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cse.c (cse_insn): In (set REG0 REG1) case, remove a REG_EQUAL note for REG1.

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* cse.c (cse_insn): In (set REG0 REG1) case, remove a REG_EQUAL
	note for REG1.

From-SVN: r33310
This commit is contained in:
Richard Kenner 2000-04-21 18:46:01 +00:00 • committed by Richard Kenner
parent 9e62c8114f
commit 403e25d0ba
2 changed files with 23 additions and 16 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
Fri Apr 21 13:30:26 2000 Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
* cse.c (cse_insn): In (set REG0 REG1) case, remove a REG_EQUAL
note for REG1.
2000-04-21 Zack Weinberg <zack@wolery.cumb.org>
* cpphash.c (struct arg, struct arglist): Const-ify strings.

34
gcc/cse.c
View file

@ -5928,13 +5928,12 @@ cse_insn (insn, libcall_insn)
}
}
/* Special handling for (set REG0 REG1)
where REG0 is the "cheapest", cheaper than REG1.
After cse, REG1 will probably not be used in the sequel,
so (if easily done) change this insn to (set REG1 REG0) and
replace REG1 with REG0 in the previous insn that computed their value.
Then REG1 will become a dead store and won't cloud the situation
for later optimizations.
/* Special handling for (set REG0 REG1) where REG0 is the
"cheapest", cheaper than REG1. After cse, REG1 will probably not
be used in the sequel, so (if easily done) change this insn to
(set REG1 REG0) and replace REG1 with REG0 in the previous insn
that computed their value. Then REG1 will become a dead store
and won't cloud the situation for later optimizations.
Do not make this change if REG1 is a hard register, because it will
then be used in the sequel and we may be changing a two-operand insn
@ -5958,19 +5957,18 @@ cse_insn (insn, libcall_insn)
if ((src_ent->first_reg == REGNO (SET_DEST (sets[0].rtl)))
&& ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
{
rtx prev = PREV_INSN (insn);
while (prev && GET_CODE (prev) == NOTE)
prev = PREV_INSN (prev);
rtx prev = prev_nonnote_insn (insn);
if (prev && GET_CODE (prev) == INSN && GET_CODE (PATTERN (prev)) == SET
if (prev != 0 && GET_CODE (prev) == INSN
&& GET_CODE (PATTERN (prev)) == SET
&& SET_DEST (PATTERN (prev)) == SET_SRC (sets[0].rtl))
{
rtx dest = SET_DEST (sets[0].rtl);
rtx src = SET_SRC (sets[0].rtl);
rtx note = find_reg_note (prev, REG_EQUIV, NULL_RTX);
validate_change (prev, & SET_DEST (PATTERN (prev)), dest, 1);
validate_change (insn, & SET_DEST (sets[0].rtl),
SET_SRC (sets[0].rtl), 1);
validate_change (insn, & SET_DEST (sets[0].rtl), src, 1);
validate_change (insn, & SET_SRC (sets[0].rtl), dest, 1);
apply_change_group ();
@ -5992,10 +5990,14 @@ cse_insn (insn, libcall_insn)
REG_NOTES (prev) = note;
}
/* If INSN has a REG_EQUAL note, and this note mentions REG0,
then we must delete it, because the value in REG0 has changed. */
/* If INSN has a REG_EQUAL note, and this note mentions
REG0, then we must delete it, because the value in
REG0 has changed. If the note's value is REG1, we must
also delete it because that is now this insn's dest. */
note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
if (note && reg_mentioned_p (dest, XEXP (note, 0)))
if (note != 0
&& (reg_mentioned_p (dest, XEXP (note, 0))
|| rtx_equal_p (src, XEXP (note, 0))))
remove_note (insn, note);
}
}