vendor/cranelift-codegen/src/opts/icmp.isle

;; `icmp`-related rewrites

;; `x == x` is always true for integers; `x != x` is false. Strict
;; inequalities are false, and loose inequalities are true.
(rule (simplify (eq  (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 1)))
(rule (simplify (ne  (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 0)))
(rule (simplify (ugt (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 0)))
(rule (simplify (uge (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 1)))
(rule (simplify (sgt (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 0)))
(rule (simplify (sge (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 1)))
(rule (simplify (ult (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 0)))
(rule (simplify (ule (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 1)))
(rule (simplify (slt (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 0)))
(rule (simplify (sle (fits_in_64 (ty_int ty)) x x)) (iconst ty (imm64 1)))

;; Optimize icmp-of-icmp.
(rule (simplify (ne ty
                      (uextend _ inner @ (icmp ty _ _ _))
                      (iconst _ (u64_from_imm64 0))))
      (subsume inner))

(rule (simplify (eq ty
                      (uextend _ (icmp ty cc x y))
                      (iconst _ (u64_from_imm64 0))))
      (subsume (icmp ty (intcc_inverse cc) x y)))

;; Optimize select-of-uextend-of-icmp to select-of-icmp, because
;; select can take an I8 condition too.
(rule (simplify
       (select ty (uextend _ c @ (icmp _ _ _ _)) x y))
      (select ty c x y))
(rule (simplify
       (select ty (uextend _ c @ (icmp _ _ _ _)) x y))
      (select ty c x y))

;; Masking the result of a comparison with 1 always results in the comparison
;; itself. Note that comparisons in wasm may sometimes be hidden behind
;; extensions.
(rule (simplify
       (band (ty_int _)
             cmp @ (icmp _ _ _ _)
             (iconst _ (u64_from_imm64 1))))
      cmp)
(rule (simplify
       (band (ty_int _)
             extend @ (uextend _ (icmp _ _ _ _))
             (iconst _ (u64_from_imm64 1))))
      extend)

;; Comparisons against largest/smallest signed/unsigned values:
;; ult(x, 0) == false.
(rule (simplify (ult (fits_in_64 (ty_int bty)) x zero @ (iconst _ (u64_from_imm64 0))))
      (subsume (iconst bty (imm64 0))))

;; ule(x, 0) == eq(x, 0)
(rule (simplify (ule (fits_in_64 (ty_int bty)) x zero @ (iconst _ (u64_from_imm64 0))))
      (eq bty x zero))

;; ugt(x, 0) == ne(x, 0).
(rule (simplify (ugt (fits_in_64 (ty_int bty)) x zero @ (iconst _ (u64_from_imm64 0))))
      (ne bty x zero))

;; uge(x, 0) == true.
(rule (simplify (uge (fits_in_64 (ty_int bty)) x zero @ (iconst _ (u64_from_imm64 0))))
      (subsume (iconst bty (imm64 1))))

;; ult(x, UMAX) == ne(x, UMAX).
(rule (simplify (ult (fits_in_64 (ty_int bty)) x umax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_umax cty)))
       (ne bty x umax))

;; ule(x, UMAX) == true.
(rule (simplify (ule (fits_in_64 (ty_int bty)) x umax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_umax cty)))
       (subsume (iconst bty (imm64 1))))

;; ugt(x, UMAX) == false.
(rule (simplify (ugt (fits_in_64 (ty_int bty)) x umax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_umax cty)))
       (subsume (iconst bty (imm64 0))))

;; uge(x, UMAX) == eq(x, UMAX).
(rule (simplify (uge (fits_in_64 (ty_int bty)) x umax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_umax cty)))
       (eq bty x umax))

;; slt(x, SMIN) == false.
(rule (simplify (slt (fits_in_64 (ty_int bty)) x smin @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smin cty)))
       (subsume (iconst bty (imm64 0))))

;; sle(x, SMIN) == eq(x, SMIN).
(rule (simplify (sle (fits_in_64 (ty_int bty)) x smin @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smin cty)))
       (eq bty x smin))

;; sgt(x, SMIN) == ne(x, SMIN).
(rule (simplify (sgt (fits_in_64 (ty_int bty)) x smin @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smin cty)))
       (ne bty x smin))

;; sge(x, SMIN) == true.
(rule (simplify (sge (fits_in_64 (ty_int bty)) x smin @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smin cty)))
       (subsume (iconst bty (imm64 1))))

;; slt(x, SMAX) == ne(x, SMAX).
(rule (simplify (slt (fits_in_64 (ty_int bty)) x smax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smax cty)))
       (ne bty x smax))

