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tokhash: Speed up the rejection of unhashed values

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Speed up the rejection of unhashed values (typically identifiers) by
filling unused hash slots with a large value (but not so large that
it is likely to overflow.)  This means those values will be rejected
already by the range check, not needing strcmp().
This commit is contained in:
H. Peter Anvin 2007-08-31 07:23:31 +00:00
parent 535af831f1
commit 91a86cdb31
2 changed files with 18 additions and 5 deletions
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12
perllib/phash.ph
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@ -156,10 +156,16 @@ sub gen_hash_n($$$) {
# for the edge (which is our hash index.) Since the graph is
# acyclic, this is always doable.
for ($i = 0; $i < $gsize; $i++) {
if (!$gr->has_vertex_attribute($i, "val")) {
walk_graph($gr,$i,0); # First vertex in a cluster
if ($gr->degree($i)) {
# This vertex has neighbors (is used)
if (!$gr->has_vertex_attribute($i, "val")) {
walk_graph($gr,$i,0); # First vertex in a cluster
}
push(@g, $gr->get_vertex_attribute($i, "val"));
} else {
# Unused vertex
push(@g, undef);
}
push(@g, $gr->get_vertex_attribute($i, "val"));
}
# for ($i = 0; $i < $n; $i++) {

11
tokhash.pl
View File

@ -148,17 +148,24 @@ print "\n";
print "int nasm_token_hash(const char *token, struct tokenval *tv)\n";
print "{\n";
# Put a large value in unused slots. This makes it extremely unlikely
# that any combination that involves unused slot will pass the range test.
# This speeds up rejection of unrecognized tokens, i.e. identifiers.
$unused = 16383;
print "\tstatic const int16_t hash1[$n] =\n";
print "\t{\n";
for ($i = 0; $i < $n; $i++) {
print "\t\t", ${$g}[${$f1}[$i]], ",\n";
my $h = ${$g}[${$f1}[$i]];
printf "\t\t%d,\n", defined($h) ? $h : $unused;
}
print "\t};\n\n";
print "\tstatic const int16_t hash2[$n] =\n";
print "\t{\n";
for ($i = 0; $i < $n; $i++) {
print "\t\t", ${$g}[${$f2}[$i]], ",\n";
my $h = ${$g}[${$f2}[$i]];
printf "\t\t%d,\n", defined($h) ? $h : $unused;
}
print "\t};\n\n";