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cse.c (delete_dead_from_cse): If a libcall produces a constant result and that result can be substituted into...

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* cse.c (delete_dead_from_cse): If a libcall produces a constant
        result and that result can be substituted into SET_SRC of the
        insn with the REG_RETVAL note, then perform the substitution
        and delete the libcall.

From-SVN: r17871
This commit is contained in:
Jeffrey A Law 1998-02-12 14:26:47 +00:00 • committed by Jeff Law
parent 00bb4b6208
commit 614bb5d45d
2 changed files with 40 additions and 6 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
Thu Feb 12 15:26:50 1998 Jeffrey A Law (law@cygnus.com)
* cse.c (delete_dead_from_cse): If a libcall produces a constant
result and that result can be substituted into SET_SRC of the
insn with the REG_RETVAL note, then perform the substitution
and delete the libcall.
Thu Feb 12 14:04:09 1998 Gavin Koch <gavin@cygnus.com>
* mips.md (trucndihi2,truncdiqi2): Change these to support

39
gcc/cse.c
View file

@ -8754,7 +8754,7 @@ delete_dead_from_cse (insns, nreg)
rtx insn, prev;
rtx tem;
int i;
int in_libcall = 0;
int in_libcall = 0, dead_libcall = 0;
/* First count the number of times each register is used. */
bzero ((char *) counts, sizeof (int) * nreg);
@ -8767,17 +8767,41 @@ delete_dead_from_cse (insns, nreg)
for (insn = prev_real_insn (get_last_insn ()); insn; insn = prev)
{
int live_insn = 0;
rtx note;
prev = prev_real_insn (insn);
/* Don't delete any insns that are part of a libcall block.
/* Don't delete any insns that are part of a libcall block unless
we can delete the whole libcall block.
Flow or loop might get confused if we did that. Remember
that we are scanning backwards. */
if (find_reg_note (insn, REG_RETVAL, NULL_RTX))
in_libcall = 1;
{
in_libcall = 1;
live_insn = 1;
dead_libcall = 0;
if (in_libcall)
live_insn = 1;
/* See if there's a REG_EQUAL note on this insn and try to
replace the source with the REG_EQUAL expression.
We assume that insns with REG_RETVALs can only be reg->reg
copies at this point. */
note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
if (note)
{
rtx set = single_set (insn);
if (set
&& validate_change (insn, &SET_SRC (set), XEXP (note, 0), 0))
{
remove_note (insn,
find_reg_note (insn, REG_RETVAL, NULL_RTX));
dead_libcall = 1;
}
}
}
else if (in_libcall)
live_insn = ! dead_libcall;
else if (GET_CODE (PATTERN (insn)) == SET)
{
if (GET_CODE (SET_DEST (PATTERN (insn))) == REG
@ -8839,6 +8863,9 @@ delete_dead_from_cse (insns, nreg)
}
if (find_reg_note (insn, REG_LIBCALL, NULL_RTX))
in_libcall = 0;
{
in_libcall = 0;
dead_libcall = 0;
}
}
}