git: 93fc67896550 - main - Fix incorrect powf(3) result with x near 1 and |y| much larger than 1
Dimitry Andric
dim at FreeBSD.org
Mon Feb 8 19:49:01 UTC 2021
The branch main has been updated by dim:
URL: https://cgit.FreeBSD.org/src/commit/?id=93fc67896550548f91b307dbe3053f11db5d4a8a
commit 93fc67896550548f91b307dbe3053f11db5d4a8a
Author: Steve Kargl <sgk at troutmask.apl.washington.edu>
AuthorDate: 2021-02-08 19:45:30 +0000
Commit: Dimitry Andric <dim at FreeBSD.org>
CommitDate: 2021-02-08 19:48:43 +0000
Fix incorrect powf(3) result with x near 1 and |y| much larger than 1
This adjusts the check to trigger overflow/underflow to a slightly lower
value.
Before: powf(9.999995e-01, -1.342177e+08) -> inf
After: powf(9.999995e-01, -1.342177e+08) -> 1.858724e+31
MFC after: 1 week
---
lib/msun/src/e_powf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/msun/src/e_powf.c b/lib/msun/src/e_powf.c
index 53f1d37d6bec..33eedad50b16 100644
--- a/lib/msun/src/e_powf.c
+++ b/lib/msun/src/e_powf.c
@@ -136,7 +136,7 @@ __ieee754_powf(float x, float y)
/* |y| is huge */
if(iy>0x4d000000) { /* if |y| > 2**27 */
/* over/underflow if x is not close to one */
- if(ix<0x3f7ffff8) return (hy<0)? sn*huge*huge:sn*tiny*tiny;
+ if(ix<0x3f7ffff7) return (hy<0)? sn*huge*huge:sn*tiny*tiny;
if(ix>0x3f800007) return (hy>0)? sn*huge*huge:sn*tiny*tiny;
/* now |1-x| is tiny <= 2**-20, suffice to compute
log(x) by x-x^2/2+x^3/3-x^4/4 */
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