Basile Starynkevitch
2018-07-04 21:08:02
I suggest also using -fverbose-asm because then the generated assembler has some generated comments which "explains" the code. For example:
gcc -S -fverbose-asm -O2 foo.c
would generate in foo.s (with some comments) the assembler code produced by compiling foo.c
And to understand what the GCC optimizations are doing one could even try -fdump-tree-all (but this produces hundreds of files!).
Related: How to remove "noise" from GCC/clang assembly output? for more ways to make asm more readable, and an excellent intro video to reading x86 asm, from Matt Godbolt (of online compiler-explorer fame).