On Tue, Feb 7, 2012 at 1:57 PM, Konstantin Vladimirov <konstantin.vladimi...@gmail.com> wrote: > Hi, > > That is good solution, thanks. > > But what if I want to compile e.o and d.o with cross-module inlining > (but also with fixed regs and so, without lto, as you are suggesting)? > On gcc-4.3.3, I had "combine" option for such cases. Is it completely > impossible in gcc 4.6.2?
You then can do gcc $OPTIONS -flto a.c -o a.o gcc $OPTIONS -flto b.c -o b.o gcc $OPTIONS -ffixed-r9 -ffixed-r10 -flto d.c -o d.o gcc $OPTIONS -ffixed-r9 -ffixed-r10 -flto e.c -o e.o gcc $OPTIONS -flto a.o b.o -o non-fixed-reg-part.o -r -nostdlib gcc $OPTIONS -flto -ffixed-r9 -ffixed-r10 d.o e.o -o fixed-reg-part.o -r -nostdlib gcc non-fixed-reg-part.o fixed-reg-part.o thus, optimize both pieces via partial LTO linking (-r, maybe the -nostdlib is not needed) and then do the final link separately. Richard. > --- > With best regards, Konstantin > > On Tue, Feb 7, 2012 at 4:37 PM, Richard Guenther > <richard.guent...@gmail.com> wrote: >> On Tue, Feb 7, 2012 at 1:26 PM, Konstantin Vladimirov >> <konstantin.vladimi...@gmail.com> wrote: >>> Hi, >>> >>> Consider some project, consisting of files: a.c, b.c, d.c and e.c >>> >>> Compiler is gcc 4.6.2 >>> >>> Files a.c and b.c are performance bottlenecks and requires heavy >>> cross-module inline, so must be compiled with -flto option >>> Files d.c and e.c is preffered to be compiled with lto option too, but >>> they are of special usage, and requires some registers (say r9 and >>> r10) to be fixed (with -ffixed-<reg> option) during compilation. >>> >>> All these files forms single binary. >>> >>> Now the problem is: if I compiling >>> >>> gcc $OPTIONS -flto a.c -o a.o >>> gcc $OPTIONS -flto b.c -o b.o >>> gcc $OPTIONS -ffixed-r9 -ffixed-r10 -flto d.c -o d.o >>> gcc $OPTIONS -ffixed-r9 -ffixed-r10 -flto e.c -o d.o >>> >>> and then >>> >>> gcc $OPTIONS -flto a.o b.o d.o e.o -o a.out >>> >>> Then registers inside d.o and e.o are being reallocated at link time, >>> and r9, r10 are used in the d.o and e.o parts in the resulted binary. >>> Also I can not specify fixed regs to final link, because this will fix >>> registers in a.o and b.o parts, that will affect performance. >>> >>> The best way for me seems to somehow separately link pseudo-object >>> files a.o and b.o with -flto to simple object (say x.o), and then link >>> e.o and d.o to single, say, y.o, and then call linker to finally link >>> binary without cross-module optimizations. But I can not find >>> possibility to do it, and I doubt if this at all conforms with lto >>> ideology. >> >> That's indeed the way to go, but you don't need anything fancy like >> partial linking. >> >> gcc $OPTIONS -flto a.c -o a.o >> gcc $OPTIONS -flto b.c -o b.o >> gcc $OPTIONS -ffixed-r9 -ffixed-r10 d.c -o d.o >> gcc $OPTIONS -ffixed-r9 -ffixed-r10 e.c -o e.o >> gcc $OPTIONS -flto a.o b.o d.o e.o >> >> should do it automatically. Just make sure to not compile d.o and e.o >> with -flto. >> >> Richard. >> >>> So, I want to perform link-time optimizations between a.o and b.o, and >>> don't want them between (a.o or b.o) and (d.o or e.o) >>> >>> How can I approach this? >>> >>> Thanks in advance for everyone, who will help. >>> >>> --- >>> With best regards, Konstantin
