https://gcc.gnu.org/g:214985f6b35ea8038c4e96590b435aaef2919769
commit r15-5822-g214985f6b35ea8038c4e96590b435aaef2919769
Author: Georg-Johann Lay <a...@gjlay.de>
Date: Sat Nov 30 14:58:05 2024 +0100
AVR: ad target/84211 - Split MOVW into MOVs in try_split_any.
When splitting multi-byte REG-REG moves in try_split_any(),
it's not clear whether propagating constants will turn
out as profitable. When MOVW is available, split into
REG-REG moves instead of a possible REG-CONST.
gcc/
PR target/84211
* config/avr/avr-passes.cc (try_split_any) [SET, MOVW]: Prefer
reg=reg move over reg=const when splitting a reg=reg insn.
Diff:
---
gcc/config/avr/avr-passes.cc | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/gcc/config/avr/avr-passes.cc b/gcc/config/avr/avr-passes.cc
index 68ebd31390ec..7be5ec25fbce 100644
--- a/gcc/config/avr/avr-passes.cc
+++ b/gcc/config/avr/avr-passes.cc
@@ -2912,6 +2912,14 @@ optimize_data_t::try_split_any (bbinfo_t *)
xsrc = gen_rtx_REG (HImode, r16);
i += step;
}
+ // ...or a reg-reg move from a multi-byte move...
+ else if (r_src
+ // Prefer a reg-reg move over a (potential) load
+ // of a constant, because the subsequent RTL
+ // peephole pass may combine it to a MOVW again.
+ && AVR_HAVE_MOVW
+ && REG_P (curr.ii.m_src))
+ xsrc = gen_rtx_REG (QImode, r_src);
// ...or a cheap constant...
else if (val8 >= 0
&& AVRasm::constant_cost (SET, r_dest, val8) <= 1)
