Source file src/cmd/compile/internal/walk/expr.go

Documentation: cmd/compile/internal/walk

     1  // Copyright 2009 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 walk
     6  
     7  import (
     8  	"fmt"
     9  	"go/constant"
    10  	"internal/abi"
    11  	"internal/buildcfg"
    12  	"strings"
    13  
    14  	"cmd/compile/internal/base"
    15  	"cmd/compile/internal/ir"
    16  	"cmd/compile/internal/objw"
    17  	"cmd/compile/internal/reflectdata"
    18  	"cmd/compile/internal/rttype"
    19  	"cmd/compile/internal/staticdata"
    20  	"cmd/compile/internal/typecheck"
    21  	"cmd/compile/internal/types"
    22  	"cmd/internal/obj"
    23  	"cmd/internal/objabi"
    24  )
    25  
    26  // The result of walkExpr MUST be assigned back to n, e.g.
    27  //
    28  //	n.Left = walkExpr(n.Left, init)
    29  func walkExpr(n ir.Node, init *ir.Nodes) ir.Node {
    30  	if n == nil {
    31  		return n
    32  	}
    33  
    34  	if n, ok := n.(ir.InitNode); ok && init == n.PtrInit() {
    35  		// not okay to use n->ninit when walking n,
    36  		// because we might replace n with some other node
    37  		// and would lose the init list.
    38  		base.Fatalf("walkExpr init == &n->ninit")
    39  	}
    40  
    41  	if len(n.Init()) != 0 {
    42  		walkStmtList(n.Init())
    43  		init.Append(ir.TakeInit(n)...)
    44  	}
    45  
    46  	lno := ir.SetPos(n)
    47  
    48  	if base.Flag.LowerW > 1 {
    49  		ir.Dump("before walk expr", n)
    50  	}
    51  
    52  	if n.Typecheck() != 1 {
    53  		base.Fatalf("missed typecheck: %+v", n)
    54  	}
    55  
    56  	if n.Type().IsUntyped() {
    57  		base.Fatalf("expression has untyped type: %+v", n)
    58  	}
    59  
    60  	n = walkExpr1(n, init)
    61  
    62  	// Eagerly compute sizes of all expressions for the back end.
    63  	if typ := n.Type(); typ != nil && typ.Kind() != types.TBLANK && !typ.IsFuncArgStruct() {
    64  		types.CheckSize(typ)
    65  	}
    66  	if n, ok := n.(*ir.Name); ok && n.Heapaddr != nil {
    67  		types.CheckSize(n.Heapaddr.Type())
    68  	}
    69  	if ir.IsConst(n, constant.String) {
    70  		// Emit string symbol now to avoid emitting
    71  		// any concurrently during the backend.
    72  		_ = staticdata.StringSym(n.Pos(), constant.StringVal(n.Val()))
    73  	}
    74  
    75  	if base.Flag.LowerW != 0 && n != nil {
    76  		ir.Dump("after walk expr", n)
    77  	}
    78  
    79  	base.Pos = lno
    80  	return n
    81  }
    82  
    83  func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
    84  	switch n.Op() {
    85  	default:
    86  		ir.Dump("walk", n)
    87  		base.Fatalf("walkExpr: switch 1 unknown op %+v", n.Op())
    88  		panic("unreachable")
    89  
    90  	case ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP:
    91  		return n
    92  
    93  	case ir.OTYPE, ir.ONAME, ir.OLITERAL, ir.ONIL, ir.OLINKSYMOFFSET:
    94  		// TODO(mdempsky): Just return n; see discussion on CL 38655.
    95  		// Perhaps refactor to use Node.mayBeShared for these instead.
    96  		// If these return early, make sure to still call
    97  		// StringSym for constant strings.
    98  		return n
    99  
   100  	case ir.OMETHEXPR:
   101  		// TODO(mdempsky): Do this right after type checking.
   102  		n := n.(*ir.SelectorExpr)
   103  		return n.FuncName()
   104  
   105  	case ir.OMIN, ir.OMAX:
   106  		n := n.(*ir.CallExpr)
   107  		return walkMinMax(n, init)
   108  
   109  	case ir.ONOT, ir.ONEG, ir.OPLUS, ir.OBITNOT, ir.OREAL, ir.OIMAG, ir.OSPTR, ir.OITAB, ir.OIDATA:
   110  		n := n.(*ir.UnaryExpr)
   111  		n.X = walkExpr(n.X, init)
   112  		return n
   113  
   114  	case ir.ODOTMETH, ir.ODOTINTER:
   115  		n := n.(*ir.SelectorExpr)
   116  		n.X = walkExpr(n.X, init)
   117  		return n
   118  
   119  	case ir.OADDR:
   120  		n := n.(*ir.AddrExpr)
   121  		n.X = walkExpr(n.X, init)
   122  		return n
   123  
   124  	case ir.ODEREF:
   125  		n := n.(*ir.StarExpr)
   126  		n.X = walkExpr(n.X, init)
   127  		return n
   128  
   129  	case ir.OMAKEFACE, ir.OAND, ir.OANDNOT, ir.OSUB, ir.OMUL, ir.OADD, ir.OOR, ir.OXOR, ir.OLSH, ir.ORSH,
   130  		ir.OUNSAFEADD:
   131  		n := n.(*ir.BinaryExpr)
   132  		n.X = walkExpr(n.X, init)
   133  		n.Y = walkExpr(n.Y, init)
   134  		return n
