Source file src/cmd/compile/internal/ssa/_gen/rulegen.go

Documentation: cmd/compile/internal/ssa/_gen

     1  // Copyright 2015 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  // This program generates Go code that applies rewrite rules to a Value.
     6  // The generated code implements a function of type func (v *Value) bool
     7  // which reports whether if did something.
     8  // Ideas stolen from Swift: http://www.hpl.hp.com/techreports/Compaq-DEC/WRL-2000-2.html
     9  
    10  package main
    11  
    12  import (
    13  	"bufio"
    14  	"bytes"
    15  	"flag"
    16  	"fmt"
    17  	"go/ast"
    18  	"go/format"
    19  	"go/parser"
    20  	"go/printer"
    21  	"go/token"
    22  	"io"
    23  	"log"
    24  	"os"
    25  	"path"
    26  	"regexp"
    27  	"sort"
    28  	"strconv"
    29  	"strings"
    30  
    31  	"golang.org/x/tools/go/ast/astutil"
    32  )
    33  
    34  // rule syntax:
    35  //  sexpr [&& extra conditions] => [@block] sexpr
    36  //
    37  // sexpr are s-expressions (lisp-like parenthesized groupings)
    38  // sexpr ::= [variable:](opcode sexpr*)
    39  //         | variable
    40  //         | <type>
    41  //         | [auxint]
    42  //         | {aux}
    43  //
    44  // aux      ::= variable | {code}
    45  // type     ::= variable | {code}
    46  // variable ::= some token
    47  // opcode   ::= one of the opcodes from the *Ops.go files
    48  
    49  // special rules: trailing ellipsis "..." (in the outermost sexpr?) must match on both sides of a rule.
    50  //                trailing three underscore "___" in the outermost match sexpr indicate the presence of
    51  //                   extra ignored args that need not appear in the replacement
    52  
    53  // extra conditions is just a chunk of Go that evaluates to a boolean. It may use
    54  // variables declared in the matching tsexpr. The variable "v" is predefined to be
    55  // the value matched by the entire rule.
    56  
    57  // If multiple rules match, the first one in file order is selected.
    58  
    59  var (
    60  	genLog  = flag.Bool("log", false, "generate code that logs; for debugging only")
    61  	addLine = flag.Bool("line", false, "add line number comment to generated rules; for debugging only")
    62  )
    63  
    64  type Rule struct {
    65  	Rule string
    66  	Loc  string // file name & line number
    67  }
    68  
    69  func (r Rule) String() string {
    70  	return fmt.Sprintf("rule %q at %s", r.Rule, r.Loc)
    71  }
    72  
    73  func normalizeSpaces(s string) string {
    74  	return strings.Join(strings.Fields(strings.TrimSpace(s)), " ")
    75  }
    76  
    77  // parse returns the matching part of the rule, additional conditions, and the result.
    78  func (r Rule) parse() (match, cond, result string) {
    79  	s := strings.Split(r.Rule, "=>")
    80  	match = normalizeSpaces(s[0])
    81  	result = normalizeSpaces(s[1])
    82  	cond = ""
    83  	if i := strings.Index(match, "&&"); i >= 0 {
    84  		cond = normalizeSpaces(match[i+2:])
    85  		match = normalizeSpaces(match[:i])
    86  	}
    87  	return match, cond, result
    88  }
    89  
    90  func genRules(arch arch)          { genRulesSuffix(arch, "") }
    91  func genSplitLoadRules(arch arch) { genRulesSuffix(arch, "splitload") }
    92  func genLateLowerRules(arch arch) { genRulesSuffix(arch, "latelower") }
    93  
    94  func genRulesSuffix(arch arch, suff string) {
    95  	// Open input file.
    96  	text, err := os.Open(arch.name + suff + ".rules")
    97  	if err != nil {
    98  		if suff == "" {
    99  			// All architectures must have a plain rules file.
   100  			log.Fatalf("can't read rule file: %v", err)
   101  		}
   102  		// Some architectures have bonus rules files that others don't share. That's fine.
   103  		return
   104  	}
   105  
   106  	// oprules contains a list of rules for each block and opcode
   107  	blockrules := map[string][]Rule{}
   108  	oprules := map[string][]Rule{}
   109  
   110  	// read rule file
   111  	scanner := bufio.NewScanner(text)
   112  	rule := ""
   113  	var lineno int
   114  	var ruleLineno int // line number of "=>"
   115  	for scanner.Scan() {
   116  		lineno++
   117  		line := scanner.Text()
   118  		if i := strings.Index(line, "//"); i >= 0 {
   119  			// Remove comments. Note that this isn't string safe, so
   120  			// it will truncate lines with // inside strings. Oh well.
   121  			line = line[:i]
   122  		}
   123  		rule += " " + line
   124  		rule = strings.TrimSpace(rule)
   125  		if rule == "" {
   126  			continue
   127  		}
   128  		if !strings.Contains(rule, "=>") {
   129  			continue
   130  		}
   131  		if ruleLineno == 0 {
   132  			ruleLineno = lineno
   133  		}
   134  		if strings.HasSuffix(rule, "=>") {
   135  			continue // continue on the next line
   136  		}
   137  		if n := balance(rule); n > 0 {
   138  			continue // open parentheses remain, continue on the next line
   139  		} else if n < 0 {
   140  			break // continuing the line can't help, and it will only make errors worse
   141  		}
   142  
   143  		loc := fmt.Sprintf("%s%s.rules:%d", arch.name, suff, ruleLineno)
   144  		for _, rule2 := range expandOr(rule) {
   145  			r := Rule{Rule: rule2, Loc: loc}
   146  			if rawop := strings.Split(rule2, " ")[0][1:]; isBlock(rawop, arch) {
   147  				blockrules[rawop] = append(blockrules[rawop], r)
   148  				continue
   149  			}
   150  			// Do fancier value op matching.
   151  			match, _, _ := r.parse()
   152  			op, oparch, _, _, _, _ := parseValue(match, arch, loc)
   153  			opname := fmt.Sprintf("Op%s%s", oparch, op.name)
   154  			oprules[opname] = append(oprules[opname], r)
   155  		}
   156  		rule = ""
   157  		ruleLineno = 0
   158  	}
   159  	if err := scanner.Err(); err != nil {
   160  		log.Fatalf("scanner failed: %v\n", err)
   161  	}
   162  	if balance(rule) != 0 {
   163  		log.Fatalf("%s.rules:%d: unbalanced rule: %v\n", arch.name, lineno, rule)
   164  	}
   165  
   166  	// Order all the ops.
   167  	var ops []string
   168  	for op := range oprules {
   169  		ops = append(ops, op)
   170  	}
   171  	sort.Strings(ops)
   172  
   173  	genFile := &File{Arch: arch, Suffix: suff}
   174  	// Main rewrite routine is a switch on v.Op.
   175  	fn := &Func{Kind: "Value", ArgLen: -1}
   176  
   177  	sw := &Switch{Expr: exprf("v.Op")}
   178  	for _, op := range ops {
   179  		eop, ok := parseEllipsisRules(oprules[op], arch)
   180  		if ok {
   181  			if strings.Contains(oprules[op][0].Rule, "=>") && opByName(arch, op).aux != opByName(arch, eop).aux {
   182  				panic(fmt.Sprintf("can't use ... for ops that have different aux types: %s and %s", op, eop))
   183  			}
   184  			swc := &Case{Expr: exprf("%s", op)}
   185  			swc.add(stmtf("v.Op = %s", eop))
   186  			swc.add(stmtf("return true"))
   187  			sw.add(swc)
   188  			continue
   189  		}
   190  
   191  		swc := &Case{Expr: exprf("%s", op)}
   192  		swc.add(stmtf("return rewriteValue%s%s_%s(v)", arch.name, suff, op))
   193  		sw.add(swc)
   194  	}
   195  	if len(sw.List) > 0 { // skip if empty
   196  		fn.add(sw)
   197  	}
   198  	fn.add(stmtf("return false"))
   199  	genFile.add(fn)
   200  
   201  	// Generate a routine per op. Note that we don't make one giant routine
   202  	// because it is too big for some compilers.
   203  	for _, op := range ops {
   204  		rules := oprules[op]
   205  		_, ok := parseEllipsisRules(oprules[op], arch)
   206  		if ok {
   207  			continue
   208  		}
   209  
   210  		// rr is kept between iterations, so that each rule can check
   211  		// that the previous rule wasn't unconditional.
   212  		var rr *RuleRewrite
   213  		fn := &Func{
   214  			Kind:   "Value",
   215  			Suffix: fmt.Sprintf("_%s", op),
   216  			ArgLen: opByName(arch, op).argLength,
   217  		}
   218  		fn.add(declReserved("b", "v.Block"))
   219  		fn.add(declReserved("config", "b.Func.Config"))
   220  		fn.add(declReserved("fe", "b.Func.fe"))
   221  		fn.add(declReserved("typ", "&b.Func.Config.Types"))
   222  		for _, rule := range rules {
   223  			if rr != nil && !rr.CanFail {
   224  				log.Fatalf("unconditional rule %s is followed by other rules", rr.Match)
   225  			}
   226  			rr = &RuleRewrite{Loc: rule.Loc}
   227  			rr.Match, rr.Cond, rr.Result = rule.parse()
   228  			pos, _ := genMatch(rr, arch, rr.Match, fn.ArgLen >= 0)
   229  			if pos == "" {
   230  				pos = "v.Pos"
   231  			}
   232  			if rr.Cond != "" {
   233  				rr.add(breakf("!(%s)", rr.Cond))
   234  			}
   235  			genResult(rr, arch, rr.Result, pos)
   236  			if *genLog {
   237  				rr.add(stmtf("logRule(%q)", rule.Loc))
   238  			}
   239  			fn.add(rr)
   240  		}
   241  		if rr.CanFail {
   242  			fn.add(stmtf("return false"))
   243  		}
   244  		genFile.add(fn)
   245  	}
   246  
   247  	// Generate block rewrite function. There are only a few block types
   248  	// so we can make this one function with a switch.
