Function Prologue and Epilogue

Function Entry and Exit Sequences

Every compiled function needs a prologue to set up the stack frame and an epilogue to tear it down. x86-64 SysV ABI: push rbp; mov rbp, rsp; sub rsp, N in prologue; mov rsp, rbp; pop rbp; ret in epilogue. Clang and GCC emit these around every function body.

Stack Frame Setup

Save caller's frame pointer. Establish new frame pointer. Allocate space for locals and spilled registers. On return, reverse the sequence and restore callee-saved registers.

asmCopy
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• Callee-saved: rbx, rbp, r12-r15 on x86-64
• Caller-saved argument registers may be clobbered
• Local size must be 16-byte aligned on macOS/Linux
• Epilogue must run on every exit path, including early return

Connecting to real compilers

Production compilers embed this step inside a longer pipeline. GCC flows through cpp, cc1, assembly, and ld; Clang uses the driver, Sema, LLVM IR passes, and a target backend. LLVM bitcode, JVM bytecode, and WASM are other familiar IRs at the same layer. The exercise isolates one pass so you can test it alone before chaining it to the next stage.

Why for this exercise

You will generate function prologue and epilogue assembly. This exercise asks you to emit stack frame setup and teardown instructions that bracket the function body per the target ABI.