PR tree-optimization/23320

        * tree-data-ref.c (base_addr_differ_p): Add comment. Check
        data-refs' types instead of base object nullness. Add check for
        pointer type data-refs before first location comparison. Remove
        assert.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@103076 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1168018..028dfc7 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2005-08-14  Ira Rosen  <irar@il.ibm.com>
+
+       PR tree-optimization/23320
+       * tree-data-ref.c (base_addr_differ_p): Add comment. Check 
+       data-refs' types instead of base object nullness. Add check for 
+       pointer type data-refs before first location comparison. Remove 
+       assert.
+
 2005-08-14  Andreas Schwab  <schwab@suse.de>
 
        * doc/md.texi (Machine Constraints): Fix misplaced @end table.

diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index 7fc6424..24856ed 100644 (file)
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -384,11 +384,18 @@ base_object_differ_p (struct data_reference *a,
 /* Function base_addr_differ_p.
 
    This is the simplest data dependence test: determines whether the
-   data references A and B access the same array/region.  Returns
+   data references DRA and DRB access the same array/region.  Returns
    false when the property is not computable at compile time.
-   Otherwise return true, and DIFFER_P will record the result. This
-   utility will not be necessary when alias_sets_conflict_p will be
-   less conservative.  */
+   Otherwise return true, and DIFFER_P will record the result.
+
+   The algorithm:   
+   1. if (both DRA and DRB are represented as arrays)
+          compare DRA.BASE_OBJECT and DRB.BASE_OBJECT
+   2. else if (both DRA and DRB are represented as pointers)
+          try to prove that DRA.FIRST_LOCATION == DRB.FIRST_LOCATION
+   3. else if (DRA and DRB are represented differently or 2. fails)
+          only try to prove that the bases are surely different
+*/
 
 
 static bool
@@ -409,26 +416,27 @@ base_addr_differ_p (struct data_reference *dra,
 
   gcc_assert (POINTER_TYPE_P (type_a) &&  POINTER_TYPE_P (type_b));
   
-  /* Compare base objects first if possible. If DR_BASE_OBJECT is NULL, it means
-     that the data-ref is of INDIRECT_REF, and alias analysis will be applied to 
-     reveal the dependence.  */
-  if (DR_BASE_OBJECT (dra) && DR_BASE_OBJECT (drb))
+  /* 1. if (both DRA and DRB are represented as arrays)
+            compare DRA.BASE_OBJECT and DRB.BASE_OBJECT.  */
+  if (DR_TYPE (dra) == ARRAY_REF_TYPE && DR_TYPE (drb) == ARRAY_REF_TYPE)
     return base_object_differ_p (dra, drb, differ_p);
 
+
+  /* 2. else if (both DRA and DRB are represented as pointers)
+           try to prove that DRA.FIRST_LOCATION == DRB.FIRST_LOCATION.  */
   /* If base addresses are the same, we check the offsets, since the access of 
      the data-ref is described by {base addr + offset} and its access function,
      i.e., in order to decide whether the bases of data-refs are the same we 
      compare both base addresses and offsets.  */
-  if (addr_a == addr_b 
-      || (TREE_CODE (addr_a) == ADDR_EXPR && TREE_CODE (addr_b) == ADDR_EXPR
-         && TREE_OPERAND (addr_a, 0) == TREE_OPERAND (addr_b, 0)))
+  if (DR_TYPE (dra) == POINTER_REF_TYPE && DR_TYPE (drb) == POINTER_REF_TYPE
+      && (addr_a == addr_b 
+         || (TREE_CODE (addr_a) == ADDR_EXPR && TREE_CODE (addr_b) == ADDR_EXPR
+             && TREE_OPERAND (addr_a, 0) == TREE_OPERAND (addr_b, 0))))
     {
       /* Compare offsets.  */
       tree offset_a = DR_OFFSET (dra); 
       tree offset_b = DR_OFFSET (drb);
       
-      gcc_assert (!DR_BASE_OBJECT (dra) && !DR_BASE_OBJECT (drb));
-
       STRIP_NOPS (offset_a);
       STRIP_NOPS (offset_b);
 
@@ -445,6 +453,9 @@ base_addr_differ_p (struct data_reference *dra,
        }
     }
 
+  /*  3. else if (DRA and DRB are represented differently or 2. fails) 
+              only try to prove that the bases are surely different.  */
+
   /* Apply alias analysis.  */
   if (may_alias_p (addr_a, addr_b, dra, drb, &aliased) && !aliased)
     {