X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fmath%2Fi386%2Facos.s;h=47f365efb1ea7493c34f7d64b7db33761e4337bd;hb=6f64505df37c41d7496612dffe86048765339a7a;hp=4f0168f623d1f0294324b286ad90e2e9d2c46785;hpb=804fbf0b8c00fd4e2f37ef0769a610614d06138f;p=musl

diff --git a/src/math/i386/acos.s b/src/math/i386/acos.s
index 4f0168f6..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:
@@ -14,19 +16,13 @@ acosl:
 .type acos,@function
 acos:
 	fldl 4(%esp)
-1:	fld1
-	fld %st(1)
+1:	fld %st(0)
 	fld1
-	fsubp
-	fxch %st(2)
-	faddp
-	fdivp
+	fsub %st(0),%st(1)
+	fadd %st(2)
+	fmulp
 	fsqrt
-	fld1
+	fabs         # fix sign of zero (matters in downward rounding mode)
 	fxch %st(1)
 	fpatan
-	fld1
-	fld1
-	faddp
-	fmulp
 	ret