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Start optimizing the use of the fenv interfaces in libm itself
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Ulrich Drepper
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15
ChangeLog
15
ChangeLog
@ -1,3 +1,18 @@
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2011-10-18 Ulrich Drepper <drepper@gmail.com>
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* math/math_private.h: Define defaults for libc_fegetround,
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libc_fegetroundf, libc_fegetroundl, libc_fesetround, libc_fesetroundf,
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libc_fesetroundl, libc_feholdexcept, libc_feholdexceptf,
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libc_feholdexceptl, libc_fesetenv, libc_fesetenvf, libc_fesetenvl.
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* sysdeps/ieee754/dbl-64/wordsize-64/s_nearbyint.c: Use
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libc_feholdexcept, libc_fesetround, libc_fesetenv instead of the
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standard functions.
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* sysdeps/ieee754/dbl-64/e_exp2.c: Likewise.
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Remove comments and hacks for old compiler versions.
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* sysdeps/x86_64/fpu/math_private.h: Define special versions of
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libc_fegetround, libc_fesetround, libc_feholdexcept, and
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libc_feholdexceptl.
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2011-10-18 Andreas Schwab <schwab@redhat.com>
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* sysdeps/x86_64/fpu/bits/fenv.h: Add C linkage markers.
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@ -358,4 +358,26 @@ extern void __docos (double __x, double __dx, double __v[]);
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#define math_force_eval(x) __asm __volatile ("" : : "m" (x))
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#endif
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/* The standards only specify one variant of the fenv.h interfaces.
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But at least for some architectures we can be more efficient if we
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know what operations are going to be performed. Therefore we
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define additional interfaces. By default they refer to the normal
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interfaces. */
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#define libc_fegetround() fegetround ()
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#define libc_fegetroundf() fegetround ()
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#define libc_fegetroundl() fegetround ()
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#define libc_fesetround(r) (void) fesetround (r)
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#define libc_fesetroundf(r) (void) fesetround (r)
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#define libc_fesetroundl(r) (void) fesetround (r)
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#define libc_feholdexcept(e) (void) feholdexcept (e)
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#define libc_feholdexceptf(e) (void) feholdexcept (e)
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#define libc_feholdexceptl(e) (void) feholdexcept (e)
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#define libc_fesetenv(e) (void) fesetenv (e)
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#define libc_fesetenvf(e) (void) fesetenv (e)
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#define libc_fesetenvl(e) (void) fesetenv (e)
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#endif /* _MATH_PRIVATE_H_ */
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@ -25,9 +25,6 @@
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17 (1), March 1991, pp. 26-45.
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It has been slightly modified to compute 2^x instead of e^x.
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*/
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#ifndef _GNU_SOURCE
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#define _GNU_SOURCE
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#endif
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#include <stdlib.h>
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#include <float.h>
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#include <ieee754.h>
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@ -38,13 +35,8 @@
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#include "t_exp2.h"
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/* XXX I know the assembler generates a warning about incorrect section
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attributes. But without the attribute here the compiler places the
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constants in the .data section. Ideally the constant is placed in
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.rodata.cst8 so that it can be merged, but gcc sucks, it ICEs when
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we try to force this section on it. --drepper */
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static const volatile double TWO1023 = 8.988465674311579539e+307;
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static const volatile double TWOM1000 = 9.3326361850321887899e-302;
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static const double TWO1023 = 8.988465674311579539e+307;
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static const double TWOM1000 = 9.3326361850321887899e-302;
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double
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__ieee754_exp2 (double x)
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@ -72,10 +64,10 @@ __ieee754_exp2 (double x)
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union ieee754_double ex2_u, scale_u;
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fenv_t oldenv;
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feholdexcept (&oldenv);
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libc_feholdexcept (&oldenv);
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#ifdef FE_TONEAREST
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/* If we don't have this, it's too bad. */
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fesetround (FE_TONEAREST);
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libc_fesetround (FE_TONEAREST);
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#endif
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/* 1. Argument reduction.
