This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[PATCH] Avoid useless temporary with VIEW_CONVERT_EXPR
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 11 Jun 2008 09:14:11 +0200
- Subject: [PATCH] Avoid useless temporary with VIEW_CONVERT_EXPR
Hi,
In Ada we now try to promote the alignment of stand-alone objects beyond that
of their type and, when they are small, to promote their machine mode as well.
This means that we introduce VIEW_CONVERT_EXPRs when converting back to the
nominal type of the object and they are from integral modes to BLKmode.
While the RTL expander of VIEW_CONVERT_EXPR deals with the other cases quite
reasonably, it doesn't really with this one since it will always create a
stack temporary
/* As a last resort, spill op0 to memory, and reload it in a
different mode. */
else if (!MEM_P (op0))
{
When the source object is already a MEM, this is just plain wasteful and the
temporary cannot be eliminated because it involves mode frobbing. The patch
makes it so that the RTL expander fetches an inner memory reference in this
case instead of creating the temporary.
Tested on i586-suse-linux, OK for mainline?
2008-06-11 Eric Botcazou <ebotcazou@adacore.com>
* expr.c (expand_expr_real_1) <VIEW_CONVERT_EXPR>: When converting
to BLKmode, try to fetch an inner memory reference. Use 'mode' in
lieu of TYPE_MODE (type) throughout.
--
Eric Botcazou
Index: expr.c
===================================================================
--- expr.c (revision 136584)
+++ expr.c (working copy)
@@ -8132,26 +8132,89 @@ expand_expr_real_1 (tree exp, rtx target
return REDUCE_BIT_FIELD (op0);
case VIEW_CONVERT_EXPR:
- op0 = expand_expr (TREE_OPERAND (exp, 0), NULL_RTX, mode, modifier);
+ op0 = NULL_RTX;
+
+ /* If we are converting to BLKmode, try to avoid an intermediate
+ temporary by fetching an inner memory reference. */
+ if (mode == BLKmode
+ && TREE_CODE (TYPE_SIZE (TREE_TYPE (exp))) == INTEGER_CST
+ && TYPE_MODE (TREE_TYPE (TREE_OPERAND (exp, 0))) != BLKmode
+ && handled_component_p (TREE_OPERAND (exp, 0)))
+ {
+ enum machine_mode mode1;
+ HOST_WIDE_INT bitsize, bitpos;
+ tree offset;
+ int unsignedp;
+ int volatilep = 0;
+ tree tem
+ = get_inner_reference (TREE_OPERAND (exp, 0), &bitsize, &bitpos,
+ &offset, &mode1, &unsignedp, &volatilep,
+ true);
+ rtx orig_op0;
+
+ /* ??? We should work harder and deal with non-zero offsets. */
+ if (!offset
+ && (bitpos % BITS_PER_UNIT) == 0
+ && bitsize >= 0
+ && compare_tree_int (TYPE_SIZE (TREE_TYPE (exp)), bitsize) == 0)
+ {
+ /* See the normal_inner_ref case for the rationale. */
+ orig_op0
+ = expand_expr (tem,
+ (TREE_CODE (TREE_TYPE (tem)) == UNION_TYPE
+ && (TREE_CODE (TYPE_SIZE (TREE_TYPE (tem)))
+ != INTEGER_CST)
+ && modifier != EXPAND_STACK_PARM
+ ? target : NULL_RTX),
+ VOIDmode,
+ (modifier == EXPAND_INITIALIZER
+ || modifier == EXPAND_CONST_ADDRESS
+ || modifier == EXPAND_STACK_PARM)
+ ? modifier : EXPAND_NORMAL);
+
+ if (MEM_P (orig_op0))
+ {
+ op0 = orig_op0;
+