   249  	fn = &Func{Kind: "Block"}
   250  	fn.add(declReserved("config", "b.Func.Config"))
   251  	fn.add(declReserved("typ", "&b.Func.Config.Types"))
   252  
   253  	sw = &Switch{Expr: exprf("b.Kind")}
   254  	ops = ops[:0]
   255  	for op := range blockrules {
   256  		ops = append(ops, op)
   257  	}
   258  	sort.Strings(ops)
   259  	for _, op := range ops {
   260  		name, data := getBlockInfo(op, arch)
   261  		swc := &Case{Expr: exprf("%s", name)}
   262  		for _, rule := range blockrules[op] {
   263  			swc.add(genBlockRewrite(rule, arch, data))
   264  		}
   265  		sw.add(swc)
   266  	}
   267  	if len(sw.List) > 0 { // skip if empty
   268  		fn.add(sw)
   269  	}
   270  	fn.add(stmtf("return false"))
   271  	genFile.add(fn)
   272  
   273  	// Remove unused imports and variables.
   274  	buf := new(bytes.Buffer)
   275  	fprint(buf, genFile)
   276  	fset := token.NewFileSet()
   277  	file, err := parser.ParseFile(fset, "", buf, parser.ParseComments)
   278  	if err != nil {
   279  		filename := fmt.Sprintf("%s_broken.go", arch.name)
   280  		if err := os.WriteFile(filename, buf.Bytes(), 0644); err != nil {
   281  			log.Printf("failed to dump broken code to %s: %v", filename, err)
   282  		} else {
   283  			log.Printf("dumped broken code to %s", filename)
   284  		}
   285  		log.Fatalf("failed to parse generated code for arch %s: %v", arch.name, err)
   286  	}
   287  	tfile := fset.File(file.Pos())
   288  
   289  	// First, use unusedInspector to find the unused declarations by their
   290  	// start position.
   291  	u := unusedInspector{unused: make(map[token.Pos]bool)}
   292  	u.node(file)
   293  
   294  	// Then, delete said nodes via astutil.Apply.
   295  	pre := func(c *astutil.Cursor) bool {
   296  		node := c.Node()
   297  		if node == nil {
   298  			return true
   299  		}
   300  		if u.unused[node.Pos()] {
   301  			c.Delete()
   302  			// Unused imports and declarations use exactly
   303  			// one line. Prevent leaving an empty line.
   304  			tfile.MergeLine(tfile.Position(node.Pos()).Line)
   305  			return false
   306  		}
   307  		return true
   308  	}
   309  	post := func(c *astutil.Cursor) bool {
   310  		switch node := c.Node().(type) {
   311  		case *ast.GenDecl:
   312  			if len(node.Specs) == 0 {
   313  				// Don't leave a broken or empty GenDecl behind,
   314  				// such as "import ()".
   315  				c.Delete()
   316  			}
   317  		}
   318  		return true
   319  	}
   320  	file = astutil.Apply(file, pre, post).(*ast.File)
   321  
   322  	// Write the well-formatted source to file
   323  	f, err := os.Create("../rewrite" + arch.name + suff + ".go")
   324  	if err != nil {
   325  		log.Fatalf("can't write output: %v", err)
   326  	}
   327  	defer f.Close()
   328  	// gofmt result; use a buffered writer, as otherwise go/format spends
   329  	// far too much time in syscalls.
   330  	bw := bufio.NewWriter(f)
   331  	if err := format.Node(bw, fset, file); err != nil {
   332  		log.Fatalf("can't format output: %v", err)
   333  	}
   334  	if err := bw.Flush(); err != nil {
   335  		log.Fatalf("can't write output: %v", err)
   336  	}
   337  	if err := f.Close(); err != nil {
   338  		log.Fatalf("can't write output: %v", err)
   339  	}
   340  }
   341  
   342  // unusedInspector can be used to detect unused variables and imports in an
   343  // ast.Node via its node method. The result is available in the "unused" map.
   344  //
   345  // note that unusedInspector is lazy and best-effort; it only supports the node
   346  // types and patterns used by the rulegen program.
   347  type unusedInspector struct {
   348  	// scope is the current scope, which can never be nil when a declaration
   349  	// is encountered. That is, the unusedInspector.node entrypoint should
   350  	// generally be an entire file or block.
   351  	scope *scope
   352  
   353  	// unused is the resulting set of unused declared names, indexed by the
   354  	// starting position of the node that declared the name.
   355  	unused map[token.Pos]bool
   356  
   357  	// defining is the object currently being defined; this is useful so
   358  	// that if "foo := bar" is unused and removed, we can then detect if
   359  	// "bar" becomes unused as well.
   360  	defining *object
   361  }
   362  
   363  // scoped opens a new scope when called, and returns a function which closes
   364  // that same scope. When a scope is closed, unused variables are recorded.
   365  func (u *unusedInspector) scoped() func() {
   366  	outer := u.scope
   367  	u.scope = &scope{outer: outer, objects: map[string]*object{}}
   368  	return func() {
   369  		for anyUnused := true; anyUnused; {
   370  			anyUnused = false
   371  			for _, obj := range u.scope.objects {
   372  				if obj.numUses > 0 {
   373  					continue
   374  				}
   375  				u.unused[obj.pos] = true
   376  				for _, used := range obj.used {
   377  					if used.numUses--; used.numUses == 0 {
   378  						anyUnused = true
   379  					}
   380  				}
   381  				// We've decremented numUses for each of the
   382  				// objects in used. Zero this slice too, to keep
   383  				// everything consistent.
   384  				obj.used = nil
   385  			}
   386  		}
   387  		u.scope = outer
   388  	}
   389  }
   390  
   391  func (u *unusedInspector) exprs(list []ast.Expr) {
   392  	for _, x := range list {
   393  		u.node(x)
   394  	}
   395  }
   396  
   397  func (u *unusedInspector) node(node ast.Node) {
   398  	switch node := node.(type) {
   399  	case *ast.File:
   400  		defer u.scoped()()
   401  		for _, decl := range node.Decls {
   402  			u.node(decl)
   403  		}
   404  	case *ast.GenDecl:
   405  		for _, spec := range node.Specs {
   406  			u.node(spec)
   407  		}
   408  	case *ast.ImportSpec:
   409  		impPath, _ := strconv.Unquote(node.Path.Value)
   410  		name := path.Base(impPath)
   411  		u.scope.objects[name] = &object{
   412  			name: name,
   413  			pos:  node.Pos(),
   414  		}
   415  	case *ast.FuncDecl:
   416  		u.node(node.Type)
   417  		if node.Body != nil {
   418  			u.node(node.Body)
   419  		}
   420  	case *ast.FuncType:
   421  		if node.Params != nil {
   422  			u.node(node.Params)
   423  		}
   424  		if node.Results != nil {
   425  			u.node(node.Results)
   426  		}
   427  	case *ast.FieldList:
   428  		for _, field := range node.List {
   429  			u.node(field)
   430  		}
   431  	case *ast.Field:
   432  		u.node(node.Type)
   433  
   434  	// statements
   435  
   436  	case *ast.BlockStmt:
   437  		defer u.scoped()()
   438  		for _, stmt := range node.List {
   439  			u.node(stmt)
   440  		}
   441  	case *ast.DeclStmt:
   442  		u.node(node.Decl)
   443  	case *ast.IfStmt:
   444  		if node.Init != nil {
   445  			u.node(node.Init)
   446  		}
   447  		u.node(node.Cond)
   448  		u.node(node.Body)
   449  		if node.Else != nil {
   450  			u.node(node.Else)
   451  		}
   452  	case *ast.ForStmt:
   453  		if node.Init != nil {
   454  			u.node(node.Init)
   455  		}
   456  		if node.Cond != nil {
   457  			u.node(node.Cond)
   458  		}
   459  		if node.Post != nil {
   460  			u.node(node.Post)
   461  		}
   462  		u.node(node.Body)
   463  	case *ast.SwitchStmt:
   464  		if node.Init != nil {
   465  			u.node(node.Init)
   466  		}
   467  		if node.Tag != nil {
   468  			u.node(node.Tag)
   469  		}
   470  		u.node(node.Body)
   471  	case *ast.CaseClause:
   472  		u.exprs(node.List)
   473  		defer u.scoped()()
   474  		for _, stmt := range node.Body {
   475  			u.node(stmt)
   476  		}
   477  	case *ast.BranchStmt:
   478  	case *ast.ExprStmt:
   479  		u.node(node.X)
   480  	case *ast.AssignStmt:
   481  		if node.Tok != token.DEFINE {
   482  			u.exprs(node.Rhs)
   483  			u.exprs(node.Lhs)
   484  			break
   485  		}
   486  		lhs := node.Lhs
   487  		if len(lhs) == 2 && lhs[1].(*ast.Ident).Name == "_" {
   488  			lhs = lhs[:1]
   489  		}
   490  		if len(lhs) != 1 {
   491  			panic("no support for := with multiple names")
   492  		}
   493  
   494  		name := lhs[0].(*ast.Ident)
   495  		obj := &object{
   496  			name: name.Name,
   497  			pos:  name.NamePos,
   498  		}
   499  
   500  		old := u.defining
   501  		u.defining = obj
   502  		u.exprs(node.Rhs)
   503  		u.defining = old
   504  
   505  		u.scope.objects[name.Name] = obj
   506  	case *ast.ReturnStmt:
   507  		u.exprs(node.Results)
   508  	case *ast.IncDecStmt:
   509  		u.node(node.X)
   510  
   511  	// expressions
   512  
   513  	case *ast.CallExpr:
   514  		u.node(node.Fun)
   515  		u.exprs(node.Args)
   516  	case *ast.SelectorExpr:
   517  		u.node(node.X)
   518  	case *ast.UnaryExpr:
   519  		u.node(node.X)
   520  	case *ast.BinaryExpr:
   521  		u.node(node.X)
   522  		u.node(node.Y)
   523  	case *ast.StarExpr:
   524  		u.node(node.X)
   525  	case *ast.ParenExpr:
   526  		u.node(node.X)
   527  	case *ast.IndexExpr:
   528  		u.node(node.X)
   529  		u.node(node.Index)
   530  	case *ast.TypeAssertExpr:
   531  		u.node(node.X)
   532  		u.node(node.Type)
   533  	case *ast.Ident:
   534  		if obj := u.scope.Lookup(node.Name); obj != nil {
   535  			obj.numUses++
   536  			if u.defining != nil {
   537  				u.defining.used = append(u.defining.used, obj)
   538  			}
   539  		}
   540  	case *ast.BasicLit:
   541  	case *ast.ValueSpec:
   542  		u.exprs(node.Values)
   543  	default:
   544  		panic(fmt.Sprintf("unhandled node: %T", node))
   545  	}
   546  }
   547  
   548  // scope keeps track of a certain scope and its declared names, as well as the
   549  // outer (parent) scope.
