;; Algebraic optimizations.
;; Rules here are allowed to rewrite pure expressions arbitrarily,
;; using the same inputs as the original, or fewer. In other words, we
;; cannot pull a new eclass id out of thin air and refer to it, other
;; than a piece of the input or a new node that we construct; but we
;; can freely rewrite e.g. `x+y-y` to `x`.
;; uextend/sextend of a constant.
(rule (simplify (uextend $I64 (iconst $I32 (u64_from_imm64 imm))))
(iconst $I64 (imm64 (u64_uextend_u32 imm))))
(rule (simplify (sextend $I64 (iconst $I32 (u64_from_imm64 imm))))
(iconst $I64 (imm64 (u64_sextend_u32 imm))))
;; x+0 == 0+x == x.
(rule (simplify (iadd ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
(rule (simplify (iadd ty
(iconst ty (u64_from_imm64 0))
x))
(subsume x))
;; x-0 == x.
(rule (simplify (isub ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
;; 0-x == (ineg x).
(rule (simplify (isub ty
(iconst ty (u64_from_imm64 0))
x))
(ineg ty x))
;; x*1 == 1*x == x.
(rule (simplify (imul ty
x
(iconst ty (u64_from_imm64 1))))
(subsume x))
(rule (simplify (imul ty
(iconst ty (u64_from_imm64 1))
x))
(subsume x))
;; x*0 == 0*x == x.
(rule (simplify (imul ty
x
(iconst ty (u64_from_imm64 0))))
(iconst ty (imm64 0)))
(rule (simplify (imul ty
(iconst ty (u64_from_imm64 0))
x))
(iconst ty (imm64 0)))
;; x/1 == x.
(rule (simplify (sdiv ty
x
(iconst ty (u64_from_imm64 1))))
(subsume x))
(rule (simplify (udiv ty
x
(iconst ty (u64_from_imm64 1))))
(subsume x))
;; x>>0 == x<<0 == x rotr 0 == x rotl 0 == x.
(rule (simplify (ishl ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
(rule (simplify (ushr ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
(rule (simplify (sshr ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
(rule (simplify (rotr ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
(rule (simplify (rotl ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
;; x | 0 == 0 | x == x | x == x.
(rule (simplify (bor ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
(rule (simplify (bor ty
(iconst ty (u64_from_imm64 0))
x))
(subsume x))
(rule (simplify (bor ty x x))
(subsume x))
;; x ^ 0 == 0 ^ x == x.
(rule (simplify (bxor ty
x
(iconst ty (u64_from_imm64 0))))
(subsume x))
(rule (simplify (bxor ty
(iconst ty (u64_from_imm64 0))
x))
(subsume x))
;; x ^ x == 0.
(rule (simplify (bxor (fits_in_64 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 & -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))
;; 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)))
;; not(not(x)) == x.
(rule (simplify (bnot ty (bnot ty x))) (subsume x))
;; DeMorgan's rule (two versions):
;; bnot(bor(x, y)) == band(bnot(x), bnot(y))
(rule (simplify (bnot ty (bor ty x y)))
(band ty (bnot ty x) (bnot ty y)))
;; bnot(band(x, y)) == bor(bnot(x), bnot(y))
(rule (simplify (bnot ty (band t x y)))
(bor ty (bnot ty x) (bnot ty y)))
;; x*2 == 2*x == x+x.
(rule (simplify (imul ty x (iconst _ (simm32 2))))
(iadd ty x x))
(rule (simplify (imul ty (iconst _ (simm32 2)) x))
(iadd ty x x))
;; x<<32>>32: uextend/sextend 32->64.
(rule (simplify (ushr $I64 (ishl $I64 (uextend $I64 x @ (value_type $I32)) (iconst _ (simm32 32))) (iconst _ (simm32 32))))
(uextend $I64 x))
(rule (simplify (sshr $I64 (ishl $I64 (uextend $I64 x @ (value_type $I32)) (iconst _ (simm32 32))) (iconst _ (simm32 32))))
(sextend $I64 x))
;; TODO: strength reduction: mul/div to shifts
;; TODO: div/rem by constants -> magic multiplications
;; Rematerialize ALU-op-with-imm and iconsts in each block where they're
;; used. This is neutral (add-with-imm) or positive (iconst) for
;; register pressure, and these ops are very cheap.
(rule (simplify x @ (iadd _ (iconst _ _) _))
(remat x))
(rule (simplify x @ (iadd _ _ (iconst _ _)))
(remat x))
(rule (simplify x @ (isub _ (iconst _ _) _))
(remat x))
(rule (simplify x @ (isub _ _ (iconst _ _)))
(remat x))
(rule (simplify x @ (band _ (iconst _ _) _))
(remat x))
(rule (simplify x @ (band _ _ (iconst _ _)))
(remat x))
(rule (simplify x @ (bor _ (iconst _ _) _))
(remat x))
(rule (simplify x @ (bor _ _ (iconst _ _)))
(remat x))
(rule (simplify x @ (bxor _ (iconst _ _) _))
(remat x))
(rule (simplify x @ (bxor _ _ (iconst _ _)))
(remat x))
(rule (simplify x @ (bnot _ _))
(remat x))
(rule (simplify x @ (iconst _ _))
(remat x))
(rule (simplify x @ (f32const _ _))
(remat x))
(rule (simplify x @ (f64const _ _))
(remat x))
;; Optimize icmp-of-icmp.
(rule (simplify (icmp ty
(IntCC.NotEqual)
(uextend _ inner @ (icmp ty _ _ _))
(iconst _ (u64_from_imm64 0))))
(subsume inner))
(rule (simplify (icmp ty
(IntCC.Equal)
(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))
;; `x == x` is always true for integers; `x != x` is false. Strict
;; inequalities are false, and loose inequalities are true.
(rule (simplify
(icmp (ty_int ty) (IntCC.Equal) x x))
(iconst ty (imm64 1)))
(rule (simplify
(icmp (ty_int ty) (IntCC.NotEqual) x x))
(iconst ty (imm64 0)))
(rule (simplify
(icmp (ty_int ty) (IntCC.UnsignedGreaterThan) x x))
(iconst ty (imm64 0)))
(rule (simplify
(icmp (ty_int ty) (IntCC.UnsignedGreaterThanOrEqual) x x))
(iconst ty (imm64 1)))
(rule (simplify
(icmp (ty_int ty) (IntCC.SignedGreaterThan) x x))
(iconst ty (imm64 0)))
(rule (simplify
(icmp (ty_int ty) (IntCC.SignedGreaterThanOrEqual) x x))
(iconst ty (imm64 1)))
(rule (simplify
(icmp (ty_int ty) (IntCC.UnsignedLessThan) x x))
(iconst ty (imm64 0)))
(rule (simplify
(icmp (ty_int ty) (IntCC.UnsignedLessThanOrEqual) x x))
(iconst ty (imm64 1)))
(rule (simplify
(icmp (ty_int ty) (IntCC.SignedLessThan) x x))
(iconst ty (imm64 0)))
(rule (simplify
(icmp (ty_int ty) (IntCC.SignedLessThanOrEqual) x x))
(iconst ty (imm64 1)))