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c28bf6e069
CanonicalPos was inadequate since many pairs of instruction share the same pos (e.g. Allocs and Phis). Instead, we generalize the DebugRef instruction to associate not just Idents but Exprs with ssa.Values.
We no longer store any DebugRefs for constant expressions, to save space. (The type and value of such expressions can be obtained by other means, at a cost in complexity.)
Function.ValueForExpr queries the DebugRef info to return the ssa.Value of a given Expr.
Added tests.
Also:
- the DebugInfo flag is now per package, not global.
It must be set between Create and Build phases if desired.
- {Value,Instruction}.Pos() documentation updated: we still maintain
this information in the instruction stream even in non-debug mode,
but we make fewer claims about its invariants.
- Go and Defer instructions can now use their respective go/defer
token positions (not the call's lparen), so they do.
- SelectState:
Posn token.Pos indicates the <- position
DebugNode ast.Expr is the send stmt or receive expr.
- In building SelectStmt, we introduce extra temporaries in debug
mode to hold the result of the receive in 'case <-ch' even though
this value isn't ordinarily needed.
- Use *SelectState (indirectly) since the struct is getting bigger.
- Document some missing instructions in doc.go.
R=gri
CC=golang-dev
https://golang.org/cl/12147043
108 lines
3.1 KiB
Go
108 lines
3.1 KiB
Go
package ssa_test
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import (
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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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"fmt"
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"go/ast"
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"go/parser"
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"os"
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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{Loader: importer.MakeGoBuildLoader(nil)})
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// Parse the input file.
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file, err := parser.ParseFile(imp.Fset, "hello.go", hello, parser.DeclarationErrors)
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if err != nil {
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fmt.Print(err.Error()) // 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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info := imp.CreateSourcePackage("main", []*ast.File{file})
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if info.Err != nil {
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fmt.Print(info.Err.Error()) // type error
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return
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}
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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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for _, info := range imp.Packages {
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prog.CreatePackage(info)
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}
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mainPkg := prog.Package(info.Pkg)
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// Print out the package.
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mainPkg.DumpTo(os.Stdout)
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fmt.Println()
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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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// ret
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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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// a0 = new [1]interface{} *[1]interface{}
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// t0 = &a0[0:untyped integer] *interface{}
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// t1 = make interface{} <- string ("Hello, World!":string) interface{}
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// *t0 = t1
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// t2 = slice a0[:] []interface{}
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// t3 = fmt.Println(t2) (n int, err error)
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// ret
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}
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