From aa1b4dff45788f8205e32ea01da243fe09568aa8 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sun, 18 Mar 2012 23:17:28 -0400
Subject: [PATCH] fix broken exponential asm

infinities were getting converted into nans. the new code simply tests
for infinity and replaces it with a large magnitude value of the same
sign.

also, the fcomi instruction is apparently not part of the i387
instruction set, so avoid using it.
---
 src/math/i386/exp.s   |  9 +++++++++
 src/math/i386/expm1.s | 13 ++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/math/i386/exp.s b/src/math/i386/exp.s
index 18f6cd67..f4769d59 100644
--- a/src/math/i386/exp.s
+++ b/src/math/i386/exp.s
@@ -34,6 +34,15 @@ exp:
 .type exp2,@function
 exp2:
 	fldl 4(%esp)
+1:	fxam
+	fnstsw %ax
+	sahf
+	jnp 1f
+	jnc 1f
+	fstps 4(%esp)
+	mov $0xfe,%al
+	and %al,7(%esp)
+	flds 4(%esp)
 1:	fld %st(0)
 	frndint
 	fxch %st(1)
diff --git a/src/math/i386/expm1.s b/src/math/i386/expm1.s
index d6d511ef..bbb5d12e 100644
--- a/src/math/i386/expm1.s
+++ b/src/math/i386/expm1.s
@@ -14,12 +14,23 @@ expm1l:
 .type expm1,@function
 expm1:
 	fldl 4(%esp)
+1:	fxam
+	fnstsw %ax
+	sahf
+	jnp 1f
+	jnc 1f
+	fstps 4(%esp)
+	mov $0xfe,%al
+	and %al,7(%esp)
+	flds 4(%esp)
 1:	fldl2e
 	fmulp
 	fld %st(0)
 	frndint
 	fldz
-	fcompi
+	fcomp
+	fnstsw %ax
+	sahf
 	jnz 1f
 	fstp %st(0)
 	f2xm1
-- 
2.25.1