Fix i386 FP_TRAPPING_EXCEPTIONS.

The i386 sfp-machine.h defines FP_TRAPPING_EXCEPTIONS in a way that is
always wrong: it treats a set bit as indicating the exception is
trapping, when actually a set bit (both for 387 and SSE floating
point) indicates it is masked, and a clear bit indicates it is
trapping.  This patch fixes this bug.

Bootstrapped with no regressions on x86_64-unknown-linux-gnu.

libgcc:
	* config/i386/sfp-machine.h (FP_TRAPPING_EXCEPTIONS): Treat clear
	bits not set bits as indicating trapping exceptions.

gcc/testsuite:
	* gcc.dg/torture/float128-exact-underflow.c: New test.

From-SVN: r215347

gcc/testsuite/ChangeLog

+2014-09-18  Joseph Myers  <joseph@codesourcery.com>
+
+	* gcc.dg/torture/float128-exact-underflow.c: New test.
+
 2014-09-18  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/61745

gcc/testsuite/gcc.dg/torture/float128-exact-underflow.c

+/* Test that exact underflow in __float128 signals the underflow
+   exception if trapping is enabled, but does not raise the flag
+   otherwise.  */
+
+/* { dg-do run { target i?86-*-*gnu* x86_64-*-*gnu* ia64-*-*gnu* } } */
+/* { dg-options "-D_GNU_SOURCE" } */
+/* { dg-require-effective-target fenv_exceptions } */
+
+#include <fenv.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdlib.h>
+
+volatile sig_atomic_t caught_sigfpe;
+sigjmp_buf buf;
+
+static void
+handle_sigfpe (int sig)
+{
+  caught_sigfpe = 1;
+  siglongjmp (buf, 1);
+}
+
+int
+main (void)
+{
+  volatile __float128 a = 0x1p-16382q, b = 0x1p-2q;
+  volatile __float128 r;
+  r = a * b;
+  if (fetestexcept (FE_UNDERFLOW))
+    abort ();
+  if (r != 0x1p-16384q)
+    abort ();
+  feenableexcept (FE_UNDERFLOW);
+  signal (SIGFPE, handle_sigfpe);
+  if (sigsetjmp (buf, 1) == 0)
+    r = a * b;
+  if (!caught_sigfpe)
+    abort ();
+  exit (0);
+}

libgcc/ChangeLog

+2014-09-18  Joseph Myers  <joseph@codesourcery.com>
+
+	* config/i386/sfp-machine.h (FP_TRAPPING_EXCEPTIONS): Treat clear
+	bits not set bits as indicating trapping exceptions.
+
 2014-09-17  Nathan sidwell  <nathan@acm.org>
 
 	* Makefile.in (LIBGCOV_INTERFACE): Add _gcov_dump from ...

libgcc/config/i386/sfp-machine.h

@@ -60,7 +60,7 @@ void __sfp_handle_exceptions (int);
       __sfp_handle_exceptions (_fex);		\
   } while (0);
 
-#define FP_TRAPPING_EXCEPTIONS ((_fcw >> FP_EX_SHIFT) & FP_EX_ALL)
+#define FP_TRAPPING_EXCEPTIONS ((~_fcw >> FP_EX_SHIFT) & FP_EX_ALL)
 
 #define FP_ROUNDMODE		(_fcw & FP_RND_MASK)
 #endif