Revert "Cranelift: Reassociate long and narrow chains of operations into shallow and wide trees (#7466)" (#12116)

* Revert "Cranelift: Reassociate long and narrow chains of operations into shallow and wide trees (#7466)"

This reverts commit 72534b0.

This mid-end rule was shown to be the root cause of a codegen regression in
#12106 and we didn't have any
real examples that would improve from this rule, just a theoretical idea of its
benefit. Better to do actual instruction scheduling while lowering and/or during
regalloc than to do hack-y instruction scheduling in the mid-end (where we have
no idea how many registers are available, for example).

* update disas tests

Author: fitzgen

cranelift/codegen/src/opts/arithmetic.isle

@@ -196,105 +196,6 @@
 (rule (simplify (fmul ty (fneg ty x) (fneg ty y)))
       (fmul ty x y))
 
-;; (a op (b op (c op d))) ==> ((a op b) op (c op d))
-;;
-;; and
-;;
-;; (((a op b) op c) op d) ==> ((a op b) op (c op d))
-;;
-;; where `op` is an associative operation: `iadd`, `imul`, `band`, or `bxor`.
-;;
-;; This increases instruction-level parallelism and shrinks live ranges. It also
-;; canonicalizes into the shallow-and-wide form for reassociating constants
-;; together for cprop.
-;;
-;; NB: We subsume to avoid exponential e-node blow up due to reassociating very
-;; large chains of operations.
-;;
-;; TODO: We should add `bor` rules for this as well. Unfortunately, they
-;; conflict with our `bswap` recognizing rules when we `subsume`.
-
-(rule (simplify (iadd ty a (iadd ty b (iadd ty c d))))
-      (subsume (iadd ty (iadd ty a b) (iadd ty c d))))
-(rule (simplify (iadd ty (iadd ty (iadd ty a b) c) d))
-      (subsume (iadd ty (iadd ty a b) (iadd ty c d))))
-
-(rule (simplify (imul ty a (imul ty b (imul ty c d))))
-      (subsume (imul ty (imul ty a b) (imul ty c d))))
-(rule (simplify (imul ty (imul ty (imul ty a b) c) d))
-      (subsume (imul ty (imul ty a b) (imul ty c d))))
-
-(rule (simplify (band ty a (band ty b (band ty c d))))
-      (subsume (band ty (band ty a b) (band ty c d))))
-(rule (simplify (band ty (band ty (band ty a b) c) d))
-      (subsume (band ty (band ty a b) (band ty c d))))
-
-(rule (simplify (bxor ty a (bxor ty b (bxor ty c d))))
-      (subsume (bxor ty (bxor ty a b) (bxor ty c d))))
-(rule (simplify (bxor ty (bxor ty (bxor ty a b) c) d))
-      (subsume (bxor ty (bxor ty a b) (bxor ty c d))))
-
-
-;; Similar rules but for associating combinations of + and -
-
-;; a -(b-(c-d)) = (a-b) + (c-d)
-(rule (simplify (isub ty a (isub ty b (isub ty c d))))
-      (subsume (iadd ty (isub ty a b) (isub ty c d))))
-
-;; a -(b-(c+d)) = (a-b) + (c+d)
-(rule (simplify (isub ty a (isub ty b (iadd ty c d))))
-      (subsume (iadd ty (isub ty a b) (iadd ty c d))))
-
-;; a -(b+(c-d)) = (a-b) - (c-d)
-(rule (simplify (isub ty a (iadd ty b (isub ty c d))))
-      (subsume (isub ty (isub ty a b) (isub ty c d))))
-
-;; a -(b+(c+d)) = (a-b) - (c+d)
-(rule (simplify (isub ty a (iadd ty b (iadd ty c d))))
-      (subsume (isub ty (isub ty a b) (iadd ty c d))))
-
-;; a +(b-(c-d)) = (a+b) - (c-d)
-(rule (simplify (iadd ty a (isub ty b (isub ty c d))))
-      (subsume (isub ty (iadd ty a b) (isub ty c d))))
-
-;; a +(b-(c+d)) = (a+b) - (c+d)
-(rule (simplify (iadd ty a (isub ty b (iadd ty c d))))
-      (subsume (isub ty (iadd ty a b) (iadd ty c d))))
-
-;; a +(b+(c-d)) = (a+b) + (c-d)
-(rule (simplify (iadd ty a (iadd ty b (isub ty c d))))
-      (subsume (iadd ty (iadd ty a b) (isub ty c d))))
-
-;; and nested the other way
-
-;; ((a-b)-c)-d = (a-b) - (c+d)
-(rule (simplify (isub ty (isub ty (isub ty a b) c) d))
-      (subsume (isub ty (isub ty a b) (iadd ty c d))))
-
-;; ((a-b)-c)+d = (a-b) - (c-d)
-(rule (simplify (iadd ty (isub ty (isub ty a b) c) d))
-      (subsume (isub ty (isub ty a b) (isub ty c d))))
-
-;; ((a-b)+c)-d = (a-b) + (c-d)
-(rule (simplify (isub ty (iadd ty (isub ty a b) c) d))
-      (subsume (iadd ty (isub ty a b) (isub ty c d))))
-
-;; ((a-b)+c)+d = (a-b) + (c+d)
-(rule (simplify (iadd ty (iadd ty (isub ty a b) c) d))
-      (subsume (iadd ty (isub ty a b) (iadd ty c d))))
-
-;; ((a+b)-c)-d = (a+b) - (c+d)
-(rule (simplify (isub ty (isub ty (iadd ty a b) c) d))
-      (subsume (isub ty (iadd ty a b) (iadd ty c d))))
-
-;; ((a+b)-c)+d = (a+b) - (c-d)
-(rule (simplify (iadd ty (isub ty (iadd ty a b) c) d))
-      (subsume (isub ty (iadd ty a b) (isub ty c d))))
-
-;; ((a+b)+c)-d = (a+b) + (c-d)
-(rule (simplify (isub ty (iadd ty (iadd ty a b) c) d))
-      (subsume (iadd ty (iadd ty a b) (isub ty c d))))
-
 ;; Detect people open-coding `mulhi`: (x as big * y as big) >> bits
 ;; LLVM doesn't have an intrinsic for it, so you'll see it in code like
 ;; <https://github.com/rust-lang/rust/blob/767453eb7ca188e991ac5568c17b984dd4893e77/library/core/src/num/mod.rs#L174-L180>