buildssa.go

Documentation: golang.org/x/tools/go/analysis/passes/buildssa

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package buildssa defines an Analyzer that constructs the SSA
     6  // representation of an error-free package and returns the set of all
     7  // functions within it. It does not report any diagnostics itself but
     8  // may be used as an input to other analyzers.
     9  package buildssa
    10  
    11  import (
    12  	"go/ast"
    13  	"go/types"
    14  	"reflect"
    15  
    16  	"golang.org/x/tools/go/analysis"
    17  	"golang.org/x/tools/go/ssa"
    18  )
    19  
    20  var Analyzer = &analysis.Analyzer{
    21  	Name:       "buildssa",
    22  	Doc:        "build SSA-form IR for later passes",
    23  	URL:        "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/buildssa",
    24  	Run:        run,
    25  	ResultType: reflect.TypeOf(new(SSA)),
    26  }
    27  
    28  // SSA provides SSA-form intermediate representation for all the
    29  // source functions in the current package.
    30  type SSA struct {
    31  	Pkg      *ssa.Package
    32  	SrcFuncs []*ssa.Function
    33  }
    34  
    35  func run(pass *analysis.Pass) (interface{}, error) {
    36  	// We must create a new Program for each Package because the
    37  	// analysis API provides no place to hang a Program shared by
    38  	// all Packages. Consequently, SSA Packages and Functions do not
    39  	// have a canonical representation across an analysis session of
    40  	// multiple packages. This is unlikely to be a problem in
    41  	// practice because the analysis API essentially forces all
    42  	// packages to be analysed independently, so any given call to
    43  	// Analysis.Run on a package will see only SSA objects belonging
    44  	// to a single Program.
    45  
    46  	// Some Analyzers may need GlobalDebug, in which case we'll have
    47  	// to set it globally, but let's wait till we need it.
    48  	mode := ssa.BuilderMode(0)
    49  
    50  	prog := ssa.NewProgram(pass.Fset, mode)
    51  
    52  	// Create SSA packages for direct imports.
    53  	for _, p := range pass.Pkg.Imports() {
    54  		prog.CreatePackage(p, nil, nil, true)
    55  	}
    56  
    57  	// Create and build the primary package.
    58  	ssapkg := prog.CreatePackage(pass.Pkg, pass.Files, pass.TypesInfo, false)
    59  	ssapkg.Build()
    60  
    61  	// Compute list of source functions, including literals,
    62  	// in source order.
    63  	var funcs []*ssa.Function
    64  	for _, f := range pass.Files {
    65  		for _, decl := range f.Decls {
    66  			if fdecl, ok := decl.(*ast.FuncDecl); ok {
    67  				// (init functions have distinct Func
    68  				// objects named "init" and distinct
    69  				// ssa.Functions named "init#1", ...)
    70  
    71  				fn := pass.TypesInfo.Defs[fdecl.Name].(*types.Func)
    72  				if fn == nil {
    73  					panic(fn)
    74  				}
    75  
    76  				f := ssapkg.Prog.FuncValue(fn)
    77  				if f == nil {
    78  					panic(fn)
    79  				}
    80  
    81  				var addAnons func(f *ssa.Function)
    82  				addAnons = func(f *ssa.Function) {
    83  					funcs = append(funcs, f)
    84  					for _, anon := range f.AnonFuncs {
    85  						addAnons(anon)
    86  					}
    87  				}
    88  				addAnons(f)
    89  			}
    90  		}
    91  	}
    92  
    93  	return &SSA{Pkg: ssapkg, SrcFuncs: funcs}, nil
    94  }
    95
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