On Mon, Aug 20, 2012 at 7:03 PM, Dimitrios Apostolou <ji...@gmx.net> wrote: > 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.
I think the proper thing would indeed have been to pass down the length of the string to relevant functions. Richard. > > Thanks, > Dimitris >
