expr.go

     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.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, nil)
   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  // walkAddString walks a string concatenation expression x.
   468  // If conv is non nil, x is the conv.X field.
   469  func walkAddString(x *ir.AddStringExpr, init *ir.Nodes, conv *ir.ConvExpr) ir.Node {
   470  	c := len(x.List)
   471  	if c < 2 {
   472  		base.Fatalf("walkAddString count %d too small", c)
   473  	}
   474  
   475  	typ := x.Type()
   476  	if conv != nil {
   477  		typ = conv.Type()
   478  	}
   479  
   480  	// list of string arguments
   481  	var args []ir.Node
   482  
   483  	var fn, fnsmall, fnbig string
   484  
   485  	buf := typecheck.NodNil()
   486  	switch {
   487  	default:
   488  		base.FatalfAt(x.Pos(), "unexpected type: %v", typ)
   489  	case typ.IsString():
   490  		if x.Esc() == ir.EscNone {
   491  			sz := int64(0)
   492  			for _, n1 := range x.List {
   493  				if n1.Op() == ir.OLITERAL {
   494  					sz += int64(len(ir.StringVal(n1)))
   495  				}
   496  			}
   497  
   498  			// Don't allocate the buffer if the result won't fit.
   499  			if sz < tmpstringbufsize {
   500  				// Create temporary buffer for result string on stack.
   501  				buf = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
   502  			}
   503  		}
   504  
   505  		args = []ir.Node{buf}
   506  		fnsmall, fnbig = "concatstring%d", "concatstrings"
   507  	case typ.IsSlice() && typ.Elem().IsKind(types.TUINT8): // Optimize []byte(str1+str2+...)
   508  		if conv != nil && conv.Esc() == ir.EscNone {
   509  			buf = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
   510  		}
   511  		args = []ir.Node{buf}
   512  		fnsmall, fnbig = "concatbyte%d", "concatbytes"
   513  	}
   514  
   515  	if c <= 5 {
   516  		// small numbers of strings use direct runtime helpers.
   517  		// note: order.expr knows this cutoff too.
   518  		fn = fmt.Sprintf(fnsmall, c)
   519  
   520  		for _, n2 := range x.List {
   521  			args = append(args, typecheck.Conv(n2, types.Types[types.TSTRING]))
   522  		}
   523  	} else {
   524  		// large numbers of strings are passed to the runtime as a slice.
   525  		fn = fnbig
   526  		t := types.NewSlice(types.Types[types.TSTRING])
   527  
   528  		slargs := make([]ir.Node, len(x.List))
   529  		for i, n2 := range x.List {
   530  			slargs[i] = typecheck.Conv(n2, types.Types[types.TSTRING])
   531  		}
   532  		slice := ir.NewCompLitExpr(base.Pos, ir.OCOMPLIT, t, slargs)
   533  		slice.Prealloc = x.Prealloc
   534  		args = append(args, slice)
   535  		slice.SetEsc(ir.EscNone)
   536  	}
   537  
   538  	cat := typecheck.LookupRuntime(fn)
   539  	r := ir.NewCallExpr(base.Pos, ir.OCALL, cat, nil)
   540  	r.Args = args
   541  	r1 := typecheck.Expr(r)
   542  	r1 = walkExpr(r1, init)
   543  	r1.SetType(typ)
   544  
   545  	return r1
   546  }
   547  
   548  type hookInfo struct {
   549  	paramType   types.Kind
   550  	argsNum     int
   551  	runtimeFunc string
   552  }
   553  
   554  var hooks = map[string]hookInfo{
   555  	"strings.EqualFold": {paramType: types.TSTRING, argsNum: 2, runtimeFunc: "libfuzzerHookEqualFold"},
   556  }
   557  
   558  // walkCall walks an OCALLFUNC or OCALLINTER node.
   559  func walkCall(n *ir.CallExpr, init *ir.Nodes) ir.Node {
   560  	if n.Op() == ir.OCALLMETH {
   561  		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
   562  	}
   563  	if n.Op() == ir.OCALLINTER || n.Fun.Op() == ir.OMETHEXPR {
   564  		// We expect both interface call reflect.Type.Method and concrete
   565  		// call reflect.(*rtype).Method.
