JIT: Canonicalize '(A & pow2) == pow2' -> '(A & pow2) != 0'

[BoyBaykiller]

Basically so we always have 0 at the right-side:

1. '(A & pow2) == pow2' -> '(A & pow2) != 0'
2. '(A & pow2) != pow2' -> '(A & pow2) == 0'

Tthis currently helps optimizeBools, but I am also adding this with the future in mind.
Here is one example:

static bool Example(int foo)
{
    return ((foo & 4) == 4) || ((foo & 8) == 8);
}

;; ------ BASE
G_M000_IG02:                ;; offset=0x0000
       test     cl, 4
       je       SHORT G_M000_IG05
 
G_M000_IG03:                ;; offset=0x0005
       mov      eax, 1
 
G_M000_IG04:                ;; offset=0x000A
       ret      
 
G_M000_IG05:                ;; offset=0x000B
       test     cl, 8
       setne    al
       movzx    rax, al
 
G_M000_IG06:                ;; offset=0x0014
       ret      

;; ------ DIFF
G_M33938_IG02:  ;; offset=0x0000
       mov      eax, ecx
       and      eax, 4
       and      ecx, 8
       or       eax, ecx
       setne    al
       movzx    rax, al

Note: With #126852 this would then get transformed into just test 12.

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[MichalPetryka]

@MihuBot -nuget

[Copilot]

Pull request overview

Canonicalizes (A & pow2) == pow2 to (A & pow2) != 0 (and the inverse for !=) during morph relational-comparison optimization. This puts the comparison into a uniform form with 0 on the right, which immediately helps optimizeBools and sets the stage for further follow-on optimizations (e.g., the distributive transform in #126852).

Changes:

• Add a canonicalization in fgOptimizeRelationalComparison that, when matching (A & pow2) ==/!= pow2, reverses the relop and bashes the RHS constant to zero, with VN updated accordingly.

[BoyBaykiller]

@EgorBo I fixed the merge conflicts.

[BoyBaykiller]

Are we good to merge :) ? I'd like to continue follow up work @EgorBo

[EgorBo]

/ba-g known CSharpMissingShebangInFileBasedProgram failure