re PR fortran/56872 (Incorrect SUM evaluation, involving implied-do loop, with -ffrontend-optimize)

2013-04-08  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/56782
	* frontend-passes.c (callback_reduction):  Dont't do
	any simplification if there is only a single element
	which has an iterator.

2013-04-08  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/56782
	* gfortran.dg/array_constructor_44.f90:  New test.

From-SVN: r197610

gcc/fortran/ChangeLog

+2013-04-08  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/56782
+	* frontend-passes.c (callback_reduction):  Dont't do
+	any simplification if there is only a single element
+	which has an iterator.
+
 2013-04-07  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/56849

gcc/fortran/frontend-passes.c

@@ -300,7 +300,12 @@ callback_reduction (gfc_expr **e, int *walk_subtrees ATTRIBUTE_UNUSED,
 
   c = gfc_constructor_first (arg->value.constructor);
 
-  if (c == NULL)
+  /* Don't do any simplififcation if we have
+     - no element in the constructor or
+     - only have a single element in the array which contains an
+     iterator.  */
+
+  if (c == NULL || (c->iterator != NULL && gfc_constructor_next (c) == NULL))
     return 0;
 
   res = copy_walk_reduction_arg (c->expr, fn);

gcc/testsuite/ChangeLog

+2013-04-08  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/56782
+	* gfortran.dg/array_constructor_44.f90:  New test.
+
 2013-04-08  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/56871

gcc/testsuite/gfortran.dg/array_constructor_44.f90

+! { dg-do run }
+! { dg-options "-ffrontend-optimize" }
+! PR 56872 - wrong front-end optimization with a single constructor.
+! Original bug report by Rich Townsend.
+  integer :: k
+  real :: s
+  integer :: m
+  s = 2.0
+  m = 4
+  res = SUM([(s**(REAL(k-1)/REAL(m-1)),k=1,m)])
+  if (abs(res - 5.84732246) > 1e-6) call abort
+  end