This adds the possibility to specify a predicate-function that is called as part of decoding in multi-patterns; it is intended for use-cases (such as vendor-defined instructions in RISC-V) where the same bitpattern may decode into different functions depending on the overall configuration of the emulation target.
At this time, we only support predicates for multi-patterns. Signed-off-by: Philipp Tomsich <[email protected]> --- docs/devel/decodetree.rst | 7 ++++++- scripts/decodetree.py | 24 +++++++++++++++++++++--- 2 files changed, 27 insertions(+), 4 deletions(-) diff --git a/docs/devel/decodetree.rst b/docs/devel/decodetree.rst index 49ea50c2a7..241aaec8bb 100644 --- a/docs/devel/decodetree.rst +++ b/docs/devel/decodetree.rst @@ -144,9 +144,10 @@ Patterns Syntax:: pat_def := identifier ( pat_elt )+ - pat_elt := fixedbit_elt | field_elt | field_ref | args_ref | fmt_ref | const_elt + pat_elt := fixedbit_elt | field_elt | field_ref | args_ref | fmt_ref | const_elt | predicate fmt_ref := '@' identifier const_elt := identifier '=' number + predicate := '|' identifier The *fixedbit_elt* and *field_elt* specifiers are unchanged from formats. A pattern that does not specify a named format will have one inferred @@ -156,6 +157,10 @@ A *const_elt* allows a argument to be set to a constant value. This may come in handy when fields overlap between patterns and one has to include the values in the *fixedbit_elt* instead. +A *predicate* allows to specify a predicate function (returing true or +false) to determine the applicability of the pattern. Currently, this +will change the decode-behaviour for overlapping multi-patterns only. + The decoder will call a translator function for each pattern matched. Pattern examples:: diff --git a/scripts/decodetree.py b/scripts/decodetree.py index a03dc6b5e3..7da2282411 100644 --- a/scripts/decodetree.py +++ b/scripts/decodetree.py @@ -52,6 +52,7 @@ re_fld_ident = '%[a-zA-Z0-9_]*' re_fmt_ident = '@[a-zA-Z0-9_]*' re_pat_ident = '[a-zA-Z0-9_]*' +re_predicate_ident = '\|[a-zA-Z_][a-zA-Z0-9_]*' def error_with_file(file, lineno, *args): """Print an error message from file:line and args and exit.""" @@ -119,6 +120,14 @@ def whexC(val): suffix = 'u' return whex(val) + suffix +def predicate(val): + """Return a string for calling a predicate function + (if specified, accepting 'None' as an indication + that no predicate is to be emitted) with the ctx + as a parameter.""" + if (val == None): + return '' + return ' && ' + val + '(ctx)' def str_match_bits(bits, mask): """Return a string pretty-printing BITS/MASK""" @@ -340,7 +349,7 @@ def output_def(self): class General: """Common code between instruction formats and instruction patterns""" - def __init__(self, name, lineno, base, fixb, fixm, udfm, fldm, flds, w): + def __init__(self, name, lineno, base, fixb, fixm, udfm, fldm, flds, w, p = None): self.name = name self.file = input_file self.lineno = lineno @@ -351,6 +360,7 @@ def __init__(self, name, lineno, base, fixb, fixm, udfm, fldm, flds, w): self.fieldmask = fldm self.fields = flds self.width = w + self.predicate = p def __str__(self): return self.name + ' ' + str_match_bits(self.fixedbits, self.fixedmask) @@ -499,7 +509,7 @@ def output_code(self, i, extracted, outerbits, outermask): if outermask != p.fixedmask: innermask = p.fixedmask & ~outermask innerbits = p.fixedbits & ~outermask - output(ind, f'if ((insn & {whexC(innermask)}) == {whexC(innerbits)}) {{\n') + output(ind, f'if ((insn & {whexC(innermask)}) == {whexC(innerbits)}{predicate(p.predicate)}) {{\n') output(ind, f' /* {str_match_bits(p.fixedbits, p.fixedmask)} */\n') p.output_code(i + 4, extracted, p.fixedbits, p.fixedmask) output(ind, '}\n') @@ -826,6 +836,7 @@ def parse_generic(lineno, parent_pat, name, toks): global re_fld_ident global re_fmt_ident global re_C_ident + global re_predicate_ident global insnwidth global insnmask global variablewidth @@ -839,6 +850,7 @@ def parse_generic(lineno, parent_pat, name, toks): flds = {} arg = None fmt = None + predicate = None for t in toks: # '&Foo' gives a format an explicit argument set. if re.fullmatch(re_arg_ident, t): @@ -881,6 +893,12 @@ def parse_generic(lineno, parent_pat, name, toks): flds = add_field(lineno, flds, fname, ConstField(value)) continue + # '|predicate' sets a predicate function to be called. + if re.fullmatch(re_predicate_ident, t): + tt = t[1:] + predicate = tt; + continue + # Pattern of 0s, 1s, dots and dashes indicate required zeros, # required ones, or dont-cares. if re.fullmatch('[01.-]+', t): @@ -979,7 +997,7 @@ def parse_generic(lineno, parent_pat, name, toks): if f not in flds.keys() and f not in fmt.fields.keys(): error(lineno, f'field {f} not initialized') pat = Pattern(name, lineno, fmt, fixedbits, fixedmask, - undefmask, fieldmask, flds, width) + undefmask, fieldmask, flds, width, predicate) parent_pat.pats.append(pat) allpatterns.append(pat) -- 2.33.1
