X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fmath%2Fi386%2Facos.s;h=47f365efb1ea7493c34f7d64b7db33761e4337bd;hb=58bba42d1bd14e1ab01f3249ffc98afdbf841a6a;hp=bfff0c5c9a89d3332ea7df6a8e5d3cd0a68a01f3;hpb=a4a0c91275788407763b1e5a9da17b777495ca85;p=musl

diff --git a/src/math/i386/acos.s b/src/math/i386/acos.s
index bfff0c5c..47f365ef 100644
--- a/src/math/i386/acos.s
+++ b/src/math/i386/acos.s
@@ -1,3 +1,5 @@
+# use acos(x) = atan2(fabs(sqrt((1-x)*(1+x))), x)
+
 .global acosf
 .type acosf,@function
 acosf:
@@ -14,17 +16,13 @@ acosl:
 .type acos,@function
 acos:
 	fldl 4(%esp)
-1:	fld1
-	fld %st(1)
+1:	fld %st(0)
 	fld1
-	fsubp
-	fsqrt
-	fxch %st(2)
-	faddp
+	fsub %st(0),%st(1)
+	fadd %st(2)
+	fmulp
 	fsqrt
+	fabs         # fix sign of zero (matters in downward rounding mode)
+	fxch %st(1)
 	fpatan
-	fld1
-	fld1
-	faddp
-	fmulp
 	ret