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Fix incorrect powf(3) result with x near 1 and |y| much larger than 1

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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
This commit is contained in:
Steve Kargl 2021-02-08 20:45:30 +01:00 committed by Dimitry Andric
parent b577047027
commit 93fc678965
1 changed files with 1 additions and 1 deletions
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2
lib/msun/src/e_powf.c
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@ -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 */