transformations: (eqsat) add pass to convert non-eclass functions to eclass

[jianyicheng]

This PR addresses #3170:

• Added initial front end pass eqsat-create-eclasses for the minimal example
• Added an initial test case for the pass

[superlopuh]

Oh interesting, I forgot about function returns, they seem useful enough to have from the get-go, could you please change the check to rather be len(results) > 1? I would then recommend using the test dialect in filecheck, to make sure we're testing exactly what we mean to test:

Suggested change

	func.func @test(%x : index) -> (index) {
	%c2 = arith.constant 2 : index
	%res = arith.muli %x, %c2 : index
	func.return %res : index
	}
	// CHECK: Error while applying pattern: Ops with non-single results not handled
	func.func @test(%x : index) -> (index) {
	%r0, %r1 = "test.op"() : () -> (index, index)
	}
	// CHECK: Error while applying pattern: Only single-result operations can be converted to eclasses, got 2 results

(I also changed the message do include the length of the results, should hopefully help debug this in the future)

[superlopuh]

Could you please add a test with a successful transform also?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.04%. Comparing base (364be97) to head (884a4e0).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3189   +/-   ##
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  Coverage   90.03%   90.04%           
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  Files         445      446    +1     
  Lines       56205    56239   +34     
  Branches     5399     5403    +4     
=======================================
+ Hits        50606    50639   +33     
+ Misses       4180     4177    -3     
- Partials     1419     1423    +4     

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[superlopuh]

Perfect, thank you!