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.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_9-branch@215348 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 51 insertions, 1 deletions

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8cc090071ce..e30eae74151 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2014-09-18  Joseph Myers  <joseph@codesourcery.com>
+
+	* gcc.dg/torture/float128-exact-underflow.c: New test.
+
 2014-09-17  Jakub Jelinek  <jakub@redhat.com>
 
 	PR debug/63284
diff --git a/gcc/testsuite/gcc.dg/torture/float128-exact-underflow.c b/gcc/testsuite/gcc.dg/torture/float128-exact-underflow.c
new file mode 100644
index 00000000000..ea11f26e22d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/float128-exact-underflow.c
@@ -0,0 +1,41 @@
+/* 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* } } */
+/* { 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);
+}
diff --git a/libgcc/ChangeLog b/libgcc/ChangeLog
index 8f7094d345d..ec295541630 100644
--- a/libgcc/ChangeLog
+++ b/libgcc/ChangeLog
@@ -1,3 +1,8 @@
+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.
+
 2014-09-11  Georg-Johann Lay  <avr@gjlay.de>
 
 	Backport from 2014-09-11 trunk r215152.
diff --git a/libgcc/config/i386/sfp-machine.h b/libgcc/config/i386/sfp-machine.h
index 148044a6920..8a1923b6c1a 100644
--- a/libgcc/config/i386/sfp-machine.h
+++ b/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