Fix ilogb exception and errno (bug 6794)

[BZ #6794]
Following Joseph comments about bug 6794, here is a proposed fix. It turned out
to be a large fix mainly because I had to move some file along to follow libm
files/names conventions.

Basically I have added wrappers (w_ilogb.c, w_ilogbf.c, w_ilogbl.c) that now calls
the symbol '__ieee754_ilogb'. The wrappers checks for '__ieee754_ilogb' output and
set the errno and raise exceptions as expected.

The '__ieee754_ilogb' is implemented in sysdeps. I have moved the 's_ilogb[f|l]' files
to e_ilogb[f|l] and renamed the '__ilogb[f|l]' to '__ieee754_ilogb[f|l]'.

I also found out a bug in i386 and x86-64 assembly coded ilogb implementation where
it raises a FE_DIVBYZERO when argument is '0.0'. I corrected this issue as well.

Finally I added the errno and FE_INVALID tests for 0.0, NaN and +-InF argument. Tested
on i386, x86-64, ppc32 and ppc64.

3 files changed, 24 insertions, 9 deletions

diff --git a/sysdeps/i386/fpu/s_ilogb.S b/sysdeps/i386/fpu/e_ilogb.S
index 0cf1ad7..4fb6350 100644
--- a/sysdeps/i386/fpu/s_ilogb.S
+++ b/sysdeps/i386/fpu/e_ilogb.S
@@ -7,7 +7,7 @@
 
 RCSID("$NetBSD: s_ilogb.S,v 1.5 1995/10/12 15:53:09 jtc Exp $")
 
-ENTRY(__ilogb)
+ENTRY(__ieee754_ilogb)
 	fldl	4(%esp)
 /* I added the following ugly construct because ilogb(+-Inf) is
    required to return INT_MAX in ISO C99.
@@ -18,6 +18,8 @@ ENTRY(__ilogb)
 	andb    %ah, %dh
 	cmpb    $0x05, %dh
 	je      1f		/* Is +-Inf, jump.  */
+	cmpb    $0x40, %dh
+	je      2f		/* Is +-0, jump.  */
 
 	fxtract
 	pushl	%eax
@@ -34,5 +36,8 @@ ENTRY(__ilogb)
 1:	fstp	%st
 	movl	$0x7fffffff, %eax
 	ret
-END (__ilogb)
-weak_alias (__ilogb, ilogb)
+2:	fstp	%st
+	movl	$0x80000000, %eax	/* FP_ILOGB0  */
+	ret
+END (__ieee754_ilogb)
+weak_alias (__ieee754_ilogb, __ilogb_finite)
diff --git a/sysdeps/i386/fpu/s_ilogbf.S b/sysdeps/i386/fpu/e_ilogbf.S
index 99e53ed..fbb50be 100644
--- a/sysdeps/i386/fpu/s_ilogbf.S
+++ b/sysdeps/i386/fpu/e_ilogbf.S
@@ -7,7 +7,7 @@
 
 RCSID("$NetBSD: s_ilogbf.S,v 1.4 1995/10/22 20:32:43 pk Exp $")
 
-ENTRY(__ilogbf)
+ENTRY(__ieee754_ilogbf)
 	flds	4(%esp)
 /* I added the following ugly construct because ilogb(+-Inf) is
    required to return INT_MAX in ISO C99.
@@ -18,6 +18,8 @@ ENTRY(__ilogbf)
 	andb    %ah, %dh
 	cmpb    $0x05, %dh
 	je      1f		/* Is +-Inf, jump.  */
+	cmpb    $0x40, %dh
+	je      2f		/* Is +-0, jump.  */
 
 	fxtract
 	pushl	%eax
@@ -34,5 +36,8 @@ ENTRY(__ilogbf)
 1:	fstp	%st
 	movl	$0x7fffffff, %eax
 	ret
-END (__ilogbf)
-weak_alias (__ilogbf, ilogbf)
+2:	fstp	%st
+	movl	$0x80000000, %eax	/* FP_ILOGB0  */
+	ret
+END (__ieee754_ilogbf)
+weak_alias (__ieee754_ilogbf, __ilogbf_finite)
diff --git a/sysdeps/i386/fpu/s_ilogbl.S b/sysdeps/i386/fpu/e_ilogbl.S
index 1f559b3..6e2be9a 100644
--- a/sysdeps/i386/fpu/s_ilogbl.S
+++ b/sysdeps/i386/fpu/e_ilogbl.S
@@ -8,7 +8,7 @@
 
 RCSID("$NetBSD: $")
 
-ENTRY(__ilogbl)
+ENTRY(__ieee754_ilogbl)
 	fldt	4(%esp)
 /* I added the following ugly construct because ilogb(+-Inf) is
    required to return INT_MAX in ISO C99.
@@ -19,6 +19,8 @@ ENTRY(__ilogbl)
 	andb    %ah, %dh
 	cmpb    $0x05, %dh
 	je      1f		/* Is +-Inf, jump.  */
+	cmpb    $0x40, %dh
+	je      2f		/* Is +-0, jump.  */
 
 	fxtract
 	pushl	%eax
@@ -35,5 +37,8 @@ ENTRY(__ilogbl)
 1:	fstp	%st
 	movl	$0x7fffffff, %eax
 	ret
-END (__ilogbl)
-weak_alias (__ilogbl, ilogbl)
+2:	fstp	%st
+	movl	$0x80000000, %eax	/* FP_ILOGB0  */
+	ret
+END (__ieee754_ilogbl)
+weak_alias (__ieee754_ilogbl, __ilogbl_finite)