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authorDenys Vlasenko <vda.linux@googlemail.com>2010-10-30 22:45:06 (GMT)
committerDenys Vlasenko <vda.linux@googlemail.com>2010-10-30 22:45:06 (GMT)
commite9807e243b454b06f279d7593abaeb74c73aef1e (patch)
treef78686c8bdd4e92e69232d10e5dd5452e9486c30 /libm
parent4435b3ae24b6f76892b7c06c300687c23fab2729 (diff)
libm: fix remaining failures in test-float
These two failures are fixed: Failure: Test: ilogb (0.0) == FP_ILOGB0 plus exceptions allowed Failure: Test: ilogb (NaN) == FP_ILOGBNAN plus exceptions allowed Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'libm')
-rw-r--r--libm/s_ilogb.c47
1 files changed, 31 insertions, 16 deletions
diff --git a/libm/s_ilogb.c b/libm/s_ilogb.c
index ce30296..259ae7b 100644
--- a/libm/s_ilogb.c
+++ b/libm/s_ilogb.c
@@ -10,9 +10,10 @@
*/
/* ilogb(double x)
- * return the binary exponent of non-zero x
- * ilogb(0) = 0x80000001
- * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
+ * return the binary exponent of x
+ * ilogb(+-0) = FP_ILOGB0
+ * ilogb(+-inf) = INT_MAX
+ * ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
*/
#include "math.h"
@@ -22,21 +23,35 @@ int ilogb(double x)
{
int32_t hx,lx,ix;
- GET_HIGH_WORD(hx,x);
+ GET_HIGH_WORD(hx, x);
hx &= 0x7fffffff;
- if(hx<0x00100000) {
- GET_LOW_WORD(lx,x);
- if((hx|lx)==0)
- return 0x80000001; /* ilogb(0) = 0x80000001 */
- else /* subnormal x */
- if(hx==0) {
- for (ix = -1043; lx>0; lx<<=1) ix -=1;
- } else {
- for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
+
+ if (hx < 0x00100000) {
+ GET_LOW_WORD(lx, x);
+ if ((hx|lx)==0) /* +-0, ilogb(0) = FP_ILOGB0 */
+ return FP_ILOGB0;
+ /* subnormal x */
+ ix = -1043;
+ if (hx != 0) {
+ ix = -1022;
+ lx = (hx << 11);
}
- return ix;
+ /* each leading zero mantissa bit makes exponent smaller */
+ for (; lx > 0; lx <<= 1)
+ ix--;
+ return ix;
}
- else if (hx<0x7ff00000) return (hx>>20)-1023;
- else return 0x7fffffff;
+
+ if (hx < 0x7ff00000) /* normal x */
+ return (hx>>20) - 1023;
+
+ if (FP_ILOGBNAN != (~0U >> 1)) {
+ GET_LOW_WORD(lx, x);
+ if (hx == 0x7ff00000 && lx == 0) /* +-inf */
+ return ~0U >> 1; /* = INT_MAX */
+ }
+
+ /* NAN. ilogb(NAN) = FP_ILOGBNAN */
+ return FP_ILOGBNAN;
}
libm_hidden_def(ilogb)