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(try_combine): Always call set_significant on new patterns, so don't call

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just in split case.

(subst): Move sign extension inside arithmetic when we have a constant
computation inside another computation.

From-SVN: r2194
This commit is contained in:
Richard Kenner 1992-09-20 20:05:40 -04:00
parent 80b0e34e58
commit 22609cbf24
1 changed files with 50 additions and 7 deletions
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57
gcc/combine.c
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@ -1585,17 +1585,12 @@ try_combine (i3, i2, i1)
newpat = newi3pat;
/* It is possible that both insns now set the destination of I3.
If so, we must show an extra use of it and update
reg_significant. */
If so, we must show an extra use of it. */
if (insn_code_number >= 0 && GET_CODE (SET_DEST (i3set)) == REG
&& GET_CODE (SET_DEST (i2set)) == REG
&& REGNO (SET_DEST (i3set)) == REGNO (SET_DEST (i2set)))
{
reg_n_sets[REGNO (SET_DEST (i2set))]++;
set_significant (SET_DEST (i2set), i2set);
set_significant (SET_DEST (i3set), i3set);
}
reg_n_sets[REGNO (SET_DEST (i2set))]++;
}
/* If we can split it and use I2DEST, go ahead and see if that
@ -2073,6 +2068,13 @@ try_combine (i3, i2, i1)
}
}
/* Update reg_significant et al for any changes that may have been made
to this insn. */
note_stores (newpat, set_significant);
if (newi2pat)
note_stores (newi2pat, set_significant);
/* If I3 is now an unconditional jump, ensure that it has a
BARRIER following it since it may have initially been a
conditional jump. */
@ -2670,6 +2672,47 @@ subst (x, from, to, in_dest, unique_copy)
SUBST (XEXP (x, 1), temp);
}
/* If this is a PLUS, MINUS, or MULT, and the first operand is the
sign extension of a PLUS with a constant, reverse the order of the sign
extension and the addition. Note that this not the same as the original
code, but overflow is undefined for signed values. Also note that the
PLUS will have been partially moved "inside" the sign-extension, so that
the first operand of X will really look like:
(ashiftrt (plus (ashift A C4) C5) C4).
We convert this to
(plus (ashiftrt (ashift A C4) C2) C4)
and replace the first operand of X with that expression. Later parts
of this function may simplify the expression further.
For example, if we start with (mult (sign_extend (plus A C1)) C2),
we swap the SIGN_EXTEND and PLUS. Later code will apply the
distributive law to produce (plus (mult (sign_extend X) C1) C3).
We do this to simplify address expressions. */
if ((code == PLUS || code == MINUS || code == MULT)
&& GET_CODE (XEXP (x, 0)) == ASHIFTRT
&& GET_CODE (XEXP (XEXP (x, 0), 0)) == PLUS
&& GET_CODE (XEXP (XEXP (XEXP (x, 0), 0), 0)) == ASHIFT
&& GET_CODE (XEXP (XEXP (XEXP (XEXP (x, 0), 0), 0), 1)) == CONST_INT
&& GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
&& XEXP (XEXP (XEXP (XEXP (x, 0), 0), 0), 1) == XEXP (XEXP (x, 0), 1)
&& GET_CODE (XEXP (XEXP (XEXP (x, 0), 0), 1)) == CONST_INT
&& (temp = simplify_binary_operation (ASHIFTRT, mode,
XEXP (XEXP (XEXP (x, 0), 0), 1),
XEXP (XEXP (x, 0), 1))) != 0)
{
rtx new
= simplify_shift_const (NULL_RTX, ASHIFT, mode,
XEXP (XEXP (XEXP (XEXP (x, 0), 0), 0), 0),
INTVAL (XEXP (XEXP (x, 0), 1)));
new = simplify_shift_const (NULL_RTX, ASHIFTRT, mode, new,
INTVAL (XEXP (XEXP (x, 0), 1)));
SUBST (XEXP (x, 0), gen_binary (PLUS, mode, new, temp));
}
/* If this is a simple operation applied to an IF_THEN_ELSE, try
applying it to the arms of the IF_THEN_ELSE. This often simplifies
things. Don't deal with operations that change modes here. */