On a change of tack, this tackles some redundant code in combine.
It has code to convert a variable bit position to the mode required
by the bit position operand to insv, extv or extzv:
[A]
else if (pos_rtx != 0
&& GET_MODE_SIZE (pos_mode) < GET_MODE_SIZE (GET_MODE (pos_rtx)))
pos_rtx = gen_lowpart (pos_mode, pos_rtx);
However, this is protected by an earlier:
[B]
if (pos_rtx && GET_MODE (pos_rtx) != VOIDmode
&& GET_MODE_SIZE (pos_mode) < GET_MODE_SIZE (GET_MODE (pos_rtx)))
pos_mode = GET_MODE (pos_rtx);
so [B] makes [A] redundant. That leaves this block:
/* Adjust mode of POS_RTX, if needed. If we want a wider mode, we
have to zero extend. Otherwise, we can just use a SUBREG. */
if (pos_rtx != 0
&& GET_MODE_SIZE (pos_mode) > GET_MODE_SIZE (GET_MODE (pos_rtx)))
{
as the only use of pos_mode, so [B] can go too.
Similarly, the memory case has:
[C]
/* If we have to change the mode of memory and cannot, the desired mode
is EXTRACTION_MODE. */
if (inner_mode != wanted_inner_mode
&& (mode_dependent_address_p (XEXP (inner, 0), MEM_ADDR_SPACE (inner))
|| MEM_VOLATILE_P (inner)
|| pos_rtx))
wanted_inner_mode = extraction_mode;
but those same conditions are repeated in the code that actually
applies wanted_inner_mode:
/* If INNER has a wider mode, and this is a constant extraction, try to
make it smaller and adjust the byte to point to the byte containing
the value. */
if (wanted_inner_mode != VOIDmode
&& inner_mode != wanted_inner_mode
&& ! pos_rtx
&& GET_MODE_SIZE (wanted_inner_mode) < GET_MODE_SIZE (is_mode)
&& MEM_P (inner)
&& ! mode_dependent_address_p (XEXP (inner, 0), MEM_ADDR_SPACE (inner))
&& ! MEM_VOLATILE_P (inner))
{
so [C] too is unnecessary.
Tested as described in the covering note. OK to install?
Richard
gcc/
* combine.c (make_extraction): Remove dead wanted_inner_mode-
and pos_rtx-related code.
Index: gcc/combine.c
===================================================================
--- gcc/combine.c 2012-10-27 22:22:45.000000000 +0100
+++ gcc/combine.c 2012-10-27 22:32:26.811370582 +0100
@@ -7211,10 +7211,6 @@ make_extraction (enum machine_mode mode,
&& GET_MODE_SIZE (extraction_mode) < GET_MODE_SIZE (mode))
extraction_mode = mode;
- if (pos_rtx && GET_MODE (pos_rtx) != VOIDmode
- && GET_MODE_SIZE (pos_mode) < GET_MODE_SIZE (GET_MODE (pos_rtx)))
- pos_mode = GET_MODE (pos_rtx);
-
/* If this is not from memory, the desired mode is the preferred mode
for an extraction pattern's first input operand, or word_mode if there
is none. */
@@ -7231,14 +7227,6 @@ make_extraction (enum machine_mode mode,
wanted_inner_mode = GET_MODE_WIDER_MODE (wanted_inner_mode);
gcc_assert (wanted_inner_mode != VOIDmode);
}
-
- /* If we have to change the mode of memory and cannot, the desired mode
- is EXTRACTION_MODE. */
- if (inner_mode != wanted_inner_mode
- && (mode_dependent_address_p (XEXP (inner, 0), MEM_ADDR_SPACE (inner))
- || MEM_VOLATILE_P (inner)
- || pos_rtx))
- wanted_inner_mode = extraction_mode;
}
orig_pos = pos;
@@ -7359,9 +7347,6 @@ make_extraction (enum machine_mode mode,
}
pos_rtx = temp;
}
- else if (pos_rtx != 0
- && GET_MODE_SIZE (pos_mode) < GET_MODE_SIZE (GET_MODE (pos_rtx)))
- pos_rtx = gen_lowpart (pos_mode, pos_rtx);
/* Make POS_RTX unless we already have it and it is correct. If we don't
have a POS_RTX but we do have an ORIG_POS_RTX, the latter must
