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powerpc: Use sqrt{f} builtin

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The powerpc sqrt implementation is also simplified:

  - the static constants are open coded within the implementation.
  - for !USE_SQRT_BUILTIN the function is implemented directly on
    __ieee754_sqrt (it avoid an superflous extra jump).

Checked on powerpc-linux-gnu and powerpc64le-linux-gnu.
This commit is contained in:
Adhemerval Zanella
2020-06-04 22:47:16 +03:00
parent a2e833667d
commit 169ea8f928
3 changed files with 42 additions and 80 deletions
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57
sysdeps/powerpc/fpu/e_sqrt.c
View File

@@ -18,22 +18,16 @@
#include <math.h>
#include <math_private.h>
#include <fenv.h>
#include <fenv_libc.h>
#include <inttypes.h>
#include <stdint.h>
#include <sysdep.h>
#include <ldsodefs.h>
#include <libm-alias-finite.h>
#include <math-use-builtins.h>
#ifndef _ARCH_PPCSQ
static const double almost_half = 0.5000000000000001; /* 0.5 + 2^-53 */
static const ieee_float_shape_type a_nan = {.word = 0x7fc00000 };
static const ieee_float_shape_type a_inf = {.word = 0x7f800000 };
static const float two108 = 3.245185536584267269e+32;
static const float twom54 = 5.551115123125782702e-17;
extern const float __t_sqrt[1024];
double
__ieee754_sqrt (double x)
{
#if USE_SQRT_BUILTIN
return __builtin_sqrt (x);
#else
/* The method is based on a description in
Computation of elementary functions on the IBM RISC System/6000 processor,
P. W. Markstein, IBM J. Res. Develop, 34(1) 1990.
@@ -48,10 +42,7 @@ extern const float __t_sqrt[1024];
generated guesses (which mostly runs on the integer unit, while the
Newton-Raphson is running on the FPU). */
double
__slow_ieee754_sqrt (double x)
{
const float inf = a_inf.value;
extern const float __t_sqrt[1024];
if (x > 0)
{
@@ -60,7 +51,7 @@ __slow_ieee754_sqrt (double x)
ieee_double_shape_type ew_u;
ieee_double_shape_type iw_u;
ew_u.value = (x);
if (x != inf)
if (x != INFINITY)
{
/* Variables named starting with 's' exist in the
argument-reduced space, so that 2 > sx >= 0.5,
@@ -112,7 +103,7 @@ __slow_ieee754_sqrt (double x)
INSERT_WORDS (fsg, fsgi, 0);
iw_u.parts.msw = fsgi;
iw_u.parts.lsw = (0);
e = -__builtin_fma (sy, sg, -almost_half);
e = -__builtin_fma (sy, sg, -0x1.0000000000001p-1);
sd = -__builtin_fma (sg, sg, -sx);
if ((xi0 & 0x7ff00000) == 0)
goto denorm;
@@ -122,7 +113,7 @@ __slow_ieee754_sqrt (double x)
sy2 = sy + sy;
/* complete the INSERT_WORDS (fsg, fsgi, 0) operation. */
fsg = iw_u.value;
e = -__builtin_fma (sy, sg, -almost_half);
e = -__builtin_fma (sy, sg, -0x1.0000000000001p-1);
sd = -__builtin_fma (sg, sg, -sx);
sy = __builtin_fma (e, sy2, sy);
shx = sx * fsg;
@@ -131,7 +122,7 @@ __slow_ieee754_sqrt (double x)
rounded incorrectly. */
sy2 = sy + sy;
g = sg * fsg;
e = -__builtin_fma (sy, sg, -almost_half);
e = -__builtin_fma (sy, sg, -0x1.0000000000001p-1);
d = -__builtin_fma (g, sg, -shx);
sy = __builtin_fma (e, sy2, sy);
fesetenv_register (fe);
@@ -140,38 +131,24 @@ __slow_ieee754_sqrt (double x)
/* For denormalised numbers, we normalise, calculate the
square root, and return an adjusted result. */
fesetenv_register (fe);
return __slow_ieee754_sqrt (x * two108) * twom54;
return __ieee754_sqrt (x * 0x1p+108f) * 0x1p-54f;
}
}
else if (x < 0)
{
/* For some reason, some PowerPC32 processors don't implement
FE_INVALID_SQRT. */
#ifdef FE_INVALID_SQRT
# ifdef FE_INVALID_SQRT
__feraiseexcept (FE_INVALID_SQRT);
fenv_union_t u = { .fenv = fegetenv_register () };
if ((u.l & FE_INVALID) == 0)
#endif
# endif
__feraiseexcept (FE_INVALID);
x = a_nan.value;
x = NAN;
}
return f_wash (x);
#endif /* USE_SQRT_BUILTIN */
}
#endif /* _ARCH_PPCSQ */
#undef __ieee754_sqrt
double
__ieee754_sqrt (double x)
{
double z;
#ifdef _ARCH_PPCSQ
asm ("fsqrt %0,%1\n" :"=f" (z):"f" (x));
#else
z = __slow_ieee754_sqrt (x);
#endif
return z;
}
libm_alias_finite (__ieee754_sqrt, __sqrt)

