2011-05-26 Paul Thomas <pault@gcc.gnu.org>

	    Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/48955
	* trans-expr.c (gfc_trans_assignment_1): GFC_REVERSE_NOT_SET
	changed to GFC_ENABLE_REVERSE.
	* trans-array.c (gfc_init_loopinfo): GFC_CANNOT_REVERSE changed
	to GFC_INHIBIT_REVERSE.
	* gfortran.h : Enum gfc_reverse is now GFC_ENABLE_REVERSE,
	GFC_FORWARD_SET, GFC_REVERSE_SET and GFC_INHIBIT_REVERSE.
	* dependency.c (gfc_dep_resolver): Change names for elements of
	gfc_reverse as necessary. Change the logic so that forward
	dependences are remembered as well as backward ones. When both
	have appeared, force a temporary.

2011-05-26  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/48955
	* gfortran.dg/dependency_40.f90 : New test.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_6-branch@174308 138bc75d-0d04-0410-961f-82ee72b054a4

7 files changed, 76 insertions, 18 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 0a5b8ced0bc..58360dd195b 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,18 @@
+2011-05-26  Paul Thomas  <pault@gcc.gnu.org>
+	    Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/48955
+	* trans-expr.c (gfc_trans_assignment_1): GFC_REVERSE_NOT_SET
+	changed to GFC_ENABLE_REVERSE.
+	* trans-array.c (gfc_init_loopinfo): GFC_CANNOT_REVERSE changed
+	to GFC_INHIBIT_REVERSE.
+	* gfortran.h : Enum gfc_reverse is now GFC_ENABLE_REVERSE,
+	GFC_FORWARD_SET, GFC_REVERSE_SET and GFC_INHIBIT_REVERSE.
+	* dependency.c (gfc_dep_resolver): Change names for elements of
+	gfc_reverse as necessary. Change the logic so that forward
+	dependences are remembered as well as backward ones. When both
+	have appeared, force a temporary.
+
 2011-05-11  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/48889
diff --git a/gcc/fortran/dependency.c b/gcc/fortran/dependency.c
index 77e8df72b68..58cfb65bce1 100644
--- a/gcc/fortran/dependency.c
+++ b/gcc/fortran/dependency.c
@@ -1793,7 +1793,7 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 
 	      /* Now deal with the loop reversal logic:  This only works on
 		 ranges and is activated by setting
-				reverse[n] == GFC_CAN_REVERSE
+				reverse[n] == GFC_ENABLE_REVERSE
 		 The ability to reverse or not is set by previous conditions
 		 in this dimension.  If reversal is not activated, the
 		 value GFC_DEP_BACKWARD is reset to GFC_DEP_OVERLAP.  */
@@ -1801,25 +1801,34 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 		    && lref->u.ar.dimen_type[n] == DIMEN_RANGE)
 		{
 		  /* Set reverse if backward dependence and not inhibited.  */
-		  if (reverse && reverse[n] != GFC_CANNOT_REVERSE)
+		  if (reverse && reverse[n] == GFC_ENABLE_REVERSE)
 		    reverse[n] = (this_dep == GFC_DEP_BACKWARD) ?
 			         GFC_REVERSE_SET : reverse[n];
 
-		  /* Inhibit loop reversal if dependence not compatible.  */
-		  if (reverse && reverse[n] != GFC_REVERSE_NOT_SET
-		        && this_dep != GFC_DEP_EQUAL
-		        && this_dep != GFC_DEP_BACKWARD
-		        && this_dep != GFC_DEP_NODEP)
+		  /* Set forward if forward dependence and not inhibited.  */
+		  if (reverse && reverse[n] == GFC_ENABLE_REVERSE)
+		    reverse[n] = (this_dep == GFC_DEP_FORWARD) ?
+			         GFC_FORWARD_SET : reverse[n];
+
+		  /* Flag up overlap if dependence not compatible with
+		     the overall state of the expression.  */
+		  if (reverse && reverse[n] == GFC_REVERSE_SET
+		        && this_dep == GFC_DEP_FORWARD)
+		    {
+	              reverse[n] = GFC_INHIBIT_REVERSE;
+		      this_dep = GFC_DEP_OVERLAP;
+		    }
+		  else if (reverse && reverse[n] == GFC_FORWARD_SET
+		        && this_dep == GFC_DEP_BACKWARD)
 		    {
-	              reverse[n] = GFC_CANNOT_REVERSE;
-		      if (this_dep != GFC_DEP_FORWARD)
-			this_dep = GFC_DEP_OVERLAP;
+	              reverse[n] = GFC_INHIBIT_REVERSE;
+		      this_dep = GFC_DEP_OVERLAP;
 		    }
 
