[patch, fortran] Fix PR 51858, wrong-code regression with function elimination

[Thomas Koenig <tkoenig at netcologne dot de>]

Hello world,

the attached patch fixes the PR by converting

if (foo) then
...
else if (bar) then
...
end if

to if (foo) then
else
  if (bar) then
  end if
end if

so inserting a block for temporary variables around the converted
if statement works.

OK for trunk?

	Thomas

2012-01-29  Thomas König  <tkoenig@gcc.gnu.org>

        PR fortran/51858
        * frontend-passes.c (convert_elseif):  New function.
        (optimize_namespace):  Call it.

2012-01-29  Thomas König  <tkoenig@gcc.gnu.org>

        PR fortran/51858
        * gfortran.dg/function_optimize_10.f90:  New test.

Index: frontend-passes.c
===================================================================
--- frontend-passes.c	(Revision 183449)
+++ frontend-passes.c	(Arbeitskopie)
@@ -509,6 +509,63 @@ convert_do_while (gfc_code **c, int *walk_subtrees
   return 0;
 }
 
+/* Code callback function for converting
+   if (a) then
+   ...
+   else if (b) then
+   end if
+
+   into
+   if (a) then
+   else
+     if (b) then
+     end if
+   end if
+
+   because otherwise common function elimination would place the BLOCKs
+   into the wrong place.  */
+
+static int
+convert_elseif (gfc_code **c, int *walk_subtrees ATTRIBUTE_UNUSED,
+		void *data ATTRIBUTE_UNUSED)
+{
+  gfc_code *co = *c;
+  gfc_code *c_if1, *c_if2, *else_stmt;
+
+  if (co->op != EXEC_IF)
+    return 0;
+
+  /* This loop starts out with the first ELSE statement.  */
+  for (else_stmt = co->block->block; else_stmt != NULL;
+       else_stmt = else_stmt->block)
+    {
+      /* If there is no condition, we're set.  */
+      if (else_stmt->expr1 == NULL)
+	break;
+
+      /* Generate the new IF statement.  */
+      c_if2 = XCNEW (gfc_code);
+      c_if2->op = EXEC_IF;
+      c_if2->expr1 = else_stmt->expr1;
+      c_if2->next = else_stmt->next;
+      c_if2->loc = else_stmt->loc;
+      c_if2->block = else_stmt->block;
+
+      /* ... plus the one to chain it to.  */
+      c_if1 = XCNEW (gfc_code);
+      c_if1->op = EXEC_IF;
+      c_if1->block = c_if2;
+      c_if1->loc = else_stmt->loc;
+
+      /* Insert the new IF after the ELSE.  */
+      else_stmt->expr1 = NULL;
+      else_stmt->next = c_if1;
+      else_stmt->block = NULL;
+      else_stmt->next = c_if1;
+    }
+  /*  Don't walk subtrees.  */
+  return 1;
+}
 /* Optimize a namespace, including all contained namespaces.  */
 
 static void
@@ -520,6 +577,7 @@ optimize_namespace (gfc_namespace *ns)
   in_omp_workshare = false;
 
   gfc_code_walker (&ns->code, convert_do_while, dummy_expr_callback, NULL);
+  gfc_code_walker (&ns->code, convert_elseif, dummy_expr_callback, NULL);
   gfc_code_walker (&ns->code, cfe_code, cfe_expr_0, NULL);
   gfc_code_walker (&ns->code, optimize_code, optimize_expr, NULL);

Attachment: function_optimize_10.f90
Description: Text document