From 292815eac623035493854f133200a4b1041fa246 Mon Sep 17 00:00:00 2001 From: Mark Murray Date: Mon, 6 Sep 2021 18:26:39 +0100 Subject: [PATCH] Fix powf(). Summary: From Steve Kargl: Paul Zimmermann has identified a bug in Openlibm's powf(), which is identical to FreeBSD's libm. Both derived from fdlibm. https://github.com/JuliaMath/openlibm/issues/212. Consider % cat h.c int main(void) { float x, y, z; x = 0x1.ffffecp-1F; y = -0x1.000002p+27F; z = 0x1.557a86p115F; printf("%e %e %e <-- should be %e\n", x, y, powf(x,y), z); return 0; } % cc -o h -fno-builtin h.c -lm && ./h 9.999994e-01 -1.342177e+08 inf <-- should be 5.540807e+34 Reviewers: manu Subscribers: imp, andrew, emaste Differential Revision: https://reviews.freebsd.org/D31865 --- 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 33eedad50b16..122da455f740 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<0x3f7ffff7) return (hy<0)? sn*huge*huge:sn*tiny*tiny; + if(ix<0x3f7ffff6) 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 */