Improve booleans on generated code

[PalumboN]

Now when Druid interprets a complex condition (using and:/or:) like

isFixedSizePointerFormat: format
    <api>
    ^format <= self nonIndexablePointerFormat
      or: [format = self ephemeronFormat]

It's generates an IR like

# Block1
-------------------------------
t1 := GetConditionCode(cond1)
JumpIf(cond1 = true)
-------------------------------

# BlockTrue
-------------------------------
t2 := GetConditionCode(cond2)
Jump(Merge)
-------------------------------

# BlockMerge
-------------------------------
t3 := Phi(t1, t2)
JumpIf(t3 = true)
-------------------------------

And it generates, after not optimal register allocations because of the phi, Cogit's code that move constants to the compare

DruidJIT >> gen_PrimitiveNew
        "..."
        self CmpCq: 5 R: Extra1Reg.
        jumpTrue := self JumpZero: 0.
        self MoveCq: 0 R: Extra1Reg.
        jumpNext := self Jump: 0.
        jumpTrue jmpTarget: self Label.
        self MoveCq: 1 R: Extra1Reg.
        jumpNext jmpTarget: self Label.
        currentBlock := self Label.
        jump2 jmpTarget: currentBlock.
        self CmpCq: 1 R: Extra1Reg.
        jump2 := self JumpNonZero: 0.
        "..."

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What to do?

Well, we can avoid these unnecesary copies, compares and jumps by solving the phi in the IR.

• One simple way to solve a phi is tail duplicate the merge block (and the run others optimisations).
• Check DRBranchCollapse
  • That optimisation "propagate" GetConditionCode conditions to JumpIf for cases = true
  • I'm not sure if we should extend that, or what, but it is related
• Check DRCogitCanonicaliser
  • It find some common patterns in the IR and try to simplify them. Maybe it can check the jump with the phi.
  • Also maybe we want to move the logic of the DRBranchCollapse there also

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I make a POC doing the tail duplication by hand in the IR, this is the result: