Improve ECF_NOTHROW flags for direct internal functions

[Richard Sandiford]

Internal functions that map directly to an optab can only throw an
exception for -fnon-call-exceptions.  This patch handles that in
internal_fn_flags, in a similar way to ATTR_*NOTHROW in builtins.def.

(Functions that don't throw even for flag_non_call_exceptions should be
explicitly marked ECF_NOTHROW in internal-fn.def.)

Tested on aarch64-linux-gnu and x86_64-linux-gnu.  OK to install?

Richard


2017-08-17  Richard Sandiford  <richard.sandif...@linaro.org>

gcc/
        * internal-fn.h (internal_fn_flags): Just declare and move
        the actual implementation out-of-line to...
        * internal-fn.c (internal_fn_flags): ...here.  Set ECF_NOTHROW for
        directly-mapped internal functions if !flag_non_call_exceptions.

Index: gcc/internal-fn.h
===================================================================
--- gcc/internal-fn.h   2017-02-23 19:54:03.000000000 +0000
+++ gcc/internal-fn.h   2017-08-17 09:05:37.459968561 +0100
@@ -107,15 +107,7 @@ internal_fn_name (enum internal_fn fn)
   return internal_fn_name_array[(int) fn];
 }
 
-/* Return the ECF_* flags for function FN.  */
-
-extern const int internal_fn_flags_array[];
-
-static inline int
-internal_fn_flags (enum internal_fn fn)
-{
-  return internal_fn_flags_array[(int) fn];
-}
+extern int internal_fn_flags (enum internal_fn fn);
 
 /* Return fnspec for function FN.  */
 
Index: gcc/internal-fn.c
===================================================================
--- gcc/internal-fn.c   2017-08-10 14:36:07.453493083 +0100
+++ gcc/internal-fn.c   2017-08-17 09:05:37.459968561 +0100
@@ -2814,3 +2814,18 @@ expand_PHI (internal_fn, gcall *)
 {
     gcc_unreachable ();
 }
+
+/* Return the ECF_* flags for function FN.  */
+
+int
+internal_fn_flags (enum internal_fn fn)
+{
+  int flags = internal_fn_flags_array[(int) fn];
+  /* Functions that map to optabs can only throw a catchable exception
+     when non-call exceptions are enabled.  The non-call exceptions in
+     these cases will typically come from things like IEEE exceptions,
+     divide by zero errors and SEGVs.  */
+  if (direct_internal_fn_p (fn) && !flag_non_call_exceptions)
+    flags |= ECF_NOTHROW;
+  return flags;
+}