https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64215
Jeffrey A. Law <law at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |law at gcc dot gnu.org
--- Comment #5 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Andrew, the reason the patch you referenced doesn't help this case is because
we don't have an unconditional jump to a return only block.
To optimize this case we'd have to detect that we have a return only block that
is immediately preceded by another return block after bbro.
ie:
(note 48 23 59 6 [bb 6] NOTE_INSN_BASIC_BLOCK)
(insn 59 48 49 6 (use (reg/i:SI 10 a0)) -1
(nil))
(jump_insn 49 59 37 6 (simple_return) 346 {simple_return}
(nil)
-> simple_return)
;; lr out 1 [ra] 2 [sp] 10 [a0]
;; live out 1 [ra] 2 [sp] 10 [a0]
;; succ: EXIT [always] count:52738306 (estimated locally, freq 0.4591)
;; basic block 7, loop depth 0, count 6317494 (estimated locally, freq 0.0550),
maybe hot
;; prev block 6, next block 1, flags: (REACHABLE, RTL)
;; pred: 2 [5.5% (guessed)] count:6317494 (estimated locally, freq
0.0550) (CAN_FALLTHRU)
;; bb 7 artificial_defs: { }
;; bb 7 artificial_uses: { u-1(2){ }}
;; lr in 1 [ra] 2 [sp] 10 [a0]
;; lr use 2 [sp] 10 [a0]
;; lr def
;; live in 1 [ra] 2 [sp] 10 [a0]
;; live gen
;; live kill
(code_label 37 49 36 7 4 (nil) [1 uses])
(note 36 37 60 7 [bb 7] NOTE_INSN_BASIC_BLOCK)
(insn 60 36 51 7 (use (reg/i:SI 10 a0)) -1
(nil))
(jump_insn 51 60 41 7 (simple_return) 346 {simple_return}
(nil)
-> simple_return)
