re PR fortran/88678 (Many gfortran.dg/ieee/ieee_X.f90 test cases fail starting with r267465)

	PR fortran/88678
	* config/fpu-glibc.h (set_fpu_trap_exceptions): Clear stalled
	exception flags before changing trap mode.  Optimize to call
	feenableexcept and fedisableexcept only once.

From-SVN: r268392

libgfortran/ChangeLog

+2019-01-30  Uroš Bizjak  <ubizjak@gmail.com>
+
+	PR fortran/88678
+	* config/fpu-glibc.h (set_fpu_trap_exceptions): Clear stalled
+	exception flags before changing trap mode.  Optimize to call
+	feenableexcept and fedisableexcept only once.
+
 2019-01-28  Sebastian Huber  <sebastian.huber@embedded-brains.de>
 
 	* io/async.c (init_adv_cond): Use __GTHREAD_COND_INIT_FUNCTION().

libgfortran/config/fpu-glibc.h

@@ -39,48 +39,56 @@ _Static_assert (sizeof(fenv_t) <= (size_t) GFC_FPE_STATE_BUFFER_SIZE,
 
 void set_fpu_trap_exceptions (int trap, int notrap)
 {
+  int mode_set = 0, mode_clr = 0;
+
 #ifdef FE_INVALID
   if (trap & GFC_FPE_INVALID)
-    feenableexcept (FE_INVALID);
+    mode_set |= FE_INVALID;
   if (notrap & GFC_FPE_INVALID)
-    fedisableexcept (FE_INVALID);
+    mode_clr |= FE_INVALID;
 #endif
 
 /* Some glibc targets (like alpha) have FE_DENORMAL, but not many.  */
 #ifdef FE_DENORMAL
   if (trap & GFC_FPE_DENORMAL)
-    feenableexcept (FE_DENORMAL);
+    mode_set |= FE_DENORMAL;
   if (notrap & GFC_FPE_DENORMAL)
-    fedisableexcept (FE_DENORMAL);
+    mode_clr |= FE_DENORMAL;
 #endif
 
 #ifdef FE_DIVBYZERO
   if (trap & GFC_FPE_ZERO)
-    feenableexcept (FE_DIVBYZERO);
+    mode_set |= FE_DIVBYZERO;
   if (notrap & GFC_FPE_ZERO)
-    fedisableexcept (FE_DIVBYZERO);
+    mode_clr |= FE_DIVBYZERO;
 #endif
 
 #ifdef FE_OVERFLOW
   if (trap & GFC_FPE_OVERFLOW)
-    feenableexcept (FE_OVERFLOW);
+    mode_set |= FE_OVERFLOW;
   if (notrap & GFC_FPE_OVERFLOW)
-    fedisableexcept (FE_OVERFLOW);
+    mode_clr |= FE_OVERFLOW;
 #endif
 
 #ifdef FE_UNDERFLOW
   if (trap & GFC_FPE_UNDERFLOW)
-    feenableexcept (FE_UNDERFLOW);
+    mode_set |= FE_UNDERFLOW;
   if (notrap & GFC_FPE_UNDERFLOW)
-    fedisableexcept (FE_UNDERFLOW);
+    mode_clr |= FE_UNDERFLOW;
 #endif
 
 #ifdef FE_INEXACT
   if (trap & GFC_FPE_INEXACT)
-    feenableexcept (FE_INEXACT);
+    mode_set |= FE_INEXACT;
   if (notrap & GFC_FPE_INEXACT)
-    fedisableexcept (FE_INEXACT);
+    mode_clr |= FE_INEXACT;
 #endif
+
+  /* Clear stalled exception flags.  */
+  feclearexcept (FE_ALL_EXCEPT);
+
+  feenableexcept (mode_set);
+  fedisableexcept (mode_clr);
 }