   566  		usemethod(n)
   567  	}
   568  	if n.Op() == ir.OCALLINTER {
   569  		reflectdata.MarkUsedIfaceMethod(n)
   570  	}
   571  
   572  	if n.Op() == ir.OCALLFUNC && n.Fun.Op() == ir.OCLOSURE {
   573  		directClosureCall(n)
   574  	}
   575  
   576  	if ir.IsFuncPCIntrinsic(n) {
   577  		// For internal/abi.FuncPCABIxxx(fn), if fn is a defined function, rewrite
   578  		// it to the address of the function of the ABI fn is defined.
   579  		name := n.Fun.(*ir.Name).Sym().Name
   580  		arg := n.Args[0]
   581  		var wantABI obj.ABI
   582  		switch name {
   583  		case "FuncPCABI0":
   584  			wantABI = obj.ABI0
   585  		case "FuncPCABIInternal":
   586  			wantABI = obj.ABIInternal
   587  		}
   588  		if n.Type() != types.Types[types.TUINTPTR] {
   589  			base.FatalfAt(n.Pos(), "FuncPC intrinsic should return uintptr, got %v", n.Type()) // as expected by typecheck.FuncPC.
   590  		}
   591  		n := ir.FuncPC(n.Pos(), arg, wantABI)
   592  		return walkExpr(n, init)
   593  	}
   594  
   595  	if n.Op() == ir.OCALLFUNC {
   596  		fn := ir.StaticCalleeName(n.Fun)
   597  		if fn != nil && fn.Sym().Pkg.Path == "hash/maphash" && strings.HasPrefix(fn.Sym().Name, "escapeForHash[") {
   598  			// hash/maphash.escapeForHash[T] is a compiler intrinsic
   599  			// for the escape analysis to escape its argument based on
   600  			// the type. The call itself is no-op. Just walk the
   601  			// argument.
   602  			ps := fn.Type().Params()
   603  			if len(ps) == 2 && ps[1].Type.IsShape() {
   604  				return walkExpr(n.Args[1], init)
   605  			}
   606  		}
   607  	}
   608  
   609  	if name, ok := n.Fun.(*ir.Name); ok {
   610  		sym := name.Sym()
   611  		if sym.Pkg.Path == "go.runtime" && sym.Name == "deferrangefunc" {
   612  			// Call to runtime.deferrangefunc is being shared with a range-over-func
   613  			// body that might add defers to this frame, so we cannot use open-coded defers
   614  			// and we need to call deferreturn even if we don't see any other explicit defers.
   615  			ir.CurFunc.SetHasDefer(true)
   616  			ir.CurFunc.SetOpenCodedDeferDisallowed(true)
   617  		}
   618  	}
   619  
   620  	walkCall1(n, init)
   621  	return n
   622  }
   623  
   624  func walkCall1(n *ir.CallExpr, init *ir.Nodes) {
   625  	if n.Walked() {
   626  		return // already walked
   627  	}
   628  	n.SetWalked(true)
   629  
   630  	if n.Op() == ir.OCALLMETH {
   631  		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
   632  	}
   633  
   634  	args := n.Args
   635  	params := n.Fun.Type().Params()
   636  
   637  	n.Fun = walkExpr(n.Fun, init)
   638  	walkExprList(args, init)
   639  
   640  	for i, arg := range args {
   641  		// Validate argument and parameter types match.
   642  		param := params[i]
   643  		if !types.Identical(arg.Type(), param.Type) {
   644  			base.FatalfAt(n.Pos(), "assigning %L to parameter %v (type %v)", arg, param.Sym, param.Type)
   645  		}
   646  
   647  		// For any argument whose evaluation might require a function call,
   648  		// store that argument into a temporary variable,
   649  		// to prevent that calls from clobbering arguments already on the stack.
