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.

5 files changed, 136 insertions, 8 deletions

diff --git a/math/Makefile b/math/Makefile
index 3a671aa..abeba7a 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -42,14 +42,16 @@ libm-support = k_standard s_lib_version s_matherr s_signgam		\
 libm-calls = e_acos e_acosh e_asin e_atan2 e_atanh e_cosh e_exp e_fmod	\
 	     e_hypot e_j0 e_j1 e_jn e_lgamma_r e_log e_log10 e_pow	\
 	     e_rem_pio2 e_remainder e_scalb e_sinh e_sqrt e_gamma_r	\
+	     e_ilogb							\
 	     k_cos k_rem_pio2 k_sin k_tan s_asinh s_atan s_cbrt		\
 	     s_ceil s_cos s_erf s_expm1 s_fabs				\
-	     s_floor s_ilogb s_log1p s_logb				\
+	     s_floor s_log1p s_logb					\
 	     s_nextafter s_nexttoward s_rint s_scalbln			\
 	     s_significand s_sin s_tan s_tanh w_acos w_acosh w_asin	\
 	     w_atan2 w_atanh w_cosh w_drem w_exp w_exp2 w_exp10 w_fmod	\
 	     w_tgamma w_hypot w_j0 w_j1 w_jn w_lgamma w_lgamma_r	\
 	     w_log w_log10 w_pow w_remainder w_scalb w_sinh w_sqrt	\
+	     w_ilogb							\
 	     s_fpclassify s_fmax s_fmin s_fdim s_nan s_trunc		\
 	     s_remquo e_log2 e_exp2 s_round s_nearbyint s_sincos	\
 	     conj cimag creal cabs carg s_cexp s_csinh s_ccosh s_clog	\
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 2809d57..94d60bf 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -3802,13 +3802,22 @@ ilogb_test (void)
   TEST_f_i (ilogb, 1024, 10);
   TEST_f_i (ilogb, -2000, 10);
 
-  /* XXX We have a problem here: the standard does not tell us whether
-     exceptions are allowed/required.  ignore them for now.  */
-
-  TEST_f_i (ilogb, 0.0, FP_ILOGB0, EXCEPTIONS_OK);
-  TEST_f_i (ilogb, nan_value, FP_ILOGBNAN, EXCEPTIONS_OK);
-  TEST_f_i (ilogb, plus_infty, INT_MAX, EXCEPTIONS_OK);
-  TEST_f_i (ilogb, minus_infty, INT_MAX, EXCEPTIONS_OK);
+  /* ilogb (0.0) == FP_ILOGB0 plus invalid exception  */
+  errno = 0;
+  TEST_f_i (ilogb, 0.0, FP_ILOGB0, INVALID_EXCEPTION);
+  check_int ("errno for ilogb(0.0) unchanged", errno, EDOM, 0, 0, 0);
+  /* ilogb (NaN) == FP_ILOGBNAN plus invalid exception  */
+  errno = 0;
+  TEST_f_i (ilogb, nan_value, FP_ILOGBNAN, INVALID_EXCEPTION);
+  check_int ("errno for ilogb(NaN) unchanged", errno, EDOM, 0, 0, 0);
+  /* ilogb (inf) == INT_MAX plus invalid exception  */
+  errno = 0;
+  TEST_f_i (ilogb, plus_infty, INT_MAX, INVALID_EXCEPTION);
+  check_int ("errno for ilogb(Inf) unchanged", errno, EDOM, 0, 0, 0);
+  /* ilogb (-inf) == INT_MAX plus invalid exception  */
+  errno = 0;
+  TEST_f_i (ilogb, minus_infty, INT_MAX, INVALID_EXCEPTION);
+  check_int ("errno for ilogb(-Inf) unchanged", errno, EDOM, 0, 0, 0);
 
   END (ilogb);
 }
diff --git a/math/w_ilogb.c b/math/w_ilogb.c
new file mode 100644
index 0000000..c87b517
--- /dev/null
+++ b/math/w_ilogb.c
@@ -0,0 +1,42 @@
+/* Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Adhemerval Zanella <azanella@linux.vnet.ibm.com>, 2011.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <errno.h>
+#include <math_private.h>
+
+/* wrapper ilogb */
+int
+__ilogb (double x)
+{
+  int r = __ieee754_ilogb (x);
+  if (__builtin_expect (r == FP_ILOGB0, 0)
+      || __builtin_expect (r == FP_ILOGBNAN, 0)
+      || __builtin_expect (r == INT_MAX, 0))
+    {
+      __set_errno (EDOM);
+      feraiseexcept (FE_INVALID);
+    }
+  return r;
+}
+
+weak_alias (__ilogb, ilogb)
+#ifdef NO_LONG_DOUBLE
+strong_alias (__ilogb, __ilogbl)
+weak_alias (__ilogb, ilogbl)
+#endif
diff --git a/math/w_ilogbf.c b/math/w_ilogbf.c
new file mode 100644
index 0000000..ae3574a
--- /dev/null
+++ b/math/w_ilogbf.c
@@ -0,0 +1,38 @@
+/* Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Adhemerval Zanella <azanella@linux.vnet.ibm.com>, 2011.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <errno.h>
+#include <math_private.h>
+
+/* wrapper ilogbf */
+int
+__ilogbf (float x)
+{
+  int r = __ieee754_ilogbf (x);
+  if (__builtin_expect (r == FP_ILOGB0, 0)
+      || __builtin_expect (r == FP_ILOGBNAN, 0)
+      || __builtin_expect (r == INT_MAX, 0))
+    {
+      __set_errno (EDOM);
+      feraiseexcept (FE_INVALID);
+    }
+  return r;
+}
+
+weak_alias (__ilogbf, ilogbf)
diff --git a/math/w_ilogbl.c b/math/w_ilogbl.c
new file mode 100644
index 0000000..8c30caa
--- /dev/null
+++ b/math/w_ilogbl.c
@@ -0,0 +1,37 @@
+/* Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Adhemerval Zanella <azanella@linux.vnet.ibm.com>, 2011.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <errno.h>
+#include <math_private.h>
+
+/* wrapper ilogbl */
+int
+__ilogbl (long double x)
+{
+  int r = __ieee754_ilogbl (x);
+  if (__builtin_expect (r == FP_ILOGB0, 0)
+      || __builtin_expect (r == FP_ILOGBNAN, 0)
+      || __builtin_expect (r == INT_MAX, 0))
+    {
+      __set_errno (EDOM);
+      feraiseexcept (FE_INVALID);
+    }
+  return r;
+}
+weak_alias (__ilogbl, ilogbl)