   550  type scope struct {
   551  	outer   *scope             // can be nil, if this is the top-level scope
   552  	objects map[string]*object // indexed by each declared name
   553  }
   554  
   555  func (s *scope) Lookup(name string) *object {
   556  	if obj := s.objects[name]; obj != nil {
   557  		return obj
   558  	}
   559  	if s.outer == nil {
   560  		return nil
   561  	}
   562  	return s.outer.Lookup(name)
   563  }
   564  
   565  // object keeps track of a declared name, such as a variable or import.
   566  type object struct {
   567  	name string
   568  	pos  token.Pos // start position of the node declaring the object
   569  
   570  	numUses int       // number of times this object is used
   571  	used    []*object // objects that its declaration makes use of
   572  }
   573  
   574  func fprint(w io.Writer, n Node) {
   575  	switch n := n.(type) {
   576  	case *File:
   577  		file := n
   578  		seenRewrite := make(map[[3]string]string)
   579  		fmt.Fprintf(w, "// Code generated from _gen/%s%s.rules using 'go generate'; DO NOT EDIT.\n", n.Arch.name, n.Suffix)
   580  		fmt.Fprintf(w, "\npackage ssa\n")
   581  		for _, path := range append([]string{
   582  			"fmt",
   583  			"internal/buildcfg",
   584  			"math",
   585  			"cmd/internal/obj",
   586  			"cmd/compile/internal/base",
   587  			"cmd/compile/internal/types",
   588  			"cmd/compile/internal/ir",
   589  		}, n.Arch.imports...) {
   590  			fmt.Fprintf(w, "import %q\n", path)
   591  		}
   592  		for _, f := range n.List {
   593  			f := f.(*Func)
   594  			fmt.Fprintf(w, "func rewrite%s%s%s%s(", f.Kind, n.Arch.name, n.Suffix, f.Suffix)
   595  			fmt.Fprintf(w, "%c *%s) bool {\n", strings.ToLower(f.Kind)[0], f.Kind)
   596  			if f.Kind == "Value" && f.ArgLen > 0 {
   597  				for i := f.ArgLen - 1; i >= 0; i-- {
   598  					fmt.Fprintf(w, "v_%d := v.Args[%d]\n", i, i)
   599  				}
   600  			}
   601  			for _, n := range f.List {
   602  				fprint(w, n)
   603  
   604  				if rr, ok := n.(*RuleRewrite); ok {
   605  					k := [3]string{
   606  						normalizeMatch(rr.Match, file.Arch),
   607  						normalizeWhitespace(rr.Cond),
   608  						normalizeWhitespace(rr.Result),
   609  					}
   610  					if prev, ok := seenRewrite[k]; ok {
   611  						log.Fatalf("duplicate rule %s, previously seen at %s\n", rr.Loc, prev)
   612  					}
   613  					seenRewrite[k] = rr.Loc
   614  				}
   615  			}
   616  			fmt.Fprintf(w, "}\n")
   617  		}
   618  	case *Switch:
   619  		fmt.Fprintf(w, "switch ")
   620  		fprint(w, n.Expr)
   621  		fmt.Fprintf(w, " {\n")
   622  		for _, n := range n.List {
   623  			fprint(w, n)
   624  		}
   625  		fmt.Fprintf(w, "}\n")
   626  	case *Case:
   627  		fmt.Fprintf(w, "case ")
   628  		fprint(w, n.Expr)
   629  		fmt.Fprintf(w, ":\n")
   630  		for _, n := range n.List {
   631  			fprint(w, n)
   632  		}
   633  	case *RuleRewrite:
   634  		if *addLine {
   635  			fmt.Fprintf(w, "// %s\n", n.Loc)
   636  		}
   637  		fmt.Fprintf(w, "// match: %s\n", n.Match)
   638  		if n.Cond != "" {
   639  			fmt.Fprintf(w, "// cond: %s\n", n.Cond)
   640  		}
   641  		fmt.Fprintf(w, "// result: %s\n", n.Result)
   642  		fmt.Fprintf(w, "for %s {\n", n.Check)
   643  		nCommutative := 0
   644  		for _, n := range n.List {
   645  			if b, ok := n.(*CondBreak); ok {
   646  				b.InsideCommuteLoop = nCommutative > 0
   647  			}
   648  			fprint(w, n)
   649  			if loop, ok := n.(StartCommuteLoop); ok {
   650  				if nCommutative != loop.Depth {
   651  					panic("mismatch commute loop depth")
   652  				}
   653  				nCommutative++
   654  			}
   655  		}
   656  		fmt.Fprintf(w, "return true\n")
   657  		for i := 0; i < nCommutative; i++ {
   658  			fmt.Fprintln(w, "}")
   659  		}
   660  		if n.CommuteDepth > 0 && n.CanFail {
   661  			fmt.Fprint(w, "break\n")
   662  		}
   663  		fmt.Fprintf(w, "}\n")
   664  	case *Declare:
   665  		fmt.Fprintf(w, "%s := ", n.Name)
   666  		fprint(w, n.Value)
   667  		fmt.Fprintln(w)
   668  	case *CondBreak:
   669  		fmt.Fprintf(w, "if ")
   670  		fprint(w, n.Cond)
   671  		fmt.Fprintf(w, " {\n")
   672  		if n.InsideCommuteLoop {
   673  			fmt.Fprintf(w, "continue")
   674  		} else {
   675  			fmt.Fprintf(w, "break")
   676  		}
   677  		fmt.Fprintf(w, "\n}\n")
   678  	case ast.Node:
   679  		printConfig.Fprint(w, emptyFset, n)
   680  		if _, ok := n.(ast.Stmt); ok {
   681  			fmt.Fprintln(w)
   682  		}
   683  	case StartCommuteLoop:
   684  		fmt.Fprintf(w, "for _i%[1]d := 0; _i%[1]d <= 1; _i%[1]d, %[2]s_0, %[2]s_1 = _i%[1]d + 1, %[2]s_1, %[2]s_0 {\n", n.Depth, n.V)
   685  	default:
   686  		log.Fatalf("cannot print %T", n)
   687  	}
   688  }
   689  
   690  var printConfig = printer.Config{
   691  	Mode: printer.RawFormat, // we use go/format later, so skip work here
   692  }
   693  
   694  var emptyFset = token.NewFileSet()
   695  
   696  // Node can be a Statement or an ast.Expr.
   697  type Node interface{}
   698  
   699  // Statement can be one of our high-level statement struct types, or an
   700  // ast.Stmt under some limited circumstances.
   701  type Statement interface{}
   702  
   703  // BodyBase is shared by all of our statement pseudo-node types which can
   704  // contain other statements.
   705  type BodyBase struct {
   706  	List    []Statement
   707  	CanFail bool
   708  }
   709  
   710  func (w *BodyBase) add(node Statement) {
   711  	var last Statement
   712  	if len(w.List) > 0 {
   713  		last = w.List[len(w.List)-1]
   714  	}
   715  	if node, ok := node.(*CondBreak); ok {
   716  		w.CanFail = true
   717  		if last, ok := last.(*CondBreak); ok {
   718  			// Add to the previous "if <cond> { break }" via a
   719  			// logical OR, which will save verbosity.
