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Create and use libc_feupdateenv_test.

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We can reduce the number of STMXCSR, and often we can avoid the
call to __feraiseexcept.
This commit is contained in:
Richard Henderson 2012-03-10 08:53:05 -08:00
parent eb92c487b3
commit 0fe0f1f86f
5 changed files with 73 additions and 19 deletions
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9
ChangeLog
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@ -1,5 +1,14 @@
2012-03-19 Richard Henderson <rth@twiddle.net>
* sysdeps/generic/math_private.h (default_libc_feupdateenv_test): New.
(libc_feupdateenv_test, libc_feupdateenv_testf): New.
(libc_feupdateenv_testl): New.
* sysdeps/x86_64/fpu/math_private.h (libc_feupdateenv_test): New.
(libc_feupdateenv_testf): New.
(libc_feupdateenv): Use libc_feupdateenv_test.
* sysdeps/ieee754/dbl-64/s_fma.c (__fma): Use libc_feupdateenv_test.
* sysdeps/ieee754/dbl-64/s_fmaf.c (__fmaf): Likewise.
* sysdeps/generic/math_private.h (libc_feholdsetround): New.
(libc_feholdsetroundf, libc_feholdsetroundl): New.
(libc_feresetround, libc_feresetroundf, libc_feresetroundl): New.

18
sysdeps/generic/math_private.h
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@ -457,6 +457,24 @@ default_libc_feupdateenv (fenv_t *e)
# define libc_feupdateenv_53bit libc_feupdateenv
#endif
static __always_inline int
default_libc_feupdateenv_test (fenv_t *e, int ex)
{
int ret = fetestexcept (ex);
feupdateenv (e);
return ret;
}
#ifndef libc_feupdateenv_test
# define libc_feupdateenv_test default_libc_feupdateenv_test
#endif
#ifndef libc_feupdateenv_testf
# define libc_feupdateenv_testf default_libc_feupdateenv_test
#endif
#ifndef libc_feupdateenv_testl
# define libc_feupdateenv_testl default_libc_feupdateenv_test
#endif
/* Save and set the rounding mode. The use of fenv_t to store the old mode
allows a target-specific version of this function to avoid converting the
rounding mode from the fpu format. By default we have no choice but to

25
sysdeps/ieee754/dbl-64/s_fma.c
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@ -149,35 +149,36 @@ __fma (double x, double y, double z)
fenv_t env;
libc_feholdexcept_setround (&env, FE_TOWARDZERO);
/* Perform m2 + a2 addition with round to odd. */
u.d = a2 + m2;
if (__builtin_expect (adjust < 0, 0))
{
if ((u.ieee.mantissa1 & 1) == 0)
u.ieee.mantissa1 |= libc_fetestexcept (FE_INEXACT) != 0;
v.d = a1 + u.d;
}
/* Reset rounding mode and test for inexact simultaneously. */
int j = libc_feupdateenv_test (&env, FE_INEXACT) != 0;
if (__builtin_expect (adjust == 0, 1))
{
if ((u.ieee.mantissa1 & 1) == 0 && u.ieee.exponent != 0x7ff)
u.ieee.mantissa1 |= libc_fetestexcept (FE_INEXACT) != 0;
libc_feupdateenv (&env);
u.ieee.mantissa1 |= j;
/* Result is a1 + u.d. */
return a1 + u.d;
}
else if (__builtin_expect (adjust > 0, 1))
{
if ((u.ieee.mantissa1 & 1) == 0 && u.ieee.exponent != 0x7ff)
u.ieee.mantissa1 |= libc_fetestexcept (FE_INEXACT) != 0;
libc_feupdateenv (&env);
u.ieee.mantissa1 |= j;
/* Result is a1 + u.d, scaled up. */
return (a1 + u.d) * 0x1p53;
}
else
{
if ((u.ieee.mantissa1 & 1) == 0)
u.ieee.mantissa1 |= libc_fetestexcept (FE_INEXACT) != 0;
v.d = a1 + u.d;
int j = libc_fetestexcept (FE_INEXACT) != 0;
libc_feupdateenv (&env);
/* Ensure the following computations are performed in default rounding
mode instead of just reusing the round to zero computation. */
asm volatile ("" : "=m" (u) : "m" (u));
/* If a1 + u.d is exact, the only rounding happens during
scaling down. */
if (j == 0)

12
sysdeps/ieee754/dbl-64/s_fmaf.c
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@ -35,12 +35,18 @@ __fmaf (float x, float y, float z)
/* Multiplication is always exact. */
double temp = (double) x * (double) y;
union ieee754_double u;
libc_feholdexcept_setroundf (&env, FE_TOWARDZERO);
libc_feholdexcept_setround (&env, FE_TOWARDZERO);
/* Perform addition with round to odd. */
u.d = temp + (double) z;
/* Reset rounding mode and test for inexact simultaneously. */
int j = libc_feupdateenv_test (&env, FE_INEXACT) != 0;
if ((u.ieee.mantissa1 & 1) == 0 && u.ieee.exponent != 0x7ff)
u.ieee.mantissa1 |= libc_fetestexcept (FE_INEXACT) != 0;
libc_feupdateenv (&env);
u.ieee.mantissa1 |= j;
/* And finally truncation with round to nearest. */
return (float) u.d;
}

28
sysdeps/x86_64/fpu/math_private.h
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@ -108,13 +108,33 @@ libc_fesetenv (fenv_t *e)
#define libc_fesetenv libc_fesetenv
#define libc_fesetenvf libc_fesetenv
static __always_inline int
libc_feupdateenv_test (fenv_t *e, int ex)
{
unsigned int mxcsr, old_mxcsr, cur_ex;
asm volatile (STMXCSR " %0" : "=m" (*&mxcsr));
cur_ex = mxcsr & FE_ALL_EXCEPT;
/* Merge current exceptions with the old environment. */
old_mxcsr = e->__mxcsr;
mxcsr = old_mxcsr | cur_ex;
asm volatile (LDMXCSR " %0" : : "m" (*&mxcsr));
/* Raise SIGFPE for any new exceptions since the hold. Expect that
the normal environment has all exceptions masked. */
if (__builtin_expect ((old_mxcsr >> 7) & cur_ex, 0))
__feraiseexcept (cur_ex);
/* Test for exceptions raised since the hold. */
return cur_ex & ex;
}
#define libc_feupdateenv_test libc_feupdateenv_test
#define libc_feupdateenv_testf libc_feupdateenv_test
static __always_inline void
libc_feupdateenv (fenv_t *e)
{
unsigned int mxcsr;
asm volatile (STMXCSR " %0" : "=m" (*&mxcsr));
asm volatile (LDMXCSR " %0" : : "m" ((e)->__mxcsr));
__feraiseexcept (mxcsr & FE_ALL_EXCEPT);
libc_feupdateenv_test (e, 0);
}
#define libc_feupdateenv libc_feupdateenv
#define libc_feupdateenvf libc_feupdateenv