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ISLE: simplify select/bitselect when both choices are the same #6141

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Merged
jameysharp merged 1 commit into from
Apr 11, 2023
Merged

ISLE: simplify select/bitselect when both choices are the same #6141

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4 changes: 4 additions & 0 deletions cranelift/codegen/src/opts/selects.isle
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Original file line number Diff line number Diff line change
@@ -1,5 +1,9 @@
;; `select`/`bitselect`-related rewrites

;; remove select when both choices are the same
(rule (simplify (select ty _ x x)) x)
(rule (simplify (bitselect ty _ x x)) x)

;; Transform select-of-icmp into {u,s}{min,max} instructions where possible.
(rule (simplify (select ty (sgt _ x y) x y)) (smax ty x y))
(rule (simplify (select ty (sge _ x y) x y)) (smax ty x y))
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14 changes: 14 additions & 0 deletions cranelift/filetests/filetests/egraph/select.clif
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,20 @@ target aarch64
target s390x
target riscv64

function %select_self(i8, i32) -> i32 {
block0(v0: i8, v1: i32):
v2 = select v0, v1, v1
return v2
; check: return v1
}

function %bitselect_self(i32, i32) -> i32 {
block0(v0: i32, v1: i32):
v2 = bitselect v0, v1, v1
return v2
; check: return v1
}

function %select_sgt_to_smax(i32, i32) -> i32 {
block0(v0: i32, v1: i32):
v2 = icmp sgt v0, v1
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