Summary - Compiler

Combine SSA, escape and inline to write a compilation analysis.

Compiler summary

Source → type checking → IR (escape analysis + inlining) → SSA (constant folding, dead code, BCE) → machine code → linking. Your inspection tools: -gcflags=-m (escape and inlining), -gcflags=-S (assembly), GOSSAFUNC (SSA passes), -d=ssa/check_bce (bounds checks). With directives (//go:build, //go:embed, //go:noinline) you instruct the compiler.

Readability comes first

Compiler knowledge should be applied at the hot spots a profile shows. Adding BCE hints and noinline everywhere hurts readability and may become unnecessary in later Go versions, as the compiler gets smarter with each release. The rule: measure, find the hot spot, confirm the change with a benchmark.

Exercise A buffer that stays on the stack

Write an allocation-light function using a fixed-size array: inside hex(b byte) string fill var buf [2]byte and return string(buf[:]). Print hex(255) (output ff).

Show example solution

package main

import "fmt"

const rakam = "0123456789abcdef"

func hex(b byte) string {
    var buf [2]byte
    buf[0] = rakam[b>>4]
    buf[1] = rakam[b&0x0f]
    return string(buf[:])
}

func main() {
    fmt.Println(hex(255))
}

Test yourself

If a hot function allocates on the heap every call, which output do you check first?
- go mod tidy
- gofmt -d
- go build -gcflags=-m
- go vet
Show answer

go build -gcflags=-m — The -m output tells which variable escapes to the heap and why, with line numbers.

SSA visualization

____=topla go build .

Show answer

GOSSAFUNC=topla go build .

Group summary

Escape analysis

Stack or heap?
Inlining

Replace call with body
SSA

Optimization form
//go:build

Conditional compilation

Next lesson: The runtime package

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