diff --git a/lib/msun/i387/s_cos.S b/lib/msun/i387/s_cos.S
index 9c3f2caac73b..9951ab0674aa 100644
--- a/lib/msun/i387/s_cos.S
+++ b/lib/msun/i387/s_cos.S
@@ -40,16 +40,16 @@ ENTRY(cos)
 	fldl	4(%esp)
 	fcos
 	fnstsw	%ax
-	andw	$0x400,%ax
-	jnz	1f
+	sahf
+	jp	1f
 	ret	
 1:	fldpi
 	fadd	%st(0)
 	fxch	%st(1)
-2:	fprem1
+2:	fprem
 	fnstsw	%ax
-	andw	$0x400,%ax
-	jnz	2b
+	sahf
+	jp	2b
 	fstp	%st(1)
 	fcos
 	ret
diff --git a/lib/msun/i387/s_sin.S b/lib/msun/i387/s_sin.S
index 11c4d63bbb75..eb047540d736 100644
--- a/lib/msun/i387/s_sin.S
+++ b/lib/msun/i387/s_sin.S
@@ -40,16 +40,16 @@ ENTRY(sin)
 	fldl	4(%esp)
 	fsin
 	fnstsw	%ax
-	andw	$0x400,%ax
-	jnz	1f
+	sahf
+	jp	1f
 	ret
 1:	fldpi
 	fadd	%st(0)
 	fxch	%st(1)
-2:	fprem1
+2:	fprem
 	fnstsw	%ax
-	andw	$0x400,%ax
-	jnz	2b
+	sahf
+	jp	2b
 	fstp	%st(1)
 	fsin
 	ret
diff --git a/lib/msun/i387/s_tan.S b/lib/msun/i387/s_tan.S
index e31ebdff00a3..182b9f76459e 100644
--- a/lib/msun/i387/s_tan.S
+++ b/lib/msun/i387/s_tan.S
@@ -40,17 +40,17 @@ ENTRY(tan)
 	fldl	4(%esp)
 	fptan
 	fnstsw	%ax
-	andw	$0x400,%ax
-	jnz	1f
+	sahf
+	jp	1f
 	fstp	%st(0)
 	ret
 1:	fldpi
 	fadd	%st(0)
 	fxch	%st(1)
-2:	fprem1
-	fstsw	%ax
-	andw	$0x400,%ax
-	jnz	2b
+2:	fprem
+	fnstsw	%ax
+	sahf
+	jp	2b
 	fstp	%st(1)
 	fptan
 	fstp	%st(0)