   720  			last.Cond = &ast.BinaryExpr{
   721  				Op: token.LOR,
   722  				X:  last.Cond,
   723  				Y:  node.Cond,
   724  			}
   725  			return
   726  		}
   727  	}
   728  
   729  	w.List = append(w.List, node)
   730  }
   731  
   732  // predeclared contains globally known tokens that should not be redefined.
   733  var predeclared = map[string]bool{
   734  	"nil":   true,
   735  	"false": true,
   736  	"true":  true,
   737  }
   738  
   739  // declared reports if the body contains a Declare with the given name.
   740  func (w *BodyBase) declared(name string) bool {
   741  	if predeclared[name] {
   742  		// Treat predeclared names as having already been declared.
   743  		// This lets us use nil to match an aux field or
   744  		// true and false to match an auxint field.
   745  		return true
   746  	}
   747  	for _, s := range w.List {
   748  		if decl, ok := s.(*Declare); ok && decl.Name == name {
   749  			return true
   750  		}
   751  	}
   752  	return false
   753  }
   754  
   755  // These types define some high-level statement struct types, which can be used
   756  // as a Statement. This allows us to keep some node structs simpler, and have
   757  // higher-level nodes such as an entire rule rewrite.
   758  //
   759  // Note that ast.Expr is always used as-is; we don't declare our own expression
   760  // nodes.
   761  type (
   762  	File struct {
   763  		BodyBase // []*Func
   764  		Arch     arch
   765  		Suffix   string
   766  	}
   767  	Func struct {
   768  		BodyBase
   769  		Kind   string // "Value" or "Block"
   770  		Suffix string
   771  		ArgLen int32 // if kind == "Value", number of args for this op
   772  	}
   773  	Switch struct {
   774  		BodyBase // []*Case
   775  		Expr     ast.Expr
   776  	}
   777  	Case struct {
   778  		BodyBase
   779  		Expr ast.Expr
   780  	}
   781  	RuleRewrite struct {
   782  		BodyBase
   783  		Match, Cond, Result string // top comments
   784  		Check               string // top-level boolean expression
   785  
   786  		Alloc        int    // for unique var names
   787  		Loc          string // file name & line number of the original rule
   788  		CommuteDepth int    // used to track depth of commute loops
   789  	}
   790  	Declare struct {
   791  		Name  string
   792  		Value ast.Expr
   793  	}
   794  	CondBreak struct {
   795  		Cond              ast.Expr
   796  		InsideCommuteLoop bool
   797  	}
   798  	StartCommuteLoop struct {
   799  		Depth int
   800  		V     string
   801  	}
   802  )
   803  
   804  // exprf parses a Go expression generated from fmt.Sprintf, panicking if an
   805  // error occurs.
   806  func exprf(format string, a ...interface{}) ast.Expr {
   807  	src := fmt.Sprintf(format, a...)
   808  	expr, err := parser.ParseExpr(src)
   809  	if err != nil {
   810  		log.Fatalf("expr parse error on %q: %v", src, err)
   811  	}
   812  	return expr
   813  }
   814  
   815  // stmtf parses a Go statement generated from fmt.Sprintf. This function is only
   816  // meant for simple statements that don't have a custom Statement node declared
   817  // in this package, such as ast.ReturnStmt or ast.ExprStmt.
   818  func stmtf(format string, a ...interface{}) Statement {
   819  	src := fmt.Sprintf(format, a...)
   820  	fsrc := "package p\nfunc _() {\n" + src + "\n}\n"
   821  	file, err := parser.ParseFile(token.NewFileSet(), "", fsrc, 0)
   822  	if err != nil {
   823  		log.Fatalf("stmt parse error on %q: %v", src, err)
   824  	}
   825  	return file.Decls[0].(*ast.FuncDecl).Body.List[0]
   826  }
   827  
   828  var reservedNames = map[string]bool{
   829  	"v":      true, // Values[i], etc
   830  	"b":      true, // v.Block
   831  	"config": true, // b.Func.Config
   832  	"fe":     true, // b.Func.fe
   833  	"typ":    true, // &b.Func.Config.Types
   834  }
   835  
   836  // declf constructs a simple "name := value" declaration,
   837  // using exprf for its value.
   838  //
   839  // name must not be one of reservedNames.
   840  // This helps prevent unintended shadowing and name clashes.
   841  // To declare a reserved name, use declReserved.
   842  func declf(loc, name, format string, a ...interface{}) *Declare {
   843  	if reservedNames[name] {
   844  		log.Fatalf("rule %s uses the reserved name %s", loc, name)
   845  	}
   846  	return &Declare{name, exprf(format, a...)}
   847  }
   848  
   849  // declReserved is like declf, but the name must be one of reservedNames.
   850  // Calls to declReserved should generally be static and top-level.
   851  func declReserved(name, value string) *Declare {
   852  	if !reservedNames[name] {
   853  		panic(fmt.Sprintf("declReserved call does not use a reserved name: %q", name))
   854  	}
   855  	return &Declare{name, exprf(value)}
   856  }
   857  
   858  // breakf constructs a simple "if cond { break }" statement, using exprf for its
   859  // condition.
   860  func breakf(format string, a ...interface{}) *CondBreak {
   861  	return &CondBreak{Cond: exprf(format, a...)}
   862  }
   863  
   864  func genBlockRewrite(rule Rule, arch arch, data blockData) *RuleRewrite {
   865  	rr := &RuleRewrite{Loc: rule.Loc}
   866  	rr.Match, rr.Cond, rr.Result = rule.parse()
   867  	_, _, auxint, aux, s := extract(rr.Match) // remove parens, then split
   868  
   869  	// check match of control values
   870  	if len(s) < data.controls {
   871  		log.Fatalf("incorrect number of arguments in %s, got %v wanted at least %v", rule, len(s), data.controls)
   872  	}
   873  	controls := s[:data.controls]
   874  	pos := make([]string, data.controls)
   875  	for i, arg := range controls {
   876  		cname := fmt.Sprintf("b.Controls[%v]", i)
   877  		if strings.Contains(arg, "(") {
   878  			vname, expr := splitNameExpr(arg)
   879  			if vname == "" {
   880  				vname = fmt.Sprintf("v_%v", i)
   881  			}
   882  			rr.add(declf(rr.Loc, vname, cname))
   883  			p, op := genMatch0(rr, arch, expr, vname, nil, false) // TODO: pass non-nil cnt?
   884  			if op != "" {
   885  				check := fmt.Sprintf("%s.Op == %s", cname, op)
   886  				if rr.Check == "" {
   887  					rr.Check = check
   888  				} else {
   889  					rr.Check += " && " + check
   890  				}
   891  			}
   892  			if p == "" {
   893  				p = vname + ".Pos"
   894  			}
   895  			pos[i] = p
   896  		} else {
   897  			rr.add(declf(rr.Loc, arg, cname))
   898  			pos[i] = arg + ".Pos"
   899  		}
   900  	}
   901  	for _, e := range []struct {
   902  		name, field, dclType string
   903  	}{
   904  		{auxint, "AuxInt", data.auxIntType()},
   905  		{aux, "Aux", data.auxType()},
   906  	} {
   907  		if e.name == "" {
   908  			continue
   909  		}
   910  
   911  		if e.dclType == "" {
   912  			log.Fatalf("op %s has no declared type for %s", data.name, e.field)
   913  		}
   914  		if !token.IsIdentifier(e.name) || rr.declared(e.name) {
   915  			rr.add(breakf("%sTo%s(b.%s) != %s", unTitle(e.field), title(e.dclType), e.field, e.name))
   916  		} else {
   917  			rr.add(declf(rr.Loc, e.name, "%sTo%s(b.%s)", unTitle(e.field), title(e.dclType), e.field))
   918  		}
   919  	}
   920  	if rr.Cond != "" {
   921  		rr.add(breakf("!(%s)", rr.Cond))
   922  	}
   923  
   924  	// Rule matches. Generate result.
   925  	outop, _, auxint, aux, t := extract(rr.Result) // remove parens, then split
   926  	blockName, outdata := getBlockInfo(outop, arch)
   927  	if len(t) < outdata.controls {
   928  		log.Fatalf("incorrect number of output arguments in %s, got %v wanted at least %v", rule, len(s), outdata.controls)
   929  	}
   930  
   931  	// Check if newsuccs is the same set as succs.
   932  	succs := s[data.controls:]
   933  	newsuccs := t[outdata.controls:]
   934  	m := map[string]bool{}
   935  	for _, succ := range succs {
   936  		if m[succ] {
   937  			log.Fatalf("can't have a repeat successor name %s in %s", succ, rule)
   938  		}
   939  		m[succ] = true
   940  	}
   941  	for _, succ := range newsuccs {
   942  		if !m[succ] {
   943  			log.Fatalf("unknown successor %s in %s", succ, rule)
   944  		}
   945  		delete(m, succ)
   946  	}
   947  	if len(m) != 0 {
   948  		log.Fatalf("unmatched successors %v in %s", m, rule)
   949  	}
   950  
   951  	var genControls [2]string
   952  	for i, control := range t[:outdata.controls] {
   953  		// Select a source position for any new control values.
   954  		// TODO: does it always make sense to use the source position
   955  		// of the original control values or should we be using the
   956  		// block's source position in some cases?
   957  		newpos := "b.Pos" // default to block's source position
   958  		if i < len(pos) && pos[i] != "" {
   959  			// Use the previous control value's source position.
