Date: Mon, 27 Apr 2015 23:23:40 -0700 From: Andre McCurdy <armccurdy@...il.com> To: musl@...ts.openwall.com Subject: Re: building musl libc.so with gcc -flto On Mon, Apr 27, 2015 at 5:24 PM, Rich Felker <dalias@...c.org> wrote: > On Mon, Apr 27, 2015 at 05:16:12PM -0700, Andre McCurdy wrote: >> > OK, it looks like the _dlstart_c symbol got removed before linking the >> > asm. What about selectively compiling this file with -fno-lto via >> > something like this in config.mak: >> > >> > src/ldso/dlstart.lo: CFLAGS += -fno-lto >> >> That works. Should I send a patch? > > Yes, but configure would need to detect support for -fno-lto and add > it appropriately. See what's done for CFLAGS_NOSSP. I suspect the crt > files also need -fno-lto in principle even if they're not currently > breaking for lack of it. Patch sent. I think the crt files might be OK as they are, since the _start_c symbol isn't being hidden? >> >> > Also seems rather like what I would expect. Any idea if performance is >> >> > significantly better? It's not very comprehensive but you could try >> >> > libc-bench. >> >> >> >> I modified libc-bench so that it loops though everything in main() ten >> >> times and then ran the same libc-bench binary with each version of >> >> libc.so, sending output to /dev/null. >> >> >> >> The -O3 -flto build seems to be consistently very slightly *slower* >> >> than the non -flto version... >> > >> > That makes the whole thing somewhat less interesting. LTO is probably >> > more interesting for static libc. >> >> Yes, quite disappointing... >> >> I'll try to experiment a little with static linking. > > Great. Let us know how it goes. > > Rich
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