mirror of
https://github.com/golang/go
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109 lines
3.2 KiB
Go
109 lines
3.2 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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"go/build"
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"go/parser"
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"os"
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"code.google.com/p/go.tools/importer"
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"code.google.com/p/go.tools/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 in this package if you want a
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// standalone tool with similar functionality.
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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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// Construct an importer. Imports will be loaded as if by 'go build'.
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imp := importer.New(&importer.Config{Build: &build.Default})
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// Parse the input file.
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file, err := parser.ParseFile(imp.Fset, "hello.go", hello, 0)
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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 a "main" package containing one file.
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mainInfo := imp.LoadMainPackage(file)
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// Create SSA-form program representation.
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var mode ssa.BuilderMode
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prog := ssa.NewProgram(imp.Fset, mode)
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if err := prog.CreatePackages(imp); 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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mainPkg := prog.Package(mainInfo.Pkg)
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// Print out the package.
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mainPkg.DumpTo(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").DumpTo(os.Stdout)
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mainPkg.Func("main").DumpTo(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$guard *bool
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// func main func()
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// const message message = "Hello, World!":untyped string
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//
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// # Name: main.init
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// # Synthetic: package initializer
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// func init():
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// .0.entry: P:0 S:2
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// t0 = *init$guard bool
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// if t0 goto 2.init.done else 1.init.start
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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.init.done
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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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// # 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:untyped integer] *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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