re PR rtl-optimization/42461 (missed optimization for pure functions)

PR rtl-optimization/42461
	* dce.c (deletable_insn_p): Return true for const or pure calls again.
	* except.c (insn_could_throw_p): Return false if !flag_exceptions.

From-SVN: r160507

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2010-06-09  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR rtl-optimization/42461
+	* dce.c (deletable_insn_p): Return true for const or pure calls again.
+	* except.c (insn_could_throw_p): Return false if !flag_exceptions.
+
 2010-06-09  Jan Hubicka  <jh@suse.cz>
 
 	* bitmap.c (bitmap_and): Walk array forward.

gcc/dce.c

@@ -94,14 +94,6 @@ deletable_insn_p (rtx insn, bool fast, bitmap arg_stores)
   rtx body, x;
   int i;
 
-  /* Don't delete jumps, notes and the like.  */
-  if (!NONJUMP_INSN_P (insn))
-    return false;
-
-  /* Don't delete insns that can throw.  */
-  if (!insn_nothrow_p (insn))
-    return false;
-
   if (CALL_P (insn)
       /* We cannot delete calls inside of the recursive dce because
 	 this may cause basic blocks to be deleted and this messes up
@@ -116,6 +108,14 @@ deletable_insn_p (rtx insn, bool fast, bitmap arg_stores)
 	  && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)))
     return find_call_stack_args (insn, false, fast, arg_stores);
 
+  /* Don't delete jumps, notes and the like.  */
+  if (!NONJUMP_INSN_P (insn))
+    return false;
+
+  /* Don't delete insns that can throw.  */
+  if (!insn_nothrow_p (insn))
+    return false;
+
   body = PATTERN (insn);
   switch (GET_CODE (body))
     {

gcc/except.c

@@ -1617,6 +1617,8 @@ make_reg_eh_region_note_nothrow_nononlocal (rtx insn)
 bool
 insn_could_throw_p (const_rtx insn)
 {
+  if (!flag_exceptions)
+    return false;
   if (CALL_P (insn))
     return true;
   if (INSN_P (insn) && cfun->can_throw_non_call_exceptions)

gcc/testsuite/ChangeLog

@@ -1,7 +1,11 @@
+2010-06-09  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc.dg/pr42461.c: New test.
+
 2010-06-09  Daniel Franke  <franke.daniel@gmail.com>
 
-        PR fortran/44347
-        * gfortran.dg/selected_real_kind_1.f90: New.
+	PR fortran/44347
+	* gfortran.dg/selected_real_kind_1.f90: New.
 
 2010-06-09  Daniel Franke  <franke.daniel@gmail.com>
 

gcc/testsuite/gcc.dg/pr42461.c

@@ -0,0 +1,14 @@
+/* PR rtl-optimization/42461 */
+/* Reported by Patrick Pelissier <patrick.pelissier@gmail.com> */
+
+/* { dg-do link } */
+/* { dg-options "-O" } */
+
+extern int link_failure (int) __attribute__ ((pure));
+
+int main (void)
+{
+  if (link_failure (0) < 1)
+    __builtin_unreachable ();
+  return 0;
+}