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cranelift: Remove redundant branch and select instructions (#5097)

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As discussed in the 2022/10/19 meeting, this PR removes many of the branch and select instructions that used iflags, in favor if using brz/brnz and select in their place. Additionally, it reworks selectif_spectre_guard to take an i8 input instead of an iflags input.

For reference, the removed instructions are: br_icmp, brif, brff, trueif, trueff, and selectif.
This commit is contained in:
Trevor Elliott
2022-10-24 16:14:35 -07:00
committed by GitHub
parent 30589170b4
commit ec12415b1f
40 changed files with 579 additions and 2527 deletions
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22
cranelift/codegen/src/isa/x64/lower.isle
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@@ -2760,16 +2760,6 @@
(rule (lower_branch (jump _ _) (single_target target))
(side_effect (jmp_known target)))
;; Rules for `brif` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(rule (lower_branch (brif cc (ifcmp a b) _ _) (two_targets taken not_taken))
(side_effect (jmp_cond_icmp (emit_cmp cc a b) taken not_taken)))
;; Rules for `brff` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(rule (lower_branch (brff cc (ffcmp a b) _ _) (two_targets taken not_taken))
(side_effect (jmp_cond_fcmp (emit_fcmp cc a b) taken not_taken)))
;; Rules for `brz` and `brnz` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(rule 2 (lower_branch (brz (icmp cc a b) _ _) (two_targets taken not_taken))
@@ -2828,22 +2818,14 @@
(src Gpr val))
(x64_test size src src)))
;; Rules for `bricmp` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(rule (lower_branch (br_icmp cc a b _ _) (two_targets taken not_taken))
(side_effect (jmp_cond_icmp (emit_cmp cc a b) taken not_taken)))
;; Rules for `br_table` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(rule (lower_branch (br_table idx @ (value_type ty) _ _) (jump_table_targets default_target jt_targets))
(side_effect (jmp_table_seq ty idx default_target jt_targets)))
;; Rules for `selectif` and `selectif_spectre_guard` ;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Rules for `select_spectre_guard` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(rule (lower (selectif cc (ifcmp a b) x y))
(select_icmp (emit_cmp cc a b) x y))
(rule (lower (selectif_spectre_guard cc (ifcmp a b) x y))
(rule (lower (select_spectre_guard (icmp cc a b) x y))
(select_icmp (emit_cmp cc a b) x y))
;; Rules for `fcvt_from_sint` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;