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Where can I find the sequence of optimizations used by clang according to -OX?

sepp2k
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dalibocai
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1 Answers1

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clang executes the precisely same sequence of passes as opt -ON. So, you can do something like 

llvm-as < /dev/null | opt -O3 -disable-output -debug-pass=Arguments

to derive the "full" set of passes which are run at O3.

Anton Korobeynikov
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    But I only see up to O3 in opt. Why clang has O4? – dalibocai Oct 18 '11 at 13:47
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    -O4 usually means link-time optimization, thus it cannot be performed via opt alone. The set of passes suitable for LTO can be found via opt -std-link-opts. – Anton Korobeynikov Oct 18 '11 at 17:07
  • Thanks! I parsed and posted the output for all optimization levels [here](http://stackoverflow.com/a/15548189/762488) for llvm 3.2 – Antoine Mar 21 '13 at 13:26