   650  		if mayCall(arg) {
   651  			// assignment of arg to Temp
   652  			tmp := typecheck.TempAt(base.Pos, ir.CurFunc, param.Type)
   653  			init.Append(convas(typecheck.Stmt(ir.NewAssignStmt(base.Pos, tmp, arg)).(*ir.AssignStmt), init))
   654  			// replace arg with temp
   655  			args[i] = tmp
   656  		}
   657  	}
   658  
   659  	funSym := n.Fun.Sym()
   660  	if base.Debug.Libfuzzer != 0 && funSym != nil {
   661  		if hook, found := hooks[funSym.Pkg.Path+"."+funSym.Name]; found {
   662  			if len(args) != hook.argsNum {
   663  				panic(fmt.Sprintf("%s.%s expects %d arguments, but received %d", funSym.Pkg.Path, funSym.Name, hook.argsNum, len(args)))
   664  			}
   665  			var hookArgs []ir.Node
   666  			for _, arg := range args {
   667  				hookArgs = append(hookArgs, tracecmpArg(arg, types.Types[hook.paramType], init))
   668  			}
   669  			hookArgs = append(hookArgs, fakePC(n))
   670  			init.Append(mkcall(hook.runtimeFunc, nil, init, hookArgs...))
   671  		}
   672  	}
   673  }
   674  
   675  // walkDivMod walks an ODIV or OMOD node.
   676  func walkDivMod(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
   677  	n.X = walkExpr(n.X, init)
   678  	n.Y = walkExpr(n.Y, init)
   679  
   680  	// rewrite complex div into function call.
   681  	et := n.X.Type().Kind()
   682  
   683  	if types.IsComplex[et] && n.Op() == ir.ODIV {
   684  		t := n.Type()
   685  		call := mkcall("complex128div", types.Types[types.TCOMPLEX128], init, typecheck.Conv(n.X, types.Types[types.TCOMPLEX128]), typecheck.Conv(n.Y, types.Types[types.TCOMPLEX128]))
   686  		return typecheck.Conv(call, t)
   687  	}
   688  
   689  	// Nothing to do for float divisions.
   690  	if types.IsFloat[et] {
   691  		return n
   692  	}
   693  
   694  	// rewrite 64-bit div and mod on 32-bit architectures.
   695  	// TODO: Remove this code once we can introduce
   696  	// runtime calls late in SSA processing.
   697  	if types.RegSize < 8 && (et == types.TINT64 || et == types.TUINT64) {
   698  		if n.Y.Op() == ir.OLITERAL {
   699  			// Leave div/mod by constant powers of 2 or small 16-bit constants.
   700  			// The SSA backend will handle those.
   701  			switch et {
   702  			case types.TINT64:
   703  				c := ir.Int64Val(n.Y)
   704  				if c < 0 {
   705  					c = -c
   706  				}
   707  				if c != 0 && c&(c-1) == 0 {
   708  					return n
   709  				}
   710  			case types.TUINT64:
   711  				c := ir.Uint64Val(n.Y)
   712  				if c < 1<<16 {
   713  					return n
   714  				}
   715  				if c != 0 && c&(c-1) == 0 {
   716  					return n
   717  				}
   718  			}
   719  		}
   720  		var fn string
   721  		if et == types.TINT64 {
   722  			fn = "int64"
   723  		} else {
   724  			fn = "uint64"
   725  		}
   726  		if n.Op() == ir.ODIV {
   727  			fn += "div"
   728  		} else {
   729  			fn += "mod"
   730  		}
   731  		return mkcall(fn, n.Type(), init, typecheck.Conv(n.X, types.Types[et]), typecheck.Conv(n.Y, types.Types[et]))
   732  	}
   733  	return n
   734  }
   735  
   736  // walkDot walks an ODOT or ODOTPTR node.
   737  func walkDot(n *ir.SelectorExpr, init *ir.Nodes) ir.Node {
   738  	usefield(n)
   739  	n.X = walkExpr(n.X, init)
   740  	return n
   741  }
   742  
   743  // walkDotType walks an ODOTTYPE or ODOTTYPE2 node.
   744  func walkDotType(n *ir.TypeAssertExpr, init *ir.Nodes) ir.Node {
   745  	n.X = walkExpr(n.X, init)
   746  	// Set up interface type addresses for back end.
   747  	if !n.Type().IsInterface() && !n.X.Type().IsEmptyInterface() {
   748  		n.ITab = reflectdata.ITabAddrAt(base.Pos, n.Type(), n.X.Type())
   749  	}
   750  	if n.X.Type().IsInterface() && n.Type().IsInterface() && !n.Type().IsEmptyInterface() {
   751  		// This kind of conversion needs a runtime call. Allocate
   752  		// a descriptor for that call.
