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Algebraic opts: Reuse iconst 0 from LHS (#5724)

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We don't need to spend time going through the GVN map to dedup a
newly-constructed `iconst 0` when we already matched that value on the
left-hand side of these rules.

Also, mark these rules as subsuming any others since we can't do better
than reducing an expression to a constant.
This commit is contained in:
Jamey Sharp
2023-02-07 16:11:07 -08:00
committed by GitHub
parent 116e5a665f
commit f3b408d5e2
1 changed files with 8 additions and 8 deletions
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16
cranelift/codegen/src/opts/algebraic.isle
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@@ -38,13 +38,13 @@
;; x*0 == 0*x == x.
(rule (simplify (imul ty
x
(iconst ty (u64_from_imm64 0))))
(iconst ty (imm64 0)))
_
zero @ (iconst ty (u64_from_imm64 0))))
(subsume zero))
(rule (simplify (imul ty
(iconst ty (u64_from_imm64 0))
x))
(iconst ty (imm64 0)))
zero @ (iconst ty (u64_from_imm64 0))
_))
(subsume zero))
;; x/1 == x.
(rule (simplify (sdiv ty
@@ -118,8 +118,8 @@
(rule (simplify (band $I64 (iconst $I64 (u64_from_imm64 0xffff_ffff_ffff_ffff)) x)) (subsume x))
;; x & 0 == 0 & x == 0.
(rule (simplify (band ty x (iconst ty (u64_from_imm64 0)))) (iconst ty (imm64 0)))
(rule (simplify (band ty (iconst ty (u64_from_imm64 0)) x)) (iconst ty (imm64 0)))
(rule (simplify (band ty _ zero @ (iconst ty (u64_from_imm64 0)))) (subsume zero))
(rule (simplify (band ty zero @ (iconst ty (u64_from_imm64 0)) _)) (subsume zero))
;; not(not(x)) == x.
(rule (simplify (bnot ty (bnot ty x))) (subsume x))