Vlad recently introduced a new gate @ira_in_progress, similar to
counterparts @{reload,lra}_in_progress.
Use this to hide the constant synthesis splitter from being recog* ()
by IRA register equivalence logic which is eager to undo the splits,
generating worse code for constants (and sometimes no code at all).
See PR/109279 (large constant), PR/110748 (const -0.0) ...
Granted the IRA logic is subsided with -fsched-pressure which is now
enabled for RISC-V backend, the gate makes this future-proof in
addition to helping with -O1 etc.
This fixes 1 addition test
========= Summary of gcc testsuite =========
| # of unexpected case / # of unique unexpected case
| gcc | g++ | gfortran |
rv32imac/ ilp32/ medlow | 416 / 103 | 13 / 6 | 67 / 12 |
rv32imafdc/ ilp32d/ medlow | 416 / 103 | 13 / 6 | 24 / 4 |
rv64imac/ lp64/ medlow | 417 / 104 | 9 / 3 | 67 / 12 |
rv64imafdc/ lp64d/ medlow | 416 / 103 | 5 / 2 | 6 / 1 |
Also similar to v1, this doesn't move RISC-V SPEC scores at all.
gcc/ChangeLog:
* config/riscv/riscv.md (mvconst_internal): Add !ira_in_progress.
Suggested-by: Jeff Law <jeffreya...@gmail.com>
Signed-off-by: Vineet Gupta <vine...@rivosinc.com>
---
changes since v1:
- Fix bug: new condition to prevent recognition not splitting itself
---
gcc/config/riscv/riscv.md | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index e00b8ee3579d..9b990ec2566d 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -1997,13 +1997,16 @@
;; Pretend to have the ability to load complex const_int in order to get
;; better code generation around them.
-;;
;; But avoid constants that are special cased elsewhere.
+;;
+;; Hide it from IRA register equiv recog* () to elide potential undoing of
split
+;;
(define_insn_and_split "*mvconst_internal"
[(set (match_operand:GPR 0 "register_operand" "=r")
(match_operand:GPR 1 "splittable_const_int_operand" "i"))]
- "!(p2m1_shift_operand (operands[1], <MODE>mode)
- || high_mask_shift_operand (operands[1], <MODE>mode))"
+ "!ira_in_progress
+ && !(p2m1_shift_operand (operands[1], <MODE>mode)
+ || high_mask_shift_operand (operands[1], <MODE>mode))"
"#"
"&& 1"
[(const_int 0)]
--
2.34.1
