Fix modf (sNaN) (bug 20240).

Various modf implementations return sNaN (both outputs) for sNaN
input.  In fact they contain code to convert sNaN to qNaN for both
outputs, but the way this is done is multiplying by 1.0 (for a wider
range of inputs that includes NaNs as well as numbers with exponent
large enough to ensure that they are integers), and that
multiplication by 1.0 is optimized away by GCC in the absence of
-fsignaling-nans, unlike other operations on NaNs used for this
purpose that are not no-ops for non-sNaN input.  This patch arranges
for those files to be built with -fsignaling-nans so that this
existing code is effective as intended.

Tested for x86_64 and x86.

	[BZ #20240]
	* math/Makefile (CFLAGS-s_modf.c): New variable.
	(CFLAGS-s_modff.c): Likewise.
	(CFLAGS-s_modfl.c): Likewise.
	* math/libm-test.inc (modf_test_data): Add sNaN tests.

diff --git a/ChangeLog b/ChangeLog
index fd2ea8ae084f3b3f1a3f5a996a5eb6301b47b2f4..94caf576157aedcfb3bd101f608f96bef89754e8 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2016-06-10  Joseph Myers  <joseph@codesourcery.com>
+
+       [BZ #20240]
+       * math/Makefile (CFLAGS-s_modf.c): New variable.
+       (CFLAGS-s_modff.c): Likewise.
+       (CFLAGS-s_modfl.c): Likewise.
+       * math/libm-test.inc (modf_test_data): Add sNaN tests.
+
 2016-06-09  Carlos O'Donell  <carlos@redhat.com>
 
        [BZ #20215]

diff --git a/math/Makefile b/math/Makefile
index f0265bb640a82c909eb909bd5525a39a6a8b058d..6cd3cf1f65564c7c29d1caec0e4338b747d9e946 100644 (file)
--- a/math/Makefile
+++ b/math/Makefile
@@ -302,6 +302,12 @@ ifneq ($(long-double-fcts),yes)
 math-CPPFLAGS += -DNO_LONG_DOUBLE -D_Mlong_double_=double
 endif
 
+# These files quiet sNaNs in a way that is optimized away without
+# -fsignaling-nans.
+CFLAGS-s_modf.c += -fsignaling-nans
+CFLAGS-s_modff.c += -fsignaling-nans
+CFLAGS-s_modfl.c += -fsignaling-nans
+
 # The -lieee library is actually an object file.
 # The module just defines the _LIB_VERSION_ variable.
 # It's not a library to make sure it is linked in instead of s_lib_version.o.

diff --git a/math/libm-test.inc b/math/libm-test.inc
index 2df6f29a346ed5bcaae42e0b40c1ae82d25d9954..3d901ae96a5ac3cf9099e9ae6d760b91eec3cd09 100644 (file)
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -9759,6 +9759,8 @@ static const struct test_fF_f1_data modf_test_data[] =
     TEST_fF_f1 (modf, minus_infty, minus_zero, minus_infty, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_fF_f1 (modf, qnan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_fF_f1 (modf, -qnan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_fF_f1 (modf, snan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|INVALID_EXCEPTION),
+    TEST_fF_f1 (modf, -snan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|INVALID_EXCEPTION),
     TEST_fF_f1 (modf, 0, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_fF_f1 (modf, minus_zero, minus_zero, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_fF_f1 (modf, min_value, min_value, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),