From 02343946215a7ae03634c6490abcc69da68df589 Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <nsz@port70.net>
Date: Thu, 5 Sep 2013 12:23:44 +0000
Subject: math: fix expm1l on x86_64 (avoid underflow for large negative x)

copy the fix from i386: return -1 instead of exp2l(x)-1 when x <= -65
---
 src/math/x86_64/exp2l.s | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

(limited to 'src/math/x86_64/exp2l.s')

diff --git a/src/math/x86_64/exp2l.s b/src/math/x86_64/exp2l.s
index e7145881..0d6cd563 100644
--- a/src/math/x86_64/exp2l.s
+++ b/src/math/x86_64/exp2l.s
@@ -4,8 +4,18 @@ expm1l:
 	fldt 8(%rsp)
 	fldl2e
 	fmulp
+	movl $0xc2820000,-4(%rsp)
+	flds -4(%rsp)
+	fucomp %st(1)
+	fnstsw %ax
+	sahf
 	fld1
-	fld %st(1)
+	jb 1f
+		# x*log2e <= -65, return -1 without underflow
+	fstp %st(1)
+	fchs
+	ret
+1:	fld %st(1)
 	fabs
 	fucom %st(1)
 	fnstsw %ax
-- 
cgit v1.2.1