Where to find the optimization sequence for clang -OX?

Question

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

Answer 1

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.