Why Do Some Compilers Generate Assembly Code Instead of Direct Machine Code?

Not all compilers generate assembly code; some might use a different kind of intermediate representation. One reason for generating assembly is to optimize the final compilation step based on the CPU's features, like utilizing specific instruction sets. Plus, it allows different languages to share a common backend compiler, which can streamline the process, especially with systems like .NET's IL or LLVM. Also, fun fact: Turbo Pascal went straight from source code to machine code without an Abstract Syntax Tree (AST), which was quite something for its time!

It's worth mentioning that generating assembly isn't just for the sake of it; the assembly must also create a binary file that fits the target system's requirements. This separation helps to keep the complexity manageable in compilers. If the binary format changes, only the assembly step needs to be updated, not the whole compilation process. Also, this approach follows a long-standing Unix philosophy where each tool does one job well.

Another reason to have that intermediate assembly stage is that it simplifies debugging and optimization. When you generate assembly, you can go in and tweak things manually where necessary. It's also easier to read assembly than raw machine code, which can help developers understand what's actually happening at a low level. Plus, some languages and compilers do things like output specific intermediate languages which get compiled later—think of compilers like LLVM that can optimize code for multiple architectures.

You're spot on about assembly being easier to work with. It creates a level of abstraction that helps developers during debugging. Sometimes, compilers serve assembly for performance optimization, allowing programmers to manually intervene on critical sections of code. And while some compilers do allow you to compile directly to machine code, generating assembly gives many advantages, such as targeting different CPU architectures more flexibly.