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Generalize and/or/xor optimizations (#5744)

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* Generalize `n ^ !n` optimization to more types

* Generalize `x & -1` optimization to more types

Also mark the `x & x` rewrite to `subsume`.

* Cranelift: Optimize x|!x and x&!x to constants

These cases are much like the existing x^!x rules.
This commit is contained in:
Jamey Sharp
2023-02-07 18:18:36 -08:00
committed by GitHub
parent d71c9458dc
commit 7bf89683e9
1 changed files with 17 additions and 11 deletions
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28
cranelift/codegen/src/opts/algebraic.isle
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@@ -104,22 +104,28 @@
(rule (simplify (bxor (fits_in_64 (ty_int ty)) x x))
(subsume (iconst ty (imm64 0))))
;; x ^ not(x) == not(x) ^ x == -1.
(rule (simplify (bxor $I32 x (bnot $I32 x))) (subsume (iconst $I32 (imm64 0xffff_ffff))))
(rule (simplify (bxor $I32 (bnot $I32 x) x)) (subsume (iconst $I32 (imm64 0xffff_ffff))))
(rule (simplify (bxor $I64 x (bnot $I64 x))) (subsume (iconst $I64 (imm64 0xffff_ffff_ffff_ffff))))
(rule (simplify (bxor $I64 (bnot $I64 x) x)) (subsume (iconst $I64 (imm64 0xffff_ffff_ffff_ffff))))
;; x ^ not(x) == not(x) ^ x == x | not(x) == not(x) | x == -1.
;; This identity also holds for non-integer types, vectors, and wider types.
;; But `iconst` is only valid for integers up to 64 bits wide.
(rule (simplify (bxor (fits_in_64 (ty_int ty)) x (bnot ty x))) (subsume (iconst ty (imm64 (ty_mask ty)))))
(rule (simplify (bxor (fits_in_64 (ty_int ty)) (bnot ty x) x)) (subsume (iconst ty (imm64 (ty_mask ty)))))
(rule (simplify (bor (fits_in_64 (ty_int ty)) x (bnot ty x))) (subsume (iconst ty (imm64 (ty_mask ty)))))
(rule (simplify (bor (fits_in_64 (ty_int ty)) (bnot ty x) x)) (subsume (iconst ty (imm64 (ty_mask ty)))))
;; x & -1 == -1 & x == x & x == x.
(rule (simplify (band ty x x)) x)
(rule (simplify (band $I32 x (iconst $I32 (u64_from_imm64 0xffff_ffff)))) (subsume x))
(rule (simplify (band $I32 (iconst $I32 (u64_from_imm64 0xffff_ffff)) x)) (subsume x))
(rule (simplify (band $I64 x (iconst $I64 (u64_from_imm64 0xffff_ffff_ffff_ffff)))) (subsume x))
(rule (simplify (band $I64 (iconst $I64 (u64_from_imm64 0xffff_ffff_ffff_ffff)) x)) (subsume x))
(rule (simplify (band ty x x)) (subsume x))
(rule (simplify (band ty x (iconst ty k)))
(if-let -1 (i64_sextend_imm64 ty k))
(subsume x))
(rule (simplify (band ty (iconst ty k) x))
(if-let -1 (i64_sextend_imm64 ty k))
(subsume x))
;; x & 0 == 0 & x == 0.
;; x & 0 == 0 & x == x & not(x) == not(x) & x == 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))
(rule (simplify (band (fits_in_64 (ty_int ty)) x (bnot ty x))) (subsume (iconst ty (imm64 0))))
(rule (simplify (band (fits_in_64 (ty_int ty)) (bnot ty x) x)) (subsume (iconst ty (imm64 0))))
;; not(not(x)) == x.
(rule (simplify (bnot ty (bnot ty x))) (subsume x))