   135  
   136  	case ir.OUNSAFESLICE:
   137  		n := n.(*ir.BinaryExpr)
   138  		return walkUnsafeSlice(n, init)
   139  
   140  	case ir.OUNSAFESTRING:
   141  		n := n.(*ir.BinaryExpr)
   142  		return walkUnsafeString(n, init)
   143  
   144  	case ir.OUNSAFESTRINGDATA, ir.OUNSAFESLICEDATA:
   145  		n := n.(*ir.UnaryExpr)
   146  		return walkUnsafeData(n, init)
   147  
   148  	case ir.ODOT, ir.ODOTPTR:
   149  		n := n.(*ir.SelectorExpr)
   150  		return walkDot(n, init)
   151  
   152  	case ir.ODOTTYPE, ir.ODOTTYPE2:
   153  		n := n.(*ir.TypeAssertExpr)
   154  		return walkDotType(n, init)
   155  
   156  	case ir.ODYNAMICDOTTYPE, ir.ODYNAMICDOTTYPE2:
   157  		n := n.(*ir.DynamicTypeAssertExpr)
   158  		return walkDynamicDotType(n, init)
   159  
   160  	case ir.OLEN, ir.OCAP:
   161  		n := n.(*ir.UnaryExpr)
   162  		return walkLenCap(n, init)
   163  
   164  	case ir.OCOMPLEX:
   165  		n := n.(*ir.BinaryExpr)
   166  		n.X = walkExpr(n.X, init)
   167  		n.Y = walkExpr(n.Y, init)
   168  		return n
   169  
   170  	case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
   171  		n := n.(*ir.BinaryExpr)
   172  		return walkCompare(n, init)
   173  
   174  	case ir.OANDAND, ir.OOROR:
   175  		n := n.(*ir.LogicalExpr)
   176  		return walkLogical(n, init)
   177  
   178  	case ir.OPRINT, ir.OPRINTLN:
   179  		return walkPrint(n.(*ir.CallExpr), init)
   180  
   181  	case ir.OPANIC:
   182  		n := n.(*ir.UnaryExpr)
   183  		return mkcall("gopanic", nil, init, n.X)
   184  
   185  	case ir.ORECOVERFP:
   186  		return walkRecoverFP(n.(*ir.CallExpr), init)
   187  
   188  	case ir.OCFUNC:
   189  		return n
   190  
   191  	case ir.OCALLINTER, ir.OCALLFUNC:
   192  		n := n.(*ir.CallExpr)
   193  		return walkCall(n, init)
   194  
   195  	case ir.OAS, ir.OASOP:
   196  		return walkAssign(init, n)
   197  
   198  	case ir.OAS2:
   199  		n := n.(*ir.AssignListStmt)
   200  		return walkAssignList(init, n)
   201  
   202  	// a,b,... = fn()
   203  	case ir.OAS2FUNC:
   204  		n := n.(*ir.AssignListStmt)
   205  		return walkAssignFunc(init, n)
   206  
   207  	// x, y = <-c
   208  	// order.stmt made sure x is addressable or blank.
   209  	case ir.OAS2RECV:
   210  		n := n.(*ir.AssignListStmt)
   211  		return walkAssignRecv(init, n)
   212  
   213  	// a,b = m[i]
   214  	case ir.OAS2MAPR:
   215  		n := n.(*ir.AssignListStmt)
   216  		return walkAssignMapRead(init, n)
   217  
   218  	case ir.ODELETE:
   219  		n := n.(*ir.CallExpr)
   220  		return walkDelete(init, n)
   221  
   222  	case ir.OAS2DOTTYPE:
   223  		n := n.(*ir.AssignListStmt)
   224  		return walkAssignDotType(n, init)
   225  
   226  	case ir.OCONVIFACE:
   227  		n := n.(*ir.ConvExpr)
   228  		return walkConvInterface(n, init)
   229  
   230  	case ir.OCONV, ir.OCONVNOP:
   231  		n := n.(*ir.ConvExpr)
   232  		return walkConv(n, init)
   233  
   234  	case ir.OSLICE2ARR:
   235  		n := n.(*ir.ConvExpr)
   236  		return walkSliceToArray(n, init)
   237  
   238  	case ir.OSLICE2ARRPTR:
   239  		n := n.(*ir.ConvExpr)
   240  		n.X = walkExpr(n.X, init)
   241  		return n
   242  
   243  	case ir.ODIV, ir.OMOD:
   244  		n := n.(*ir.BinaryExpr)
   245  		return walkDivMod(n, init)
   246  
   247  	case ir.OINDEX:
   248  		n := n.(*ir.IndexExpr)
   249  		return walkIndex(n, init)
   250  
   251  	case ir.OINDEXMAP:
   252  		n := n.(*ir.IndexExpr)
   253  		return walkIndexMap(n, init)
   254  
   255  	case ir.ORECV:
   256  		base.Fatalf("walkExpr ORECV") // should see inside OAS only
   257  		panic("unreachable")
   258  
   259  	case ir.OSLICEHEADER:
   260  		n := n.(*ir.SliceHeaderExpr)
   261  		return walkSliceHeader(n, init)
   262  
   263  	case ir.OSTRINGHEADER:
   264  		n := n.(*ir.StringHeaderExpr)
   265  		return walkStringHeader(n, init)
   266  
   267  	case ir.OSLICE, ir.OSLICEARR, ir.OSLICESTR, ir.OSLICE3, ir.OSLICE3ARR:
   268  		n := n.(*ir.SliceExpr)
   269  		return walkSlice(n, init)
   270  
   271  	case ir.ONEW:
   272  		n := n.(*ir.UnaryExpr)
   273  		return walkNew(n, init)
   274  
   275  	case ir.OADDSTR:
   276  		return walkAddString(n.(*ir.AddStringExpr), init)
   277  
   278  	case ir.OAPPEND:
   279  		// order should make sure we only see OAS(node, OAPPEND), which we handle above.
