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author | Patrick McGehearty <patrick.mcgehearty@oracle.com> | 2017-12-19 17:25:14 +0000 |
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committer | Joseph Myers <joseph@codesourcery.com> | 2017-12-19 17:27:31 +0000 |
commit | 6fd0a3c6a887a91b1554730c977657a7e65334cc (patch) | |
tree | 6a0b347f2435cdd23fb55f3f39f22e7a0fb83096 /sysdeps/x86_64/fpu | |
parent | 3bb1ef58b989012f8199b82af6ec136da2f9fda3 (diff) | |
download | glibc-6fd0a3c6a887a91b1554730c977657a7e65334cc.tar.gz glibc-6fd0a3c6a887a91b1554730c977657a7e65334cc.tar.xz glibc-6fd0a3c6a887a91b1554730c977657a7e65334cc.zip |
Improve __ieee754_exp() performance by greater than 5x on sparc/x86.
These changes will be active for all platforms that don't provide their own exp() routines. They will also be active for ieee754 versions of ccos, ccosh, cosh, csin, csinh, sinh, exp10, gamma, and erf. Typical performance gains is typically around 5x when measured on Sparc s7 for common values between exp(1) and exp(40). Using the glibc perf tests on sparc, sparc (nsec) x86 (nsec) old new old new max 17629 395 5173 144 min 399 54 15 13 mean 5317 200 1349 23 The extreme max times for the old (ieee754) exp are due to the multiprecision computation in the old algorithm when the true value is very near 0.5 ulp away from an value representable in double precision. The new algorithm does not take special measures for those cases. The current glibc exp perf tests overrepresent those values. Informal testing suggests approximately one in 200 cases might invoke the high cost computation. The performance advantage of the new algorithm for other values is still large but not as large as indicated by the chart above. Glibc correctness tests for exp() and expf() were run. Within the test suite 3 input values were found to cause 1 bit differences (ulp) when "FE_TONEAREST" rounding mode is set. No differences in exp() were seen for the tested values for the other rounding modes. Typical example: exp(-0x1.760cd2p+0) (-1.46113312244415283203125) new code: 2.31973271630014299393707e-01 0x1.db14cd799387ap-3 old code: 2.31973271630014271638132e-01 0x1.db14cd7993879p-3 exp = 2.31973271630014285508337 (high precision) Old delta: off by 0.49 ulp New delta: off by 0.51 ulp In addition, because ieee754_exp() is used by other routines, cexp() showed test results with very small imaginary input values where the imaginary portion of the result was off by 3 ulp when in upward rounding mode, but not in the other rounding modes. For x86, tgamma showed a few values where the ulp increased to 6 (max ulp for tgamma is 5). Sparc tgamma did not show these failures. I presume the tgamma differences are due to compiler optimization differences within the gamma function.The gamma function is known to be difficult to compute accurately. * sysdeps/ieee754/dbl-64/e_exp.c: Include <math-svid-compat.h> and <errno.h>. Include "eexp.tbl". (half): New constant. (one): Likewise. (__ieee754_exp): Rewrite. (__slowexp): Remove prototype. * sysdeps/ieee754/dbl-64/eexp.tbl: New file. * sysdeps/ieee754/dbl-64/slowexp.c: Remove file. * sysdeps/i386/fpu/slowexp.c: Likewise. * sysdeps/ia64/fpu/slowexp.c: Likewise. * sysdeps/m68k/m680x0/fpu/slowexp.c: Likewise. * sysdeps/x86_64/fpu/multiarch/slowexp-avx.c: Likewise. * sysdeps/x86_64/fpu/multiarch/slowexp-fma.c: Likewise. * sysdeps/x86_64/fpu/multiarch/slowexp-fma4.c: Likewise. * sysdeps/generic/math_private.h (__slowexp): Remove prototype. * sysdeps/ieee754/dbl-64/e_pow.c: Remove mention of slowexp.c in comment. * sysdeps/powerpc/power4/fpu/Makefile [$(subdir) = math] (CPPFLAGS-slowexp.c): Remove variable. * sysdeps/x86_64/fpu/multiarch/Makefile (libm-sysdep_routines): Remove slowexp-fma, slowexp-fma4 and slowexp-avx. (CFLAGS-slowexp-fma.c): Remove variable. (CFLAGS-slowexp-fma4.c): Likewise. (CFLAGS-slowexp-avx.c): Likewise. * sysdeps/x86_64/fpu/multiarch/e_exp-avx.c (__slowexp): Do not define as macro. * sysdeps/x86_64/fpu/multiarch/e_exp-fma.c (__slowexp): Likewise. * sysdeps/x86_64/fpu/multiarch/e_exp-fma4.c (__slowexp): Likewise. * math/Makefile (type-double-routines): Remove slowexp. * manual/probes.texi (slowexp_p6): Remove. (slowexp_p32): Likewise.