56
sysdeps/powerpc/fpu/e_sqrtf.c
View File

@@ -18,22 +18,16 @@
#include <math.h>
#include <math_private.h>
#include <fenv.h>
#include <fenv_libc.h>
#include <inttypes.h>
#include <stdint.h>
#include <sysdep.h>
#include <ldsodefs.h>
#include <libm-alias-finite.h>
#include <math-use-builtins.h>
#ifndef _ARCH_PPCSQ
static const float almost_half = 0.50000006; /* 0.5 + 2^-24 */
static const ieee_float_shape_type a_nan = {.word = 0x7fc00000 };
static const ieee_float_shape_type a_inf = {.word = 0x7f800000 };
static const float two48 = 281474976710656.0;
static const float twom24 = 5.9604644775390625e-8;
extern const float __t_sqrt[1024];
float
__ieee754_sqrtf (float x)
{
#if USE_SQRTF_BUILTIN
return __builtin_sqrtf (x);
#else
/* The method is based on a description in
Computation of elementary functions on the IBM RISC System/6000 processor,
P. W. Markstein, IBM J. Res. Develop, 34(1) 1990.
@@ -48,14 +42,11 @@ extern const float __t_sqrt[1024];
generated guesses (which mostly runs on the integer unit, while the
Newton-Raphson is running on the FPU). */
float
__slow_ieee754_sqrtf (float x)
{
const float inf = a_inf.value;
extern const float __t_sqrt[1024];
if (x > 0)
{
if (x != inf)
if (x != INFINITY)
{
/* Variables named starting with 's' exist in the
argument-reduced space, so that 2 > sx >= 0.5,
@@ -94,7 +85,7 @@ __slow_ieee754_sqrtf (float x)
sy2 = sy + sy;
sg = __builtin_fmaf (sy, sd, sg); /* 16-bit approximation to
sqrt(sx). */
e = -__builtin_fmaf (sy, sg, -almost_half);
e = -__builtin_fmaf (sy, sg, -0x1.0000020365653p-1);
SET_FLOAT_WORD (fsg, fsgi);
sd = -__builtin_fmaf (sg, sg, -sx);
sy = __builtin_fmaf (e, sy2, sy);
@@ -106,7 +97,7 @@ __slow_ieee754_sqrtf (float x)
rounded incorrectly. */
sy2 = sy + sy;
g = sg * fsg;
e = -__builtin_fmaf (sy, sg, -almost_half);
e = -__builtin_fmaf (sy, sg, -0x1.0000020365653p-1);
d = -__builtin_fmaf (g, sg, -shx);
sy = __builtin_fmaf (e, sy2, sy);
fesetenv_register (fe);
@@ -115,38 +106,23 @@ __slow_ieee754_sqrtf (float x)
/* For denormalised numbers, we normalise, calculate the
square root, and return an adjusted result. */
fesetenv_register (fe);
return __slow_ieee754_sqrtf (x * two48) * twom24;
return __ieee754_sqrtf (x * 0x1p+48) * 0x1p-24;
}
}
else if (x < 0)
{
/* For some reason, some PowerPC32 processors don't implement
FE_INVALID_SQRT. */
#ifdef FE_INVALID_SQRT
# ifdef FE_INVALID_SQRT
feraiseexcept (FE_INVALID_SQRT);
fenv_union_t u = { .fenv = fegetenv_register () };
if ((u.l & FE_INVALID) == 0)
#endif
# endif
feraiseexcept (FE_INVALID);
x = a_nan.value;
x = NAN;
}
return f_washf (x);
}
#endif /* _ARCH_PPCSQ */
#undef __ieee754_sqrtf
float
__ieee754_sqrtf (float x)
{
float z;
#ifdef _ARCH_PPCSQ
asm ("fsqrts %0,%1\n" :"=f" (z):"f" (x));
#else
z = __slow_ieee754_sqrtf (x);
#endif
return z;
#endif /* USE_SQRTF_BUILTIN */
}
libm_alias_finite (__ieee754_sqrtf, __sqrtf)

9
sysdeps/powerpc/fpu/math-use-builtins-sqrt.h Normal file
View File

@@ -0,0 +1,9 @@
#ifdef _ARCH_PPCSQ
# define USE_SQRT_BUILTIN 1
# define USE_SQRTF_BUILTIN 1
#else
# define USE_SQRT_BUILTIN 0
# define USE_SQRTF_BUILTIN 0
#endif
#define USE_SQRTL_BUILTIN 0
#define USE_SQRTF128_BUILTIN 0