   280  		base.Fatalf("append outside assignment")
   281  		panic("unreachable")
   282  
   283  	case ir.OCOPY:
   284  		return walkCopy(n.(*ir.BinaryExpr), init, base.Flag.Cfg.Instrumenting && !base.Flag.CompilingRuntime)
   285  
   286  	case ir.OCLEAR:
   287  		n := n.(*ir.UnaryExpr)
   288  		return walkClear(n)
   289  
   290  	case ir.OCLOSE:
   291  		n := n.(*ir.UnaryExpr)
   292  		return walkClose(n, init)
   293  
   294  	case ir.OMAKECHAN:
   295  		n := n.(*ir.MakeExpr)
   296  		return walkMakeChan(n, init)
   297  
   298  	case ir.OMAKEMAP:
   299  		n := n.(*ir.MakeExpr)
   300  		return walkMakeMap(n, init)
   301  
   302  	case ir.OMAKESLICE:
   303  		n := n.(*ir.MakeExpr)
   304  		return walkMakeSlice(n, init)
   305  
   306  	case ir.OMAKESLICECOPY:
   307  		n := n.(*ir.MakeExpr)
   308  		return walkMakeSliceCopy(n, init)
   309  
   310  	case ir.ORUNESTR:
   311  		n := n.(*ir.ConvExpr)
   312  		return walkRuneToString(n, init)
   313  
   314  	case ir.OBYTES2STR, ir.ORUNES2STR:
   315  		n := n.(*ir.ConvExpr)
   316  		return walkBytesRunesToString(n, init)
   317  
   318  	case ir.OBYTES2STRTMP:
   319  		n := n.(*ir.ConvExpr)
   320  		return walkBytesToStringTemp(n, init)
   321  
   322  	case ir.OSTR2BYTES:
   323  		n := n.(*ir.ConvExpr)
   324  		return walkStringToBytes(n, init)
   325  
   326  	case ir.OSTR2BYTESTMP:
   327  		n := n.(*ir.ConvExpr)
   328  		return walkStringToBytesTemp(n, init)
   329  
   330  	case ir.OSTR2RUNES:
   331  		n := n.(*ir.ConvExpr)
   332  		return walkStringToRunes(n, init)
   333  
   334  	case ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT, ir.OSTRUCTLIT, ir.OPTRLIT:
   335  		return walkCompLit(n, init)
   336  
   337  	case ir.OSEND:
   338  		n := n.(*ir.SendStmt)
   339  		return walkSend(n, init)
   340  
   341  	case ir.OCLOSURE:
   342  		return walkClosure(n.(*ir.ClosureExpr), init)
   343  
   344  	case ir.OMETHVALUE:
   345  		return walkMethodValue(n.(*ir.SelectorExpr), init)
   346  	}
   347  
   348  	// No return! Each case must return (or panic),
   349  	// to avoid confusion about what gets returned
   350  	// in the presence of type assertions.
   351  }
   352  
   353  // walk the whole tree of the body of an
   354  // expression or simple statement.
   355  // the types expressions are calculated.
   356  // compile-time constants are evaluated.
   357  // complex side effects like statements are appended to init.
   358  func walkExprList(s []ir.Node, init *ir.Nodes) {
   359  	for i := range s {
   360  		s[i] = walkExpr(s[i], init)
   361  	}
   362  }
   363  
   364  func walkExprListCheap(s []ir.Node, init *ir.Nodes) {
   365  	for i, n := range s {
   366  		s[i] = cheapExpr(n, init)
   367  		s[i] = walkExpr(s[i], init)
   368  	}
   369  }
   370  
   371  func walkExprListSafe(s []ir.Node, init *ir.Nodes) {
   372  	for i, n := range s {
   373  		s[i] = safeExpr(n, init)
   374  		s[i] = walkExpr(s[i], init)
   375  	}
   376  }
   377  
   378  // return side-effect free and cheap n, appending side effects to init.
   379  // result may not be assignable.
   380  func cheapExpr(n ir.Node, init *ir.Nodes) ir.Node {
   381  	switch n.Op() {
   382  	case ir.ONAME, ir.OLITERAL, ir.ONIL:
   383  		return n
   384  	}
   385  
   386  	return copyExpr(n, n.Type(), init)
   387  }
   388  
   389  // return side effect-free n, appending side effects to init.
   390  // result is assignable if n is.
   391  func safeExpr(n ir.Node, init *ir.Nodes) ir.Node {
   392  	if n == nil {
   393  		return nil
   394  	}
   395  
   396  	if len(n.Init()) != 0 {
   397  		walkStmtList(n.Init())
   398  		init.Append(ir.TakeInit(n)...)