+ /* Get a reference to just this component. */
+ if (modifier == EXPAND_CONST_ADDRESS
+ || modifier == EXPAND_SUM
+ || modifier == EXPAND_INITIALIZER)
+ op0 = adjust_address_nv (op0, mode, bitpos / BITS_PER_UNIT);
+ else
+ op0 = adjust_address (op0, mode, bitpos / BITS_PER_UNIT);
+
+ if (op0 == orig_op0)
+ op0 = copy_rtx (op0);
+
+ set_mem_attributes (op0, TREE_OPERAND (exp, 0), 0);
+ if (REG_P (XEXP (op0, 0)))
+ mark_reg_pointer (XEXP (op0, 0), MEM_ALIGN (op0));
+
+ MEM_VOLATILE_P (op0) |= volatilep;
+ }
+ }
+ }
+
+ if (!op0)
+ op0 = expand_expr (TREE_OPERAND (exp, 0), NULL_RTX, mode, modifier);
/* If the input and output modes are both the same, we are done. */
- if (TYPE_MODE (type) == GET_MODE (op0))
+ if (mode == GET_MODE (op0))
;
/* If neither mode is BLKmode, and both modes are the same size
then we can use gen_lowpart. */
- else if (TYPE_MODE (type) != BLKmode && GET_MODE (op0) != BLKmode
- && GET_MODE_SIZE (TYPE_MODE (type))
- == GET_MODE_SIZE (GET_MODE (op0)))
+ else if (mode != BLKmode && GET_MODE (op0) != BLKmode
+ && GET_MODE_SIZE (mode) == GET_MODE_SIZE (GET_MODE (op0)))
{
if (GET_CODE (op0) == SUBREG)
op0 = force_reg (GET_MODE (op0), op0);
- op0 = gen_lowpart (TYPE_MODE (type), op0);
+ op0 = gen_lowpart (mode, op0);
}
/* If both modes are integral, then we can convert from one to the
other. */
- else if (SCALAR_INT_MODE_P (GET_MODE (op0))
- && SCALAR_INT_MODE_P (TYPE_MODE (type)))
- op0 = convert_modes (TYPE_MODE (type), GET_MODE (op0), op0,
+ else if (SCALAR_INT_MODE_P (GET_MODE (op0)) && SCALAR_INT_MODE_P (mode))
+ op0 = convert_modes (mode, GET_MODE (op0), op0,
TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (exp, 0))));
/* As a last resort, spill op0 to memory, and reload it in a
different mode. */
@@ -8185,22 +8248,22 @@ expand_expr_real_1 (tree exp, rtx target
if (TYPE_ALIGN_OK (type))
set_mem_align (op0, MAX (MEM_ALIGN (op0), TYPE_ALIGN (type)));
- else if (TYPE_MODE (type) != BLKmode && STRICT_ALIGNMENT
- && MEM_ALIGN (op0) < GET_MODE_ALIGNMENT (TYPE_MODE (type)))
+ else if (STRICT_ALIGNMENT
+ && mode != BLKmode
+ && MEM_ALIGN (op0) < GET_MODE_ALIGNMENT (mode))
{
tree inner_type = TREE_TYPE (TREE_OPERAND (exp, 0));
HOST_WIDE_INT temp_size
= MAX (int_size_in_bytes (inner_type),
- (HOST_WIDE_INT) GET_MODE_SIZE (TYPE_MODE (type)));
- rtx new = assign_stack_temp_for_type (TYPE_MODE (type),
- temp_size, 0, type);
+ (HOST_WIDE_INT) GET_MODE_SIZE (mode));
+ rtx new = assign_stack_temp_for_type (mode, temp_size, 0, type);
rtx new_with_op0_mode = adjust_address (new, GET_MODE (op0), 0);
gcc_assert (!TREE_ADDRESSABLE (exp));
if (GET_MODE (op0) == BLKmode)
emit_block_move (new_with_op0_mode, op0,
- GEN_INT (GET_MODE_SIZE (TYPE_MODE (type))),
+ GEN_INT (GET_MODE_SIZE (mode)),
(modifier == EXPAND_STACK_PARM
? BLOCK_OP_CALL_PARM : BLOCK_OP_NORMAL));
else
@@ -8209,7 +8272,7 @@ expand_expr_real_1 (tree exp, rtx target
op0 = new;
}
- op0 = adjust_address (op0, TYPE_MODE (type), 0);
+ op0 = adjust_address (op0, mode, 0);
}
return op0;