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RISC-V: const: hide mvconst splitter from IRA

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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 <jeffreyalaw@gmail.com>
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
This commit is contained in:
Vineet Gupta 2023-10-06 11:21:51 -07:00
parent 837a12a227
commit c1bc7513b1
1 changed files with 6 additions and 3 deletions
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9
gcc/config/riscv/riscv.md
View file

@ -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)]