Work on updating the QASM3 MLIR

#include "expression_handler.hpp"

#include "qasm3_visitor.hpp"

#include "mlir/Dialect/SCF/SCF.h"

namespace {

// ATM, we don't try to convert everything to the

// special Quantum If-Then-Else Op.

    }

  }

  // TODO: The below code could be rewritten to an AffineIfOp/SCF::IfOp:

  // Map it to a Value

  qasm3_expression_generator exp_generator(builder, symbol_table, file_name);

  exp_generator.visit(conditional_expr);

  // Boolean check value:

  auto expr_value = exp_generator.current_value;

  // build up the program block

  auto currRegion = builder.getBlock()->getParent();

  auto savept = builder.saveInsertionPoint();

  auto thenBlock = builder.createBlock(currRegion, currRegion->end());

  auto elseBlock = builder.createBlock(currRegion, currRegion->end());

  mlir::Block* exitBlock = nullptr;

  // If we have an else block from programBlock,

  // then create a stand alone exit block that both

  // then and else can fall to

  if (context->programBlock().size() == 2) {

    exitBlock = builder.createBlock(currRegion, currRegion->end());

  } else {

    exitBlock = elseBlock;

  }

  // Build up the THEN Block

  builder.setInsertionPointToStart(thenBlock);

  // Create SCF If Op:

  // SCF IfOp (switching on a boolean value) matches what we need here,

  // an AffineIfOp requires an integer set and will be lowered to SCF's IfOp later,

  // hence is not a good solution.

  const bool hasElseBlock = context->programBlock().size() == 2;

  auto scfIfOp = builder.create<mlir::scf::IfOp>(location, mlir::TypeRange(),

                                           expr_value, hasElseBlock);

  // Build up the 'then' region:

  auto thenBodyBuilder = scfIfOp.getThenBodyBuilder();

  auto cached_builder = builder;

  builder = thenBodyBuilder;

  symbol_table.enter_new_scope();

  // Get the conditional code and visit the nodes

  auto conditional_code = context->programBlock(0);

  visitChildren(conditional_code);    

  // Need to check if we have a branch out of

  // this thenBlock, if so do not add a branch

  // to the exitblock

  mlir::Operation& last_op = thenBlock->back();

  auto branchOps = thenBlock->getOps<mlir::BranchOp>();

  auto branch_to_exit = true;

  for (auto b : branchOps) {

    if (b.dest() == current_loop_exit_block ||

        b.dest() == current_loop_header_block ||

        b.dest() == current_loop_incrementor_block) {

      branch_to_exit = false;

      break;

    }

  }

  if (branch_to_exit) {

    builder.create<mlir::BranchOp>(location, exitBlock);

  }

  symbol_table.exit_scope();

  // If we have a second program block then we have an else stmt

  builder.setInsertionPointToStart(elseBlock);

  if (context->programBlock().size() == 2) {

  if (hasElseBlock) {

    auto elseBodyBuilder = scfIfOp.getElseBodyBuilder();

    builder = elseBodyBuilder;

    symbol_table.enter_new_scope();

    // Visit the second programBlock

    visitChildren(context->programBlock(1));

    branch_to_exit = true;

    for (auto b : branchOps) {

      if (b.dest() == current_loop_exit_block ||

          b.dest() == current_loop_header_block ||

          b.dest() == current_loop_incrementor_block) {

        branch_to_exit = false;

        break;

      }

    }

    if (branch_to_exit) {

      builder.create<mlir::BranchOp>(location, exitBlock);

    }

    symbol_table.exit_scope();

  }

  // Restore the insertion point and create the conditional statement

  builder.restoreInsertionPoint(savept);

  builder.create<mlir::CondBranchOp>(location, expr_value, thenBlock,

                                     elseBlock);

  builder.setInsertionPointToStart(exitBlock);

  symbol_table.set_last_created_block(exitBlock);

  // Restore builder

  builder = cached_builder;

  return 0;

}

}  // namespace qcor

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