How Inlining Works in the Go Compiler

Inlining in the Go compiler replaces a function call with the function's body to reduce overhead, occurring during the middle-end optimization phase in cmd/compile/internal/inline. The compiler decides whether to inline based on heuristics like function size and call frequency, which can be disabled globally with the -l flag or inspected with -m.

go tool compile -l main.go

This command compiles main.go with inlining disabled, ensuring function calls remain as distinct instructions rather than being expanded inline.

Inlining is when the compiler copies a function's code directly into the place where it is called, skipping the overhead of jumping to and from the function. This makes your program run faster but can make the compiled code larger. You would use this automatically when building for performance, or disable it with the -l flag if you need to debug specific function boundaries.