;; sle(x, SMAX) == true.
(rule (simplify (sle (fits_in_64 (ty_int bty)) x smax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smax cty)))
       (subsume (iconst bty (imm64 1))))

;; sgt(x, SMAX) == false.
(rule (simplify (sgt (fits_in_64 (ty_int bty)) x smax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smax cty)))
       (subsume (iconst bty (imm64 0))))

;; sge(x, SMAX) == eq(x, SMAX).
(rule (simplify (sge (fits_in_64 (ty_int bty)) x smax @ (iconst cty (u64_from_imm64 y))))
       (if-let $true (u64_eq y (ty_smax cty)))
       (eq bty x smax))

;; `band`/`bor` of 2 comparisons:
(rule (simplify (band ty (icmp ty cc1 x y) (icmp ty cc2 x y)))
  (if-let signed (intcc_comparable cc1 cc2))
  (compose_icmp ty (u64_and (decompose_intcc cc1) (decompose_intcc cc2)) signed x y))

(rule (simplify (bor ty (icmp ty cc1 x y) (icmp ty cc2 x y)))
  (if-let signed (intcc_comparable cc1 cc2))
  (compose_icmp ty (u64_or (decompose_intcc cc1) (decompose_intcc cc2)) signed x y))

(decl pure partial intcc_comparable (IntCC IntCC) bool)
(rule (intcc_comparable x y)
  (if-let (u64_nonzero class) (u64_and (intcc_class x) (intcc_class y)))
  (u64_eq 2 class))

(decl pure decompose_intcc (IntCC) u64)
(rule (decompose_intcc (IntCC.Equal)) 1)
(rule (decompose_intcc (IntCC.UnsignedLessThan)) 2)
(rule (decompose_intcc (IntCC.SignedLessThan)) 2)
(rule (decompose_intcc (IntCC.UnsignedLessThanOrEqual)) 3)
(rule (decompose_intcc (IntCC.SignedLessThanOrEqual)) 3)
(rule (decompose_intcc (IntCC.UnsignedGreaterThan)) 4)
(rule (decompose_intcc (IntCC.SignedGreaterThan)) 4)
(rule (decompose_intcc (IntCC.UnsignedGreaterThanOrEqual)) 5)
(rule (decompose_intcc (IntCC.SignedGreaterThanOrEqual)) 5)
(rule (decompose_intcc (IntCC.NotEqual)) 6)

(decl compose_icmp (Type u64 bool Value Value) Value)
(rule (compose_icmp ty 0 _ _ _) (subsume (iconst ty (imm64 0))))
(rule (compose_icmp ty 1 _ x y) (icmp ty (IntCC.Equal) x y))
(rule (compose_icmp ty 2 $false x y) (icmp ty (IntCC.UnsignedLessThan) x y))
(rule (compose_icmp ty 2 $true x y) (icmp ty (IntCC.SignedLessThan) x y))
(rule (compose_icmp ty 3 $false x y) (icmp ty (IntCC.UnsignedLessThanOrEqual) x y))
(rule (compose_icmp ty 3 $true x y) (icmp ty (IntCC.SignedLessThanOrEqual) x y))
(rule (compose_icmp ty 4 $false x y) (icmp ty (IntCC.UnsignedGreaterThan) x y))
(rule (compose_icmp ty 4 $true x y) (icmp ty (IntCC.SignedGreaterThan) x y))
(rule (compose_icmp ty 5 $false x y) (icmp ty (IntCC.UnsignedGreaterThanOrEqual) x y))
(rule (compose_icmp ty 5 $true x y) (icmp ty (IntCC.SignedGreaterThanOrEqual) x y))
(rule (compose_icmp ty 6 _ x y) (icmp ty (IntCC.NotEqual) x y))
(rule (compose_icmp ty 7 _ _ _) (subsume (iconst ty (imm64 1))))

(decl pure intcc_class (IntCC) u64)
(rule (intcc_class (IntCC.UnsignedLessThan)) 1)
(rule (intcc_class (IntCC.UnsignedLessThanOrEqual)) 1)
(rule (intcc_class (IntCC.UnsignedGreaterThan)) 1)
(rule (intcc_class (IntCC.UnsignedGreaterThanOrEqual)) 1)
(rule (intcc_class (IntCC.SignedLessThan)) 2)
(rule (intcc_class (IntCC.SignedLessThanOrEqual)) 2)
(rule (intcc_class (IntCC.SignedGreaterThan)) 2)
(rule (intcc_class (IntCC.SignedGreaterThanOrEqual)) 2)
(rule (intcc_class (IntCC.Equal)) 3)
(rule (intcc_class (IntCC.NotEqual)) 3)