Commit 17560e93 authored by Richard Henderson's avatar Richard Henderson
Browse files

decodetree: Initial support for variable-length ISAs 



Assuming that the ISA clearly describes how to determine
the length of the instruction, and the ISA has a reasonable
maximum instruction length, the input to the decoder can be
right-justified in an appropriate insn word.

This is not 100% convenient, as out-of-line %fields are
numbered relative to the maximum instruction length, but
this appears to still be usable.

Signed-off-by: default avatarRichard Henderson <richard.henderson@linaro.org>
parent a6ae2383

scripts/decodetree.py

+37 −12
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ import getopt 


insnwidth = 32

insnmask = 0xffffffff

variablewidth = False

fields = {}

arguments = {}

formats = {}
@@ -289,7 +290,7 @@ class Arguments: 


class General:

    """Common code between instruction formats and instruction patterns"""

    def __init__(self, name, lineno, base, fixb, fixm, udfm, fldm, flds):

    def __init__(self, name, lineno, base, fixb, fixm, udfm, fldm, flds, w):

        self.name = name

        self.file = input_file

        self.lineno = lineno
@@ -299,6 +300,7 @@ class General: 
        self.undefmask = udfm

        self.fieldmask = fldm

        self.fields = flds

        self.width = w



    def __str__(self):

        return self.name + ' ' + str_match_bits(self.fixedbits, self.fixedmask)
@@ -352,7 +354,7 @@ class Pattern(General): 
class MultiPattern(General):

    """Class representing an overlapping set of instruction patterns"""



    def __init__(self, lineno, pats, fixb, fixm, udfm):

    def __init__(self, lineno, pats, fixb, fixm, udfm, w):

        self.file = input_file

        self.lineno = lineno

        self.pats = pats
@@ -360,6 +362,7 @@ class MultiPattern(General): 
        self.fixedbits = fixb

        self.fixedmask = fixm

        self.undefmask = udfm

        self.width = w



    def __str__(self):

        r = "{"
@@ -502,7 +505,7 @@ def infer_argument_set(flds): 
    return arg





def infer_format(arg, fieldmask, flds):

def infer_format(arg, fieldmask, flds, width):

    global arguments

    global formats

    global decode_function
@@ -521,6 +524,8 @@ def infer_format(arg, fieldmask, flds): 
            continue

        if fieldmask != fmt.fieldmask:

            continue

        if width != fmt.width:

            continue

        if not eq_fields_for_fmts(flds, fmt.fields):

            continue

        return (fmt, const_flds)
@@ -529,7 +534,7 @@ def infer_format(arg, fieldmask, flds): 
    if not arg:

        arg = infer_argument_set(flds)



    fmt = Format(name, 0, arg, 0, 0, 0, fieldmask, var_flds)

    fmt = Format(name, 0, arg, 0, 0, 0, fieldmask, var_flds, width)

    formats[name] = fmt



    return (fmt, const_flds)
@@ -546,6 +551,7 @@ def parse_generic(lineno, is_format, name, toks): 
    global re_ident

    global insnwidth

    global insnmask

    global variablewidth



    fixedmask = 0

    fixedbits = 0
@@ -633,8 +639,15 @@ def parse_generic(lineno, is_format, name, toks): 
            error(lineno, 'invalid token "{0}"'.format(t))

        width += shift



    if variablewidth and width < insnwidth and width % 8 == 0:

        shift = insnwidth - width

        fixedbits <<= shift

        fixedmask <<= shift

        undefmask <<= shift

        undefmask |= (1 << shift) - 1



    # We should have filled in all of the bits of the instruction.

    if not (is_format and width == 0) and width != insnwidth:

    elif not (is_format and width == 0) and width != insnwidth:

        error(lineno, 'definition has {0} bits'.format(width))



    # Do not check for fields overlaping fields; one valid usage
@@ -660,7 +673,7 @@ def parse_generic(lineno, is_format, name, toks): 
        if name in formats:

            error(lineno, 'duplicate format name', name)

        fmt = Format(name, lineno, arg, fixedbits, fixedmask,

                     undefmask, fieldmask, flds)

                     undefmask, fieldmask, flds, width)

        formats[name] = fmt

    else:

        # Patterns can reference a format ...
@@ -670,12 +683,14 @@ def parse_generic(lineno, is_format, name, toks): 
                error(lineno, 'pattern specifies both format and argument set')

            if fixedmask & fmt.fixedmask:

                error(lineno, 'pattern fixed bits overlap format fixed bits')

            if width != fmt.width:

                error(lineno, 'pattern uses format of different width')

            fieldmask |= fmt.fieldmask

            fixedbits |= fmt.fixedbits

            fixedmask |= fmt.fixedmask

            undefmask |= fmt.undefmask

        else:

            (fmt, flds) = infer_format(arg, fieldmask, flds)

            (fmt, flds) = infer_format(arg, fieldmask, flds, width)

        arg = fmt.base

        for f in flds.keys():

            if f not in arg.fields:
@@ -687,7 +702,7 @@ def parse_generic(lineno, is_format, name, toks): 
            if f not in flds.keys() and f not in fmt.fields.keys():

                error(lineno, 'field {0} not initialized'.format(f))

        pat = Pattern(name, lineno, fmt, fixedbits, fixedmask,

                      undefmask, fieldmask, flds)

                      undefmask, fieldmask, flds, width)

        patterns.append(pat)

        allpatterns.append(pat)
@@ -727,6 +742,13 @@ def build_multi_pattern(lineno, pats): 
        if p.lineno < lineno:

            lineno = p.lineno



    width = None

    for p in pats:

        if width is None:

            width = p.width

        elif width != p.width:

            error(lineno, 'width mismatch in patterns within braces')



    repeat = True

    while repeat:

        if fixedmask == 0:
@@ -742,7 +764,7 @@ def build_multi_pattern(lineno, pats): 
        else:

            repeat = False



    mp = MultiPattern(lineno, pats, fixedbits, fixedmask, undefmask)

    mp = MultiPattern(lineno, pats, fixedbits, fixedmask, undefmask, width)

    patterns.append(mp)

# end build_multi_pattern
@@ -979,13 +1001,14 @@ def main(): 
    global insntype

    global insnmask

    global decode_function

    global variablewidth



    decode_scope = 'static '



    long_opts = ['decode=', 'translate=', 'output=', 'insnwidth=',

                 'static-decode=']

                 'static-decode=', 'varinsnwidth=']

    try:

        (opts, args) = getopt.getopt(sys.argv[1:], 'o:w:', long_opts)

        (opts, args) = getopt.getopt(sys.argv[1:], 'o:vw:', long_opts)

    except getopt.GetoptError as err:

        error(0, err)

    for o, a in opts:
@@ -999,7 +1022,9 @@ def main(): 
        elif o == '--translate':

            translate_prefix = a

            translate_scope = ''

        elif o in ('-w', '--insnwidth'):

        elif o in ('-w', '--insnwidth', '--varinsnwidth'):

            if o == '--varinsnwidth':

                variablewidth = True

            insnwidth = int(a)

            if insnwidth == 16:

                insntype = 'uint16_t'