   960  			newpos = pos[i]
   961  		}
   962  
   963  		// Generate a new control value (or copy an existing value).
   964  		genControls[i] = genResult0(rr, arch, control, false, false, newpos, nil)
   965  	}
   966  	switch outdata.controls {
   967  	case 0:
   968  		rr.add(stmtf("b.Reset(%s)", blockName))
   969  	case 1:
   970  		rr.add(stmtf("b.resetWithControl(%s, %s)", blockName, genControls[0]))
   971  	case 2:
   972  		rr.add(stmtf("b.resetWithControl2(%s, %s, %s)", blockName, genControls[0], genControls[1]))
   973  	default:
   974  		log.Fatalf("too many controls: %d", outdata.controls)
   975  	}
   976  
   977  	if auxint != "" {
   978  		// Make sure auxint value has the right type.
   979  		rr.add(stmtf("b.AuxInt = %sToAuxInt(%s)", unTitle(outdata.auxIntType()), auxint))
   980  	}
   981  	if aux != "" {
   982  		// Make sure aux value has the right type.
   983  		rr.add(stmtf("b.Aux = %sToAux(%s)", unTitle(outdata.auxType()), aux))
   984  	}
   985  
   986  	succChanged := false
   987  	for i := 0; i < len(succs); i++ {
   988  		if succs[i] != newsuccs[i] {
   989  			succChanged = true
   990  		}
   991  	}
   992  	if succChanged {
   993  		if len(succs) != 2 {
   994  			log.Fatalf("changed successors, len!=2 in %s", rule)
   995  		}
   996  		if succs[0] != newsuccs[1] || succs[1] != newsuccs[0] {
   997  			log.Fatalf("can only handle swapped successors in %s", rule)
   998  		}
   999  		rr.add(stmtf("b.swapSuccessors()"))
  1000  	}
  1001  
  1002  	if *genLog {
  1003  		rr.add(stmtf("logRule(%q)", rule.Loc))
  1004  	}
  1005  	return rr
  1006  }
  1007  
  1008  // genMatch returns the variable whose source position should be used for the
  1009  // result (or "" if no opinion), and a boolean that reports whether the match can fail.
  1010  func genMatch(rr *RuleRewrite, arch arch, match string, pregenTop bool) (pos, checkOp string) {
  1011  	cnt := varCount(rr)
  1012  	return genMatch0(rr, arch, match, "v", cnt, pregenTop)
  1013  }
  1014  
  1015  func genMatch0(rr *RuleRewrite, arch arch, match, v string, cnt map[string]int, pregenTop bool) (pos, checkOp string) {
  1016  	if match[0] != '(' || match[len(match)-1] != ')' {
  1017  		log.Fatalf("%s: non-compound expr in genMatch0: %q", rr.Loc, match)
  1018  	}
  1019  	op, oparch, typ, auxint, aux, args := parseValue(match, arch, rr.Loc)
  1020  
  1021  	checkOp = fmt.Sprintf("Op%s%s", oparch, op.name)
  1022  
  1023  	if op.faultOnNilArg0 || op.faultOnNilArg1 {
  1024  		// Prefer the position of an instruction which could fault.
  1025  		pos = v + ".Pos"
  1026  	}
  1027  
  1028  	// If the last argument is ___, it means "don't care about trailing arguments, really"
  1029  	// The likely/intended use is for rewrites that are too tricky to express in the existing pattern language
  1030  	// Do a length check early because long patterns fed short (ultimately not-matching) inputs will
  1031  	// do an indexing error in pattern-matching.
  1032  	if op.argLength == -1 {
  1033  		l := len(args)
  1034  		if l == 0 || args[l-1] != "___" {
  1035  			rr.add(breakf("len(%s.Args) != %d", v, l))
  1036  		} else if l > 1 && args[l-1] == "___" {
  1037  			rr.add(breakf("len(%s.Args) < %d", v, l-1))
  1038  		}
  1039  	}
  1040  
  1041  	for _, e := range []struct {
  1042  		name, field, dclType string
  1043  	}{
  1044  		{typ, "Type", "*types.Type"},
  1045  		{auxint, "AuxInt", op.auxIntType()},
  1046  		{aux, "Aux", op.auxType()},
  1047  	} {
  1048  		if e.name == "" {
  1049  			continue
  1050  		}
  1051  
  1052  		if e.dclType == "" {
  1053  			log.Fatalf("op %s has no declared type for %s", op.name, e.field)
  1054  		}
  1055  		if !token.IsIdentifier(e.name) || rr.declared(e.name) {
  1056  			switch e.field {
  1057  			case "Aux":
  1058  				rr.add(breakf("auxTo%s(%s.%s) != %s", title(e.dclType), v, e.field, e.name))
  1059  			case "AuxInt":
  1060  				rr.add(breakf("auxIntTo%s(%s.%s) != %s", title(e.dclType), v, e.field, e.name))
  1061  			case "Type":
  1062  				rr.add(breakf("%s.%s != %s", v, e.field, e.name))
  1063  			}
  1064  		} else {
  1065  			switch e.field {
  1066  			case "Aux":
  1067  				rr.add(declf(rr.Loc, e.name, "auxTo%s(%s.%s)", title(e.dclType), v, e.field))
  1068  			case "AuxInt":
  1069  				rr.add(declf(rr.Loc, e.name, "auxIntTo%s(%s.%s)", title(e.dclType), v, e.field))
  1070  			case "Type":
  1071  				rr.add(declf(rr.Loc, e.name, "%s.%s", v, e.field))
  1072  			}
  1073  		}
  1074  	}
  1075  
  1076  	commutative := op.commutative
  1077  	if commutative {
  1078  		if args[0] == args[1] {
  1079  			// When we have (Add x x), for any x,
  1080  			// even if there are other uses of x besides these two,
  1081  			// and even if x is not a variable,
  1082  			// we can skip the commutative match.
  1083  			commutative = false
  1084  		}
  1085  		if cnt[args[0]] == 1 && cnt[args[1]] == 1 {
  1086  			// When we have (Add x y) with no other uses
  1087  			// of x and y in the matching rule and condition,
  1088  			// then we can skip the commutative match (Add y x).
  1089  			commutative = false
  1090  		}
  1091  	}
  1092  
  1093  	if !pregenTop {
  1094  		// Access last argument first to minimize bounds checks.
  1095  		for n := len(args) - 1; n > 0; n-- {
  1096  			a := args[n]
  1097  			if a == "_" {
  1098  				continue
  1099  			}
  1100  			if !rr.declared(a) && token.IsIdentifier(a) && !(commutative && len(args) == 2) {
  1101  				rr.add(declf(rr.Loc, a, "%s.Args[%d]", v, n))
  1102  				// delete the last argument so it is not reprocessed
  1103  				args = args[:n]
  1104  			} else {
  1105  				rr.add(stmtf("_ = %s.Args[%d]", v, n))
  1106  			}
  1107  			break
  1108  		}
  1109  	}
  1110  	if commutative && !pregenTop {
  1111  		for i := 0; i <= 1; i++ {
  1112  			vname := fmt.Sprintf("%s_%d", v, i)
  1113  			rr.add(declf(rr.Loc, vname, "%s.Args[%d]", v, i))
  1114  		}
  1115  	}
  1116  	if commutative {
  1117  		rr.add(StartCommuteLoop{rr.CommuteDepth, v})
  1118  		rr.CommuteDepth++
  1119  	}
  1120  	for i, arg := range args {
  1121  		if arg == "_" {
  1122  			continue
  1123  		}
  1124  		var rhs string
  1125  		if (commutative && i < 2) || pregenTop {
  1126  			rhs = fmt.Sprintf("%s_%d", v, i)
  1127  		} else {
  1128  			rhs = fmt.Sprintf("%s.Args[%d]", v, i)
  1129  		}
  1130  		if !strings.Contains(arg, "(") {
  1131  			// leaf variable
  1132  			if rr.declared(arg) {
  1133  				// variable already has a definition. Check whether
  1134  				// the old definition and the new definition match.
  1135  				// For example, (add x x).  Equality is just pointer equality
  1136  				// on Values (so cse is important to do before lowering).
  1137  				rr.add(breakf("%s != %s", arg, rhs))
  1138  			} else {
  1139  				if arg != rhs {
  1140  					rr.add(declf(rr.Loc, arg, "%s", rhs))
  1141  				}
  1142  			}
  1143  			continue
  1144  		}
  1145  		// compound sexpr
  1146  		argname, expr := splitNameExpr(arg)
  1147  		if argname == "" {
  1148  			argname = fmt.Sprintf("%s_%d", v, i)
  1149  		}
  1150  		if argname == "b" {
  1151  			log.Fatalf("don't name args 'b', it is ambiguous with blocks")
  1152  		}
  1153  
  1154  		if argname != rhs {
  1155  			rr.add(declf(rr.Loc, argname, "%s", rhs))
  1156  		}
  1157  		bexpr := exprf("%s.Op != addLater", argname)
  1158  		rr.add(&CondBreak{Cond: bexpr})
  1159  		argPos, argCheckOp := genMatch0(rr, arch, expr, argname, cnt, false)
  1160  		bexpr.(*ast.BinaryExpr).Y.(*ast.Ident).Name = argCheckOp
  1161  
  1162  		if argPos != "" {
  1163  			// Keep the argument in preference to the parent, as the
  1164  			// argument is normally earlier in program flow.
