mkbuiltin.go

Documentation: cmd/compile/internal/typecheck

     1  // Copyright 2016 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  //go:build ignore
     6  // +build ignore
     7  
     8  // Generate builtin.go from builtin/runtime.go.
     9  
    10  package main
    11  
    12  import (
    13  	"bytes"
    14  	"flag"
    15  	"fmt"
    16  	"go/ast"
    17  	"go/format"
    18  	"go/parser"
    19  	"go/token"
    20  	"io"
    21  	"io/ioutil"
    22  	"log"
    23  	"os"
    24  	"path/filepath"
    25  	"strconv"
    26  	"strings"
    27  )
    28  
    29  var stdout = flag.Bool("stdout", false, "write to stdout instead of builtin.go")
    30  
    31  func main() {
    32  	flag.Parse()
    33  
    34  	var b bytes.Buffer
    35  	fmt.Fprintln(&b, "// Code generated by mkbuiltin.go. DO NOT EDIT.")
    36  	fmt.Fprintln(&b)
    37  	fmt.Fprintln(&b, "package typecheck")
    38  	fmt.Fprintln(&b)
    39  	fmt.Fprintln(&b, `import (`)
    40  	fmt.Fprintln(&b, `      "cmd/compile/internal/types"`)
    41  	fmt.Fprintln(&b, `      "cmd/internal/src"`)
    42  	fmt.Fprintln(&b, `)`)
    43  
    44  	mkbuiltin(&b, "runtime")
    45  
    46  	out, err := format.Source(b.Bytes())
    47  	if err != nil {
    48  		log.Fatal(err)
    49  	}
    50  	if *stdout {
    51  		_, err = os.Stdout.Write(out)
    52  	} else {
    53  		err = ioutil.WriteFile("builtin.go", out, 0666)
    54  	}
    55  	if err != nil {
    56  		log.Fatal(err)
    57  	}
    58  }
    59  
    60  func mkbuiltin(w io.Writer, name string) {
    61  	fset := token.NewFileSet()
    62  	f, err := parser.ParseFile(fset, filepath.Join("builtin", name+".go"), nil, 0)
    63  	if err != nil {
    64  		log.Fatal(err)
    65  	}
    66  
    67  	var interner typeInterner
    68  
    69  	fmt.Fprintf(w, "var %sDecls = [...]struct { name string; tag int; typ int }{\n", name)
    70  	for _, decl := range f.Decls {
    71  		switch decl := decl.(type) {
    72  		case *ast.FuncDecl:
    73  			if decl.Recv != nil {
    74  				log.Fatal("methods unsupported")
    75  			}
    76  			if decl.Body != nil {
    77  				log.Fatal("unexpected function body")
    78  			}
    79  			fmt.Fprintf(w, "{%q, funcTag, %d},\n", decl.Name.Name, interner.intern(decl.Type))
    80  		case *ast.GenDecl:
    81  			if decl.Tok == token.IMPORT {
    82  				if len(decl.Specs) != 1 || decl.Specs[0].(*ast.ImportSpec).Path.Value != "\"unsafe\"" {
    83  					log.Fatal("runtime cannot import other package")
    84  				}
    85  				continue
    86  			}
    87  			if decl.Tok != token.VAR {
    88  				log.Fatal("unhandled declaration kind", decl.Tok)
    89  			}
    90  			for _, spec := range decl.Specs {
    91  				spec := spec.(*ast.ValueSpec)
    92  				if len(spec.Values) != 0 {
    93  					log.Fatal("unexpected values")
    94  				}
    95  				typ := interner.intern(spec.Type)
    96  				for _, name := range spec.Names {
    97  					fmt.Fprintf(w, "{%q, varTag, %d},\n", name.Name, typ)
    98  				}
    99  			}
   100  		default:
   101  			log.Fatal("unhandled decl type", decl)
   102  		}
   103  	}
   104  	fmt.Fprintln(w, "}")
   105  
   106  	fmt.Fprintln(w, `
   107  // Not inlining this function removes a significant chunk of init code.
   108  //go:noinline
   109  func newSig(params, results []*types.Field) *types.Type {
   110  	return types.NewSignature(types.NoPkg, nil, nil, params, results)
   111  }
   112  
   113  func params(tlist ...*types.Type) []*types.Field {
   114  	flist := make([]*types.Field, len(tlist))
   115  	for i, typ := range tlist {
   116  		flist[i] = types.NewField(src.NoXPos, nil, typ)
   117  	}
   118  	return flist
   119  }`)
   120  
   121  	fmt.Fprintln(w)
   122  	fmt.Fprintf(w, "func %sTypes() []*types.Type {\n", name)
   123  	fmt.Fprintf(w, "var typs [%d]*types.Type\n", len(interner.typs))
   124  	for i, typ := range interner.typs {
   125  		fmt.Fprintf(w, "typs[%d] = %s\n", i, typ)
   126  	}
   127  	fmt.Fprintln(w, "return typs[:]")
   128  	fmt.Fprintln(w, "}")
   129  }
   130  
   131  // typeInterner maps Go type expressions to compiler code that
   132  // constructs the denoted type. It recognizes and reuses common
   133  // subtype expressions.
