tl;dr: A free online textbook by Prof. Douglas Thain (Notre Dame) covering a one-semester introduction to compiler construction, guiding readers through building a compiler that translates a C-like language into X86 or ARM assembly. Chapters cover scanning, parsing, AST construction, semantic analysis, IR, code generation, and optimization, with accompanying GitHub code examples. Targeted at undergraduates with C programming, data structures, and computer architecture backgrounds; hardcover and paperback versions are also available.