From: nsz <nsz@port70.net>
Date: Thu, 22 Mar 2012 13:54:47 +0000 (+0100)
Subject: acos.s fix: use the formula acos(x) = atan2(sqrt(1-x),sqrt(1+x))
X-Git-Tag: v0.8.8~75
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=a4a0c91275788407763b1e5a9da17b777495ca85;p=oweals%2Fmusl.git

acos.s fix: use the formula acos(x) = atan2(sqrt(1-x),sqrt(1+x))

the old formula atan2(1,sqrt((1+x)/(1-x))) was faster but
could give nan result at x=1 when the rounding mode is
FE_DOWNWARD (so 1-1 == -0 and 2/-0 == -inf), the new formula
gives -0 at x=+-1 with downward rounding.
---

diff --git a/src/math/i386/acos.s b/src/math/i386/acos.s
index 4f0168f6..bfff0c5c 100644
--- a/src/math/i386/acos.s
+++ b/src/math/i386/acos.s
@@ -18,12 +18,10 @@ acos:
 	fld %st(1)
 	fld1
 	fsubp
+	fsqrt
 	fxch %st(2)
 	faddp
-	fdivp
 	fsqrt
-	fld1
-	fxch %st(1)
 	fpatan
 	fld1
 	fld1
diff --git a/src/math/x86_64/acosl.s b/src/math/x86_64/acosl.s
index 92c29870..db68d2de 100644
--- a/src/math/x86_64/acosl.s
+++ b/src/math/x86_64/acosl.s
@@ -6,12 +6,10 @@ acosl:
 	fld %st(1)
 	fld1
 	fsubp
+	fsqrt
 	fxch %st(2)
 	faddp
-	fdivp
 	fsqrt
-	fld1
-	fxch %st(1)
 	fpatan
 	fld1
 	fld1