   134  type typeInterner struct {
   135  	typs []string
   136  	hash map[string]int
   137  }
   138  
   139  func (i *typeInterner) intern(t ast.Expr) int {
   140  	x := i.mktype(t)
   141  	v, ok := i.hash[x]
   142  	if !ok {
   143  		v = len(i.typs)
   144  		if i.hash == nil {
   145  			i.hash = make(map[string]int)
   146  		}
   147  		i.hash[x] = v
   148  		i.typs = append(i.typs, x)
   149  	}
   150  	return v
   151  }
   152  
   153  func (i *typeInterner) subtype(t ast.Expr) string {
   154  	return fmt.Sprintf("typs[%d]", i.intern(t))
   155  }
   156  
   157  func (i *typeInterner) mktype(t ast.Expr) string {
   158  	switch t := t.(type) {
   159  	case *ast.Ident:
   160  		switch t.Name {
   161  		case "byte":
   162  			return "types.ByteType"
   163  		case "rune":
   164  			return "types.RuneType"
   165  		}
   166  		return fmt.Sprintf("types.Types[types.T%s]", strings.ToUpper(t.Name))
   167  	case *ast.SelectorExpr:
   168  		if t.X.(*ast.Ident).Name != "unsafe" || t.Sel.Name != "Pointer" {
   169  			log.Fatalf("unhandled type: %#v", t)
   170  		}
   171  		return "types.Types[types.TUNSAFEPTR]"
   172  
   173  	case *ast.ArrayType:
   174  		if t.Len == nil {
   175  			return fmt.Sprintf("types.NewSlice(%s)", i.subtype(t.Elt))
   176  		}
   177  		return fmt.Sprintf("types.NewArray(%s, %d)", i.subtype(t.Elt), intconst(t.Len))
   178  	case *ast.ChanType:
   179  		dir := "types.Cboth"
   180  		switch t.Dir {
   181  		case ast.SEND:
   182  			dir = "types.Csend"
   183  		case ast.RECV:
   184  			dir = "types.Crecv"
   185  		}
   186  		return fmt.Sprintf("types.NewChan(%s, %s)", i.subtype(t.Value), dir)
   187  	case *ast.FuncType:
   188  		return fmt.Sprintf("newSig(%s, %s)", i.fields(t.Params, false), i.fields(t.Results, false))
   189  	case *ast.InterfaceType:
   190  		if len(t.Methods.List) != 0 {
   191  			log.Fatal("non-empty interfaces unsupported")
   192  		}
   193  		return "types.Types[types.TINTER]"
   194  	case *ast.MapType:
   195  		return fmt.Sprintf("types.NewMap(%s, %s)", i.subtype(t.Key), i.subtype(t.Value))
   196  	case *ast.StarExpr:
   197  		return fmt.Sprintf("types.NewPtr(%s)", i.subtype(t.X))
   198  	case *ast.StructType:
   199  		return fmt.Sprintf("types.NewStruct(types.NoPkg, %s)", i.fields(t.Fields, true))
   200  
   201  	default:
   202  		log.Fatalf("unhandled type: %#v", t)
   203  		panic("unreachable")
   204  	}
   205  }
   206  
   207  func (i *typeInterner) fields(fl *ast.FieldList, keepNames bool) string {
   208  	if fl == nil || len(fl.List) == 0 {
   209  		return "nil"
   210  	}
   211  
   212  	var res []string
   213  	for _, f := range fl.List {
   214  		typ := i.subtype(f.Type)
   215  		if len(f.Names) == 0 {
   216  			res = append(res, typ)
   217  		} else {
   218  			for _, name := range f.Names {
   219  				if keepNames {
   220  					res = append(res, fmt.Sprintf("types.NewField(src.NoXPos, Lookup(%q), %s)", name.Name, typ))
   221  				} else {
   222  					res = append(res, typ)
   223  				}
   224  			}
   225  		}
   226  	}
   227  
   228  	if keepNames {
   229  		return fmt.Sprintf("[]*types.Field{%s}", strings.Join(res, ", "))
   230  	}
   231  	return fmt.Sprintf("params(%s)", strings.Join(res, ", "))
   232  }
   233  
   234  func intconst(e ast.Expr) int64 {
   235  	switch e := e.(type) {
   236  	case *ast.BasicLit:
   237  		if e.Kind != token.INT {
   238  			log.Fatalf("expected INT, got %v", e.Kind)
   239  		}
   240  		x, err := strconv.ParseInt(e.Value, 0, 64)
   241  		if err != nil {
   242  			log.Fatal(err)
   243  		}
   244  		return x
   245  	default:
   246  		log.Fatalf("unhandled expr: %#v", e)
   247  		panic("unreachable")
   248  	}
   249  }
   250
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