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@ -120,9 +112,10 @@ __ieee754_exp2 (double x)
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* x + .055504110254308625)
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* x + .240226506959100583)
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* x + .69314718055994495) * ex2_u.d;
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math_opt_barrier (x22);
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/* 5. Return (2^x2-1) * 2^(t/512+e+ex) + 2^(t/512+e+ex). */
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fesetenv (&oldenv);
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libc_fesetenv (&oldenv);
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result = x22 * x + ex2_u.d;
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@ -24,22 +24,14 @@
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#include "math.h"
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#include "math_private.h"
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#ifdef __STDC__
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static const double
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#else
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static double
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#endif
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TWO52[2]={
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4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
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-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
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};
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#ifdef __STDC__
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double __nearbyint(double x)
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#else
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double __nearbyint(x)
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double x;
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#endif
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double
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__nearbyint(double x)
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{
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fenv_t env;
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int64_t i0,sx;
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@ -47,20 +39,19 @@ TWO52[2]={
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EXTRACT_WORDS64(i0,x);
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sx = (i0>>63)&1;
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j0 = ((i0>>52)&0x7ff)-0x3ff;
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if(j0<52) {
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if(__builtin_expect(j0<52, 1)) {
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if(j0<0) {
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if((i0&UINT64_C(0x7fffffffffffffff))==0) return x;
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uint64_t i = i0 & UINT64_C(0xfffffffffffff);
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i0 &= UINT64_C(0xfffe000000000000);
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i0 |= (((i|-i) >> 12) & UINT64_C(0x8000000000000));
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INSERT_WORDS64(x,i0);
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feholdexcept (&env);
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libc_feholdexcept (&env);
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double w = TWO52[sx]+x;
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double t = w-TWO52[sx];
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fesetenv (&env);
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EXTRACT_WORDS64(i0,t);
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INSERT_WORDS64(t,(i0&UINT64_C(0x7fffffffffffffff))|(sx<<63));
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return t;
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math_opt_barrier(t);
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libc_fesetenv (&env);
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return copysign(t, x);
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} else {
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uint64_t i = UINT64_C(0x000fffffffffffff)>>j0;
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if((i0&i)==0) return x; /* x is integral */
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@ -73,10 +64,11 @@ TWO52[2]={
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else return x; /* x is integral */
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}
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INSERT_WORDS64(x,i0);
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feholdexcept (&env);
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libc_feholdexcept (&env);
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double w = TWO52[sx]+x;
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double t = w-TWO52[sx];
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fesetenv (&env);
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math_opt_barrier (t);
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libc_fesetenv (&env);
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return t;
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}
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weak_alias (__nearbyint, nearbyint)
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@ -118,3 +118,45 @@ do { \
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__res; })
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# endif
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#endif
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/* Specialized variants of the <fenv.h> interfaces which only handle
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either the FPU or the SSE unit. */
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#undef libc_fegetround
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#define libc_fegetround() \
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({ \
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unsigned int mxcsr; \
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asm volatile ("stmxcsr %0" : "=m" (*&mxcsr)); \
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(mxcsr & 0x6000) >> 3; \
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})
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// #define libc_fegetroundf() fegetround ()
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// #define libc_fegetroundl() fegetround ()
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#undef libc_fesetround
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#define libc_fesetround(r) \
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do { \
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unsigned int mxcsr; \
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asm ("stmxcsr %0" : "=m" (*&mxcsr)); \
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mxcsr = (mxcsr & ~0x6000) | ((r) << 3); \
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asm volatile ("ldmxcsr %0" : : "m" (*&mxcsr)); \
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} while (0)
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// #define libc_fesetroundf(r) (void) fesetround (r)
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// #define libc_fesetroundl(r) (void) fesetround (r)
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#undef libc_feholdexcept
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#define libc_feholdexcept(e) \
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do { \
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unsigned int mxcsr; \
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asm ("stmxcsr %0" : "=m" (*&mxcsr)); \
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(e)->__mxcsr = mxcsr; \
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mxcsr = (mxcsr | 0x1f80) & ~0x3f; \
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asm volatile ("ldmxcsr %0" : : "m" (*&mxcsr)); \
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} while (0)
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// #define libc_feholdexceptf(e) (void) feholdexcept (e)
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// #define libc_feholdexceptl(e) (void) feholdexcept (e)
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#undef libc_fesetenv
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#define libc_fesetenv(e) \
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asm volatile ("ldmxcsr %0" : : "m" ((e)->__mxcsr))
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// #define libc_fesetenvf(e) (void) fesetenv (e)
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// #define libc_fesetenvl(e) (void) fesetenv (e)
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