1;; Chained `uextend` and `sextend`.
2(rule (simplify (uextend ty (uextend _intermediate_ty x)))
3      (uextend ty x))
4(rule (simplify (sextend ty (sextend _intermediate_ty x)))
5      (sextend ty x))
6
7;; Once something has be `uextend`ed, further `sextend`ing is the same as `uextend`
8(rule (simplify (sextend ty (uextend _intermediate_ty x)))
9      (uextend ty x))
10
11;; `icmp` is zero or one, so sign-extending is the same as zero-extending
12(rule (simplify (sextend ty x@(icmp _ _ _ _)))
13      (uextend ty x))
14
15;; Masking out any of the top bits of the result of `uextend` is a no-op. (This
16;; is like a cheap version of known-bits analysis.)
17(rule (simplify (band wide x @ (uextend _ (value_type narrow)) (iconst _ (u64_from_imm64 mask))))
18      ; Check that `narrow_mask` has a subset of the bits that `mask` does.
19      (if-let $true (let ((narrow_mask u64 (ty_mask narrow))) (u64_eq narrow_mask (u64_and mask narrow_mask))))
20      x)
21
22;; Masking out the sign-extended bits of an `sextend` turns it into a `uextend`.
23(rule (simplify (band wide (sextend _ x @ (value_type narrow)) (iconst _ (u64_from_imm64 mask))))
24      (if-let $true (u64_eq mask (ty_mask narrow)))
25      (uextend wide x))
26
27;; 32-bit integers zero-extended to 64-bit integers are never negative
28(rule (simplify
29       (slt ty
30             (uextend $I64 x @ (value_type $I32))
31             (iconst_u _ 0)))
32      (iconst_u ty 0))
33(rule (simplify
34       (sge ty
35             (uextend $I64 x @ (value_type $I32))
36             (iconst_u _ 0)))
37      (iconst_u ty 1))
38
39;; Sign-extending can't change whether a number is zero nor how it signed-compares to zero
40(rule (simplify (eq _ (sextend _ x@(value_type ty)) (iconst_s _ 0)))
41      (eq ty x (iconst_s ty 0)))
42(rule (simplify (ne _ (sextend _ x@(value_type ty)) (iconst_s _ 0)))
43      (ne ty x (iconst_s ty 0)))
44(rule (simplify (icmp _ cc (sextend _ x@(value_type ty)) (iconst_s _ 0)))
45      (if (signed_cond_code cc))
46      (icmp ty cc x (iconst_s ty 0)))
47
48;; A reduction-of-an-extend back to the same original type is the same as not
49;; actually doing the extend in the first place.
50(rule (simplify (ireduce ty (sextend _ x @ (value_type ty)))) x)
51(rule (simplify (ireduce ty (uextend _ x @ (value_type ty)))) x)
52