Fixed aliasing bugs in TRUNC() by using the fdlibm macros for access
to doubles as bits. fdlibm-1.1 had similar aliasing bugs, but these were fixed by NetBSD or Cygnus before a modified version of fdlibm was imported in 1994. TRUNC() is only used by tgamma() and some implementation-detail functions. The aliasing bugs were detected by compiling with gcc -O2 but don't seem to have broken tgamma() on i386's or amd64's. They broke my modified version of tgamma(). Moved the definition of TRUNC() to mathimpl.h so that it can be fixed in one place, although the general version is even slower than necessary because it has to operate on pointers to volatiles to handle its arg sometimes being volatile. Inefficiency of the fdlibm macros slows down libm generally, and tgamma() is a relatively unimportant part of libm. The macros act as if on 32-bit words in memory, so they are hard to optimize to direct actions on 64-bit double registers for (non-i386) machines where this is possible. The optimization is too hard for gcc on amd64's, and declaring variables as volatile makes it impossible.
This commit is contained in:
parent
8d0e4e7eb4
commit
0b42281ee9
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=150318
@ -77,9 +77,6 @@ __FBSDID("$FreeBSD$");
|
||||
* +Inf return +Inf
|
||||
*/
|
||||
|
||||
#define endian (((*(int *) &one)) ? 1 : 0)
|
||||
#define TRUNC(x) *(((int *) &x) + endian) &= 0xf8000000
|
||||
|
||||
#define N 128
|
||||
|
||||
/* Table of log(Fj) = logF_head[j] + logF_tail[j], for Fj = 1+j/128.
|
||||
@ -438,7 +435,7 @@ __log__D(x) double x;
|
||||
#endif
|
||||
{
|
||||
int m, j;
|
||||
double F, f, g, q, u, v, u2, one = 1.0;
|
||||
double F, f, g, q, u, v, u2;
|
||||
volatile double u1;
|
||||
struct Double r;
|
||||
|
||||
|
@ -123,20 +123,12 @@ static struct Double ratfun_gam(double, double);
|
||||
#define Pa7 -1.44705562421428915453880392761e-02
|
||||
|
||||
static const double zero = 0., one = 1.0, tiny = 1e-300;
|
||||
static int endian;
|
||||
|
||||
/*
|
||||
* TRUNC sets trailing bits in a floating-point number to zero.
|
||||
* is a temporary variable.
|
||||
*/
|
||||
#define TRUNC(x) *(((int *) &x) + endian) &= 0xf8000000
|
||||
|
||||
double
|
||||
tgamma(x)
|
||||
double x;
|
||||
{
|
||||
struct Double u;
|
||||
endian = (*(int *) &one) ? 1 : 0;
|
||||
|
||||
if (x >= 6) {
|
||||
if(x > 171.63)
|
||||
|
@ -34,9 +34,32 @@
|
||||
* $FreeBSD$
|
||||
*/
|
||||
|
||||
#ifndef _MATHIMPL_H_
|
||||
#define _MATHIMPL_H_
|
||||
|
||||
#include <sys/cdefs.h>
|
||||
#include <math.h>
|
||||
|
||||
#include "../src/math_private.h"
|
||||
|
||||
/*
|
||||
* TRUNC() is a macro that sets the trailing 27 bits in the mantissa of an
|
||||
* IEEE double variable to zero. It must be expression-like for syntactic
|
||||
* reasons, and we implement this expression using an inline function
|
||||
* instead of a pure macro to avoid depending on the gcc feature of
|
||||
* statement-expressions.
|
||||
*/
|
||||
#define TRUNC(d) (_b_trunc(&(d)))
|
||||
|
||||
static __inline void
|
||||
_b_trunc(volatile double *_dp)
|
||||
{
|
||||
uint32_t _lw;
|
||||
|
||||
GET_LOW_WORD(_lw, *_dp);
|
||||
SET_LOW_WORD(*_dp, _lw & 0xf8000000);
|
||||
}
|
||||
|
||||
/*
|
||||
* Functions internal to the math package, yet not static.
|
||||
*/
|
||||
@ -45,3 +68,5 @@ extern double __exp__E();
|
||||
struct Double {double a, b;};
|
||||
double __exp__D(double, double);
|
||||
struct Double __log__D(double);
|
||||
|
||||
#endif /* !_MATHIMPL_H_ */
|
||||
|
Loading…
Reference in New Issue
Block a user