From f17ac40d7cb8e8c462476b6ab703262f6b8f6da8 Mon Sep 17 00:00:00 2001
From: Joseph Myers <joseph@codesourcery.com>
Date: Fri, 6 Jul 2012 11:17:41 +0000
Subject: Fix expm1 spurious underflow exceptions (bug 6778).

---
 sysdeps/i386/fpu/e_expl.S | 42 ++++++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 14 deletions(-)

(limited to 'sysdeps/i386/fpu/e_expl.S')

diff --git a/sysdeps/i386/fpu/e_expl.S b/sysdeps/i386/fpu/e_expl.S
index bab0a08..e42c9a1 100644
--- a/sysdeps/i386/fpu/e_expl.S
+++ b/sysdeps/i386/fpu/e_expl.S
@@ -60,10 +60,12 @@ c1:	.byte 0x20, 0xfa, 0xee, 0xc2, 0x5f, 0x70, 0xa5, 0xec, 0xed, 0x3f
 	.byte 0, 0, 0, 0, 0, 0
 	ASM_SIZE_DIRECTIVE(c1)
 #endif
+#ifndef USE_AS_EXPM1L
 	ASM_TYPE_DIRECTIVE(csat,@object)
 csat:	.byte 0, 0, 0, 0, 0, 0, 0, 0x80, 0x0e, 0x40
 	.byte 0, 0, 0, 0, 0, 0
 	ASM_SIZE_DIRECTIVE(csat)
+#endif
 
 #ifdef PIC
 # define MO(op) op##@GOTOFF(%ecx)
@@ -88,9 +90,26 @@ ENTRY(IEEE754_EXPL)
 #ifdef PIC
 	LOAD_PIC_REG (cx)
 #endif
-#ifndef USE_AS_EXPM1L
+#ifdef USE_AS_EXPM1L
+	xorb	$0x80, %ah
+	cmpl	$0xc006, %eax
+	fstsw	%ax
+	movb	$0x45, %dh
+	jb	4f
+
+	/* Below -64.0 (may be -NaN or -Inf). */
+	andb	%ah, %dh
+	cmpb	$0x01, %dh
+	je	2f		/* Is +-NaN, jump.  */
+	jmp	1f		/* -large, possibly -Inf.  */
+
+4:	/* In range -64.0 to 64.0 (may be +-0 but not NaN or +-Inf).  */
+	/* Test for +-0 as argument.  */
+	andb	%ah, %dh
+	cmpb	$0x40, %dh
+	je	2f
+#else
 	movzwl	4+8(%esp), %eax
-#endif
 	andl	$0x7fff, %eax
 	cmpl	$0x400d, %eax
 	jle	3f
@@ -108,16 +127,8 @@ ENTRY(IEEE754_EXPL)
 	andb	$2, %ah
 	jz	3f
 	fchs
-3:
-#ifdef USE_AS_EXPM1L
-	/* Test for +-0 as argument.  */
-	fstsw	%ax
-	movb	$0x45, %dh
-	andb	%ah, %dh
-	cmpb	$0x40, %dh
-	je	2f
 #endif
-	FLDLOG			/* 1  log2(base)      */
+3:	FLDLOG			/* 1  log2(base)      */
 	fmul	%st(1), %st	/* 1  x log2(base)    */
 	frndint			/* 1  i               */
 	fld	%st(1)		/* 2  x               */
@@ -154,13 +165,16 @@ ENTRY(IEEE754_EXPL)
 #endif
 	fstp	%st(1)		/* 0  */
 	jmp	2f
-1:	testl	$0x200, %eax	/* Test sign.  */
-	jz	2f		/* If positive, jump.  */
-	fstp	%st
+1:
 #ifdef USE_AS_EXPM1L
+	/* For expm1l, only negative sign gets here.  */
+	fstp	%st
 	fld1
 	fchs
 #else
+	testl	$0x200, %eax	/* Test sign.  */
+	jz	2f		/* If positive, jump.  */
+	fstp	%st
 	fldz			/* Set result to 0.  */
 #endif
 2:	ret
-- 
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