Hello,
my last attempt on improving something serious was about three weeks ago,
trying to keep all lengths of all strings parsed in the frontend for the
whole compilation phase until the assembly output. I was hoping that would
help on using faster hashes (knowing the length allows us to hash 4 or 8
bytes per iteration), quicker strcmp in various places, and using less
strlen() calls, which show especially on -g3 compilations that store huge
macro strings.
I'll post no patch here, since what I currently have is a mess in 3
different branches and most don't even compile. I tried various
approaches. First I tried adding an extra length parameter in all relevant
functions, starting from the assembly generation and working my way
upwards. This got too complex, and I'd really like to ask if you find any
meaning in changing target specific hooks and macros to actually accept
length as argument (e.g. ASM_OUTPUT_*) or return it (e.g. ASM_GENERATE_*).
Changes seemed too intrusive for me to continue.
But seeing that identifier length is there inside struct ht_identifier (or
cpp_hashnode) and not lost, I tried the approach of having the length at
str[-4] for all identifiers. To achieve this I changed ht_identifier to
store str with the flexible array hack. Unfortunately I hadn't noticed
that ht_identifier was a part of tree_node and also part of too many other
structs, so changing all those structs to have variable size was not
without side effects. In the end it compiled but I got crashes all over,
and I'm sure I didn't do things right since I broke things like the static
assert in libcpp/identifiers.c, that I don't even understand:
/* We don't need a proxy since the hash table's identifier comes first
in cpp_hashnode. However, in case this is ever changed, we have a
static assertion for it. */
-extern char proxy_assertion_broken[offsetof (struct cpp_hashnode, ident) == 0
? 1 : -1];
Anyway last attempt was to decouple ht_identifier completely from trees
and other structs by storing pointer to it, but I was pretty worn out and
quickly gave up after getting errors on gengtype-generated files that I
didn't even know how to handle.
Was all this project too ambitious? I'd appreciate all input.
Thanks,
Dimitris