   399  	}
   400  
   401  	switch n.Op() {
   402  	case ir.ONAME, ir.OLITERAL, ir.ONIL, ir.OLINKSYMOFFSET:
   403  		return n
   404  
   405  	case ir.OLEN, ir.OCAP:
   406  		n := n.(*ir.UnaryExpr)
   407  		l := safeExpr(n.X, init)
   408  		if l == n.X {
   409  			return n
   410  		}
   411  		a := ir.Copy(n).(*ir.UnaryExpr)
   412  		a.X = l
   413  		return walkExpr(typecheck.Expr(a), init)
   414  
   415  	case ir.ODOT, ir.ODOTPTR:
   416  		n := n.(*ir.SelectorExpr)
   417  		l := safeExpr(n.X, init)
   418  		if l == n.X {
   419  			return n
   420  		}
   421  		a := ir.Copy(n).(*ir.SelectorExpr)
   422  		a.X = l
   423  		return walkExpr(typecheck.Expr(a), init)
   424  
   425  	case ir.ODEREF:
   426  		n := n.(*ir.StarExpr)
   427  		l := safeExpr(n.X, init)
   428  		if l == n.X {
   429  			return n
   430  		}
   431  		a := ir.Copy(n).(*ir.StarExpr)
   432  		a.X = l
   433  		return walkExpr(typecheck.Expr(a), init)
   434  
   435  	case ir.OINDEX, ir.OINDEXMAP:
   436  		n := n.(*ir.IndexExpr)
   437  		l := safeExpr(n.X, init)
   438  		r := safeExpr(n.Index, init)
   439  		if l == n.X && r == n.Index {
   440  			return n
   441  		}
   442  		a := ir.Copy(n).(*ir.IndexExpr)
   443  		a.X = l
   444  		a.Index = r
   445  		return walkExpr(typecheck.Expr(a), init)
   446  
   447  	case ir.OSTRUCTLIT, ir.OARRAYLIT, ir.OSLICELIT:
   448  		n := n.(*ir.CompLitExpr)
   449  		if isStaticCompositeLiteral(n) {
   450  			return n
   451  		}
   452  	}
   453  
   454  	// make a copy; must not be used as an lvalue
   455  	if ir.IsAddressable(n) {
   456  		base.Fatalf("missing lvalue case in safeExpr: %v", n)
   457  	}
   458  	return cheapExpr(n, init)
   459  }
   460  
   461  func copyExpr(n ir.Node, t *types.Type, init *ir.Nodes) ir.Node {
   462  	l := typecheck.TempAt(base.Pos, ir.CurFunc, t)
   463  	appendWalkStmt(init, ir.NewAssignStmt(base.Pos, l, n))
   464  	return l
   465  }
   466  
   467  func walkAddString(n *ir.AddStringExpr, init *ir.Nodes) ir.Node {
   468  	c := len(n.List)
   469  
   470  	if c < 2 {
   471  		base.Fatalf("walkAddString count %d too small", c)
   472  	}
   473  
   474  	buf := typecheck.NodNil()
   475  	if n.Esc() == ir.EscNone {
   476  		sz := int64(0)
   477  		for _, n1 := range n.List {
   478  			if n1.Op() == ir.OLITERAL {
   479  				sz += int64(len(ir.StringVal(n1)))
   480  			}
   481  		}
   482  
   483  		// Don't allocate the buffer if the result won't fit.
   484  		if sz < tmpstringbufsize {
   485  			// Create temporary buffer for result string on stack.
   486  			buf = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
   487  		}
   488  	}
   489  
   490  	// build list of string arguments
   491  	args := []ir.Node{buf}
   492  	for _, n2 := range n.List {
   493  		args = append(args, typecheck.Conv(n2, types.Types[types.TSTRING]))
   494  	}
   495  
   496  	var fn string
   497  	if c <= 5 {
   498  		// small numbers of strings use direct runtime helpers.
   499  		// note: order.expr knows this cutoff too.
   500  		fn = fmt.Sprintf("concatstring%d", c)
   501  	} else {
   502  		// large numbers of strings are passed to the runtime as a slice.
   503  		fn = "concatstrings"
   504  
   505  		t := types.NewSlice(types.Types[types.TSTRING])
   506  		// args[1:] to skip buf arg
   507  		slice := ir.NewCompLitExpr(base.Pos, ir.OCOMPLIT, t, args[1:])
   508  		slice.Prealloc = n.Prealloc
   509  		args = []ir.Node{buf, slice}
   510  		slice.SetEsc(ir.EscNone)
   511  	}
   512  
   513  	cat := typecheck.LookupRuntime(fn)
   514  	r := ir.NewCallExpr(base.Pos, ir.OCALL, cat, nil)
   515  	r.Args = args
   516  	r1 := typecheck.Expr(r)
   517  	r1 = walkExpr(r1, init)
   518  	r1.SetType(n.Type())
   519  
   520  	return r1
   521  }
   522  
   523  type hookInfo struct {
   524  	paramType   types.Kind
   525  	argsNum     int
   526  	runtimeFunc string
   527  }
   528  
   529  var hooks = map[string]hookInfo{
   530  	"strings.EqualFold": {paramType: types.TSTRING, argsNum: 2, runtimeFunc: "libfuzzerHookEqualFold"},
   531  }
   532  
   533  // walkCall walks an OCALLFUNC or OCALLINTER node.
   534  func walkCall(n *ir.CallExpr, init *ir.Nodes) ir.Node {
   535  	if n.Op() == ir.OCALLMETH {
   536  		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
   537  	}
   538  	if n.Op() == ir.OCALLINTER || n.Fun.Op() == ir.OMETHEXPR {
   539  		// We expect both interface call reflect.Type.Method and concrete
   540  		// call reflect.(*rtype).Method.
   541  		usemethod(n)
   542  	}
   543  	if n.Op() == ir.OCALLINTER {
   544  		reflectdata.MarkUsedIfaceMethod(n)
   545  	}
   546  
   547  	if n.Op() == ir.OCALLFUNC && n.Fun.Op() == ir.OCLOSURE {
   548  		directClosureCall(n)
   549  	}
   550  
   551  	if ir.IsFuncPCIntrinsic(n) {
   552  		// For internal/abi.FuncPCABIxxx(fn), if fn is a defined function, rewrite
   553  		// it to the address of the function of the ABI fn is defined.
   554  		name := n.Fun.(*ir.Name).Sym().Name
   555  		arg := n.Args[0]
   556  		var wantABI obj.ABI
   557  		switch name {
   558  		case "FuncPCABI0":
   559  			wantABI = obj.ABI0
   560  		case "FuncPCABIInternal":
   561  			wantABI = obj.ABIInternal
   562  		}
   563  		if n.Type() != types.Types[types.TUINTPTR] {
   564  			base.FatalfAt(n.Pos(), "FuncPC intrinsic should return uintptr, got %v", n.Type()) // as expected by typecheck.FuncPC.
   565  		}
   566  		n := ir.FuncPC(n.Pos(), arg, wantABI)
   567  		return walkExpr(n, init)
   568  	}
   569  
   570  	if name, ok := n.Fun.(*ir.Name); ok {
   571  		sym := name.Sym()
   572  		if sym.Pkg.Path == "go.runtime" && sym.Name == "deferrangefunc" {
   573  			// Call to runtime.deferrangefunc is being shared with a range-over-func
   574  			// body that might add defers to this frame, so we cannot use open-coded defers
   575  			// and we need to call deferreturn even if we don't see any other explicit defers.
