2011-05-25 Richard Guenther <rguenther@suse.de>

	* tree-ssa-alias.c (indirect_ref_may_alias_decl_p): Fix
	type-based offset disambiguation, streamline MEM_REF and
	TARGET_MEM_REF handling.


git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@174206 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 45 insertions, 20 deletions

diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index ba76ae10ab1..3656b396d86 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -718,8 +718,9 @@ indirect_ref_may_alias_decl_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
 			       alias_set_type base2_alias_set, bool tbaa_p)
 {
   tree ptr1;
-  tree ptrtype1;
+  tree ptrtype1, dbase2;
   HOST_WIDE_INT offset1p = offset1, offset2p = offset2;
+  HOST_WIDE_INT doffset1, doffset2;
   double_int moff;
 
   gcc_checking_assert ((TREE_CODE (base1) == MEM_REF
@@ -766,20 +767,6 @@ indirect_ref_may_alias_decl_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
   if (base2_alias_set == -1)
     base2_alias_set = get_alias_set (base2);
 
-  /* If both references are through the same type, they do not alias
-     if the accesses do not overlap.  This does extra disambiguation
-     for mixed/pointer accesses but requires strict aliasing.
-     For MEM_REFs we require that the component-ref offset we computed
-     is relative to the start of the type which we ensure by
-     comparing rvalue and access type and disregarding the constant
-     pointer offset.  */
-  if ((TREE_CODE (base1) != TARGET_MEM_REF
-       || (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
-      && (TREE_CODE (base1) != MEM_REF
-	  || same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) == 1)
-      && same_type_for_tbaa (TREE_TYPE (ptrtype1), TREE_TYPE (base2)) == 1)
-    return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
-
   /* When we are trying to disambiguate an access with a pointer dereference
      as base versus one with a decl as base we can use both the size
      of the decl and its dynamic type for extra disambiguation.
@@ -809,13 +796,51 @@ indirect_ref_may_alias_decl_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
       && tree_int_cst_lt (DECL_SIZE (base2), TYPE_SIZE (TREE_TYPE (ptrtype1))))
     return false;
 
+  if (!ref2)
+    return true;
+
+  /* If the decl is accressed via a MEM_REF, reconstruct the base
+     we can use for TBAA and an appropriately adjusted offset.  */
+  dbase2 = ref2;
+  while (handled_component_p (dbase2))
+    dbase2 = TREE_OPERAND (dbase2, 0);
+  doffset1 = offset1;
+  doffset2 = offset2;
+  if (TREE_CODE (dbase2) == MEM_REF
+      || TREE_CODE (dbase2) == TARGET_MEM_REF)
+    {
+      double_int moff = mem_ref_offset (dbase2);
+      moff = double_int_lshift (moff,
+				BITS_PER_UNIT == 8
+				? 3 : exact_log2 (BITS_PER_UNIT),
+				HOST_BITS_PER_DOUBLE_INT, true);
+      if (double_int_negative_p (moff))
+	doffset1 -= double_int_neg (moff).low;
+      else
+	doffset2 -= moff.low;
+    }
+
+  /* If either reference is view-converted, give up now.  */
+  if (same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) != 1
+      || same_type_for_tbaa (TREE_TYPE (dbase2),
+			     TREE_TYPE (reference_alias_ptr_type (dbase2))) != 1)
+    return true;
+
+  /* If both references are through the same type, they do not alias
+     if the accesses do not overlap.  This does extra disambiguation
+     for mixed/pointer accesses but requires strict aliasing.
+     For MEM_REFs we require that the component-ref offset we computed
+     is relative to the start of the type which we ensure by
+     comparing rvalue and access type and disregarding the constant
+     pointer offset.  */
+  if ((TREE_CODE (base1) != TARGET_MEM_REF
+       || (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
+      && same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (dbase2)) == 1)
+    return ranges_overlap_p (doffset1, max_size1, doffset2, max_size2);
+
   /* Do access-path based disambiguation.  */
   if (ref1 && ref2
-      && handled_component_p (ref1)
-      && handled_component_p (ref2)
-      && TREE_CODE (base1) != TARGET_MEM_REF
-      && (TREE_CODE (base1) != MEM_REF
-	  || same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) == 1))
+      && (handled_component_p (ref1) || handled_component_p (ref2)))
     return aliasing_component_refs_p (ref1,
 				      ref1_alias_set, base1_alias_set,
 				      offset1, max_size1,