On some platforms, tolower() is implemented as a function call, in
order to handle locale support. We never change locales, so can the
result of tolower() into a table, so we don't have to sit through the
function call every time.
~1.3% overall performance improvement on a macro-heavy benchmark under
Linux x86-64.
Concentrate compiler dependencies to compiler.h; make sure compiler.h
is included first in every .c file (since some prototypes may depend
on the presence of feature request macros.)
Actually use the conditional inclusion of various functions (totally
broken in previous releases.)
Use the same crc64 that we already use for the symbol table hash as
the perfect hash function prehash. We appear to get radically faster
convergence this way, and the crc64 is probably *faster*, since the
table likely to be resident in memory.
Switch the preprocessor over to using the hash table library. On my
system, this improves the runtime of the output of test/pref/macro.pl
from over 600 seconds to 7 seconds.
Macros have an odd mix of case-sensitive and case-insensitive
behaviour, plus there are matching parameters for arguments, etc. As
a result, we use case-insensitive hash tables and use a linked list to
store all the possible isomorphs.
Define a proper hash table library, instead of the current ad hoc stuff
used for both labels and macros. This only implements the actual
library; it is not yet used.
We use a CRC64 as a prehash. This is almost certainly overkill,
although it is rather efficient (except, arguably, the table lookup)
on 64-bit platforms, and not all that bad on 32-bit platforms. All we
really need is a function which produces two independent 32-bit
results which are used as the primary and secondary hash
respectively. Either way, the prehash function is easily replacable
if/when we have a quicker alternative.
