Conditional branches in generic form

[Berke Ates]

The following MLIR:

module  {
    func @mlir_entry(%a: i32) -> i32 {
        %1 = constant 1 : i32

        %isOne = cmpi "sle", %a, %1 : i32
        cond_br %isOne, ^one, ^else

        ^one: 
            return %1 : i32

        ^else: 
            return %1 : i32
    }
}

results in the following generic form:

// out.mlir
"module"() ( {
  "func"() ( {
  ^bb0(%arg0: i32):  // no predecessors
    %c1_i32 = "std.constant"() {value = 1 : i32} : () -> i32
    %0 = "std.cmpi"(%arg0, %c1_i32) {predicate = 3 : i64} : (i32, i32) -> i1
    "std.cond_br"(%0)[^bb1, ^bb2] {operand_segment_sizes = dense<[1, 0, 0]> : vector<3xi32>} : (i1) -> ()
  ^bb1:  // pred: ^bb0
    "std.return"(%c1_i32) : (i32) -> ()
  ^bb2:  // pred: ^bb0
    "std.return"(%c1_i32) : (i32) -> ()
  }) {sym_name = "mlir_entry", type = (i32) -> i32} : () -> ()
}) : () -> ()

Executing:

import mlir
ast1 = mlir.parse_path('out.mlir')

throws this exception:

lark.exceptions.UnexpectedCharacters: No terminal matches '[' in the current parser context, at line 6 col 22

    "std.cond_br"(%0)[^bb1, ^bb2] {operand_segment_sizes = de
                     ^
Expected one of: 
        * LBRACE
        * COLON