111 lines
3.1 KiB
Go
111 lines
3.1 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ssa_test
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import (
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"fmt"
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"os"
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"golang.org/x/tools/go/loader"
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"golang.org/x/tools/go/ssa"
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)
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// This program demonstrates how to run the SSA builder on a "Hello,
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// World!" program and shows the printed representation of packages,
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// functions and instructions.
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//
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// Within the function listing, the name of each BasicBlock such as
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// ".0.entry" is printed left-aligned, followed by the block's
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// Instructions.
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//
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// For each instruction that defines an SSA virtual register
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// (i.e. implements Value), the type of that value is shown in the
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// right column.
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//
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// Build and run the ssadump.go program if you want a standalone tool
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// with similar functionality. It is located at
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// golang.org/x/tools/cmd/ssadump.
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//
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func Example() {
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const hello = `
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package main
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import "fmt"
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const message = "Hello, World!"
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func main() {
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fmt.Println(message)
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}
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`
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var conf loader.Config
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// Parse the input file.
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file, err := conf.ParseFile("hello.go", hello)
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if err != nil {
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fmt.Print(err) // parse error
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return
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}
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// Create single-file main package.
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conf.CreateFromFiles("main", file)
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// Load the main package and its dependencies.
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iprog, err := conf.Load()
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if err != nil {
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fmt.Print(err) // type error in some package
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return
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}
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// Create SSA-form program representation.
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prog := ssa.Create(iprog, ssa.SanityCheckFunctions)
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mainPkg := prog.Package(iprog.Created[0].Pkg)
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// Print out the package.
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mainPkg.WriteTo(os.Stdout)
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// Build SSA code for bodies of functions in mainPkg.
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mainPkg.Build()
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// Print out the package-level functions.
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mainPkg.Func("init").WriteTo(os.Stdout)
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mainPkg.Func("main").WriteTo(os.Stdout)
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// Output:
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//
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// package main:
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// func init func()
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// var init$guard bool
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// func main func()
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// const message message = "Hello, World!":untyped string
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//
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// # Name: main.init
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// # Package: main
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// # Synthetic: package initializer
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// func init():
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// 0: entry P:0 S:2
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// t0 = *init$guard bool
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// if t0 goto 2 else 1
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// 1: init.start P:1 S:1
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// *init$guard = true:bool
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// t1 = fmt.init() ()
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// jump 2
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// 2: init.done P:2 S:0
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// return
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//
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// # Name: main.main
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// # Package: main
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// # Location: hello.go:8:6
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// func main():
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// 0: entry P:0 S:0
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// t0 = new [1]interface{} (varargs) *[1]interface{}
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// t1 = &t0[0:int] *interface{}
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// t2 = make interface{} <- string ("Hello, World!":string) interface{}
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// *t1 = t2
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// t3 = slice t0[:] []interface{}
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// t4 = fmt.Println(t3...) (n int, err error)
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// return
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}
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