From 31c5fb80b9eae86f801be4f46025bc6532a554c5 Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <nsz@port70.net>
Date: Thu, 15 Aug 2013 10:56:57 +0000
Subject: math: fix x86 asin, atan, exp, log1p to raise underflow

underflow is raised by an inexact subnormal float store,
since subnormal operations are slow, check the underflow
flag and skip the store if it's already raised
---
 src/math/i386/asin.s | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

(limited to 'src/math/i386/asin.s')

diff --git a/src/math/i386/asin.s b/src/math/i386/asin.s
index 932c7542..a9f691bf 100644
--- a/src/math/i386/asin.s
+++ b/src/math/i386/asin.s
@@ -2,7 +2,18 @@
 .type asinf,@function
 asinf:
 	flds 4(%esp)
-	jmp 1f
+	mov 4(%esp),%eax
+	add %eax,%eax
+	cmp $0x01000000,%eax
+	jae 1f
+		# subnormal x, return x with underflow
+	fnstsw %ax
+	and $16,%ax
+	jnz 2f
+	fld %st(0)
+	fmul %st(1)
+	fstps 4(%esp)
+2:	ret
 
 .global asinl
 .type asinl,@function
@@ -14,6 +25,16 @@ asinl:
 .type asin,@function
 asin:
 	fldl 4(%esp)
+	mov 8(%esp),%eax
+	add %eax,%eax
+	cmp $0x00200000,%eax
+	jae 1f
+		# subnormal x, return x with underflow
+	fnstsw %ax
+	and $16,%ax
+	jnz 2f
+	fsts 4(%esp)
+2:	ret
 1:	fld %st(0)
 	fld1
 	fsub %st(0),%st(1)
-- 
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