[PATCH] S390: Fix fp comparison not raising FE_INVALID.

[Stefan Liebler <stli@linux.vnet.ibm.com>]

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Hi,

As gcc is using unordered comparison instructions which do not
raise invalid exception if any operand is quiet NAN,
FIX_COMPARE_INVALID is defined to 1.
Thus iseqsig is calling feraiseexcept as workaround.

ChangeLog:

	* sysdeps/s390/fpu/fix-fp-int-compare-invalid.h: New file.

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commit 2aa18f963deed0ae455b00b75e773a2972fe2071
Author: Stefan Liebler <stli@linux.vnet.ibm.com>
Date:   Mon Oct 10 08:35:54 2016 +0200

    S390: Fix fp comparison not raising FE_INVALID.
    
    As gcc is using unordered comparison instructions which do not
    raise invalid exception if any operand is quiet NAN,
    FIX_COMPARE_INVALID is defined to 1.
    Thus iseqsig is calling feraiseexcept as workaround.
    
    ChangeLog:
    
    	* sysdeps/s390/fpu/fix-fp-int-compare-invalid.h: New file.

diff --git a/sysdeps/s390/fpu/fix-fp-int-compare-invalid.h b/sysdeps/s390/fpu/fix-fp-int-compare-invalid.h
new file mode 100644
index 0000000..c4c119f
--- /dev/null
+++ b/sysdeps/s390/fpu/fix-fp-int-compare-invalid.h
@@ -0,0 +1,36 @@
+/* Fix for missing "invalid" exceptions from floating-point
+   comparisons.  s390 version.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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/>.  */
+
+#ifndef FIX_FP_INT_COMPARE_INVALID_H
+#define FIX_FP_INT_COMPARE_INVALID_H	1
+
+/* GCC uses unordered comparison instructions like cebr (Short BFP COMPARE)
+   when it should use ordered comparison instructions like kebr
+   (Short BFP COMPARE AND SIGNAL) in order to raise invalid exceptions if
+   any operand is quiet (or signaling) NAN. See gcc bugzilla:
+   <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77918>.
+   There exists an equivalent gcc bugzilla for Intel:
+   <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52451>.
+   Once the s390 gcc bug is fixed, the definition of FIX_COMPARE_INVALID
+   should have a __GNUC_PREREQ conditional added so that e.g. the workaround
+   to call feraiseexcept (FE_INVALID) in math/s_iseqsig_template.c can be
+   avoided.  */
+#define FIX_COMPARE_INVALID 1
+
+#endif /* fix-fp-int-compare-invalid.h */