re PR fortran/71902 (Unneeded temporary on reallocatable character assignment)

2016-07-19  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/71902
	* dependency.c (gfc_check_dependency): Use dep_ref.  Handle case
	if identical is true and two array element references differ.
	(gfc_dep_resovler):  Move most of the code to dep_ref.
	(dep_ref):  New function.
	* frontend-passes.c (realloc_string_callback):  Name temporary
	variable "realloc_string".

2016-07-19  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/71902
	* gfortran.dg/dependency_47.f90:  New test.

From-SVN: r238497

gcc/fortran/ChangeLog

@@ -1,3 +1,13 @@
+2016-07-19  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/71902
+	* dependency.c (gfc_check_dependency): Use dep_ref.  Handle case
+	if identical is true and two array element references differ.
+	(gfc_dep_resovler):  Move most of the code to dep_ref.
+	(dep_ref):  New function.
+	* frontend-passes.c (realloc_string_callback):  Name temporary
+	variable "realloc_string".
+
 2016-07-17  Fritz Reese  <fritzoreese@gmail.com>
 
 	PR fortran/71523

gcc/fortran/dependency.c

@@ -54,6 +54,8 @@ enum gfc_dependency
 static gfc_dependency check_section_vs_section (gfc_array_ref *,
 						gfc_array_ref *, int);
 
+static gfc_dependency dep_ref (gfc_ref *, gfc_ref *, gfc_reverse *);
+
 /* Returns 1 if the expr is an integer constant value 1, 0 if it is not or
    def if the value could not be determined.  */
 
@@ -1316,13 +1318,33 @@ gfc_check_dependency (gfc_expr *expr1, gfc_expr *expr2, bool identical)
 	  return 0;
 	}
 
-      if (identical)
-	return 1;
-
       /* Identical and disjoint ranges return 0,
 	 overlapping ranges return 1.  */
       if (expr1->ref && expr2->ref)
-	return gfc_dep_resolver (expr1->ref, expr2->ref, NULL);
+	{
+	  gfc_dependency dep;
+	  dep = dep_ref (expr1->ref, expr2->ref, NULL);
+	  switch (dep)
+	    {
+	    case GFC_DEP_EQUAL:
+	      return identical;
+
+	    case GFC_DEP_FORWARD:
+	      return 0;
+
+	    case GFC_DEP_BACKWARD:
+	      return 1;
+
+	    case GFC_DEP_OVERLAP:
+	      return 1;
+
+	    case GFC_DEP_NODEP:
+	      return 0;
+
+	    default:
+	      gcc_unreachable();
+	    }
+	}
 
       return 1;
 
@@ -2052,10 +2074,38 @@ ref_same_as_full_array (gfc_ref *full_ref, gfc_ref *ref)
    	2 : array references are overlapping but reversal of one or
 	    more dimensions will clear the dependency.
    	1 : array references are overlapping.
-   	0 : array references are identical or not overlapping.  */
+   	0 : array references are identical or can be handled in a forward loop.  */
 
 int
 gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
+{
+  enum gfc_dependency dep;
+  dep = dep_ref (lref, rref, reverse);
+  switch (dep)
+    {
+    case GFC_DEP_EQUAL:
+      return 0;
+
+    case GFC_DEP_FORWARD:
+      return 0;
+
+    case GFC_DEP_BACKWARD:
+      return 2;
+
+    case GFC_DEP_OVERLAP:
+      return 1;
+
+    case GFC_DEP_NODEP:
+      return 0;
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+
+static gfc_dependency
+dep_ref (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 {
   int n;
   int m;
@@ -2079,21 +2129,22 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 	  /* The two ranges can't overlap if they are from different
 	     components.  */
 	  if (lref->u.c.component != rref->u.c.component)
-	    return 0;
+	    return GFC_DEP_NODEP;
 	  break;
 
 	case REF_SUBSTRING:
 	  /* Substring overlaps are handled by the string assignment code
 	     if there is not an underlying dependency.  */
-	  return (fin_dep == GFC_DEP_OVERLAP) ? 1 : 0;
+
+	  return fin_dep == GFC_DEP_ERROR ? GFC_DEP_NODEP : fin_dep;
 
 	case REF_ARRAY:
 
 	  if (ref_same_as_full_array (lref, rref))
-	    return 0;
+	    return GFC_DEP_EQUAL;
 
 	  if (ref_same_as_full_array (rref, lref))
-	    return 0;
+	    return GFC_DEP_EQUAL;
 
 	  if (lref->u.ar.dimen != rref->u.ar.dimen)
 	    {
@@ -2104,7 +2155,7 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 		fin_dep = gfc_full_array_ref_p (lref, NULL) ? GFC_DEP_EQUAL
 							    : GFC_DEP_OVERLAP;
 	      else
-		return 1;
+		return GFC_DEP_OVERLAP;
 	      break;
 	    }
 
@@ -2148,7 +2199,7 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 
 	      /* If any dimension doesn't overlap, we have no dependency.  */
 	      if (this_dep == GFC_DEP_NODEP)
-		return 0;
+		return GFC_DEP_NODEP;
 
 	      /* Now deal with the loop reversal logic:  This only works on
 		 ranges and is activated by setting
@@ -2215,7 +2266,7 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 	  /* Exactly matching and forward overlapping ranges don't cause a
 	     dependency.  */
 	  if (fin_dep < GFC_DEP_BACKWARD)
-	    return 0;
+	    return fin_dep == GFC_DEP_ERROR ? GFC_DEP_NODEP : fin_dep;
 
 	  /* Keep checking.  We only have a dependency if
 	     subsequent references also overlap.  */
@@ -2233,7 +2284,7 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 
   /* Assume the worst if we nest to different depths.  */
   if (lref || rref)
-    return 1;
+    return GFC_DEP_OVERLAP;
 
-  return fin_dep == GFC_DEP_OVERLAP;
+  return fin_dep;
 }

gcc/fortran/frontend-passes.c

@@ -185,7 +185,7 @@ realloc_string_callback (gfc_code **c, int *walk_subtrees ATTRIBUTE_UNUSED,
   current_code = c;
   inserted_block = NULL;
   changed_statement = NULL;
-  n = create_var (expr2, "trim");
+  n = create_var (expr2, "realloc_string");
   co->expr2 = n;
   return 0;
 }

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-07-19  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/71902
+	* gfortran.dg/dependency_47.f90:  New test.
+
 2016-07-19  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/71916

gcc/testsuite/gfortran.dg/dependency_47.f90

@@ -0,0 +1,15 @@
+! { dg-do compile }
+! Make sure there is only one instance of a temporary variable here.
+! { dg-options "-fdump-tree-original" }
+
+SUBROUTINE prtdata(ilen)
+  INTEGER :: ilen
+  character(len=ilen), allocatable :: cline(:)
+  allocate(cline(2))
+  cline(1) = 'a'
+  cline(1)(2:3) = cline(1)(1:2)
+  cline(2) = cline(1)
+  print *,c
+END SUBROUTINE prtdata
+! { dg-final { scan-tree-dump-not "__var_2" "original" } }
+! { dg-final { scan-tree-dump-times "__var_1" 3 "original" } }