   576  			ir.CurFunc.SetHasDefer(true)
   577  			ir.CurFunc.SetOpenCodedDeferDisallowed(true)
   578  		}
   579  	}
   580  
   581  	walkCall1(n, init)
   582  	return n
   583  }
   584  
   585  func walkCall1(n *ir.CallExpr, init *ir.Nodes) {
   586  	if n.Walked() {
   587  		return // already walked
   588  	}
   589  	n.SetWalked(true)
   590  
   591  	if n.Op() == ir.OCALLMETH {
   592  		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
   593  	}
   594  
   595  	args := n.Args
   596  	params := n.Fun.Type().Params()
   597  
   598  	n.Fun = walkExpr(n.Fun, init)
   599  	walkExprList(args, init)
   600  
   601  	for i, arg := range args {
   602  		// Validate argument and parameter types match.
   603  		param := params[i]
   604  		if !types.Identical(arg.Type(), param.Type) {
   605  			base.FatalfAt(n.Pos(), "assigning %L to parameter %v (type %v)", arg, param.Sym, param.Type)
   606  		}
   607  
   608  		// For any argument whose evaluation might require a function call,
   609  		// store that argument into a temporary variable,
   610  		// to prevent that calls from clobbering arguments already on the stack.
   611  		if mayCall(arg) {
   612  			// assignment of arg to Temp
   613  			tmp := typecheck.TempAt(base.Pos, ir.CurFunc, param.Type)
   614  			init.Append(convas(typecheck.Stmt(ir.NewAssignStmt(base.Pos, tmp, arg)).(*ir.AssignStmt), init))
   615  			// replace arg with temp
   616  			args[i] = tmp
   617  		}
   618  	}
   619  
   620  	funSym := n.Fun.Sym()
   621  	if base.Debug.Libfuzzer != 0 && funSym != nil {
   622  		if hook, found := hooks[funSym.Pkg.Path+"."+funSym.Name]; found {
   623  			if len(args) != hook.argsNum {
   624  				panic(fmt.Sprintf("%s.%s expects %d arguments, but received %d", funSym.Pkg.Path, funSym.Name, hook.argsNum, len(args)))
   625  			}
   626  			var hookArgs []ir.Node
   627  			for _, arg := range args {
   628  				hookArgs = append(hookArgs, tracecmpArg(arg, types.Types[hook.paramType], init))
   629  			}
   630  			hookArgs = append(hookArgs, fakePC(n))
   631  			init.Append(mkcall(hook.runtimeFunc, nil, init, hookArgs...))
   632  		}
   633  	}
   634  }
   635  
   636  // walkDivMod walks an ODIV or OMOD node.
   637  func walkDivMod(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
   638  	n.X = walkExpr(n.X, init)
   639  	n.Y = walkExpr(n.Y, init)
   640  
   641  	// rewrite complex div into function call.
   642  	et := n.X.Type().Kind()
   643  
   644  	if types.IsComplex[et] && n.Op() == ir.ODIV {
   645  		t := n.Type()
   646  		call := mkcall("complex128div", types.Types[types.TCOMPLEX128], init, typecheck.Conv(n.X, types.Types[types.TCOMPLEX128]), typecheck.Conv(n.Y, types.Types[types.TCOMPLEX128]))
   647  		return typecheck.Conv(call, t)
   648  	}
   649  
   650  	// Nothing to do for float divisions.
   651  	if types.IsFloat[et] {
   652  		return n
   653  	}
   654  
   655  	// rewrite 64-bit div and mod on 32-bit architectures.
   656  	// TODO: Remove this code once we can introduce
   657  	// runtime calls late in SSA processing.
   658  	if types.RegSize < 8 && (et == types.TINT64 || et == types.TUINT64) {
   659  		if n.Y.Op() == ir.OLITERAL {
   660  			// Leave div/mod by constant powers of 2 or small 16-bit constants.
   661  			// The SSA backend will handle those.
   662  			switch et {
   663  			case types.TINT64:
   664  				c := ir.Int64Val(n.Y)
   665  				if c < 0 {
   666  					c = -c
   667  				}
   668  				if c != 0 && c&(c-1) == 0 {
   669  					return n
   670  				}
   671  			case types.TUINT64:
   672  				c := ir.Uint64Val(n.Y)
   673  				if c < 1<<16 {
   674  					return n
   675  				}
   676  				if c != 0 && c&(c-1) == 0 {
   677  					return n
   678  				}
   679  			}
   680  		}
   681  		var fn string
   682  		if et == types.TINT64 {
   683  			fn = "int64"
   684  		} else {
   685  			fn = "uint64"
   686  		}
   687  		if n.Op() == ir.ODIV {
   688  			fn += "div"
   689  		} else {
   690  			fn += "mod"
   691  		}
   692  		return mkcall(fn, n.Type(), init, typecheck.Conv(n.X, types.Types[et]), typecheck.Conv(n.Y, types.Types[et]))
   693  	}
   694  	return n
   695  }
   696  
   697  // walkDot walks an ODOT or ODOTPTR node.
   698  func walkDot(n *ir.SelectorExpr, init *ir.Nodes) ir.Node {
   699  	usefield(n)
   700  	n.X = walkExpr(n.X, init)
   701  	return n
   702  }
   703  
   704  // walkDotType walks an ODOTTYPE or ODOTTYPE2 node.
   705  func walkDotType(n *ir.TypeAssertExpr, init *ir.Nodes) ir.Node {
   706  	n.X = walkExpr(n.X, init)
   707  	// Set up interface type addresses for back end.
