof (float) ? __fpclassifyf (x) : __fpclassify (x))
# else
@@ -229,32 +236,26 @@ enum
/* Return nonzero value if sign of X is negative. */
# if __GNUC_PREREQ (4,0)
-# ifdef __NO_LONG_DOUBLE_MATH
-# define signbit(x) \
- (sizeof (x) == sizeof (float) \
- ? __builtin_signbitf (x) : __builtin_signbit (x))
-# else
-# define signbit(x) \
- (sizeof (x) == sizeof (float) \
- ? __builtin_signbitf (x) \
- : sizeof (x) == sizeof (double) \
+# define signbit(x) \
+ (sizeof (x) == sizeof (float) \
+ ? __builtin_signbitf (x) \
+ : sizeof (x) == sizeof (double) \
? __builtin_signbit (x) : __builtin_signbitl (x))
-# endif
-# else
-# ifdef __NO_LONG_DOUBLE_MATH
-# define signbit(x) \
+# elif defined __NO_LONG_DOUBLE_MATH
+# define signbit(x) \
(sizeof (x) == sizeof (float) ? __signbitf (x) : __signbit (x))
-# else
-# define signbit(x) \
+# else
+# define signbit(x) \
(sizeof (x) == sizeof (float) \
? __signbitf (x) \
: sizeof (x) == sizeof (double) \
? __signbit (x) : __signbitl (x))
-# endif
# endif
/* Return nonzero value if X is not +-Inf or NaN. */
-# ifdef __NO_LONG_DOUBLE_MATH
+# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
+# define isfinite(x) __builtin_isfinite (x)
+# elif defined __NO_LONG_DOUBLE_MATH
# define isfinite(x) \
(sizeof (x) == sizeof (float) ? __finitef (x) : __finite (x))
# else
@@ -266,11 +267,17 @@ enum
# endif
/* Return nonzero value if X is neither zero, subnormal, Inf, nor NaN. */
-# define isnormal(x) (fpclassify (x) == FP_NORMAL)
+# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
+# define isnormal(x) __builtin_isnormal (x)
+# else
+# define isnormal(x) (fpclassify (x) == FP_NORMAL)
+# endif
/* Return nonzero value if X is a NaN. We could use `fpclassify' but
we already have this functions `__isnan' and it is faster. */
-# ifdef __NO_LONG_DOUBLE_MATH
+# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
+# define isnan(x) __builtin_isnan (x)
+# elif defined __NO_LONG_DOUBLE_MATH
# define isnan(x) \
(sizeof (x) == sizeof (float) ? __isnanf (x) : __isnan (x))
# else
@@ -282,7 +289,9 @@ enum
# endif
/* Return nonzero value if X is positive or negative infinity. */
-# ifdef __NO_LONG_DOUBLE_MATH
+# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
+# define isinf(x) __builtin_isinf_sign (x)
+# elif defined __NO_LONG_DOUBLE_MATH
# define isinf(x) \
(sizeof (x) == sizeof (float) ? __isinff (x) : __isinf (x))
# else