  1165  			// Keep the argument in preference to an earlier argument,
  1166  			// as that prefers the memory argument which is also earlier
  1167  			// in the program flow.
  1168  			pos = argPos
  1169  		}
  1170  	}
  1171  
  1172  	return pos, checkOp
  1173  }
  1174  
  1175  func genResult(rr *RuleRewrite, arch arch, result, pos string) {
  1176  	move := result[0] == '@'
  1177  	if move {
  1178  		// parse @block directive
  1179  		s := strings.SplitN(result[1:], " ", 2)
  1180  		rr.add(stmtf("b = %s", s[0]))
  1181  		result = s[1]
  1182  	}
  1183  	cse := make(map[string]string)
  1184  	genResult0(rr, arch, result, true, move, pos, cse)
  1185  }
  1186  
  1187  func genResult0(rr *RuleRewrite, arch arch, result string, top, move bool, pos string, cse map[string]string) string {
  1188  	resname, expr := splitNameExpr(result)
  1189  	result = expr
  1190  	// TODO: when generating a constant result, use f.constVal to avoid
  1191  	// introducing copies just to clean them up again.
  1192  	if result[0] != '(' {
  1193  		// variable
  1194  		if top {
  1195  			// It in not safe in general to move a variable between blocks
  1196  			// (and particularly not a phi node).
  1197  			// Introduce a copy.
  1198  			rr.add(stmtf("v.copyOf(%s)", result))
  1199  		}
  1200  		return result
  1201  	}
  1202  
  1203  	w := normalizeWhitespace(result)
  1204  	if prev := cse[w]; prev != "" {
  1205  		return prev
  1206  	}
  1207  
  1208  	op, oparch, typ, auxint, aux, args := parseValue(result, arch, rr.Loc)
  1209  
  1210  	// Find the type of the variable.
  1211  	typeOverride := typ != ""
  1212  	if typ == "" && op.typ != "" {
  1213  		typ = typeName(op.typ)
  1214  	}
  1215  
  1216  	v := "v"
  1217  	if top && !move {
  1218  		rr.add(stmtf("v.reset(Op%s%s)", oparch, op.name))
  1219  		if typeOverride {
  1220  			rr.add(stmtf("v.Type = %s", typ))
  1221  		}
  1222  	} else {
  1223  		if typ == "" {
  1224  			log.Fatalf("sub-expression %s (op=Op%s%s) at %s must have a type", result, oparch, op.name, rr.Loc)
  1225  		}
  1226  		if resname == "" {
  1227  			v = fmt.Sprintf("v%d", rr.Alloc)
  1228  		} else {
  1229  			v = resname
  1230  		}
  1231  		rr.Alloc++
  1232  		rr.add(declf(rr.Loc, v, "b.NewValue0(%s, Op%s%s, %s)", pos, oparch, op.name, typ))
  1233  		if move && top {
  1234  			// Rewrite original into a copy
  1235  			rr.add(stmtf("v.copyOf(%s)", v))
  1236  		}
  1237  	}
  1238  
  1239  	if auxint != "" {
  1240  		// Make sure auxint value has the right type.
  1241  		rr.add(stmtf("%s.AuxInt = %sToAuxInt(%s)", v, unTitle(op.auxIntType()), auxint))
  1242  	}
  1243  	if aux != "" {
  1244  		// Make sure aux value has the right type.
  1245  		rr.add(stmtf("%s.Aux = %sToAux(%s)", v, unTitle(op.auxType()), aux))
  1246  	}
  1247  	all := new(strings.Builder)
  1248  	for i, arg := range args {
  1249  		x := genResult0(rr, arch, arg, false, move, pos, cse)
  1250  		if i > 0 {
  1251  			all.WriteString(", ")
  1252  		}
  1253  		all.WriteString(x)
  1254  	}
  1255  	switch len(args) {
  1256  	case 0:
  1257  	case 1:
  1258  		rr.add(stmtf("%s.AddArg(%s)", v, all.String()))
  1259  	default:
  1260  		rr.add(stmtf("%s.AddArg%d(%s)", v, len(args), all.String()))
  1261  	}
  1262  
  1263  	if cse != nil {
  1264  		cse[w] = v
  1265  	}
  1266  	return v
  1267  }
  1268  
  1269  func split(s string) []string {
  1270  	var r []string
  1271  
  1272  outer:
  1273  	for s != "" {
  1274  		d := 0               // depth of ({[<
  1275  		var open, close byte // opening and closing markers ({[< or )}]>
  1276  		nonsp := false       // found a non-space char so far
  1277  		for i := 0; i < len(s); i++ {
  1278  			switch {
  1279  			case d == 0 && s[i] == '(':
  1280  				open, close = '(', ')'
  1281  				d++
  1282  			case d == 0 && s[i] == '<':
  1283  				open, close = '<', '>'
  1284  				d++
  1285  			case d == 0 && s[i] == '[':
  1286  				open, close = '[', ']'
  1287  				d++
  1288  			case d == 0 && s[i] == '{':
  1289  				open, close = '{', '}'
  1290  				d++
  1291  			case d == 0 && (s[i] == ' ' || s[i] == '\t'):
  1292  				if nonsp {
  1293  					r = append(r, strings.TrimSpace(s[:i]))
  1294  					s = s[i:]
  1295  					continue outer
  1296  				}
  1297  			case d > 0 && s[i] == open:
  1298  				d++
  1299  			case d > 0 && s[i] == close:
  1300  				d--
  1301  			default:
  1302  				nonsp = true
  1303  			}
  1304  		}
  1305  		if d != 0 {
  1306  			log.Fatalf("imbalanced expression: %q", s)
  1307  		}
  1308  		if nonsp {
  1309  			r = append(r, strings.TrimSpace(s))
  1310  		}
  1311  		break
  1312  	}
  1313  	return r
  1314  }
  1315  
  1316  // isBlock reports whether this op is a block opcode.
  1317  func isBlock(name string, arch arch) bool {
  1318  	for _, b := range genericBlocks {
  1319  		if b.name == name {
  1320  			return true
  1321  		}
  1322  	}
  1323  	for _, b := range arch.blocks {
  1324  		if b.name == name {
  1325  			return true
  1326  		}
  1327  	}
  1328  	return false
  1329  }
  1330  
  1331  func extract(val string) (op, typ, auxint, aux string, args []string) {
  1332  	val = val[1 : len(val)-1] // remove ()
  1333  
  1334  	// Split val up into regions.
  1335  	// Split by spaces/tabs, except those contained in (), {}, [], or <>.
  1336  	s := split(val)
  1337  
  1338  	// Extract restrictions and args.
  1339  	op = s[0]
  1340  	for _, a := range s[1:] {
  1341  		switch a[0] {
  1342  		case '<':
  1343  			typ = a[1 : len(a)-1] // remove <>
  1344  		case '[':
  1345  			auxint = a[1 : len(a)-1] // remove []
  1346  		case '{':
  1347  			aux = a[1 : len(a)-1] // remove {}
  1348  		default:
  1349  			args = append(args, a)
  1350  		}
  1351  	}
  1352  	return
  1353  }
  1354  
  1355  // parseValue parses a parenthesized value from a rule.
  1356  // The value can be from the match or the result side.
  1357  // It returns the op and unparsed strings for typ, auxint, and aux restrictions and for all args.
  1358  // oparch is the architecture that op is located in, or "" for generic.
  1359  func parseValue(val string, arch arch, loc string) (op opData, oparch, typ, auxint, aux string, args []string) {
  1360  	// Resolve the op.
  1361  	var s string
  1362  	s, typ, auxint, aux, args = extract(val)
  1363  
  1364  	// match reports whether x is a good op to select.
  1365  	// If strict is true, rule generation might succeed.
  1366  	// If strict is false, rule generation has failed,
  1367  	// but we're trying to generate a useful error.
  1368  	// Doing strict=true then strict=false allows
  1369  	// precise op matching while retaining good error messages.
  1370  	match := func(x opData, strict bool, archname string) bool {
  1371  		if x.name != s {
  1372  			return false
  1373  		}
  1374  		if x.argLength != -1 && int(x.argLength) != len(args) && (len(args) != 1 || args[0] != "...") {
  1375  			if strict {
  1376  				return false
  1377  			}
  1378  			log.Printf("%s: op %s (%s) should have %d args, has %d", loc, s, archname, x.argLength, len(args))
  1379  		}
  1380  		return true
  1381  	}
  1382  
  1383  	for _, x := range genericOps {
  1384  		if match(x, true, "generic") {
  1385  			op = x
  1386  			break
  1387  		}
  1388  	}
  1389  	for _, x := range arch.ops {
  1390  		if arch.name != "generic" && match(x, true, arch.name) {
  1391  			if op.name != "" {
  1392  				log.Fatalf("%s: matches for op %s found in both generic and %s", loc, op.name, arch.name)
  1393  			}
  1394  			op = x
  1395  			oparch = arch.name
  1396  			break
  1397  		}
  1398  	}
  1399  
  1400  	if op.name == "" {
  1401  		// Failed to find the op.
  1402  		// Run through everything again with strict=false
  1403  		// to generate useful diagnostic messages before failing.
  1404  		for _, x := range genericOps {
  1405  			match(x, false, "generic")
  1406  		}
  1407  		for _, x := range arch.ops {
  1408  			match(x, false, arch.name)
  1409  		}
  1410  		log.Fatalf("%s: unknown op %s", loc, s)
  1411  	}
  1412  
  1413  	// Sanity check aux, auxint.