   708  	if !n.Type().IsInterface() && !n.X.Type().IsEmptyInterface() {
   709  		n.ITab = reflectdata.ITabAddrAt(base.Pos, n.Type(), n.X.Type())
   710  	}
   711  	if n.X.Type().IsInterface() && n.Type().IsInterface() && !n.Type().IsEmptyInterface() {
   712  		// This kind of conversion needs a runtime call. Allocate
   713  		// a descriptor for that call.
   714  		n.Descriptor = makeTypeAssertDescriptor(n.Type(), n.Op() == ir.ODOTTYPE2)
   715  	}
   716  	return n
   717  }
   718  
   719  func makeTypeAssertDescriptor(target *types.Type, canFail bool) *obj.LSym {
   720  	// When converting from an interface to a non-empty interface. Needs a runtime call.
   721  	// Allocate an internal/abi.TypeAssert descriptor for that call.
   722  	lsym := types.LocalPkg.Lookup(fmt.Sprintf(".typeAssert.%d", typeAssertGen)).LinksymABI(obj.ABI0)
   723  	typeAssertGen++
   724  	c := rttype.NewCursor(lsym, 0, rttype.TypeAssert)
   725  	c.Field("Cache").WritePtr(typecheck.LookupRuntimeVar("emptyTypeAssertCache"))
   726  	c.Field("Inter").WritePtr(reflectdata.TypeLinksym(target))
   727  	c.Field("CanFail").WriteBool(canFail)
   728  	objw.Global(lsym, int32(rttype.TypeAssert.Size()), obj.LOCAL)
   729  	lsym.Gotype = reflectdata.TypeLinksym(rttype.TypeAssert)
   730  	return lsym
   731  }
   732  
   733  var typeAssertGen int
   734  
   735  // walkDynamicDotType walks an ODYNAMICDOTTYPE or ODYNAMICDOTTYPE2 node.
   736  func walkDynamicDotType(n *ir.DynamicTypeAssertExpr, init *ir.Nodes) ir.Node {
   737  	n.X = walkExpr(n.X, init)
   738  	n.RType = walkExpr(n.RType, init)
   739  	n.ITab = walkExpr(n.ITab, init)
   740  	// Convert to non-dynamic if we can.
   741  	if n.RType != nil && n.RType.Op() == ir.OADDR {
   742  		addr := n.RType.(*ir.AddrExpr)
   743  		if addr.X.Op() == ir.OLINKSYMOFFSET {
   744  			r := ir.NewTypeAssertExpr(n.Pos(), n.X, n.Type())
   745  			if n.Op() == ir.ODYNAMICDOTTYPE2 {
   746  				r.SetOp(ir.ODOTTYPE2)
   747  			}
   748  			r.SetType(n.Type())
   749  			r.SetTypecheck(1)
   750  			return walkExpr(r, init)
   751  		}
   752  	}
   753  	return n
   754  }
   755  
   756  // walkIndex walks an OINDEX node.
   757  func walkIndex(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
   758  	n.X = walkExpr(n.X, init)
   759  
   760  	// save the original node for bounds checking elision.
   761  	// If it was a ODIV/OMOD walk might rewrite it.
   762  	r := n.Index
   763  
   764  	n.Index = walkExpr(n.Index, init)
   765  
   766  	// if range of type cannot exceed static array bound,
   767  	// disable bounds check.
   768  	if n.Bounded() {
   769  		return n
   770  	}
   771  	t := n.X.Type()
   772  	if t != nil && t.IsPtr() {
   773  		t = t.Elem()
   774  	}
   775  	if t.IsArray() {
   776  		n.SetBounded(bounded(r, t.NumElem()))
   777  		if base.Flag.LowerM != 0 && n.Bounded() && !ir.IsConst(n.Index, constant.Int) {
   778  			base.Warn("index bounds check elided")
   779  		}
   780  	} else if ir.IsConst(n.X, constant.String) {
   781  		n.SetBounded(bounded(r, int64(len(ir.StringVal(n.X)))))
   782  		if base.Flag.LowerM != 0 && n.Bounded() && !ir.IsConst(n.Index, constant.Int) {
   783  			base.Warn("index bounds check elided")
   784  		}
   785  	}
   786  	return n
   787  }
   788  
   789  // mapKeyArg returns an expression for key that is suitable to be passed
   790  // as the key argument for runtime map* functions.
   791  // n is the map indexing or delete Node (to provide Pos).
   792  func mapKeyArg(fast int, n, key ir.Node, assigned bool) ir.Node {
   793  	if fast == mapslow {
   794  		// standard version takes key by reference.
   795  		// orderState.expr made sure key is addressable.
   796  		return typecheck.NodAddr(key)
   797  	}
   798  	if assigned {
   799  		// mapassign does distinguish pointer vs. integer key.
   800  		return key
   801  	}
   802  	// mapaccess and mapdelete don't distinguish pointer vs. integer key.
   803  	switch fast {
   804  	case mapfast32ptr:
   805  		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT32], key)
   806  	case mapfast64ptr:
   807  		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT64], key)
   808  	default:
   809  		// fast version takes key by value.
   810  		return key
   811  	}
   812  }
   813  
   814  // walkIndexMap walks an OINDEXMAP node.
   815  // It replaces m[k] with *map{access1,assign}(maptype, m, &k)
   816  func walkIndexMap(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
   817  	n.X = walkExpr(n.X, init)
   818  	n.Index = walkExpr(n.Index, init)
   819  	map_ := n.X
   820  	t := map_.Type()
   821  	fast := mapfast(t)
   822  	key := mapKeyArg(fast, n, n.Index, n.Assigned)
   823  	args := []ir.Node{reflectdata.IndexMapRType(base.Pos, n), map_, key}
   824  
   825  	var mapFn ir.Node
   826  	switch {
   827  	case n.Assigned:
   828  		mapFn = mapfn(mapassign[fast], t, false)
   829  	case t.Elem().Size() > abi.ZeroValSize:
   830  		args = append(args, reflectdata.ZeroAddr(t.Elem().Size()))
   831  		mapFn = mapfn("mapaccess1_fat", t, true)
   832  	default:
   833  		mapFn = mapfn(mapaccess1[fast], t, false)
   834  	}
   835  	call := mkcall1(mapFn, nil, init, args...)
