Jakub Jelinek wrote: > On Tue, Jun 30, 2009 at 03:50:11PM +0100, Andrew Haley wrote: >> Gerald Pfeifer wrote: >>> On Tue, 30 Jun 2009, Jakub Jelinek wrote: >>>> Alternatively we could split the huge HTML_401F.java function into >>>> say 4 smaller ones. >>> Pleeeeeease! :-) This one has been causing troubles beyond the context >>> of just vta (where, for example, on some system one needs to boot with >>> a special kernel option to provide sufficient amounts of memory to GCJ).
>> I can split the function, but papering over the problem by splitting >> one function won't make the problem go away for others who use gcc. >> It'll just mean that gcc developers don't notice it. > > Sure, that's why I've spent last 2 weeks on var-tracking.c improvements > for this exact testcase. The question just is, if we really need to include > so huge testcases as part of everybody's daily bootstrap/regtest cycle, or > if it is sufficient to keep such testcases on the side, for automated > testers that track their compile time/memory usage and nag us if we regress > too much on it. > >> The big function is about 250k lines of GIMPLE. jc1 uses about 474m of >> RAM at -O2 on a 64-bit system, 414m at -O1, 536m at -O0. On what class >> of machines are you trying to build this? > > From var-tracking POV, especially on VTA branch, the main problem is > that this function has 10000 basic blocks and on VTA needs to track over > 15000 of variables/VALUEs across all those bbs. Vanilla VTA branch needs > 2.9GB of memory and 25 minutes to compile this at -g -O2, with all the > patches I've sent it needs just 1.6GB of memory and 8 minutes. > >> Don't we have some sort of heuristic that says "this function is >> freaking huge, don't do any expensive optimizations." ? > > For var-tracking we just bail out on highly connected large cfgs: > if (n_basic_blocks > 500 && n_edges / n_basic_blocks >= 20) > return 0; > > I haven't studied how exactly is --enable-java-maintainer-mode > compiling the classes; if I just gcj -C HTML_401F.java on > Fedora 11 (GCC 4.4.0, ecj 3.4.2), the compile time with patched > VTA is only 4:53 with 1.5GB top memory usage, if I patch HTML_401F.java > with the following patch, it compiles within 0:55 and maxes at 250MB. > I have no idea whether it will work correctly (what to test it with) > and whether it is or is not an ABI change. It's not an ABI change. This patch is OK iff accompanied by a comment in the code that explains the problem. Thanks, Andrew.