cranelift: rewrite x*-1 to ineg(x) (#6052)

* cranelift: rewrite `x*-1` to `ineg(x)` * Add commuted test
2023-03-17 19:52:13 +00:00
parent c3f5b71b6a
commit 208d09e9f0
2 changed files with 29 additions and 0 deletions
--- a/cranelift/codegen/src/opts/algebraic.isle
+++ b/cranelift/codegen/src/opts/algebraic.isle
@@ -62,6 +62,14 @@
                      _))
      (subsume zero))

+;; x*-1 == -1*x == ineg(x).
+(rule (simplify (imul ty x (iconst ty c)))
+      (if-let -1 (i64_sextend_imm64 ty c))
+      (ineg ty x))
+(rule (simplify (imul ty (iconst ty c) x))
+      (if-let -1 (i64_sextend_imm64 ty c))
+      (ineg ty x))
+
 ;; x/1 == x.
 (rule (simplify (sdiv ty
                      x