summaryrefslogtreecommitdiff
path: root/libm
diff options
context:
space:
mode:
authorDenys Vlasenko <vda.linux@googlemail.com>2010-10-30 19:25:35 (GMT)
committerDenys Vlasenko <vda.linux@googlemail.com>2010-10-30 19:25:35 (GMT)
commitae73aafe99fa6bb5e7422f2bdedea39f03ead72c (patch)
tree2c59bc465420754aa745281455012f2c970141cf /libm
parent0b73115a0961fca9e042e02ed644cb85e251cbb6 (diff)
libm: fix powf testcase failures
Fixed failures: Failure: Test: pow (1, NaN) == 1 Failure: Test: pow (1, inf) == 1 Failure: Test: pow (-1, inf) == 1 Failure: Test: pow (1, -inf) == 1 Failure: Test: pow (-1, -inf) == 1 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'libm')
-rw-r--r--libm/e_pow.c63
1 files changed, 35 insertions, 28 deletions
diff --git a/libm/e_pow.c b/libm/e_pow.c
index 137f600..3be9003 100644
--- a/libm/e_pow.c
+++ b/libm/e_pow.c
@@ -21,25 +21,26 @@
* 3. Return x**y = 2**n*exp(y'*log2)
*
* Special cases:
- * 1. (anything) ** 0 is 1
- * 2. (anything) ** 1 is itself
- * 3. (anything) ** NAN is NAN
- * 4. NAN ** (anything except 0) is NAN
- * 5. +-(|x| > 1) ** +INF is +INF
- * 6. +-(|x| > 1) ** -INF is +0
- * 7. +-(|x| < 1) ** +INF is +0
- * 8. +-(|x| < 1) ** -INF is +INF
- * 9. +-1 ** +-INF is NAN
- * 10. +0 ** (+anything except 0, NAN) is +0
- * 11. -0 ** (+anything except 0, NAN, odd integer) is +0
- * 12. +0 ** (-anything except 0, NAN) is +INF
- * 13. -0 ** (-anything except 0, NAN, odd integer) is +INF
- * 14. -0 ** (odd integer) = -( +0 ** (odd integer) )
- * 15. +INF ** (+anything except 0,NAN) is +INF
- * 16. +INF ** (-anything except 0,NAN) is +0
- * 17. -INF ** (anything) = -0 ** (-anything)
- * 18. (-anything) ** (integer) is (-1)**(integer)*(+anything**integer)
- * 19. (-anything except 0 and inf) ** (non-integer) is NAN
+ * 1. +-1 ** anything is 1.0
+ * 2. +-1 ** +-INF is 1.0
+ * 3. (anything) ** 0 is 1
+ * 4. (anything) ** 1 is itself
+ * 5. (anything) ** NAN is NAN
+ * 6. NAN ** (anything except 0) is NAN
+ * 7. +-(|x| > 1) ** +INF is +INF
+ * 8. +-(|x| > 1) ** -INF is +0
+ * 9. +-(|x| < 1) ** +INF is +0
+ * 10 +-(|x| < 1) ** -INF is +INF
+ * 11. +0 ** (+anything except 0, NAN) is +0
+ * 12. -0 ** (+anything except 0, NAN, odd integer) is +0
+ * 13. +0 ** (-anything except 0, NAN) is +INF
+ * 14. -0 ** (-anything except 0, NAN, odd integer) is +INF
+ * 15. -0 ** (odd integer) = -( +0 ** (odd integer) )
+ * 16. +INF ** (+anything except 0,NAN) is +INF
+ * 17. +INF ** (-anything except 0,NAN) is +0
+ * 18. -INF ** (anything) = -0 ** (-anything)
+ * 19. (-anything) ** (integer) is (-1)**(integer)*(+anything**integer)
+ * 20. (-anything except 0 and inf) ** (non-integer) is NAN
*
* Accuracy:
* pow(x,y) returns x**y nearly rounded. In particular
@@ -99,8 +100,14 @@ double attribute_hidden __ieee754_pow(double x, double y)
u_int32_t lx,ly;
EXTRACT_WORDS(hx,lx,x);
+ /* x==1: 1**y = 1 (even if y is NaN) */
+ if (hx==0x3ff00000 && lx==0) {
+ return x;
+ }
+ ix = hx&0x7fffffff;
+
EXTRACT_WORDS(hy,ly,y);
- ix = hx&0x7fffffff; iy = hy&0x7fffffff;
+ iy = hy&0x7fffffff;
/* y==zero: x**0 = 1 */
if((iy|ly)==0) return one;
@@ -132,13 +139,13 @@ double attribute_hidden __ieee754_pow(double x, double y)
/* special value of y */
if(ly==0) {
- if (iy==0x7ff00000) { /* y is +-inf */
- if(((ix-0x3ff00000)|lx)==0)
- return y - y; /* inf**+-1 is NaN */
- else if (ix >= 0x3ff00000)/* (|x|>1)**+-inf = inf,0 */
- return (hy>=0)? y: zero;
- else /* (|x|<1)**-,+inf = inf,0 */
- return (hy<0)?-y: zero;
+ if (iy==0x7ff00000) { /* y is +-inf */
+ if (((ix-0x3ff00000)|lx)==0)
+ return one; /* +-1**+-inf is 1 (yes, weird rule) */
+ if (ix >= 0x3ff00000) /* (|x|>1)**+-inf = inf,0 */
+ return (hy>=0) ? y : zero;
+ /* (|x|<1)**-,+inf = inf,0 */
+ return (hy<0) ? -y : zero;
}
if(iy==0x3ff00000) { /* y is +-1 */
if(hy<0) return one/x; else return x;
@@ -146,7 +153,7 @@ double attribute_hidden __ieee754_pow(double x, double y)
if(hy==0x40000000) return x*x; /* y is 2 */
if(hy==0x3fe00000) { /* y is 0.5 */
if(hx>=0) /* x >= +0 */
- return __ieee754_sqrt(x);
+ return __ieee754_sqrt(x);
}
}