expr.c (expand_expr, [...]): Refine slightly and also support TREE_ADDRESSABLE.

	* expr.c (expand_expr, case VIEW_CONVERT_EXPR): Refine slightly
	and also support TREE_ADDRESSABLE.
	* tree.def (VIEW_CONVERT_EXPR): Document TREE_ADDRESSABLE.

From-SVN: r47249

gcc/ChangeLog

+Wed Nov 21 17:37:16 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
+
+	* expr.c (expand_expr, case VIEW_CONVERT_EXPR): Refine slightly
+	and also support TREE_ADDRESSABLE.
+	* tree.def (VIEW_CONVERT_EXPR): Document TREE_ADDRESSABLE.
+
 2001-11-21  David Edelsohn  <edelsohn@gnu.org>
 
 	* rs6000.md (cmptf_internal1): Replace %$ with $.

gcc/expr.c

@@ -7542,47 +7542,43 @@ expand_expr (exp, target, tmode, modifier)
 
       /* If the input and output modes are both the same, we are done.
 	 Otherwise, if neither mode is BLKmode and both are within a word, we
-	 can use gen_lowpart.  If neither is true, store the operand into
-	 memory and convert the MEM to the new mode.  */
+	 can use gen_lowpart.  If neither is true, make sure the operand is
+	 in memory and convert the MEM to the new mode.  */
       if (TYPE_MODE (type) == GET_MODE (op0))
 	;
       else if (TYPE_MODE (type) != BLKmode && GET_MODE (op0) != BLKmode
 	       && GET_MODE_SIZE (TYPE_MODE (type)) <= UNITS_PER_WORD
 	       && GET_MODE_SIZE (GET_MODE (op0)) <= UNITS_PER_WORD)
 	op0 = gen_lowpart (TYPE_MODE (type), op0);
-      else
+      else if (GET_CODE (op0) != MEM)
 	{
+	  /* If the operand is not a MEM, force it into memory.  Since we
+	     are going to be be changing the mode of the MEM, don't call
+	     force_const_mem for constants because we don't allow pool
+	     constants to change mode.  */
 	  tree inner_type = TREE_TYPE (TREE_OPERAND (exp, 0));
-	  enum machine_mode non_blkmode
-	    = GET_MODE (op0) == BLKmode ? TYPE_MODE (type) : GET_MODE (op0);
 
-	  if (CONSTANT_P (op0))
-	    op0 = validize_mem (force_const_mem (TYPE_MODE (inner_type), op0));
-	  else
-	    {
+	  if (TREE_ADDRESSABLE (exp))
+	    abort ();
+
 	  if (target == 0 || GET_MODE (target) != TYPE_MODE (inner_type))
 	    target
-		  = assign_stack_temp_for_type (TYPE_MODE (inner_type),
-						GET_MODE_SIZE (non_blkmode),
-						0, inner_type);
+	      = assign_stack_temp_for_type
+		(TYPE_MODE (inner_type),
+		 GET_MODE_SIZE (TYPE_MODE (inner_type)), 0, inner_type);
 
-	      if (GET_MODE (target) == BLKmode)
-		emit_block_move (target, op0,
-				 expr_size (TREE_OPERAND (exp, 0)));
-	      else
 	  emit_move_insn (target, op0);
-
 	  op0 = target;
 	}
-	}
 
+      /* At this point, OP0 is in the correct mode.  If the output type is such
+	 that the operand is known to be aligned, indicate that it is.
+	 Otherwise, we need only be concerned about alignment for non-BLKmode
+	 results.  */
       if (GET_CODE (op0) == MEM)
 	{
 	  op0 = copy_rtx (op0);
 
-	  /* If the output type is such that the operand is known to be
-	     aligned, indicate that it is.  Otherwise, we need only be
-	     concerned about alignment for non-BLKmode results.  */
 	  if (TYPE_ALIGN_OK (type))
 	    set_mem_align (op0, MAX (MEM_ALIGN (op0), TYPE_ALIGN (type)));
 	  else if (TYPE_MODE (type) != BLKmode && STRICT_ALIGNMENT
@@ -7595,6 +7591,9 @@ expand_expr (exp, target, tmode, modifier)
 						    temp_size, 0, type);
 	      rtx new_with_op0_mode = copy_rtx (new);
 
+	      if (TREE_ADDRESSABLE (exp))
+		abort ();
+
 	      PUT_MODE (new_with_op0_mode, GET_MODE (op0));
 	      if (GET_MODE (op0) == BLKmode)
 		emit_block_move (new_with_op0_mode, op0,

gcc/tree.def

@@ -695,7 +695,12 @@ DEFTREECODE (NON_LVALUE_EXPR, "non_lvalue_expr", '1', 1)
    This corresponds to an "Unchecked Conversion" in Ada and roughly to
    the idiom *(type2 *)&X in C.  The only operand is the value to be
    viewed as being of another type.  It is undefined if the type of the
-   input and of the expression have different sizes.  */
+   input and of the expression have different sizes.
+
+   This code may also be used within the LHS of a MODIFY_EXPR, in which
+   case no actual data motion may occur.  TREE_ADDRESSABLE will be set in
+   this case and GCC must abort if it could not do the operation without
+   generating insns.  */
 DEFTREECODE (VIEW_CONVERT_EXPR, "view_convert_expr", '1', 1)
 
 /* Represents something we computed once and will use multiple times.