   836  	call.SetType(types.NewPtr(t.Elem()))
   837  	call.MarkNonNil() // mapaccess1* and mapassign always return non-nil pointers.
   838  	star := ir.NewStarExpr(base.Pos, call)
   839  	star.SetType(t.Elem())
   840  	star.SetTypecheck(1)
   841  	return star
   842  }
   843  
   844  // walkLogical walks an OANDAND or OOROR node.
   845  func walkLogical(n *ir.LogicalExpr, init *ir.Nodes) ir.Node {
   846  	n.X = walkExpr(n.X, init)
   847  
   848  	// cannot put side effects from n.Right on init,
   849  	// because they cannot run before n.Left is checked.
   850  	// save elsewhere and store on the eventual n.Right.
   851  	var ll ir.Nodes
   852  
   853  	n.Y = walkExpr(n.Y, &ll)
   854  	n.Y = ir.InitExpr(ll, n.Y)
   855  	return n
   856  }
   857  
   858  // walkSend walks an OSEND node.
   859  func walkSend(n *ir.SendStmt, init *ir.Nodes) ir.Node {
   860  	n1 := n.Value
   861  	n1 = typecheck.AssignConv(n1, n.Chan.Type().Elem(), "chan send")
   862  	n1 = walkExpr(n1, init)
   863  	n1 = typecheck.NodAddr(n1)
   864  	return mkcall1(chanfn("chansend1", 2, n.Chan.Type()), nil, init, n.Chan, n1)
   865  }
   866  
   867  // walkSlice walks an OSLICE, OSLICEARR, OSLICESTR, OSLICE3, or OSLICE3ARR node.
   868  func walkSlice(n *ir.SliceExpr, init *ir.Nodes) ir.Node {
   869  	n.X = walkExpr(n.X, init)
   870  	n.Low = walkExpr(n.Low, init)
   871  	if n.Low != nil && ir.IsZero(n.Low) {
   872  		// Reduce x[0:j] to x[:j] and x[0:j:k] to x[:j:k].
   873  		n.Low = nil
   874  	}
   875  	n.High = walkExpr(n.High, init)
   876  	n.Max = walkExpr(n.Max, init)
   877  
   878  	if (n.Op() == ir.OSLICE || n.Op() == ir.OSLICESTR) && n.Low == nil && n.High == nil {
   879  		// Reduce x[:] to x.
   880  		if base.Debug.Slice > 0 {
   881  			base.Warn("slice: omit slice operation")
   882  		}
   883  		return n.X
   884  	}
   885  	return n
   886  }
   887  
   888  // walkSliceHeader walks an OSLICEHEADER node.
   889  func walkSliceHeader(n *ir.SliceHeaderExpr, init *ir.Nodes) ir.Node {
   890  	n.Ptr = walkExpr(n.Ptr, init)
   891  	n.Len = walkExpr(n.Len, init)
   892  	n.Cap = walkExpr(n.Cap, init)
   893  	return n
   894  }
   895  
   896  // walkStringHeader walks an OSTRINGHEADER node.
   897  func walkStringHeader(n *ir.StringHeaderExpr, init *ir.Nodes) ir.Node {
   898  	n.Ptr = walkExpr(n.Ptr, init)
   899  	n.Len = walkExpr(n.Len, init)
   900  	return n
   901  }
   902  
   903  // return 1 if integer n must be in range [0, max), 0 otherwise.
   904  func bounded(n ir.Node, max int64) bool {
   905  	if n.Type() == nil || !n.Type().IsInteger() {
   906  		return false
   907  	}
   908  
   909  	sign := n.Type().IsSigned()
   910  	bits := int32(8 * n.Type().Size())
   911  
   912  	if ir.IsSmallIntConst(n) {
   913  		v := ir.Int64Val(n)
   914  		return 0 <= v && v < max
   915  	}
   916  
   917  	switch n.Op() {
   918  	case ir.OAND, ir.OANDNOT:
   919  		n := n.(*ir.BinaryExpr)
   920  		v := int64(-1)
   921  		switch {
   922  		case ir.IsSmallIntConst(n.X):
   923  			v = ir.Int64Val(n.X)
   924  		case ir.IsSmallIntConst(n.Y):
   925  			v = ir.Int64Val(n.Y)
   926  			if n.Op() == ir.OANDNOT {
   927  				v = ^v
   928  				if !sign {
   929  					v &= 1<<uint(bits) - 1
   930  				}
   931  			}
   932  		}
   933  		if 0 <= v && v < max {
   934  			return true
   935  		}
   936  
   937  	case ir.OMOD:
   938  		n := n.(*ir.BinaryExpr)
   939  		if !sign && ir.IsSmallIntConst(n.Y) {
   940  			v := ir.Int64Val(n.Y)
   941  			if 0 <= v && v <= max {
   942  				return true
   943  			}
   944  		}
   945  
   946  	case ir.ODIV:
   947  		n := n.(*ir.BinaryExpr)
   948  		if !sign && ir.IsSmallIntConst(n.Y) {
   949  			v := ir.Int64Val(n.Y)
   950  			for bits > 0 && v >= 2 {
   951  				bits--
   952  				v >>= 1
   953  			}
   954  		}
   955  
   956  	case ir.ORSH:
   957  		n := n.(*ir.BinaryExpr)
   958  		if !sign && ir.IsSmallIntConst(n.Y) {
   959  			v := ir.Int64Val(n.Y)
   960  			if v > int64(bits) {
   961  				return true
   962  			}
   963  			bits -= int32(v)
   964  		}
   965  	}
   966  
   967  	if !sign && bits <= 62 && 1<<uint(bits) <= max {
   968  		return true
   969  	}
   970  
   971  	return false
   972  }
   973  
   974  // usemethod checks calls for uses of Method and MethodByName of reflect.Value,
   975  // reflect.Type, reflect.(*rtype), and reflect.(*interfaceType).