 		  /* If no intention of reversing or reversing is explicitly
 		     inhibited, convert backward dependence to overlap.  */
-		  if (this_dep == GFC_DEP_BACKWARD
-		      && (reverse == NULL || reverse[n] == GFC_CANNOT_REVERSE))
+		  if ((reverse == NULL && this_dep == GFC_DEP_BACKWARD)
+		      || (reverse != NULL && reverse[n] == GFC_INHIBIT_REVERSE))
 		    this_dep = GFC_DEP_OVERLAP;
 		}
 
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 165bd2f23a3..f20a29bc7fa 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -578,10 +578,10 @@ gfc_fcoarray;
 
 typedef enum
 {
-  GFC_REVERSE_NOT_SET,
+  GFC_ENABLE_REVERSE,
+  GFC_FORWARD_SET,
   GFC_REVERSE_SET,
-  GFC_CAN_REVERSE,
-  GFC_CANNOT_REVERSE
+  GFC_INHIBIT_REVERSE
 }
 gfc_reverse;
 
diff --git a/gcc/fortran/trans-array.c b/gcc/fortran/trans-array.c
index 3d4a52a7ebe..b64e10d6a10 100644
--- a/gcc/fortran/trans-array.c
+++ b/gcc/fortran/trans-array.c
@@ -2223,7 +2223,7 @@ gfc_init_loopinfo (gfc_loopinfo * loop)
   for (n = 0; n < GFC_MAX_DIMENSIONS; n++)
     {
       loop->order[n] = n;
-      loop->reverse[n] = GFC_CANNOT_REVERSE;
+      loop->reverse[n] = GFC_INHIBIT_REVERSE;
     }
 
   loop->ss = gfc_ss_terminator;
diff --git a/gcc/fortran/trans-expr.c b/gcc/fortran/trans-expr.c
index 1d678e63f5c..ade7e548522 100644
--- a/gcc/fortran/trans-expr.c
+++ b/gcc/fortran/trans-expr.c
@@ -6067,8 +6067,8 @@ gfc_trans_assignment_1 (gfc_expr * expr1, gfc_expr * expr2, bool init_flag,
       /* Calculate the bounds of the scalarization.  */
       gfc_conv_ss_startstride (&loop);
       /* Enable loop reversal.  */
-      for (n = 0; n < loop.dimen; n++)
-	loop.reverse[n] = GFC_REVERSE_NOT_SET;
+      for (n = 0; n < GFC_MAX_DIMENSIONS; n++)
+	loop.reverse[n] = GFC_ENABLE_REVERSE;
       /* Resolve any data dependencies in the statement.  */
       gfc_conv_resolve_dependencies (&loop, lss, rss);
       /* Setup the scalarizing loops.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b91e7e53624..1b3827802b8 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-05-26  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/48955
+	* gfortran.dg/dependency_40.f90 : New test.
+
 2011-05-26  Jason Merrill  <jason@redhat.com>
 
 	* g++.dg/cpp0x/variadic111.C: New.
diff --git a/gcc/testsuite/gfortran.dg/dependency_40.f90 b/gcc/testsuite/gfortran.dg/dependency_40.f90
new file mode 100644
index 00000000000..b7bd4f91184
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/dependency_40.f90
@@ -0,0 +1,29 @@
+! { dg-do run }
+! PR 48955 - missing array temporary when there was both a forward
+! and a backward dependency.
+! Test case slightly modified from the original one by Kacper Kowalik.
+program ala
+   implicit none
+
+   integer, parameter  :: n = 6
+   real, dimension(n), parameter :: result = [1.,10.,30.,90.,270., 243.];
+   real, dimension(n) :: v0, v1
+   character(len=80) :: line1, line2
+
+   v0 = [1.0, 3.0, 9.0, 27.0, 81.0, 243.0]
+   v1 = v0
+
+   v1(2:n-1) = v1(1:n-2) + v1(3:n)
+   if (any(v1 /= result)) call abort
+   v1 = v0
+   v1(2:n-1) = v0(1:n-2) + v0(3:n)
+   if (any(v1 /= result)) call abort
+
+   v1 = v0
+   v1(2:n-1) = v1(3:n) + v1(1:n-2)
+   if (any(v1 /= result)) call abort
+   v1 = v0
+   v1(2:n-1) = v0(3:n) + v0(1:n-2)
+   if (any(v1 /= result)) call abort
+
+end program ala