https://gcc.gnu.org/g:bbfba1cc925d7b90d9f501d237fbe10631dbd6d1
commit r15-5351-gbbfba1cc925d7b90d9f501d237fbe10631dbd6d1
Author: Georg-Johann Lay <a...@gjlay.de>
Date: Wed Nov 6 09:46:40 2024 +0100
AVR: Add an RTL peephole to tweak lower_reg:QI o= cst.
For operations like X o= CST, regalloc may spill l-reg X to a d-reg:
D = X
D o= CST
X = D
where it is better to instead
D = CST
X o= D
This patch adds an according RTL peephole.
gcc/
* config/avr/avr.md: Add a peephole2 that improves bit operations
with a lower register and a constant.
Diff:
---
gcc/config/avr/avr.md | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/gcc/config/avr/avr.md b/gcc/config/avr/avr.md
index aae8a696a638..80ad7e97ac93 100644
--- a/gcc/config/avr/avr.md
+++ b/gcc/config/avr/avr.md
@@ -4745,6 +4745,37 @@
(clobber (reg:CC REG_CC))])])
+;; For operations like X o= CST, regalloc may spill l-reg X to a d-reg:
+;; D = X
+;; D o= CST
+;; X = D
+;; where it is better to instead
+;; D = CST
+;; X o= D
+(define_peephole2
+ [; Move l-reg to d-reg for the purpose of BITOP.
+ (parallel [(set (match_operand:ALL1 0 "d_register_operand")
+ (match_operand:ALL1 1 "l_register_operand"))
+ (clobber (reg:CC REG_CC))])
+ (parallel [(set (match_dup 0)
+ (bitop:ALL1 (match_dup 0)
+ (match_operand:ALL1 2 "const_operand")))
+ (clobber (reg:CC REG_CC))])
+ ; Move d-reg result back to l-reg.
+ (parallel [(set (match_dup 1)
+ (match_dup 0))
+ (clobber (reg:CC REG_CC))])]
+ "peep2_reg_dead_p (3, operands[0])"
+ [; "movqi_insn"
+ (parallel [(set (match_dup 0)
+ (match_dup 2))
+ (clobber (reg:CC REG_CC))])
+ (parallel [(set (match_dup 1)
+ (bitop:ALL1 (match_dup 1)
+ (match_dup 0)))
+ (clobber (reg:CC REG_CC))])])
+
+
;; swap swap swap swap swap swap swap swap swap swap swap swap swap swap swap
;; swap
