GCC: cc1

cc1 is also referred to as the compiler proper.

cc1 preprocesses a C translation unit and compiles it into assembly code. The assembly code is converted into an object file with the assembler.

Earlier versions of cc1 used /usr/bin/cpp for the preprocessing stage.

The installation location of cc1 can be determined with

$ gcc -print-file-name=cc1
/usr/lib/gcc/x86_64-linux-gnu/10/cc1