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Avoid a bit of copy propagation when there's a REG_EQUIV note 

From-SVN: r37705
This commit is contained in:
Richard Sandiford 2000-11-24 11:36:27 +00:00 committed by Bernd Schmidt
parent c34102419d
commit 58ecb5e2cd
2 changed files with 21 additions and 6 deletions
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6
gcc/ChangeLog
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@ -3,6 +3,12 @@
* combine.c (cant_combine_insn_p): New function.
(try_combine): Use it.
2000-11-24 Richard Sandiford <rsandifo@redhat.com>
* gcc/cse.c (cse_insn): Removed conversion of REG_EQUIV to REG_EQUAL
when reversing a register-to-register copy. Reversal now disabled
when the previous instruction has a REG_EQUIV.
2000-11-24 Nathan Sidwell <nathan@codesourcery.com>
* c-parse.in (unary_expr): Move VA_ARG from here ...

21
gcc/cse.c
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@ -6238,23 +6238,32 @@ cse_insn (insn, libcall_insn)
{
rtx prev = prev_nonnote_insn (insn);
/* Do not swap the registers around if the previous instruction
attaches a REG_EQUIV note to REG1.
??? It's not entirely clear whether we can transfer a REG_EQUIV
from the pseudo that originally shadowed an incoming argument
to another register. Some uses of REG_EQUIV might rely on it
being attached to REG1 rather than REG2.
This section previously turned the REG_EQUIV into a REG_EQUAL
note. We cannot do that because REG_EQUIV may provide an
uninitialised stack slot when REG_PARM_STACK_SPACE is used. */
if (prev != 0 && GET_CODE (prev) == INSN
&& GET_CODE (PATTERN (prev)) == SET
&& SET_DEST (PATTERN (prev)) == SET_SRC (sets[0].rtl))
&& SET_DEST (PATTERN (prev)) == SET_SRC (sets[0].rtl)
&& ! find_reg_note (prev, REG_EQUIV, NULL_RTX))
{
rtx dest = SET_DEST (sets[0].rtl);
rtx src = SET_SRC (sets[0].rtl);
rtx note = find_reg_note (prev, REG_EQUIV, NULL_RTX);
rtx note;
validate_change (prev, &SET_DEST (PATTERN (prev)), dest, 1);
validate_change (insn, &SET_DEST (sets[0].rtl), src, 1);
validate_change (insn, &SET_SRC (sets[0].rtl), dest, 1);
apply_change_group ();
/* If REG1 was equivalent to a constant, REG0 is not. */
if (note)
PUT_REG_NOTE_KIND (note, REG_EQUAL);
/* If there was a REG_WAS_0 note on PREV, remove it. Move
any REG_WAS_0 note on INSN to PREV. */
note = find_reg_note (prev, REG_WAS_0, NULL_RTX);