[1/3] powerpc: Add optimized ilogb* for POWER9
Commit Message
The instructions xsxexpdp and xsxexpqp introduced on POWER9 extract
the exponent from a double-precision and quad-precision floating-point
respectively, thus they can be used to improve ilogb, ilogbf and ilogbf128.
---
.../powerpc64/le/fpu/multiarch/math_private.h | 14 +++++++++
.../powerpc64/le/fpu/w_ilogb_template.c | 29 +++++++++++++++++++
2 files changed, 43 insertions(+)
create mode 100644 sysdeps/powerpc/powerpc64/le/fpu/w_ilogb_template.c
Comments
Benchtests results without and with this patch on a POWER9:
without:
"ilogbf128": {
"subnormal": {
"duration": 5.10445e+08,
"iterations": 2.5826e+07,
"max": 39.454,
"min": 3.098,
"mean": 19.7648
},
"normal": {
"duration": 5.02611e+08,
"iterations": 1.54482e+08,
"max": 6.037,
"min": 3.241,
"mean": 3.25352
}
},
"ilogb": {
"subnormal": {
"duration": 5.09116e+08,
"iterations": 4.7656e+07,
"max": 33.015,
"min": 3.042,
"mean": 10.6831
},
"normal": {
"duration": 5.01558e+08,
"iterations": 1.72702e+08,
"max": 5.6,
"min": 2.893,
"mean": 2.90418
}
},
"ilogbf": {
"subnormal": {
"duration": 5.0847e+08,
"iterations": 5.8494e+07,
"max": 15.928,
"min": 3.032,
"mean": 8.69269
},
"normal": {
"duration": 5.00965e+08,
"iterations": 1.80536e+08,
"max": 10.71,
"min": 2.756,
"mean": 2.77488
}
}
with:
"ilogbf128": {
"subnormal": {
"duration": 5.10468e+08,
"iterations": 2.534e+07,
"max": 38.864,
"min": 3.379,
"mean": 20.1448
},
"normal": {
"duration": 4.98668e+08,
"iterations": 2.1883e+08,
"max": 16.539,
"min": 2.215,
"mean": 2.27879
}
},
"ilogb": {
"subnormal": {
"duration": 5.0921e+08,
"iterations": 4.6646e+07,
"max": 21.122,
"min": 3.477,
"mean": 10.9165
},
"normal": {
"duration": 4.98203e+08,
"iterations": 2.2731e+08,
"max": 4.944,
"min": 2.12,
"mean": 2.19173
}
},
"ilogbf": {
"subnormal": {
"duration": 4.9848e+08,
"iterations": 2.2245e+08,
"max": 11.685,
"min": 2.16,
"mean": 2.24086
},
"normal": {
"duration": 4.98546e+08,
"iterations": 2.22032e+08,
"max": 5.855,
"min": 2.166,
"mean": 2.24538
}
}
On 2/26/21 10:08 AM, Raphael Moreira Zinsly wrote:
> The instructions xsxexpdp and xsxexpqp introduced on POWER9 extract
> the exponent from a double-precision and quad-precision floating-point
> respectively, thus they can be used to improve ilogb, ilogbf and ilogbf128.
> ---
> .../powerpc64/le/fpu/multiarch/math_private.h | 14 +++++++++
> .../powerpc64/le/fpu/w_ilogb_template.c | 29 +++++++++++++++++++
> 2 files changed, 43 insertions(+)
> create mode 100644 sysdeps/powerpc/powerpc64/le/fpu/w_ilogb_template.c
>
> diff --git a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h
> index 0970709cff..955497e98e 100644
> --- a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h
> +++ b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h
> @@ -1,6 +1,20 @@
> #ifndef MATH_PRIVATE_PPC64LE_MA
> #define MATH_PRIVATE_PPC64LE_MA 1
>
> +#define __builtin_test_dc_ilogbf __builtin_test_dc_ilogb
> +#define __builtin_ilogbf __builtin_ilogb
> +
> +#define __builtin_test_dc_ilogbl __builtin_test_dc_ilogbf128
> +#define __builtin_ilogbl __builtin_ilogbf128
> +
> +#define __builtin_test_dc_ilogb(x, y) \
> + __builtin_vsx_scalar_test_data_class_dp(x, y)
> +#define __builtin_ilogb(x) __builtin_vsx_scalar_extract_exp(x) - 0x3ff
> +
> +#define __builtin_test_dc_ilogbf128(x, y) \
> + __builtin_vsx_scalar_test_data_class_qp(x, y)
> +#define __builtin_ilogbf128(x) __builtin_vsx_scalar_extract_expq(x) - 0x3fff
> +
> #include_next <math_private.h>
Should these be placed in the powerpc math_private.h? I suspect this
will not build if multiarch is disabled.