   976  func usemethod(n *ir.CallExpr) {
   977  	// Don't mark reflect.(*rtype).Method, etc. themselves in the reflect package.
   978  	// Those functions may be alive via the itab, which should not cause all methods
   979  	// alive. We only want to mark their callers.
   980  	if base.Ctxt.Pkgpath == "reflect" {
   981  		// TODO: is there a better way than hardcoding the names?
   982  		switch fn := ir.CurFunc.Nname.Sym().Name; {
   983  		case fn == "(*rtype).Method", fn == "(*rtype).MethodByName":
   984  			return
   985  		case fn == "(*interfaceType).Method", fn == "(*interfaceType).MethodByName":
   986  			return
   987  		case fn == "Value.Method", fn == "Value.MethodByName":
   988  			return
   989  		}
   990  	}
   991  
   992  	dot, ok := n.Fun.(*ir.SelectorExpr)
   993  	if !ok {
   994  		return
   995  	}
   996  
   997  	// looking for either direct method calls and interface method calls of:
   998  	//	reflect.Type.Method        - func(int) reflect.Method
   999  	//	reflect.Type.MethodByName  - func(string) (reflect.Method, bool)
  1000  	//
  1001  	//	reflect.Value.Method       - func(int) reflect.Value
  1002  	//	reflect.Value.MethodByName - func(string) reflect.Value
  1003  	methodName := dot.Sel.Name
  1004  	t := dot.Selection.Type
  1005  
  1006  	// Check the number of arguments and return values.
  1007  	if t.NumParams() != 1 || (t.NumResults() != 1 && t.NumResults() != 2) {
  1008  		return
  1009  	}
  1010  
  1011  	// Check the type of the argument.
  1012  	switch pKind := t.Param(0).Type.Kind(); {
  1013  	case methodName == "Method" && pKind == types.TINT,
  1014  		methodName == "MethodByName" && pKind == types.TSTRING:
  1015  
  1016  	default:
  1017  		// not a call to Method or MethodByName of reflect.{Type,Value}.
  1018  		return
  1019  	}
  1020  
  1021  	// Check that first result type is "reflect.Method" or "reflect.Value".
  1022  	// Note that we have to check sym name and sym package separately, as
  1023  	// we can't check for exact string "reflect.Method" reliably
  1024  	// (e.g., see #19028 and #38515).
  1025  	switch s := t.Result(0).Type.Sym(); {
  1026  	case s != nil && types.ReflectSymName(s) == "Method",
  1027  		s != nil && types.ReflectSymName(s) == "Value":
  1028  
  1029  	default:
  1030  		// not a call to Method or MethodByName of reflect.{Type,Value}.
  1031  		return
  1032  	}
  1033  
  1034  	var targetName ir.Node
  1035  	switch dot.Op() {
  1036  	case ir.ODOTINTER:
  1037  		if methodName == "MethodByName" {
  1038  			targetName = n.Args[0]
  1039  		}
  1040  	case ir.OMETHEXPR:
  1041  		if methodName == "MethodByName" {
  1042  			targetName = n.Args[1]
  1043  		}
  1044  	default:
  1045  		base.FatalfAt(dot.Pos(), "usemethod: unexpected dot.Op() %s", dot.Op())
  1046  	}
  1047  
  1048  	if ir.IsConst(targetName, constant.String) {
  1049  		name := constant.StringVal(targetName.Val())
  1050  
  1051  		r := obj.Addrel(ir.CurFunc.LSym)
  1052  		r.Type = objabi.R_USENAMEDMETHOD
  1053  		r.Sym = staticdata.StringSymNoCommon(name)
  1054  	} else {
  1055  		ir.CurFunc.LSym.Set(obj.AttrReflectMethod, true)
  1056  	}
  1057  }
  1058  
  1059  func usefield(n *ir.SelectorExpr) {
  1060  	if !buildcfg.Experiment.FieldTrack {
  1061  		return
  1062  	}
  1063  
  1064  	switch n.Op() {
  1065  	default:
  1066  		base.Fatalf("usefield %v", n.Op())
  1067  
  1068  	case ir.ODOT, ir.ODOTPTR:
  1069  		break
  1070  	}
  1071  
  1072  	field := n.Selection
  1073  	if field == nil {
  1074  		base.Fatalf("usefield %v %v without paramfld", n.X.Type(), n.Sel)
  1075  	}
  1076  	if field.Sym != n.Sel {
  1077  		base.Fatalf("field inconsistency: %v != %v", field.Sym, n.Sel)
  1078  	}
  1079  	if !strings.Contains(field.Note, "go:\"track\"") {
  1080  		return
  1081  	}
  1082  
  1083  	outer := n.X.Type()
  1084  	if outer.IsPtr() {
  1085  		outer = outer.Elem()
  1086  	}
  1087  	if outer.Sym() == nil {
  1088  		base.Errorf("tracked field must be in named struct type")
  1089  	}
  1090  
  1091  	sym := reflectdata.TrackSym(outer, field)
  1092  	if ir.CurFunc.FieldTrack == nil {
  1093  		ir.CurFunc.FieldTrack = make(map[*obj.LSym]struct{})
  1094  	}
  1095  	ir.CurFunc.FieldTrack[sym] = struct{}{}
  1096  }
  1097  

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