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cranelift: rewrite x*-1 to ineg(x) #6052

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merged 2 commits into from
Mar 17, 2023
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cranelift: rewrite x*-1 to ineg(x) #6052

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d20f85a
cranelift: rewrite `x*-1` to `ineg(x)`
Kmeakin Mar 17, 2023
4c55cad
Add commuted test
Kmeakin Mar 17, 2023
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8 changes: 8 additions & 0 deletions cranelift/codegen/src/opts/algebraic.isle
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,14 @@
_))
(subsume zero))

;; x*-1 == -1*x == ineg(x).
(rule (simplify (imul ty x (iconst ty c)))
(if-let -1 (i64_sextend_imm64 ty c))
(ineg ty x))
(rule (simplify (imul ty (iconst ty c) x))
(if-let -1 (i64_sextend_imm64 ty c))
(ineg ty x))

;; x/1 == x.
(rule (simplify (sdiv ty
x
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21 changes: 21 additions & 0 deletions cranelift/filetests/filetests/egraph/algebraic.clif
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Original file line number Diff line number Diff line change
Expand Up @@ -240,6 +240,27 @@ block0(v0: i32):
; check: return v2
}

function %mul_minus_one(i32) -> i32 {
block0(v0: i32):
v1 = iconst.i32 0xffff_ffff ; -1
v2 = imul v0, v1
return v2
; check: v3 = ineg v0
; check: v4 -> v3
; check: return v3
}

function %mul_minus_one_commuted(i32) -> i32 {
block0(v0: i32):
v1 = iconst.i32 0xffff_ffff ; -1
v2 = imul v1, v0
return v2
; check: v3 = ineg v0
; check: v5 -> v3
; check: v6 -> v3
; check: return v3
}

function %or_and_y_with_not_y_i8(i8, i8) -> i8 {
block0(v0: i8, v1: i8):
v2 = band v0, v1
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