  1414  	if auxint != "" && !opHasAuxInt(op) {
  1415  		log.Fatalf("%s: op %s %s can't have auxint", loc, op.name, op.aux)
  1416  	}
  1417  	if aux != "" && !opHasAux(op) {
  1418  		log.Fatalf("%s: op %s %s can't have aux", loc, op.name, op.aux)
  1419  	}
  1420  	return
  1421  }
  1422  
  1423  func opHasAuxInt(op opData) bool {
  1424  	switch op.aux {
  1425  	case "Bool", "Int8", "Int16", "Int32", "Int64", "Int128", "UInt8", "Float32", "Float64",
  1426  		"SymOff", "CallOff", "SymValAndOff", "TypSize", "ARM64BitField", "FlagConstant", "CCop":
  1427  		return true
  1428  	}
  1429  	return false
  1430  }
  1431  
  1432  func opHasAux(op opData) bool {
  1433  	switch op.aux {
  1434  	case "String", "Sym", "SymOff", "Call", "CallOff", "SymValAndOff", "Typ", "TypSize",
  1435  		"S390XCCMask", "S390XRotateParams":
  1436  		return true
  1437  	}
  1438  	return false
  1439  }
  1440  
  1441  // splitNameExpr splits s-expr arg, possibly prefixed by "name:",
  1442  // into name and the unprefixed expression.
  1443  // For example, "x:(Foo)" yields "x", "(Foo)",
  1444  // and "(Foo)" yields "", "(Foo)".
  1445  func splitNameExpr(arg string) (name, expr string) {
  1446  	colon := strings.Index(arg, ":")
  1447  	if colon < 0 {
  1448  		return "", arg
  1449  	}
  1450  	openparen := strings.Index(arg, "(")
  1451  	if openparen < 0 {
  1452  		log.Fatalf("splitNameExpr(%q): colon but no open parens", arg)
  1453  	}
  1454  	if colon > openparen {
  1455  		// colon is inside the parens, such as in "(Foo x:(Bar))".
  1456  		return "", arg
  1457  	}
  1458  	return arg[:colon], arg[colon+1:]
  1459  }
  1460  
  1461  func getBlockInfo(op string, arch arch) (name string, data blockData) {
  1462  	for _, b := range genericBlocks {
  1463  		if b.name == op {
  1464  			return "Block" + op, b
  1465  		}
  1466  	}
  1467  	for _, b := range arch.blocks {
  1468  		if b.name == op {
  1469  			return "Block" + arch.name + op, b
  1470  		}
  1471  	}
  1472  	log.Fatalf("could not find block data for %s", op)
  1473  	panic("unreachable")
  1474  }
  1475  
  1476  // typeName returns the string to use to generate a type.
  1477  func typeName(typ string) string {
  1478  	if typ[0] == '(' {
  1479  		ts := strings.Split(typ[1:len(typ)-1], ",")
  1480  		if len(ts) != 2 {
  1481  			log.Fatalf("Tuple expect 2 arguments")
  1482  		}
  1483  		return "types.NewTuple(" + typeName(ts[0]) + ", " + typeName(ts[1]) + ")"
  1484  	}
  1485  	switch typ {
  1486  	case "Flags", "Mem", "Void", "Int128":
  1487  		return "types.Type" + typ
  1488  	default:
  1489  		return "typ." + typ
  1490  	}
  1491  }
  1492  
  1493  // balance returns the number of unclosed '(' characters in s.
  1494  // If a ')' appears without a corresponding '(', balance returns -1.
  1495  func balance(s string) int {
  1496  	balance := 0
  1497  	for _, c := range s {
  1498  		switch c {
  1499  		case '(':
  1500  			balance++
  1501  		case ')':
  1502  			balance--
  1503  			if balance < 0 {
  1504  				// don't allow ")(" to return 0
  1505  				return -1
  1506  			}
  1507  		}
  1508  	}
  1509  	return balance
  1510  }
  1511  
  1512  // findAllOpcode is a function to find the opcode portion of s-expressions.
  1513  var findAllOpcode = regexp.MustCompile(`[(](\w+[|])+\w+[)]`).FindAllStringIndex
  1514  
  1515  // excludeFromExpansion reports whether the substring s[idx[0]:idx[1]] in a rule
  1516  // should be disregarded as a candidate for | expansion.
  1517  // It uses simple syntactic checks to see whether the substring
  1518  // is inside an AuxInt expression or inside the && conditions.
  1519  func excludeFromExpansion(s string, idx []int) bool {
  1520  	left := s[:idx[0]]
  1521  	if strings.LastIndexByte(left, '[') > strings.LastIndexByte(left, ']') {
  1522  		// Inside an AuxInt expression.
  1523  		return true
  1524  	}
  1525  	right := s[idx[1]:]
  1526  	if strings.Contains(left, "&&") && strings.Contains(right, "=>") {
  1527  		// Inside && conditions.
  1528  		return true
  1529  	}
  1530  	return false
  1531  }
  1532  
  1533  // expandOr converts a rule into multiple rules by expanding | ops.
  1534  func expandOr(r string) []string {
  1535  	// Find every occurrence of |-separated things.
  1536  	// They look like MOV(B|W|L|Q|SS|SD)load or MOV(Q|L)loadidx(1|8).
  1537  	// Generate rules selecting one case from each |-form.
  1538  
  1539  	// Count width of |-forms.  They must match.
  1540  	n := 1
  1541  	for _, idx := range findAllOpcode(r, -1) {
  1542  		if excludeFromExpansion(r, idx) {
  1543  			continue
  1544  		}
  1545  		s := r[idx[0]:idx[1]]
  1546  		c := strings.Count(s, "|") + 1
  1547  		if c == 1 {
  1548  			continue
  1549  		}
  1550  		if n > 1 && n != c {
  1551  			log.Fatalf("'|' count doesn't match in %s: both %d and %d\n", r, n, c)
  1552  		}
  1553  		n = c
  1554  	}
  1555  	if n == 1 {
  1556  		// No |-form in this rule.
  1557  		return []string{r}
  1558  	}
  1559  	// Build each new rule.
  1560  	res := make([]string, n)
  1561  	for i := 0; i < n; i++ {
  1562  		buf := new(strings.Builder)
  1563  		x := 0
  1564  		for _, idx := range findAllOpcode(r, -1) {
  1565  			if excludeFromExpansion(r, idx) {
  1566  				continue
  1567  			}
  1568  			buf.WriteString(r[x:idx[0]])              // write bytes we've skipped over so far
  1569  			s := r[idx[0]+1 : idx[1]-1]               // remove leading "(" and trailing ")"
  1570  			buf.WriteString(strings.Split(s, "|")[i]) // write the op component for this rule
  1571  			x = idx[1]                                // note that we've written more bytes
  1572  		}
  1573  		buf.WriteString(r[x:])
  1574  		res[i] = buf.String()
  1575  	}
  1576  	return res
  1577  }
  1578  
  1579  // varCount returns a map which counts the number of occurrences of
  1580  // Value variables in the s-expression rr.Match and the Go expression rr.Cond.
  1581  func varCount(rr *RuleRewrite) map[string]int {
  1582  	cnt := map[string]int{}
  1583  	varCount1(rr.Loc, rr.Match, cnt)
  1584  	if rr.Cond != "" {
  1585  		expr, err := parser.ParseExpr(rr.Cond)
  1586  		if err != nil {
  1587  			log.Fatalf("%s: failed to parse cond %q: %v", rr.Loc, rr.Cond, err)
  1588  		}
  1589  		ast.Inspect(expr, func(n ast.Node) bool {
  1590  			if id, ok := n.(*ast.Ident); ok {
  1591  				cnt[id.Name]++
  1592  			}
  1593  			return true
  1594  		})
  1595  	}
  1596  	return cnt
  1597  }
  1598  
  1599  func varCount1(loc, m string, cnt map[string]int) {
  1600  	if m[0] == '<' || m[0] == '[' || m[0] == '{' {
  1601  		return
  1602  	}
  1603  	if token.IsIdentifier(m) {
  1604  		cnt[m]++
  1605  		return
  1606  	}
  1607  	// Split up input.
  1608  	name, expr := splitNameExpr(m)
  1609  	if name != "" {
  1610  		cnt[name]++
  1611  	}
  1612  	if expr[0] != '(' || expr[len(expr)-1] != ')' {
  1613  		log.Fatalf("%s: non-compound expr in varCount1: %q", loc, expr)
  1614  	}
  1615  	s := split(expr[1 : len(expr)-1])
  1616  	for _, arg := range s[1:] {
  1617  		varCount1(loc, arg, cnt)
  1618  	}
  1619  }
  1620  
  1621  // normalizeWhitespace replaces 2+ whitespace sequences with a single space.
  1622  func normalizeWhitespace(x string) string {
  1623  	x = strings.Join(strings.Fields(x), " ")
  1624  	x = strings.Replace(x, "( ", "(", -1)
  1625  	x = strings.Replace(x, " )", ")", -1)
  1626  	x = strings.Replace(x, "[ ", "[", -1)
  1627  	x = strings.Replace(x, " ]", "]", -1)
  1628  	x = strings.Replace(x, ")=>", ") =>", -1)
  1629  	return x
  1630  }
  1631  
  1632  // opIsCommutative reports whether op s is commutative.
