Index: gcc/testsuite/gcc.dg/tree-ssa/alias-27.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/alias-27.c	(revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/alias-27.c	(working copy)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+
+void f (long *p) {
+  *p = 42;
+  p[4] = 42;
+  __builtin_memset (p, 0, 100);
+}
+
+/* { dg-final { scan-tree-dump-not "= 42" "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */

Property changes on: gcc/testsuite/gcc.dg/tree-ssa/alias-27.c
___________________________________________________________________
Added: svn:keywords
## -0,0 +1 ##
+Author Date Id Revision URL
\ No newline at end of property
Added: svn:eol-style
## -0,0 +1 ##
+native
\ No newline at end of property
Index: gcc/tree-ssa-alias.c
===================================================================
--- gcc/tree-ssa-alias.c	(revision 204608)
+++ gcc/tree-ssa-alias.c	(working copy)
@@ -2001,23 +2001,24 @@ stmt_may_clobber_ref_p (gimple stmt, tre
   return stmt_may_clobber_ref_p_1 (stmt, &r);
 }
 
 /* If STMT kills the memory reference REF return true, otherwise
    return false.  */
 
 static bool
 stmt_kills_ref_p_1 (gimple stmt, ao_ref *ref)
 {
   /* For a must-alias check we need to be able to constrain
-     the access properly.  */
-  ao_ref_base (ref);
-  if (ref->max_size == -1)
+     the access properly.
+     FIXME: except for BUILTIN_FREE.  */
+  if (!ao_ref_base (ref)
+      || ref->max_size == -1)
     return false;
 
   if (gimple_has_lhs (stmt)
       && TREE_CODE (gimple_get_lhs (stmt)) != SSA_NAME
       /* The assignment is not necessarily carried out if it can throw
 	 and we can catch it in the current function where we could inspect
 	 the previous value.
 	 ???  We only need to care about the RHS throwing.  For aggregate
 	 assignments or similar calls and non-call exceptions the LHS
 	 might throw as well.  */
@@ -2090,37 +2091,47 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref
 	  case BUILT_IN_MEMPCPY:
 	  case BUILT_IN_MEMMOVE:
 	  case BUILT_IN_MEMSET:
 	  case BUILT_IN_MEMCPY_CHK:
 	  case BUILT_IN_MEMPCPY_CHK:
 	  case BUILT_IN_MEMMOVE_CHK:
 	  case BUILT_IN_MEMSET_CHK:
 	    {
 	      tree dest = gimple_call_arg (stmt, 0);
 	      tree len = gimple_call_arg (stmt, 2);
-	      tree base = NULL_TREE;
-	      HOST_WIDE_INT offset = 0;
 	      if (!host_integerp (len, 0))
 		return false;
-	      if (TREE_CODE (dest) == ADDR_EXPR)
-		base = get_addr_base_and_unit_offset (TREE_OPERAND (dest, 0),
-						      &offset);
-	      else if (TREE_CODE (dest) == SSA_NAME)
-		base = dest;
-	      if (base
-		  && base == ao_ref_base (ref))
+	      tree rbase = ref->base;
+	      double_int roffset = double_int::from_shwi (ref->offset);
+	      ao_ref dref;
+	      ao_ref_init_from_ptr_and_size (&dref, dest, len);
+	      tree base = ao_ref_base (&dref);
+	      double_int offset = double_int::from_shwi (dref.offset);
+	      double_int bpu = double_int::from_uhwi (BITS_PER_UNIT);
+	      if (!base || dref.size == -1)
+		return false;
+	      if (TREE_CODE (base) == MEM_REF)
+		{
+		  if (TREE_CODE (rbase) != MEM_REF)
+		    return false;
+		  // Compare pointers.
+		  offset += bpu * mem_ref_offset (base);
+		  roffset += bpu * mem_ref_offset (rbase);
+		  base = TREE_OPERAND (base, 0);
+		  rbase = TREE_OPERAND (rbase, 0);
+		}
+	      if (base == rbase)
 		{
-		  HOST_WIDE_INT size = TREE_INT_CST_LOW (len);
-		  if (offset <= ref->offset / BITS_PER_UNIT
-		      && (offset + size
-		          >= ((ref->offset + ref->max_size + BITS_PER_UNIT - 1)
-			      / BITS_PER_UNIT)))
+		  double_int size = bpu * tree_to_double_int (len);
+		  double_int rsize = double_int::from_uhwi (ref->max_size);
+		  if (offset.sle (roffset)
+		      && (roffset + rsize).sle (offset + size))
 		    return true;
 		}
 	      break;
 	    }
 
 	  case BUILT_IN_VA_END:
 	    {
 	      tree ptr = gimple_call_arg (stmt, 0);
 	      if (TREE_CODE (ptr) == ADDR_EXPR)
 		{
