From 70e0711ab18fa48279cd2c8cc570b57f38648598 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Thu, 31 Jan 2019 11:34:11 -0800 Subject: [PATCH] decodetree: Expand a decode_load function Read the instruction, loading no more bytes than necessary. Signed-off-by: Richard Henderson --- scripts/decodetree.py | 175 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 172 insertions(+), 3 deletions(-) diff --git a/scripts/decodetree.py b/scripts/decodetree.py index 555a46522b..4536e3a63d 100755 --- a/scripts/decodetree.py +++ b/scripts/decodetree.py @@ -965,6 +965,147 @@ def build_tree(pats, outerbits, outermask): # end build_tree +class SizeTree: + """Class representing a node in a size decode tree""" + + def __init__(self, m, w): + self.mask = m + self.subs = [] + self.base = None + self.width = w + + def str1(self, i): + ind = str_indent(i) + r = '{0}{1:08x}'.format(ind, self.mask) + r += ' [\n' + for (b, s) in self.subs: + r += '{0} {1:08x}:\n'.format(ind, b) + r += s.str1(i + 4) + '\n' + r += ind + ']' + return r + + def __str__(self): + return self.str1(0) + + def output_code(self, i, extracted, outerbits, outermask): + ind = str_indent(i) + + # If we need to load more bytes to test, do so now. + if extracted < self.width: + output(ind, 'insn = ', decode_function, + '_load_bytes(ctx, insn, {0}, {1});\n' + .format(extracted / 8, self.width / 8)); + extracted = self.width + + # Attempt to aid the compiler in producing compact switch statements. + # If the bits in the mask are contiguous, extract them. + sh = is_contiguous(self.mask) + if sh > 0: + # Propagate SH down into the local functions. + def str_switch(b, sh=sh): + return '(insn >> {0}) & 0x{1:x}'.format(sh, b >> sh) + + def str_case(b, sh=sh): + return '0x{0:x}'.format(b >> sh) + else: + def str_switch(b): + return 'insn & 0x{0:08x}'.format(b) + + def str_case(b): + return '0x{0:08x}'.format(b) + + output(ind, 'switch (', str_switch(self.mask), ') {\n') + for b, s in sorted(self.subs): + innermask = outermask | self.mask + innerbits = outerbits | b + output(ind, 'case ', str_case(b), ':\n') + output(ind, ' /* ', + str_match_bits(innerbits, innermask), ' */\n') + s.output_code(i + 4, extracted, innerbits, innermask) + output(ind, '}\n') + output(ind, 'return insn;\n') +# end SizeTree + +class SizeLeaf: + """Class representing a leaf node in a size decode tree""" + + def __init__(self, m, w): + self.mask = m + self.width = w + + def str1(self, i): + ind = str_indent(i) + return '{0}{1:08x}'.format(ind, self.mask) + + def __str__(self): + return self.str1(0) + + def output_code(self, i, extracted, outerbits, outermask): + global decode_function + ind = str_indent(i) + + # If we need to load more bytes, do so now. + if extracted < self.width: + output(ind, 'insn = ', decode_function, + '_load_bytes(ctx, insn, {0}, {1});\n' + .format(extracted / 8, self.width / 8)); + extracted = self.width + output(ind, 'return insn;\n') +# end SizeLeaf + + +def build_size_tree(pats, width, outerbits, outermask): + global insnwidth + + # Collect the mask of bits that are fixed in this width + innermask = 0xff << (insnwidth - width) + innermask &= ~outermask + minwidth = None + onewidth = True + for i in pats: + innermask &= i.fixedmask + if minwidth is None: + minwidth = i.width + elif minwidth != i.width: + onewidth = False; + if minwidth < i.width: + minwidth = i.width + + if onewidth: + return SizeLeaf(innermask, minwidth) + + if innermask == 0: + if width < minwidth: + return build_size_tree(pats, width + 8, outerbits, outermask) + + pnames = [] + for p in pats: + pnames.append(p.name + ':' + p.file + ':' + str(p.lineno)) + error_with_file(pats[0].file, pats[0].lineno, + 'overlapping patterns size {0}:'.format(width), pnames) + + bins = {} + for i in pats: + fb = i.fixedbits & innermask + if fb in bins: + bins[fb].append(i) + else: + bins[fb] = [i] + + fullmask = outermask | innermask + lens = sorted(bins.keys()) + if len(lens) == 1: + b = lens[0] + return build_size_tree(bins[b], width + 8, b | outerbits, fullmask) + + r = SizeTree(innermask, width) + for b, l in bins.items(): + s = build_size_tree(l, width, b | outerbits, fullmask) + r.subs.append((b, s)) + return r +# end build_size_tree + + def prop_format(tree): """Propagate Format objects into the decode tree""" @@ -987,6 +1128,23 @@ def prop_format(tree): # end prop_format +def prop_size(tree): + """Propagate minimum widths up the decode size tree""" + + if isinstance(tree, SizeTree): + min = None + for (b, s) in tree.subs: + width = prop_size(s) + if min is None or min > width: + min = width + assert min >= tree.width + tree.width = min + else: + min = tree.width + return min +# end prop_size + + def main(): global arguments global formats @@ -1042,8 +1200,12 @@ def main(): parse_file(f) f.close() - t = build_tree(patterns, 0, 0) - prop_format(t) + if variablewidth: + stree = build_size_tree(patterns, 8, 0, 0) + prop_size(stree) + + dtree = build_tree(patterns, 0, 0) + prop_format(dtree) if output_file: output_fd = open(output_file, 'w') @@ -1084,11 +1246,18 @@ def main(): f = arguments[n] output(i4, i4, f.struct_name(), ' f_', f.name, ';\n') output(i4, '} u;\n\n') - t.output_code(4, False, 0, 0) + dtree.output_code(4, False, 0, 0) output(i4, 'return false;\n') output('}\n') + if variablewidth: + output('\n', decode_scope, insntype, ' ', decode_function, + '_load(DisasContext *ctx)\n{\n', + ' ', insntype, ' insn = 0;\n\n') + stree.output_code(4, 0, 0, 0) + output('}\n') + if output_file: output_fd.close() # end main