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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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29
cranelift/codegen/src/isa/riscv64/lower.isle
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@@ -605,6 +605,11 @@
(gen_select ty (normalize_value cty c) x y)
)
(rule 1
(lower (has_type ty (select (icmp cc a b) x y)))
(gen_select_reg cc a b x y)
)
;;;;; Rules for `bitselect`;;;;;;;;;
(rule
@@ -832,35 +837,15 @@
(gen_float_round (FloatRoundOP.Nearest) x ty))
;;;;; Rules for `selectif`;;;;;;;;;
;;;;; Rules for `select_spectre_guard`;;;;;;;;;
(rule
(lower (has_type r_ty (selectif cc (ifcmp ca @ (value_type cty) cb) a b)))
(let
((dst VecWritableReg (alloc_vec_writable r_ty))
(r Reg (lower_icmp cc ca cb cty))
(_ Unit (emit (MInst.SelectIf $false (vec_writable_clone dst) r a b))))
(vec_writable_to_regs dst)))
;;;;; Rules for `selectif_spectre_guard`;;;;;;;;;
(rule
(lower (has_type r_ty (selectif_spectre_guard cc (ifcmp ca @ (value_type cty) cb) a b)))
(lower (has_type r_ty (select_spectre_guard (icmp cc ca @ (value_type cty) cb) a b)))
(let
((dst VecWritableReg (alloc_vec_writable r_ty))
(r Reg (lower_icmp cc ca cb cty))
(_ Unit (emit (MInst.SelectIf $true (vec_writable_clone dst) r a b))))
(vec_writable_to_regs dst)))
;;;;; Rules for `trueif`;;;;;;;;;
(rule
(lower (has_type ty (trueif cc (ifcmp ca @ (value_type cty) cb))))
(lower_icmp cc ca cb cty))
;;;;; Rules for `trueff`;;;;;;;;;
(rule
(lower (has_type ty (trueff cc (ffcmp ca @ (value_type cty) cb))))
(gen_fcmp cc ca cb cty))
;;;;; Rules for `trapif`;;;;;;;;;
(rule