mirror/glibc
2
0
Fork 0
mirror of git://sourceware.org/git/glibc.git synced 2024-12-09 04:11:27 +08:00
Code Issues Packages Projects Releases Wiki Activity

Fix sysdeps/ieee754 pow handling of sNaN arguments (bug 20916).

Browse Source 
Various pow function implementations mishandle sNaN arguments in
various ways.  This includes returning sNaN instead of qNaN for sNaN
arguments.  For arguments (1, sNaN) and (sNaN, 0), TS 18661-1
semantics are also that the result should be qNaN, whereas with a qNaN
argument there the result should be 1, but for the dbl-64
implementation of pow there are issues with sNaN arguments beyond not
implementing the TS 18661-1 semantics in those special cases.

This patch makes the implementations in sysdeps/ieee754 follow the TS
18661-1 semantics consistently.  Because x86 / x86_64 implementations
still need fixing, testcases are not included with this patch; they
will be included with the fix for the x86 / x86_64 versions.

Tested for x86_64, x86, mips64 and powerpc (with such testcases, which
pass in the mips64 and powerpc cases).

	[BZ #20916]
	* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Do not return 1
	for arguments (sNaN, 0) or (1, sNaN).  Do arithmetic on NaN
	arguments to compute result.
	* sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): Do not return
	1 for arguments (sNaN, 0) or (1, sNaN).
	* sysdeps/ieee754/ldbl-128/e_powl.c (__ieee754_powl): Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_powl.c (__ieee754_powl): Likewise.
This commit is contained in:
Joseph Myers 2016-12-02 23:21:15 +00:00
parent 72d839a42f
commit 90ab295a9e
5 changed files with 21 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
ChangeLog
View File

@ -1,5 +1,14 @@
2016-12-02 Joseph Myers <joseph@codesourcery.com>
[BZ #20916]
* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Do not return 1
for arguments (sNaN, 0) or (1, sNaN). Do arithmetic on NaN
arguments to compute result.
* sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): Do not return
1 for arguments (sNaN, 0) or (1, sNaN).
* sysdeps/ieee754/ldbl-128/e_powl.c (__ieee754_powl): Likewise.
* sysdeps/ieee754/ldbl-128ibm/e_powl.c (__ieee754_powl): Likewise.
[BZ #20919]
* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Do not return
NaN first argument when raised to power 0.

10
sysdeps/ieee754/dbl-64/e_pow.c
View File

@ -74,8 +74,8 @@ __ieee754_pow (double x, double y)
qx = u.i[HIGH_HALF] & 0x7fffffff;
/* Is x a NaN? */
if ((((qx == 0x7ff00000) && (u.i[LOW_HALF] != 0)) || (qx > 0x7ff00000))
&& y != 0)
return x;
&& (y != 0 || issignaling (x)))
return x + x;
if (y == 1.0)
return x;
if (y == 2.0)
@ -129,7 +129,7 @@ __ieee754_pow (double x, double y)
{
if (((v.i[HIGH_HALF] & 0x7fffffff) == 0x7ff00000 && v.i[LOW_HALF] != 0)
|| (v.i[HIGH_HALF] & 0x7fffffff) > 0x7ff00000) /* NaN */
return y;
return y + y;
if (fabs (y) > 1.0e20)
return (y > 0) ? 0 : 1.0 / 0.0;
k = checkint (y);
@ -143,9 +143,9 @@ __ieee754_pow (double x, double y)
qy = v.i[HIGH_HALF] & 0x7fffffff; /* no sign */
if (qx >= 0x7ff00000 && (qx > 0x7ff00000 || u.i[LOW_HALF] != 0)) /* NaN */
return x;
return x + y;
if (qy >= 0x7ff00000 && (qy > 0x7ff00000 || v.i[LOW_HALF] != 0)) /* NaN */
return x == 1.0 ? 1.0 : y;
return x == 1.0 && !issignaling (y) ? 1.0 : y + y;
/* if x<0 */
if (u.i[HIGH_HALF] < 0)

4
sysdeps/ieee754/flt-32/e_powf.c
View File

@ -62,10 +62,10 @@ __ieee754_powf(float x, float y)
ix = hx&0x7fffffff; iy = hy&0x7fffffff;
/* y==zero: x**0 = 1 */
if(iy==0) return one;
if(iy==0 && !issignaling (x)) return one;
/* x==+-1 */
if(x == 1.0) return one;
if(x == 1.0 && !issignaling (y)) return one;
if(x == -1.0 && isinf(y)) return one;
/* +-NaN return x+y */

5
sysdeps/ieee754/ldbl-128/e_powl.c
View File

@ -165,11 +165,12 @@ __ieee754_powl (_Float128 x, _Float128 y)
/* y==zero: x**0 = 1 */
if ((iy | q.parts32.w1 | q.parts32.w2 | q.parts32.w3) == 0)
if ((iy | q.parts32.w1 | q.parts32.w2 | q.parts32.w3) == 0
&& !issignaling (x))
return one;
/* 1.0**y = 1; -1.0**+-Inf = 1 */
if (x == one)
if (x == one && !issignaling (y))
return one;
if (x == -1 && iy == 0x7fff0000
&& (q.parts32.w1 | q.parts32.w2 | q.parts32.w3) == 0)

4
sysdeps/ieee754/ldbl-128ibm/e_powl.c
View File

@ -165,11 +165,11 @@ __ieee754_powl (long double x, long double y)
iy = hy & 0x7fffffff;
/* y==zero: x**0 = 1 */
if ((iy | ly) == 0)
if ((iy | ly) == 0 && !issignaling (x))
return one;
/* 1.0**y = 1; -1.0**+-Inf = 1 */
if (x == one)
if (x == one && !issignaling (y))
return one;
if (x == -1.0L && ((iy - 0x7ff00000) | ly) == 0)
return one;