cranelift: simplify x-x to 0 (#6032)

* cranelift: simplify `x-x` to `0` * Guard `x-x => 0` rewrite with `fits_in_64`
2023-03-17 15:14:28 +00:00
parent 28371bfd40
commit b53d66e634
2 changed files with 11 additions and 0 deletions
--- a/cranelift/codegen/src/opts/algebraic.isle
+++ b/cranelift/codegen/src/opts/algebraic.isle
@@ -35,6 +35,9 @@
 ;; ineg(ineg(x)) == x.
 (rule (simplify (ineg ty (ineg ty x))) (subsume x))

+;; x-x == 0.
+(rule (simplify (isub (fits_in_64 (ty_int ty)) x x)) (subsume (iconst ty (imm64 0))))
+
 ;; x*1 == 1*x == x.
 (rule (simplify (imul ty
                      x