What is the gcc optimization flag for "ENABLE_OPTIMIZED=1" in LLVM?

Dear LLVM developers,
I am wondering the gcc optimization flag for “ENABLE_OPTIMIZED=1” in LLVM is -O2 or -O3.
And what is the flag if I set “ENABLE_OPTIMIZED=0”?
If I want to manually modify the flag for “ENABLE_OPTIMIZED=1” in LLVM, what file should I refer to?

Heming Cui <heming@cs.columbia.edu> writes:

    I am wondering the gcc optimization flag for "ENABLE_OPTIMIZED=1" in
LLVM is -O2 or -O3.
    And what is the flag if I set "ENABLE_OPTIMIZED=0"?

Try

make VERBOSE=1

That would show on the console the full command used for compiling each
file.

    If I want to manually modify the flag for "ENABLE_OPTIMIZED=1" in LLVM,
what file should I refer to?

Makefile.rules ?