Re: [PATCH 0/4] Compile kernel with -fwhole-program --combine

[Jan Engelhardt <jengelh@linux01.gwdg.de>]

>> >> Compiling files on their own (`make drivers/foo/bar.o`) seems to make 
>> >> the optimization void. Sure, most people don't stop compiling in 
>> >> between. Just a note
>> >
>> >Actually I'm not entirely sure what you write is true. It'll _build_
>> >fs/jffs2/read.o, for example, but it still won't then use it when I make
>> >the kernel -- it'll just use fs/jffs2/jffs2.o which is built from all
>> >the C files with --combine. So the optimisation isn't lost.
>> 
>> Umm then it spends double the time in compilation, doing:
>> 
>>   read.o <- read.c
>>   foo.o <- foo.c
>>   bar.o <- bar.c
>>   built-in.o <- read.c foo.c bar.c
>
>Only if you invoke make explicitly for read.o, foo.o and bar.o. If you
>just type 'make' then it won't build those.

That's what I meant. Assume I explicitly built read.o foo.o and bar.o.
If I then run the regular make, it will rerun gcc for read.c foo.c and 
bar.c rather than using the already-created .o files for linking.


Jan Engelhardt
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