[PATCH] D24419: [InstCombine] use commutative matchers for patterns with commutative operators

[Sanjoy Das via llvm-commits]

sanjoy added a comment.

In https://reviews.llvm.org/D24419#550211, @spatel wrote:

> I'm not sure how to canonicalize this without possibly conflicting
>  with other canonicalization rules based on operand complexity. Ie, we
>  order binop operands depending on whether they are themselves
>  binop/unop/params/constants.


Yeah, I can't come up with a scheme that will obviously not clash with
InstCombine's operand complexity order.

An alternative may be to canonicalize "internally" -- that is first
split the expression into `(Op0 ITy0 Op1) ITy1 (Op2 ITy2 Op3)` (that
is, "explode" the contents of the operation into local variables) and
then `std::swap` the `Op0` / `Op1` or the `Op2` / `Op3` pairs in
whatever order that makes matching these easier.  That may involve too
much refactoring though.


https://reviews.llvm.org/D24419