[LLVMdev] recreate optimized clang output

[Hendrix_ at gmx.net]

On 27.01.2011, at 21:12, Devang Patel wrote:

> 
> On Jan 27, 2011, at 12:02 PM, Hendrix_ at gmx.net wrote:
> 
>> OK, I am looking for "LTO"/global optimization. So the function definition will remain "somewhere else" (externally), and the optimizer will find in some other module to possibly inline it later on.
>> 
>> I am planning to concat all the *.ll (eg "link" the files) and pass them to the "global" optimizer, as "size" is a very important optimization criterium to me. After that, the back-end will be invoked.
>> Is that a good approach?
> 
> How about just add -O4 on clang (or llvm-gcc) command line to get LTO optimizations ?
> See	http://llvm.org/docs/LinkTimeOptimization.html
> 	http://llvm.org/docs/GoldPlugin.html
> 	On Mac OS X, it is a checkbox in Xcode.
> -
> Devang

My backend doesnt supply lto :( I am trying to emulate lto like this:

clang *.c -S -emit-llvm
cat *.ll > very_big.ll
opt -O3 -extra-things...
llc very_big.ll.optimized

('Ease of use' is not so important :)

Best, Patrick