On 4/9/2013 1:47 PM, Edward Tomasz Napierała wrote:
In order to optimize - in this case for size - we need a way to measure
what should we focus on, and it looks like we don't have it yet.
Would it be possible to write a tool - e.g. by instrumenting LLVM - that
would make it possible to calculate, for every function in the call graph,
the amount of code in that function and everything it "pulls in", i.e. all
the code paths that it might call. When we have that, clustering the graph
should give us some idea what to focus on.
Or perhaps such a tool already exists?
Would clang's LTO help for size? I know work's starting on the bsd
elftools ld, but I doubt it has any LTO support yet. Running -Os on the
kernel as a whole instead of object files could probably help a lot
also. I might try to set it up and see a size comparision.
Also, what about the userland? Linux got popular for embedded partly
for busybox and uclibc. If Linux didn't exist, someone would have
ported minix instead.
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