   753  		n.Descriptor = makeTypeAssertDescriptor(n.Type(), n.Op() == ir.ODOTTYPE2)
   754  	}
   755  	return n
   756  }
   757  
   758  func makeTypeAssertDescriptor(target *types.Type, canFail bool) *obj.LSym {
   759  	// When converting from an interface to a non-empty interface. Needs a runtime call.
   760  	// Allocate an internal/abi.TypeAssert descriptor for that call.
   761  	lsym := types.LocalPkg.Lookup(fmt.Sprintf(".typeAssert.%d", typeAssertGen)).LinksymABI(obj.ABI0)
   762  	typeAssertGen++
   763  	c := rttype.NewCursor(lsym, 0, rttype.TypeAssert)
   764  	c.Field("Cache").WritePtr(typecheck.LookupRuntimeVar("emptyTypeAssertCache"))
   765  	c.Field("Inter").WritePtr(reflectdata.TypeLinksym(target))
   766  	c.Field("CanFail").WriteBool(canFail)
   767  	objw.Global(lsym, int32(rttype.TypeAssert.Size()), obj.LOCAL)
   768  	lsym.Gotype = reflectdata.TypeLinksym(rttype.TypeAssert)
   769  	return lsym
   770  }
   771  
   772  var typeAssertGen int
   773  
   774  // walkDynamicDotType walks an ODYNAMICDOTTYPE or ODYNAMICDOTTYPE2 node.
   775  func walkDynamicDotType(n *ir.DynamicTypeAssertExpr, init *ir.Nodes) ir.Node {
   776  	n.X = walkExpr(n.X, init)
   777  	n.RType = walkExpr(n.RType, init)
   778  	n.ITab = walkExpr(n.ITab, init)
   779  	// Convert to non-dynamic if we can.
   780  	if n.RType != nil && n.RType.Op() == ir.OADDR {
   781  		addr := n.RType.(*ir.AddrExpr)
   782  		if addr.X.Op() == ir.OLINKSYMOFFSET {
   783  			r := ir.NewTypeAssertExpr(n.Pos(), n.X, n.Type())
   784  			if n.Op() == ir.ODYNAMICDOTTYPE2 {
   785  				r.SetOp(ir.ODOTTYPE2)
   786  			}
   787  			r.SetType(n.Type())
   788  			r.SetTypecheck(1)
   789  			return walkExpr(r, init)
   790  		}
   791  	}
   792  	return n
   793  }
   794  
   795  // walkIndex walks an OINDEX node.
   796  func walkIndex(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
   797  	n.X = walkExpr(n.X, init)
   798  
   799  	// save the original node for bounds checking elision.
   800  	// If it was a ODIV/OMOD walk might rewrite it.
   801  	r := n.Index
   802  
   803  	n.Index = walkExpr(n.Index, init)
   804  
   805  	// if range of type cannot exceed static array bound,
   806  	// disable bounds check.
   807  	if n.Bounded() {
   808  		return n
   809  	}
   810  	t := n.X.Type()
   811  	if t != nil && t.IsPtr() {
   812  		t = t.Elem()
   813  	}
   814  	if t.IsArray() {
   815  		n.SetBounded(bounded(r, t.NumElem()))
   816  		if base.Flag.LowerM != 0 && n.Bounded() && !ir.IsConst(n.Index, constant.Int) {
   817  			base.Warn("index bounds check elided")
   818  		}
   819  	} else if ir.IsConst(n.X, constant.String) {
   820  		n.SetBounded(bounded(r, int64(len(ir.StringVal(n.X)))))
   821  		if base.Flag.LowerM != 0 && n.Bounded() && !ir.IsConst(n.Index, constant.Int) {
   822  			base.Warn("index bounds check elided")
   823  		}
   824  	}
   825  	return n
   826  }
   827  
   828  // mapKeyArg returns an expression for key that is suitable to be passed
   829  // as the key argument for runtime map* functions.
   830  // n is the map indexing or delete Node (to provide Pos).