Diffstat (limited to 'sysdeps/x86_64/fpu')
-rw-r--r-- | sysdeps/x86_64/fpu/multiarch/Makefile | 9 | ||||
-rw-r--r-- | sysdeps/x86_64/fpu/multiarch/e_exp-avx.c | 1 | ||||
-rw-r--r-- | sysdeps/x86_64/fpu/multiarch/e_exp-fma.c | 1 | ||||
-rw-r--r-- | sysdeps/x86_64/fpu/multiarch/e_exp-fma4.c | 1 | ||||
-rw-r--r-- | sysdeps/x86_64/fpu/multiarch/slowexp-avx.c | 9 | ||||
-rw-r--r-- | sysdeps/x86_64/fpu/multiarch/slowexp-fma.c | 9 | ||||
-rw-r--r-- | sysdeps/x86_64/fpu/multiarch/slowexp-fma4.c | 9 |
7 files changed, 3 insertions, 36 deletions
diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile b/sysdeps/x86_64/fpu/multiarch/Makefile index 0825340c0c..bec45e073c 100644 --- a/sysdeps/x86_64/fpu/multiarch/Makefile +++ b/sysdeps/x86_64/fpu/multiarch/Makefile @@ -10,7 +10,7 @@ libm-sysdep_routines += s_ceil-sse4_1 s_ceilf-sse4_1 s_floor-sse4_1 \ libm-sysdep_routines += e_exp-fma e_log-fma e_pow-fma s_atan-fma \ e_asin-fma e_atan2-fma s_sin-fma s_tan-fma \ - mplog-fma mpa-fma slowexp-fma slowpow-fma \ + mplog-fma mpa-fma slowpow-fma \ sincos32-fma doasin-fma dosincos-fma \ halfulp-fma mpexp-fma \ mpatan2-fma mpatan-fma mpsqrt-fma mptan-fma @@ -32,7 +32,6 @@ CFLAGS-mpsqrt-fma.c = -mfma -mavx2 CFLAGS-mptan-fma.c = -mfma -mavx2 CFLAGS-s_atan-fma.c = -mfma -mavx2 CFLAGS-sincos32-fma.c = -mfma -mavx2 -CFLAGS-slowexp-fma.c = -mfma -mavx2 CFLAGS-slowpow-fma.c = -mfma -mavx2 CFLAGS-s_sin-fma.c = -mfma -mavx2 CFLAGS-s_tan-fma.c = -mfma -mavx2 @@ -52,7 +51,7 @@ CFLAGS-s_cosf-fma.c = -mfma -mavx2 libm-sysdep_routines += e_exp-fma4 e_log-fma4 e_pow-fma4 s_atan-fma4 \ e_asin-fma4 e_atan2-fma4 s_sin-fma4 s_tan-fma4 \ - mplog-fma4 mpa-fma4 slowexp-fma4 slowpow-fma4 \ + mplog-fma4 mpa-fma4 slowpow-fma4 \ sincos32-fma4 doasin-fma4 dosincos-fma4 \ halfulp-fma4 mpexp-fma4 \ mpatan2-fma4 mpatan-fma4 mpsqrt-fma4 mptan-fma4 @@ -74,14 +73,13 @@ CFLAGS-mpsqrt-fma4.c = -mfma4 CFLAGS-mptan-fma4.c = -mfma4 CFLAGS-s_atan-fma4.c = -mfma4 CFLAGS-sincos32-fma4.c = -mfma4 -CFLAGS-slowexp-fma4.c = -mfma4 CFLAGS-slowpow-fma4.c = -mfma4 CFLAGS-s_sin-fma4.c = -mfma4 CFLAGS-s_tan-fma4.c = -mfma4 libm-sysdep_routines += e_exp-avx e_log-avx s_atan-avx \ e_atan2-avx s_sin-avx s_tan-avx \ - mplog-avx mpa-avx slowexp-avx \ + mplog-avx mpa-avx \ mpexp-avx CFLAGS-e_atan2-avx.c = -msse2avx -DSSE2AVX @@ -92,7 +90,6 @@ CFLAGS-mpexp-avx.c = -msse2avx -DSSE2AVX CFLAGS-mplog-avx.c = -msse2avx -DSSE2AVX CFLAGS-s_atan-avx.c = -msse2avx -DSSE2AVX CFLAGS-s_sin-avx.c = -msse2avx -DSSE2AVX -CFLAGS-slowexp-avx.c = -msse2avx -DSSE2AVX CFLAGS-s_tan-avx.c = -msse2avx -DSSE2AVX endif diff --git a/sysdeps/x86_64/fpu/multiarch/e_exp-avx.c b/sysdeps/x86_64/fpu/multiarch/e_exp-avx.c index ee5dd6d2dc..afd917442a 100644 --- a/sysdeps/x86_64/fpu/multiarch/e_exp-avx.c +++ b/sysdeps/x86_64/fpu/multiarch/e_exp-avx.c @@ -1,6 +1,5 @@ #define __ieee754_exp __ieee754_exp_avx #define __exp1 __exp1_avx -#define __slowexp __slowexp_avx #define SECTION __attribute__ ((section (".text.avx"))) #include <sysdeps/ieee754/dbl-64/e_exp.c> diff --git a/sysdeps/x86_64/fpu/multiarch/e_exp-fma.c b/sysdeps/x86_64/fpu/multiarch/e_exp-fma.c index 6e0fdb7941..765b1b9dd3 100644 --- a/sysdeps/x86_64/fpu/multiarch/e_exp-fma.c +++ b/sysdeps/x86_64/fpu/multiarch/e_exp-fma.c @@ -1,6 +1,5 @@ #define __ieee754_exp __ieee754_exp_fma #define __exp1 __exp1_fma -#define __slowexp __slowexp_fma #define SECTION __attribute__ ((section (".text.fma"))) #include <sysdeps/ieee754/dbl-64/e_exp.c> diff --git a/sysdeps/x86_64/fpu/multiarch/e_exp-fma4.c b/sysdeps/x86_64/fpu/multiarch/e_exp-fma4.c index ae6eb67603..9ac7acad28 100644 --- a/sysdeps/x86_64/fpu/multiarch/e_exp-fma4.c +++ b/sysdeps/x86_64/fpu/multiarch/e_exp-fma4.c @@ -1,6 +1,5 @@ #define __ieee754_exp __ieee754_exp_fma4 #define __exp1 __exp1_fma4 -#define __slowexp __slowexp_fma4 #define SECTION __attribute__ ((section (".text.fma4"))) #include <sysdeps/ieee754/dbl-64/e_exp.c> diff --git a/sysdeps/x86_64/fpu/multiarch/slowexp-avx.c b/sysdeps/x86_64/fpu/multiarch/slowexp-avx.c deleted file mode 100644 index d01c6d71a4..0000000000 --- a/sysdeps/x86_64/fpu/multiarch/slowexp-avx.c +++ /dev/null @@ -1,9 +0,0 @@ -#define __slowexp __slowexp_avx -#define __add __add_avx -#define __dbl_mp __dbl_mp_avx -#define __mpexp __mpexp_avx -#define __mul __mul_avx -#define __sub __sub_avx -#define SECTION __attribute__ ((section (".text.avx"))) - -#include <sysdeps/ieee754/dbl-64/slowexp.c> diff --git a/sysdeps/x86_64/fpu/multiarch/slowexp-fma.c b/sysdeps/x86_64/fpu/multiarch/slowexp-fma.c deleted file mode 100644 index 6fffca1a93..0000000000 --- a/sysdeps/x86_64/fpu/multiarch/slowexp-fma.c +++ /dev/null @@ -1,9 +0,0 @@ -#define __slowexp __slowexp_fma -#define __add __add_fma -#define __dbl_mp __dbl_mp_fma -#define __mpexp __mpexp_fma -#define __mul __mul_fma -#define __sub __sub_fma -#define SECTION __attribute__ ((section (".text.fma"))) - -#include <sysdeps/ieee754/dbl-64/slowexp.c> diff --git a/sysdeps/x86_64/fpu/multiarch/slowexp-fma4.c b/sysdeps/x86_64/fpu/multiarch/slowexp-fma4.c deleted file mode 100644 index 3bcde84233..0000000000 --- a/sysdeps/x86_64/fpu/multiarch/slowexp-fma4.c +++ /dev/null @@ -1,9 +0,0 @@ -#define __slowexp __slowexp_fma4 -#define __add __add_fma4 -#define __dbl_mp __dbl_mp_fma4 -#define __mpexp __mpexp_fma4 -#define __mul __mul_fma4 -#define __sub __sub_fma4 -#define SECTION __attribute__ ((section (".text.fma4"))) - -#include <sysdeps/ieee754/dbl-64/slowexp.c> |