Get Assembly code after every optimization GCC makes?

Question

From Optimization Compiler on Wikipedia,

Compiler optimization is generally implemented using a sequence of optimizing transformations

Answer 1

If you would like to study compiler optimization and are agnostic to the compiler, then take a look at the Clang/LLVM projects. Clang is a C compiler that can output LLVM IR and LLVM commands can apply specific optimization passes individually.

Output LLVM IR:

clang test.c -S -emit-llvm -o test.ll

Perform optimization pass:

opt test.ll - -S -o test_opt.ll

Compile to assembly:

llc test.ll -o test.s