transformations: Implement control-flow-hoist

[PapyChacal]

Stacked on:

• core: Implement speculability trait and helper. #3102

A couple of splittable but minor changes:

• Update on some dialects for required traits
• Make AffineEx hashable (as all attributes are expected to be! I just randomly crashed some CSE I was playing around with otherwise)

Just a simple and naive pass hoisting everything from region branches.

Thinking a bit, I realized this is all I missed for some slightly tricky cases to work the way I want in MLIR; see filecheck for more!

In a nutshell, MLIR provides some nice bits already, like loop-invariant-code-motion (Get stuff out of loop) and control-flow-sink (Nest stuff in branches) which are locally okay and smart, but contradict sometimes leading to frustrating things like, to reduce it as much as possible:

func.func @nested_loop_invariant(%n : index) {
    %0 = arith.constant 0 : index
    %1 = arith.constant 1 : index
    %100 = arith.constant 100 : index
    scf.for %i = %0 to %100 step %1 {
        %cond = "test.op"() : () -> (i1)
        %thing = "scf.if"(%cond)  ({
            %n100 = arith.muli %n, %100 : index 
            scf.yield %n100 :index
        }, {
            scf.yield %n : index
        }) : (i1) -> index
        "test.op"(%thing) : (index) -> ()
        scf.yield
    }
    return
}

From the scf.if's perspective, one should really keep the arith.muli nested. What a waste if you compute it and don't take this branch!
Thus from the loop's perspective, it's not as easy as hoisting an operation from its body and is not done.

So this pass does a typically-bad thing to help get out of this kind of local-minima frustration. Just naively hoist everything out of the conditionals to expose the loop-invariant bits, and sink the rest back if desired!

It should also help if someone wants to go from branches to precomputation + select, as I remember was a cool shader trick some amount of years ago at least 😋

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.89%. Comparing base (a2ed14d) to head (8ebba1b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3103      +/-   ##
==========================================
- Coverage   89.91%   89.89%   -0.02%     
==========================================
  Files         419      420       +1     
  Lines       53070    53129      +59     
  Branches     8226     8237      +11     
==========================================
+ Hits        47718    47761      +43     
- Misses       4023     4037      +14     
- Partials     1329     1331       +2     

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