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AVR: Improve POST_INC output in some rare cases.

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gcc/
	* config/avr/avr.cc (avr_insn_has_reg_unused_note_p): New function.
	(_reg_unused_after): Use it to recognize more cases.
	(avr_out_lpm_no_lpmx) [POST_INC]: Use reg_unused_after.
This commit is contained in:
Georg-Johann Lay 2024-08-08 16:50:39 +02:00
parent 7153173319
commit ef697f8391
1 changed files with 31 additions and 1 deletions
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32
gcc/config/avr/avr.cc
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@ -4621,7 +4621,7 @@ avr_out_lpm_no_lpmx (rtx_insn *insn, rtx *xop, int *plen)
avr_asm_len ("mov %0,r0", &reg, plen, 1);
}
if (! _reg_unused_after (insn, xop[2], false))
if (! reg_unused_after (insn, xop[2]))
avr_asm_len ("adiw %2,1", xop, plen, 1);
break; /* POST_INC */
@ -11318,6 +11318,25 @@ avr_adjust_insn_length (rtx_insn *insn, int len)
return len;
}
/* Return true when INSN has a REG_UNUSED note for hard reg REG.
rtlanal.cc::find_reg_note() uses == to compare XEXP (link, 0)
therefore use a custom function. */
static bool
avr_insn_has_reg_unused_note_p (rtx_insn *insn, rtx reg)
{
for (rtx link = REG_NOTES (insn); link; link = XEXP (link, 1))
if (REG_NOTE_KIND (link) == REG_UNUSED
&& REG_P (XEXP (link, 0))
&& REGNO (reg) >= REGNO (XEXP (link, 0))
&& END_REGNO (reg) <= END_REGNO (XEXP (link, 0)))
return true;
return false;
}
/* Return nonzero if register REG dead after INSN. */
int
@ -11344,6 +11363,17 @@ _reg_unused_after (rtx_insn *insn, rtx reg, bool look_at_insn)
if (set && !MEM_P (SET_DEST (set))
&& reg_overlap_mentioned_p (reg, SET_DEST (set)))
return 1;
/* This case occurs when fuse-add introduced a POST_INC addressing,
but the address register is unused after. */
if (set)
{
rtx mem = MEM_P (SET_SRC (set)) ? SET_SRC (set) : SET_DEST (set);
if (MEM_P (mem)
&& reg_overlap_mentioned_p (reg, XEXP (mem, 0))
&& avr_insn_has_reg_unused_note_p (insn, reg))
return 1;
}
}
while ((insn = NEXT_INSN (insn)))