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(find_split_point, case SET): If SET_SRC is NE and STORE_FLAG_VALUE is -1, see if we can convert into NEG of shift.

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(find_split_point, case SET): If SET_SRC is NE and
STORE_FLAG_VALUE is -1, see if we can convert into NEG of shift.
(force_to_mode, case NE): Make condition stricter.

From-SVN: r13370
This commit is contained in:
Richard Kenner 1997-01-04 18:48:04 -05:00
parent 4d6a19ff0f
commit 1a6ec0703b
1 changed files with 26 additions and 3 deletions
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29
gcc/combine.c
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@ -1,5 +1,5 @@
/* Optimize by combining instructions for GNU compiler.
Copyright (C) 1987, 88, 92, 93, 94, 95, 1996 Free Software Foundation, Inc.
Copyright (C) 1987, 88, 92-96, 1997 Free Software Foundation, Inc.
This file is part of GNU CC.
@ -2667,6 +2667,29 @@ find_split_point (loc, insn)
}
break;
case NE:
/* if STORE_FLAG_VALUE is -1, this is (NE X 0) and only one bit of X
is known to be on, this can be converted into a NEG of a shift. */
if (STORE_FLAG_VALUE == -1 && XEXP (SET_SRC (x), 1) == const0_rtx
&& GET_MODE (SET_SRC (x)) == GET_MODE (XEXP (SET_SRC (x), 0))
&& 1 <= (len = exact_log2
(nonzero_bits (XEXP (SET_SRC (x), 0),
GET_MODE (XEXP (SET_SRC (x), 0))))))
{
enum machine_mode mode = GET_MODE (XEXP (SET_SRC (x), 0));
SUBST (SET_SRC (x),
gen_rtx_combine (NEG, mode,
gen_rtx_combine (LSHIFTRT, mode,
XEXP (SET_SRC (x), 0),
GEN_INT (len))));
split = find_split_point (&SET_SRC (x), insn);
if (split && split != &SET_SRC (x))
return split;
}
break;
case SIGN_EXTEND:
inner = XEXP (SET_SRC (x), 0);
pos = 0;
@ -6383,10 +6406,10 @@ force_to_mode (x, mode, mask, reg, just_select)
case NE:
/* (and (ne FOO 0) CONST) can be (and FOO CONST) if CONST is included
in STORE_FLAG_VALUE and FOO has a single bit that might be nonzero,
which is in CONST. */
which is equal to STORE_FLAG_VALUE. */
if ((mask & ~ STORE_FLAG_VALUE) == 0 && XEXP (x, 1) == const0_rtx
&& exact_log2 (nonzero_bits (XEXP (x, 0), mode)) >= 0
&& (nonzero_bits (XEXP (x, 0), mode) & ~ mask) == 0)
&& nonzero_bits (XEXP (x, 0), mode) == STORE_FLAG_VALUE)
return force_to_mode (XEXP (x, 0), mode, mask, reg, next_select);
break;