gfortran.h (gfc_equiv_info): Add length field.

	* gfortran.h (gfc_equiv_info): Add length field.
	* trans-common.c (copy_equiv_list_to_ns): Set the length field.
	* dependency.c (gfc_are_equivalenced_arrays): Use both the offset
	and length fields to determine whether the two equivalenced symbols
	overlap in memory.

	* gfortran.dg/dependency_13.f90: New test case.

From-SVN: r112162

6 files changed, 57 insertions, 8 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index b09d32e..61bbcfd 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,11 @@
+2006-03-16  Roger Sayle  <roger@eyesopen.com>
+
+	* gfortran.h (gfc_equiv_info): Add length field.
+	* trans-common.c (copy_equiv_list_to_ns): Set the length field.
+	* dependency.c (gfc_are_equivalenced_arrays): Use both the offset
+	and length fields to determine whether the two equivalenced symbols
+	overlap in memory.
+
 2006-03-14  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR fortran/19101
diff --git a/gcc/fortran/dependency.c b/gcc/fortran/dependency.c
index d60b7eb..03cabf0 100644
--- a/gcc/fortran/dependency.c
+++ b/gcc/fortran/dependency.c
@@ -414,10 +414,13 @@ gfc_check_fncall_dependency (gfc_expr * other, sym_intent intent,
    directly or indirectly; ie. equivalence (a,b) for a and b
    or equivalence (a,c),(b,c).  This function uses the equiv_
    lists, generated in trans-common(add_equivalences), that are
-   guaranteed to pick up indirect equivalences.  A rudimentary
-   use is made of the offset to ensure that cases where the
-   source elements are moved down to the destination are not
-   identified as dependencies.  */
+   guaranteed to pick up indirect equivalences.  We explicitly
+   check for overlap using the offset and length of the equivalence.
+   This function is symmetric.
+   TODO: This function only checks whether the full top-level
+   symbols overlap.  An improved implementation could inspect
+   e1->ref and e2->ref to determine whether the actually accessed
+   portions of these variables/arrays potentially overlap.  */
 
 int
 gfc_are_equivalenced_arrays (gfc_expr *e1, gfc_expr *e2)
@@ -444,14 +447,33 @@ gfc_are_equivalenced_arrays (gfc_expr *e1, gfc_expr *e2)
       for (s = l->equiv; s; s = s->next)
 	{
 	  if (s->sym == e1->symtree->n.sym)
-	    fl1 = s;
+	    {
+	      fl1 = s;
+	      if (fl2)
+		break;
+	    }
 	  if (s->sym == e2->symtree->n.sym)
-	    fl2 = s;
-	  if (fl1 && fl2 && (fl1->offset > fl2->offset))
+	    {
+	      fl2 = s;
+	      if (fl1)
+		break;
+	    }
+	}
+
+      if (s)
+	{
+	  /* Can these lengths be zero?  */
+	  if (fl1->length <= 0 || fl2->length <= 0)
+	    return 1;
+	  /* These can't overlap if [f11,fl1+length] is before 
+	     [fl2,fl2+length], or [fl2,fl2+length] is before
+	     [fl1,fl1+length], otherwise they do overlap.  */
+	  if (fl1->offset + fl1->length > fl2->offset
+	      && fl2->offset + fl2->length > fl1->offset)
 	    return 1;
 	}
     }
-return 0;
+  return 0;
 }
 
 
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 2a5d01c..24c92b3 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -1352,6 +1352,7 @@ typedef struct gfc_equiv_info
 {
   gfc_symbol *sym;
   HOST_WIDE_INT offset;
+  HOST_WIDE_INT length;
   struct gfc_equiv_info *next;
 } gfc_equiv_info;
 
diff --git a/gcc/fortran/trans-common.c b/gcc/fortran/trans-common.c
index 3b34b334..3b16e5e 100644
--- a/gcc/fortran/trans-common.c
+++ b/gcc/fortran/trans-common.c
@@ -169,6 +169,7 @@ copy_equiv_list_to_ns (segment_info *c)
       l->equiv = s;
       s->sym = f->sym;
       s->offset = f->offset;
+      s->length = f->length;
     }
 }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 90dc700..63fa39d 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2006-03-16  Roger Sayle  <roger@eyesopen.com>
 
+	* gfortran.dg/dependency_13.f90: New test case.
+
+2006-03-16  Roger Sayle  <roger@eyesopen.com>
+
 	PR middle-end/21781
 	* gcc.dg/real-const-1.c: New test case.
 
diff --git a/gcc/testsuite/gfortran.dg/dependency_13.f90 b/gcc/testsuite/gfortran.dg/dependency_13.f90
new file mode 100644
index 0000000..85fb977
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/dependency_13.f90
@@ -0,0 +1,13 @@
+! { dg-do compile }
+! { dg-options "-O2 -fdump-tree-original" }
+   integer :: i(5)
+   real(4) :: x(5)
+   equivalence(x,i)
+
+   i = (/ 1, 0, 3, 5, 0 /)
+   where (i(1:4) .ne. 0)
+     x(2:5) = -42.
+   end where
+   end
+! { dg-final { scan-tree-dump-times "malloc" 1 "original" } }
+! { dg-final { cleanup-tree-dump "original" } }