Fix i386/x86_64 log* (1) zero sign for -ffinite-math-only (bug 19213).

For the -ffinite-math-only versions of various x86_64 and x86 log*
functions, a zero result from log* (1) is returned with incorrect sign
in round-downward mode.  This patch fixes this in a similar way to the
previous fixes for the non-*_finite versions of the functions.

Tested for x86_64 and x86 (including an i586 build), together with a
patch that will be applied separately to enable the main libm-test.inc
tests for the finite-math-only functions.

	[BZ #19213]
	* sysdeps/i386/fpu/e_log.S (__log_finite): Ensure +0 is always
	returned for argument 1.
	* sysdeps/i386/fpu/e_logf.S (__logf_finite): Likewise.
	* sysdeps/i386/fpu/e_logl.S (__logl_finite): Likewise.
	* sysdeps/i386/i686/fpu/e_logl.S (__logl_finite): Likewise.
	* sysdeps/x86_64/fpu/e_log10l.S (__log10l_finite): Likewise.
	* sysdeps/x86_64/fpu/e_log2l.S (__log2l_finite): Likewise.
	* sysdeps/x86_64/fpu/e_logl.S (__logl_finite): Likewise.

9 files changed, 60 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index 9c78a11..95dae4b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,15 @@
 2015-11-05  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #19213]
+	* sysdeps/i386/fpu/e_log.S (__log_finite): Ensure +0 is always
+	returned for argument 1.
+	* sysdeps/i386/fpu/e_logf.S (__logf_finite): Likewise.
+	* sysdeps/i386/fpu/e_logl.S (__logl_finite): Likewise.
+	* sysdeps/i386/i686/fpu/e_logl.S (__logl_finite): Likewise.
+	* sysdeps/x86_64/fpu/e_log10l.S (__log10l_finite): Likewise.
+	* sysdeps/x86_64/fpu/e_log2l.S (__log2l_finite): Likewise.
+	* sysdeps/x86_64/fpu/e_logl.S (__logl_finite): Likewise.
+
 	[BZ #19211]
 	* math/bits/math-finite.h (lgamma): Set signgam if [__USE_MISC ||
 	__USE_XOPEN], not if [!__USE_ISOC99].
diff --git a/NEWS b/NEWS
index b462e85..4e41998 100644
--- a/NEWS
+++ b/NEWS
@@ -22,7 +22,7 @@ Version 2.23
   19003, 19007, 19012, 19016, 19018, 19032, 19046, 19048, 19049, 19050,
   19059, 19071, 19074, 19076, 19077, 19078, 19079, 19085, 19086, 19088,
   19094, 19095, 19124, 19125, 19129, 19134, 19137, 19156, 19174, 19181,
-  19189, 19201, 19205, 19209, 19211, 19212.
+  19189, 19201, 19205, 19209, 19211, 19212, 19213.
 