  1633  func opIsCommutative(op string, arch arch) bool {
  1634  	for _, x := range genericOps {
  1635  		if op == x.name {
  1636  			if x.commutative {
  1637  				return true
  1638  			}
  1639  			break
  1640  		}
  1641  	}
  1642  	if arch.name != "generic" {
  1643  		for _, x := range arch.ops {
  1644  			if op == x.name {
  1645  				if x.commutative {
  1646  					return true
  1647  				}
  1648  				break
  1649  			}
  1650  		}
  1651  	}
  1652  	return false
  1653  }
  1654  
  1655  func normalizeMatch(m string, arch arch) string {
  1656  	if token.IsIdentifier(m) {
  1657  		return m
  1658  	}
  1659  	op, typ, auxint, aux, args := extract(m)
  1660  	if opIsCommutative(op, arch) {
  1661  		if args[1] < args[0] {
  1662  			args[0], args[1] = args[1], args[0]
  1663  		}
  1664  	}
  1665  	s := new(strings.Builder)
  1666  	fmt.Fprintf(s, "%s <%s> [%s] {%s}", op, typ, auxint, aux)
  1667  	for _, arg := range args {
  1668  		prefix, expr := splitNameExpr(arg)
  1669  		fmt.Fprint(s, " ", prefix, normalizeMatch(expr, arch))
  1670  	}
  1671  	return s.String()
  1672  }
  1673  
  1674  func parseEllipsisRules(rules []Rule, arch arch) (newop string, ok bool) {
  1675  	if len(rules) != 1 {
  1676  		for _, r := range rules {
  1677  			if strings.Contains(r.Rule, "...") {
  1678  				log.Fatalf("%s: found ellipsis in rule, but there are other rules with the same op", r.Loc)
  1679  			}
  1680  		}
  1681  		return "", false
  1682  	}
  1683  	rule := rules[0]
  1684  	match, cond, result := rule.parse()
  1685  	if cond != "" || !isEllipsisValue(match) || !isEllipsisValue(result) {
  1686  		if strings.Contains(rule.Rule, "...") {
  1687  			log.Fatalf("%s: found ellipsis in non-ellipsis rule", rule.Loc)
  1688  		}
  1689  		checkEllipsisRuleCandidate(rule, arch)
  1690  		return "", false
  1691  	}
  1692  	op, oparch, _, _, _, _ := parseValue(result, arch, rule.Loc)
  1693  	return fmt.Sprintf("Op%s%s", oparch, op.name), true
  1694  }
  1695  
  1696  // isEllipsisValue reports whether s is of the form (OpX ...).
  1697  func isEllipsisValue(s string) bool {
  1698  	if len(s) < 2 || s[0] != '(' || s[len(s)-1] != ')' {
  1699  		return false
  1700  	}
  1701  	c := split(s[1 : len(s)-1])
  1702  	if len(c) != 2 || c[1] != "..." {
  1703  		return false
  1704  	}
  1705  	return true
  1706  }
  1707  
  1708  func checkEllipsisRuleCandidate(rule Rule, arch arch) {
  1709  	match, cond, result := rule.parse()
  1710  	if cond != "" {
  1711  		return
  1712  	}
  1713  	op, _, _, auxint, aux, args := parseValue(match, arch, rule.Loc)
  1714  	var auxint2, aux2 string
  1715  	var args2 []string
  1716  	var usingCopy string
  1717  	var eop opData
  1718  	if result[0] != '(' {
  1719  		// Check for (Foo x) => x, which can be converted to (Foo ...) => (Copy ...).
  1720  		args2 = []string{result}
  1721  		usingCopy = " using Copy"
  1722  	} else {
  1723  		eop, _, _, auxint2, aux2, args2 = parseValue(result, arch, rule.Loc)
  1724  	}
  1725  	// Check that all restrictions in match are reproduced exactly in result.
  1726  	if aux != aux2 || auxint != auxint2 || len(args) != len(args2) {
  1727  		return
  1728  	}
  1729  	if strings.Contains(rule.Rule, "=>") && op.aux != eop.aux {
  1730  		return
  1731  	}
  1732  	for i := range args {
  1733  		if args[i] != args2[i] {
  1734  			return
  1735  		}
  1736  	}
  1737  	switch {
  1738  	case opHasAux(op) && aux == "" && aux2 == "":
  1739  		fmt.Printf("%s: rule silently zeros aux, either copy aux or explicitly zero\n", rule.Loc)
  1740  	case opHasAuxInt(op) && auxint == "" && auxint2 == "":
  1741  		fmt.Printf("%s: rule silently zeros auxint, either copy auxint or explicitly zero\n", rule.Loc)
  1742  	default:
  1743  		fmt.Printf("%s: possible ellipsis rule candidate%s: %q\n", rule.Loc, usingCopy, rule.Rule)
  1744  	}
  1745  }
  1746  
  1747  func opByName(arch arch, name string) opData {
  1748  	name = name[2:]
  1749  	for _, x := range genericOps {
  1750  		if name == x.name {
  1751  			return x
  1752  		}
  1753  	}
  1754  	if arch.name != "generic" {
  1755  		name = name[len(arch.name):]
  1756  		for _, x := range arch.ops {
  1757  			if name == x.name {
  1758  				return x
  1759  			}
  1760  		}
  1761  	}
  1762  	log.Fatalf("failed to find op named %s in arch %s", name, arch.name)
  1763  	panic("unreachable")
  1764  }
  1765  
  1766  // auxType returns the Go type that this operation should store in its aux field.
  1767  func (op opData) auxType() string {
  1768  	switch op.aux {
  1769  	case "String":
  1770  		return "string"
  1771  	case "Sym":
  1772  		// Note: a Sym can be an *obj.LSym, a *gc.Node, or nil.
  1773  		return "Sym"
  1774  	case "SymOff":
  1775  		return "Sym"
  1776  	case "Call":
  1777  		return "Call"
  1778  	case "CallOff":
  1779  		return "Call"
  1780  	case "SymValAndOff":
  1781  		return "Sym"
  1782  	case "Typ":
  1783  		return "*types.Type"
  1784  	case "TypSize":
  1785  		return "*types.Type"
  1786  	case "S390XCCMask":
  1787  		return "s390x.CCMask"
  1788  	case "S390XRotateParams":
  1789  		return "s390x.RotateParams"
  1790  	default:
  1791  		return "invalid"
  1792  	}
  1793  }
  1794  
  1795  // auxIntType returns the Go type that this operation should store in its auxInt field.
  1796  func (op opData) auxIntType() string {
  1797  	switch op.aux {
  1798  	case "Bool":
  1799  		return "bool"
  1800  	case "Int8":
  1801  		return "int8"
  1802  	case "Int16":
  1803  		return "int16"
  1804  	case "Int32":
  1805  		return "int32"
  1806  	case "Int64":
  1807  		return "int64"
  1808  	case "Int128":
  1809  		return "int128"
  1810  	case "UInt8":
  1811  		return "uint8"
  1812  	case "Float32":
  1813  		return "float32"
  1814  	case "Float64":
  1815  		return "float64"
  1816  	case "CallOff":
  1817  		return "int32"
  1818  	case "SymOff":
  1819  		return "int32"
  1820  	case "SymValAndOff":
  1821  		return "ValAndOff"
  1822  	case "TypSize":
  1823  		return "int64"
  1824  	case "CCop":
  1825  		return "Op"
  1826  	case "FlagConstant":
  1827  		return "flagConstant"
  1828  	case "ARM64BitField":
  1829  		return "arm64BitField"
  1830  	default:
  1831  		return "invalid"
  1832  	}
  1833  }
  1834  
  1835  // auxType returns the Go type that this block should store in its aux field.
  1836  func (b blockData) auxType() string {
  1837  	switch b.aux {
  1838  	case "Sym":
  1839  		return "Sym"
  1840  	case "S390XCCMask", "S390XCCMaskInt8", "S390XCCMaskUint8":
  1841  		return "s390x.CCMask"
  1842  	case "S390XRotateParams":
  1843  		return "s390x.RotateParams"
  1844  	default:
  1845  		return "invalid"
  1846  	}
  1847  }
  1848  
  1849  // auxIntType returns the Go type that this block should store in its auxInt field.
  1850  func (b blockData) auxIntType() string {
  1851  	switch b.aux {
  1852  	case "S390XCCMaskInt8":
  1853  		return "int8"
  1854  	case "S390XCCMaskUint8":
  1855  		return "uint8"
  1856  	case "Int64":
  1857  		return "int64"
  1858  	default:
  1859  		return "invalid"
  1860  	}
  1861  }
  1862  
  1863  func title(s string) string {
  1864  	if i := strings.Index(s, "."); i >= 0 {
  1865  		switch strings.ToLower(s[:i]) {
  1866  		case "s390x": // keep arch prefix for clarity
  1867  			s = s[:i] + s[i+1:]
  1868  		default:
  1869  			s = s[i+1:]
  1870  		}
  1871  	}
  1872  	return strings.Title(s)
  1873  }
  1874  
  1875  func unTitle(s string) string {
  1876  	if i := strings.Index(s, "."); i >= 0 {
  1877  		switch strings.ToLower(s[:i]) {
  1878  		case "s390x": // keep arch prefix for clarity
  1879  			s = s[:i] + s[i+1:]
  1880  		default:
  1881  			s = s[i+1:]
  1882  		}
  1883  	}
  1884  	return strings.ToLower(s[:1]) + s[1:]
  1885  }
  1886  

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