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combine.c (expand_compound_operation): Do not convert ZERO_EXTEND to SIGN_EXTEND, convert SIGN_EXTEND to ZERO_EXTEND.

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* combine.c (expand_compound_operation): Do not convert ZERO_EXTEND to
	SIGN_EXTEND, convert SIGN_EXTEND to ZERO_EXTEND.
	(make_compound_operation): Choose cheaper alternative between
	ZERO_EXTEND and SIGN_EXTEND when sign bit is not set.

From-SVN: r31180
This commit is contained in:
Jan Hubicka 2000-01-03 16:49:51 +01:00 committed by Jan Hubicka
parent f741a71c75
commit 0f808b6f0a
2 changed files with 69 additions and 28 deletions
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5
gcc/ChangeLog
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@ -1,5 +1,10 @@
Mon Jan 3 15:33:37 MET 2000 Jan Hubicka <hubicka@freesoft.cz>
* combine.c (expand_compound_operation): Do not convert ZERO_EXTEND to
SIGN_EXTEND, convert SIGN_EXTEND to ZERO_EXTEND.
(make_compound_operation): Choose cheaper alternative between
ZERO_EXTEND and SIGN_EXTEND when sign bit is not set.
* regclass.c (op_costs): Remove global variable.
(record_reg_classes): New parameter "op_costs" and "reg_pref".
(record_operand_costs): Break out from ...

92
gcc/combine.c
View File

@ -5486,6 +5486,20 @@ expand_compound_operation (x)
default:
return x;
}
/* Convert sign extension to zero extension, if we know that the high
bit is not set, as this is easier to optimize. It will be converted
back to cheaper alternative in make_extraction. */
if (GET_CODE (x) == SIGN_EXTEND
&& (GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT
&& ((nonzero_bits (XEXP (x, 0), GET_MODE (XEXP (x, 0)))
& ~ (((unsigned HOST_WIDE_INT)
GET_MODE_MASK (GET_MODE (XEXP (x, 0))))
>> 1))
== 0)))
{
rtx temp = gen_rtx_ZERO_EXTEND (GET_MODE (x), XEXP (x, 0));
return expand_compound_operation (temp);
}
/* We can optimize some special cases of ZERO_EXTEND. */
if (GET_CODE (x) == ZERO_EXTEND)
@ -5533,30 +5547,6 @@ expand_compound_operation (x)
& ~ GET_MODE_MASK (GET_MODE (XEXP (x, 0)))) == 0)
return SUBREG_REG (XEXP (x, 0));
/* If sign extension is cheaper than zero extension, then use it
if we know that no extraneous bits are set, and that the high
bit is not set. */
if (flag_expensive_optimizations
&& ((GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT
&& ((nonzero_bits (XEXP (x, 0), GET_MODE (x))
& ~ (((unsigned HOST_WIDE_INT)
GET_MODE_MASK (GET_MODE (XEXP (x, 0))))
>> 1))
== 0))
|| (GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == '<'
&& (GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)))
<= HOST_BITS_PER_WIDE_INT)
&& (((HOST_WIDE_INT) STORE_FLAG_VALUE
& ~ (((unsigned HOST_WIDE_INT)
GET_MODE_MASK (GET_MODE (XEXP (x, 0))))
>> 1))
== 0))))
{
rtx temp = gen_rtx_SIGN_EXTEND (GET_MODE (x), XEXP (x, 0));
if (rtx_cost (temp, SET) < rtx_cost (x, SET))
return expand_compound_operation (temp);
}
}
/* If we reach here, we want to return a pair of shifts. The inner
@ -5894,12 +5884,35 @@ make_extraction (mode, inner, pos, pos_rtx, len,
? gen_rtx_CLOBBER (tmode, const0_rtx)
: gen_rtx_combine (STRICT_LOW_PART, VOIDmode, new)));
if (mode == tmode)
return new;
/* If we know that no extraneous bits are set, and that the high
bit is not set, convert the extraction to the cheaper of
sign and zero extension, that are equivalent in these cases. */
if (flag_expensive_optimizations
&& (GET_MODE_BITSIZE (tmode) <= HOST_BITS_PER_WIDE_INT
&& ((nonzero_bits (new, tmode)
& ~ (((unsigned HOST_WIDE_INT)
GET_MODE_MASK (tmode))
>> 1))
== 0)))
{
rtx temp = gen_rtx_ZERO_EXTEND (mode, new);
rtx temp1 = gen_rtx_SIGN_EXTEND (mode, new);
/* Prefer ZERO_EXTENSION, since it gives more information to
backends. */
if (rtx_cost (temp, SET) < rtx_cost (temp1, SET))
return temp;
return temp1;
}
/* Otherwise, sign- or zero-extend unless we already are in the
proper mode. */
return (mode == tmode ? new
: gen_rtx_combine (unsignedp ? ZERO_EXTEND : SIGN_EXTEND,
mode, new));
return (gen_rtx_combine (unsignedp ? ZERO_EXTEND : SIGN_EXTEND,
mode, new));
}
/* Unless this is a COMPARE or we have a funny memory reference,
@ -6088,7 +6101,30 @@ make_extraction (mode, inner, pos, pos_rtx, len,
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)))
pos_rtx = gen_rtx_combine (ZERO_EXTEND, pos_mode, pos_rtx);
{
rtx temp = gen_rtx_combine (ZERO_EXTEND, pos_mode, pos_rtx);
/* If we know that no extraneous bits are set, and that the high
bit is not set, convert extraction to cheaper one - eighter
SIGN_EXTENSION or ZERO_EXTENSION, that are equivalent in these
cases. */
if (flag_expensive_optimizations
&& (GET_MODE_BITSIZE (GET_MODE (pos_rtx)) <= HOST_BITS_PER_WIDE_INT
&& ((nonzero_bits (pos_rtx, GET_MODE (pos_rtx))
& ~ (((unsigned HOST_WIDE_INT)
GET_MODE_MASK (GET_MODE (pos_rtx)))
>> 1))
== 0)))
{
rtx temp1 = gen_rtx_SIGN_EXTEND (pos_mode, pos_rtx);
/* Preffer ZERO_EXTENSION, since it gives more information to
backends. */
if (rtx_cost (temp1, SET) < rtx_cost (temp, SET))
temp = temp1;
}
pos_rtx = temp;
}
else if (pos_rtx != 0
&& GET_MODE_SIZE (pos_mode) < GET_MODE_SIZE (GET_MODE (pos_rtx)))
pos_rtx = gen_lowpart_for_combine (pos_mode, pos_rtx);