Also, have you tested with the minimum version of GCC required for
glibc? I am not sure when these builtins were added.
On 26/02/2021 13:16, Paul E Murphy wrote:
>
>
> On 2/26/21 10:08 AM, Raphael Moreira Zinsly wrote:
>> The instructions xsxexpdp and xsxexpqp introduced on POWER9 extract
>> the exponent from a double-precision and quad-precision floating-point
>> respectively, thus they can be used to improve ilogb, ilogbf and
>> ilogbf128.
>> ---
>> .../powerpc64/le/fpu/multiarch/math_private.h | 14 +++++++++
>> .../powerpc64/le/fpu/w_ilogb_template.c | 29 +++++++++++++++++++
>> 2 files changed, 43 insertions(+)
>> create mode 100644 sysdeps/powerpc/powerpc64/le/fpu/w_ilogb_template.c
>>
>> diff --git a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h
>> b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h
>> index 0970709cff..955497e98e 100644
>> --- a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h
>> +++ b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/math_private.h
>> @@ -1,6 +1,20 @@
>> #ifndef MATH_PRIVATE_PPC64LE_MA
>> #define MATH_PRIVATE_PPC64LE_MA 1
>> +#define __builtin_test_dc_ilogbf __builtin_test_dc_ilogb
>> +#define __builtin_ilogbf __builtin_ilogb
>> +
>> +#define __builtin_test_dc_ilogbl __builtin_test_dc_ilogbf128
>> +#define __builtin_ilogbl __builtin_ilogbf128
>> +
>> +#define __builtin_test_dc_ilogb(x, y) \
>> + __builtin_vsx_scalar_test_data_class_dp(x, y)
>> +#define __builtin_ilogb(x) __builtin_vsx_scalar_extract_exp(x) - 0x3ff
>> +
>> +#define __builtin_test_dc_ilogbf128(x, y) \
>> + __builtin_vsx_scalar_test_data_class_qp(x, y)
>> +#define __builtin_ilogbf128(x) __builtin_vsx_scalar_extract_expq(x) -
>> 0x3fff
>> +
>> #include_next <math_private.h>
>
> Should these be placed in the powerpc math_private.h? I suspect this
> will not build if multiarch is disabled.
Thanks for catching that, I'll fix that in the next version.
>
> Also, have you tested with the minimum version of GCC required for
> glibc? I am not sure when these builtins were added.
You are right, this doesn't work on GCC older than 8.4, I'll add a guard
for that on my V2.
Thanks,
@@ -1,6 +1,20 @@
#ifndef MATH_PRIVATE_PPC64LE_MA
#define MATH_PRIVATE_PPC64LE_MA 1
+#define __builtin_test_dc_ilogbf __builtin_test_dc_ilogb
+#define __builtin_ilogbf __builtin_ilogb
+
+#define __builtin_test_dc_ilogbl __builtin_test_dc_ilogbf128
+#define __builtin_ilogbl __builtin_ilogbf128
+
+#define __builtin_test_dc_ilogb(x, y) \
+ __builtin_vsx_scalar_test_data_class_dp(x, y)
+#define __builtin_ilogb(x) __builtin_vsx_scalar_extract_exp(x) - 0x3ff
+
+#define __builtin_test_dc_ilogbf128(x, y) \
+ __builtin_vsx_scalar_test_data_class_qp(x, y)
+#define __builtin_ilogbf128(x) __builtin_vsx_scalar_extract_expq(x) - 0x3fff
+
#include_next <math_private.h>
#if defined (_F128_ENABLE_IFUNC)
new file mode 100644
@@ -0,0 +1,29 @@
+#ifdef _ARCH_PWR9
+#include <math.h>
+#include <errno.h>
+#include <limits.h>
+#include <math_private.h>
+#include <fenv.h>
+
+int
+M_DECL_FUNC (__ilogb) (FLOAT x)
+{
+ int r;
+ /* Check for exceptional cases. */
+ if (! M_SUF(__builtin_test_dc_ilogb) (x, 0x7f))
+ r = M_SUF (__builtin_ilogb) (x);
+ else
+ /* Fallback to the generic ilogb if x is NaN, Inf or subnormal. */
+ r = M_SUF (__ieee754_ilogb) (x);
+ if (__builtin_expect (r == FP_ILOGB0, 0)
+ || __builtin_expect (r == FP_ILOGBNAN, 0)
+ || __builtin_expect (r == INT_MAX, 0))
+ {
+ __set_errno (EDOM);
+ __feraiseexcept (FE_INVALID);
+ }
+ return r;
+}
+declare_mgen_alias (__ilogb, ilogb)
+
+#endif