Re: [Qemu-devel] [RISU PATCH v3 01/18] risugen_common: add helper functions insnv, randint

[Alex Bennée]

Jan Bobek <address@hidden> writes:

> insnv allows emitting variable-length instructions in little-endian or
> big-endian byte order; it subsumes functionality of former insn16()
> and insn32() functions.
>
> randint can reliably generate signed or unsigned integers of arbitrary
> width.
>
> Signed-off-by: Jan Bobek <address@hidden>

Reviewed-by: Alex Bennée <address@hidden>

> ---
>  risugen_common.pm | 55 +++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 48 insertions(+), 7 deletions(-)
>
> diff --git a/risugen_common.pm b/risugen_common.pm
> index 71ee996..d63250a 100644
> --- a/risugen_common.pm
> +++ b/risugen_common.pm
> @@ -23,8 +23,9 @@ BEGIN {
>      require Exporter;
>
>      our @ISA = qw(Exporter);
> -    our @EXPORT = qw(open_bin close_bin set_endian insn32 insn16 $bytecount
> -                   progress_start progress_update progress_end
> +    our @EXPORT = qw(open_bin close_bin set_endian insn32 insn16
> +                   $bytecount insnv randint progress_start
> +                   progress_update progress_end
>                     eval_with_fields is_pow_of_2 sextract ctz
>                     dump_insn_details);
>  }
> @@ -37,7 +38,7 @@ my $bigendian = 0;
>  # (default is little endian, 0).
>  sub set_endian
>  {
> -    $bigendian = @_;
> +    ($bigendian) = @_;
>  }
>
>  sub open_bin
> @@ -52,18 +53,58 @@ sub close_bin
>      close(BIN) or die "can't close output file: $!";
>  }
>
> +sub insnv(%)
> +{
> +    my (%args) = @_;
> +
> +    # Default to big-endian order, so that the instruction bytes are
> +    # emitted in the same order as they are written in the
> +    # configuration file.
> +    $args{bigendian} = 1 unless defined $args{bigendian};
> +
> +    for (my $bitcur = 0; $bitcur < $args{width}; $bitcur += 8) {
> +        my $value = $args{value} >> ($args{bigendian}
> +                                     ? $args{width} - $bitcur - 8
> +                                     : $bitcur);
> +
> +        print BIN pack("C", $value & 0xff);
> +        $bytecount += 1;
> +    }
> +}
> +
>  sub insn32($)
>  {
>      my ($insn) = @_;
> -    print BIN pack($bigendian ? "N" : "V", $insn);
> -    $bytecount += 4;
> +    insnv(value => $insn, width => 32, bigendian => $bigendian);
>  }
>
>  sub insn16($)
>  {
>      my ($insn) = @_;
> -    print BIN pack($bigendian ? "n" : "v", $insn);
> -    $bytecount += 2;
> +    insnv(value => $insn, width => 16, bigendian => $bigendian);
> +}
> +
> +sub randint
> +{
> +    my (%args) = @_;
> +    my $width = $args{width};
> +
> +    if ($width > 32) {
> +        # Generate at most 32 bits at once; Perl's rand() does not
> +        # behave well with ranges that are too large.
> +        my $lower = randint(%args, width => 32);
> +        my $upper = randint(%args, width => $args{width} - 32);
> +        # Use arithmetic rather than bitwise operators, since bitwise
> +        # ops turn signed integers into unsigned.
> +        return $upper * (1 << 32) + $lower;
> +    } elsif ($width > 0) {
> +        my $halfrange = 1 << ($width - 1);
> +        my $value = int(rand(2 * $halfrange));
> +        $value -= $halfrange if defined $args{signed} && $args{signed};
> +        return $value;
> +    } else {
> +        return 0;
> +    }
>  }
>
>  # Progress bar implementation


--
Alex Bennée