IfScope

[jle-quel]

Hello, I was looking at the generated code from Polygeist and I stumble upon this code pattern that is created for every function.

This code is generated by the MLIRScanner Ctor as well as the IfScope Ctor:

%true = arith.constant true

%11 = memref.alloca() : memref<i1>

memref.store %true, %11[] : memref<i1>

%13 = memref.load %11[] : memref<i1>
scf.if %13 {
  scf.execute_region {
    %16 = memref.load %11[] : memref<i1>
      scf.if %16 {
        scf.execute_region {
          ... do stuff until yield

I'm not getting the importance of this "branching" code. Since it's generated on hard-coded constant value true.

Why not just have the ... do stuff inside the function region instead of creating subregions?

[wsmoses]

This pattern is generated to correctly handle return, break and continue.

For example, the register is set to false after a return has been seen to ensure no code after a return statement is run. This is necessary as MLIR does not support a return statement from a nested region.

This code should be simplified when run with mem2reg and canonicalize