 * A defect in the malloc implementation, present since glibc 2.15 (2012) or
   glibc 2.10 via --enable-experimental-malloc (2009), could result in the
diff --git a/sysdeps/i386/fpu/e_log.S b/sysdeps/i386/fpu/e_log.S
index 3fa32aa..335df22 100644
--- a/sysdeps/i386/fpu/e_log.S
+++ b/sysdeps/i386/fpu/e_log.S
@@ -80,7 +80,13 @@ ENTRY(__log_finite)
 	fnstsw			// x-1 : x : log(2)
 	andb	$0x45, %ah
 	jz	2b
-	fstp	%st(1)		// x-1 : log(2)
+	fxam
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	jne	6f
+	fabs			// log(1) is +0 in all rounding modes.
+6:	fstp	%st(1)		// x-1 : log(2)
 	fyl2xp1			// log(x)
 	ret
 END(__log_finite)
diff --git a/sysdeps/i386/fpu/e_logf.S b/sysdeps/i386/fpu/e_logf.S
index ca83d39..de967a3 100644
--- a/sysdeps/i386/fpu/e_logf.S
+++ b/sysdeps/i386/fpu/e_logf.S
@@ -81,7 +81,13 @@ ENTRY(__logf_finite)
 	fnstsw			// x-1 : x : log(2)
 	andb	$0x45, %ah
 	jz	2b
-	fstp	%st(1)		// x-1 : log(2)
+	fxam
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	jne	6f
+	fabs			// log(1) is +0 in all rounding modes.
+6:	fstp	%st(1)		// x-1 : log(2)
 	fyl2xp1			// log(x)
 	ret
 END(__logf_finite)
diff --git a/sysdeps/i386/fpu/e_logl.S b/sysdeps/i386/fpu/e_logl.S
index 828e98a..7a6d370 100644
--- a/sysdeps/i386/fpu/e_logl.S
+++ b/sysdeps/i386/fpu/e_logl.S
@@ -84,7 +84,13 @@ ENTRY(__logl_finite)
 	fnstsw			// x-1 : x : log(2)
 	andb	$0x45, %ah
 	jz	2b
-	fstp	%st(1)		// x-1 : log(2)
+	fxam
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	jne	7f
+	fabs			// log(1) is +0 in all rounding modes.
+7:	fstp	%st(1)		// x-1 : log(2)
 	fyl2xp1			// log(x)
 	ret
 END(__logl_finite)
diff --git a/sysdeps/i386/i686/fpu/e_logl.S b/sysdeps/i386/i686/fpu/e_logl.S
index 0ccc8fc..e9ecbcd 100644
--- a/sysdeps/i386/i686/fpu/e_logl.S
+++ b/sysdeps/i386/i686/fpu/e_logl.S
@@ -81,7 +81,13 @@ ENTRY(__logl_finite)
 	fcomip	%st(1)		// |x-1| : x-1 : x : log(2)
 	fstp	%st(0)		// x-1 : x : log(2)
 	jc	2b
-	fstp	%st(1)		// x-1 : log(2)
+	fxam
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	jne	6f
+	fabs			// log(1) is +0 in all rounding modes.
+6:	fstp	%st(1)		// x-1 : log(2)
 	fyl2xp1			// log(x)
 	ret
 END(__logl_finite)
diff --git a/sysdeps/x86_64/fpu/e_log10l.S b/sysdeps/x86_64/fpu/e_log10l.S
index 2607ad1..8fa6164 100644
--- a/sysdeps/x86_64/fpu/e_log10l.S
+++ b/sysdeps/x86_64/fpu/e_log10l.S
@@ -79,7 +79,13 @@ ENTRY(__log10l_finite)
 	fnstsw			// x-1 : x : log10(2)
 	andb	$0x45, %ah
 	jz	2b
-	fstp	%st(1)		// x-1 : log10(2)
+	fxam
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	jne	6f
+	fabs			// log10(1) is +0 in all rounding modes.
+6:	fstp	%st(1)		// x-1 : log10(2)
 	fyl2xp1			// log10(x)
 	ret
 END(__log10l_finite)
diff --git a/sysdeps/x86_64/fpu/e_log2l.S b/sysdeps/x86_64/fpu/e_log2l.S
index c12906d..a063255 100644
--- a/sysdeps/x86_64/fpu/e_log2l.S
+++ b/sysdeps/x86_64/fpu/e_log2l.S
@@ -78,7 +78,13 @@ ENTRY(__log2l_finite)
 	fnstsw			// x-1 : x : 1
 	andb	$0x45, %ah
 	jz	2b
-	fstp	%st(1)		// x-1 : 1
+	fxam
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	jne	6f
+	fabs			// log2(1) is +0 in all rounding modes.
+6:	fstp	%st(1)		// x-1 : 1
 	fyl2xp1			// log(x)
 	ret
 END (__log2l_finite)
diff --git a/sysdeps/x86_64/fpu/e_logl.S b/sysdeps/x86_64/fpu/e_logl.S
index 047b8db..dbe6fd5 100644
--- a/sysdeps/x86_64/fpu/e_logl.S
+++ b/sysdeps/x86_64/fpu/e_logl.S
@@ -81,7 +81,13 @@ ENTRY(__logl_finite)
 	fnstsw			// x-1 : x : log(2)
 	andb	$0x45, %ah
 	jz	2b
-	fstp	%st(1)		// x-1 : log(2)
+	fxam
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	jne	7f
+	fabs			// log(1) is +0 in all rounding modes.
+7:	fstp	%st(1)		// x-1 : log(2)
 	fyl2xp1			// log(x)
 	ret
 END (__logl_finite)