Convert scf to riscv scf

class ScfForLowering(RewritePattern):
    @op_type_rewrite_pattern
    def match_and_rewrite(self, op: scf.ForOp, rewriter: PatternRewriter) -> None:
        lb, ub, step, *args = cast_operands_to_regs(rewriter, op)
        new_region = rewriter.move_region_contents_to_new_regions(op.body)
        cast_block_args_to_regs(new_region.block, rewriter)
        mv_ops, values = move_to_unallocated_regs(args, op.iter_args.types)
        rewriter.insert(mv_ops)
        cast_op_results(rewriter, op)
        new_op = riscv_scf.ForOp(lb, ub, step, values, new_region)

        new_ops = list[Operation]()
        new_values = list[SSAValue]()

        for value, value_type in zip(new_op.results, op.iter_args.types, strict=True):
            register_type = register_type_for_type(value.type)
            move_op, new_value = move_ops_for_value(
                value, value_type, register_type.unallocated()
            )
            new_ops.append(move_op)
            new_values.append(new_value)

        mv_res_ops, res_values = new_ops, new_values

        rewriter.replace(op, (new_op, *mv_res_ops), res_values)

class ScfYieldLowering(RewritePattern):
    @op_type_rewrite_pattern
    def match_and_rewrite(self, op: scf.YieldOp, rewriter: PatternRewriter) -> None:
        rewriter.replace(op, riscv_scf.YieldOp(*cast_operands_to_regs(rewriter, op)))

class ConvertScfToRiscvPass(ModulePass):
    name = "convert-scf-to-riscv-scf"

    def apply(self, ctx: Context, op: builtin.ModuleOp) -> None:
        PatternRewriteWalker(
            GreedyRewritePatternApplier(
                [
                    ScfYieldLowering(),
                    ScfForLowering(),
                ]
            )
        ).rewrite_module(op)