   831  func mapKeyArg(fast int, n, key ir.Node, assigned bool) ir.Node {
   832  	if fast == mapslow {
   833  		// standard version takes key by reference.
   834  		// orderState.expr made sure key is addressable.
   835  		return typecheck.NodAddr(key)
   836  	}
   837  	if assigned {
   838  		// mapassign does distinguish pointer vs. integer key.
   839  		return key
   840  	}
   841  	// mapaccess and mapdelete don't distinguish pointer vs. integer key.
   842  	switch fast {
   843  	case mapfast32ptr:
   844  		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT32], key)
   845  	case mapfast64ptr:
   846  		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT64], key)
   847  	default:
   848  		// fast version takes key by value.
   849  		return key
   850  	}
   851  }
   852  
   853  // walkIndexMap walks an OINDEXMAP node.
   854  // It replaces m[k] with *map{access1,assign}(maptype, m, &k)
   855  func walkIndexMap(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
   856  	n.X = walkExpr(n.X, init)
   857  	n.Index = walkExpr(n.Index, init)
   858  	map_ := n.X
   859  	t := map_.Type()
   860  	fast := mapfast(t)
   861  	key := mapKeyArg(fast, n, n.Index, n.Assigned)
   862  	args := []ir.Node{reflectdata.IndexMapRType(base.Pos, n), map_, key}
   863  
   864  	var mapFn ir.Node
   865  	switch {
   866  	case n.Assigned:
   867  		mapFn = mapfn(mapassign[fast], t, false)
   868  	case t.Elem().Size() > abi.ZeroValSize:
   869  		args = append(args, reflectdata.ZeroAddr(t.Elem().Size()))
   870  		mapFn = mapfn("mapaccess1_fat", t, true)
   871  	default:
   872  		mapFn = mapfn(mapaccess1[fast], t, false)
   873  	}
   874  	call := mkcall1(mapFn, nil, init, args...)
   875  	call.SetType(types.NewPtr(t.Elem()))
   876  	call.MarkNonNil() // mapaccess1* and mapassign always return non-nil pointers.
   877  	star := ir.NewStarExpr(base.Pos, call)
   878  	star.SetType(t.Elem())
   879  	star.SetTypecheck(1)
   880  	return star
   881  }
   882  
   883  // walkLogical walks an OANDAND or OOROR node.
   884  func walkLogical(n *ir.LogicalExpr, init *ir.Nodes) ir.Node {
   885  	n.X = walkExpr(n.X, init)
   886  
   887  	// cannot put side effects from n.Right on init,
   888  	// because they cannot run before n.Left is checked.
   889  	// save elsewhere and store on the eventual n.Right.
   890  	var ll ir.Nodes
   891  
   892  	n.Y = walkExpr(n.Y, &ll)
   893  	n.Y = ir.InitExpr(ll, n.Y)
   894  	return n
   895  }
   896  
   897  // walkSend walks an OSEND node.
   898  func walkSend(n *ir.SendStmt, init *ir.Nodes) ir.Node {
   899  	n1 := n.Value
   900  	n1 = typecheck.AssignConv(n1, n.Chan.Type().Elem(), "chan send")
   901  	n1 = walkExpr(n1, init)
   902  	n1 = typecheck.NodAddr(n1)
   903  	return mkcall1(chanfn("chansend1", 2, n.Chan.Type()), nil, init, n.Chan, n1)
   904  }
   905  
   906  // walkSlice walks an OSLICE, OSLICEARR, OSLICESTR, OSLICE3, or OSLICE3ARR node.
   907  func walkSlice(n *ir.SliceExpr, init *ir.Nodes) ir.Node {
   908  	n.X = walkExpr(n.X, init)
   909  	n.Low = walkExpr(n.Low, init)
   910  	if n.Low != nil && ir.IsZero(n.Low) {
   911  		// Reduce x[0:j] to x[:j] and x[0:j:k] to x[:j:k].
   912  		n.Low = nil
   913  	}
   914  	n.High = walkExpr(n.High, init)
   915  	n.Max = walkExpr(n.Max, init)
   916  
   917  	if (n.Op() == ir.OSLICE || n.Op() == ir.OSLICESTR) && n.Low == nil && n.High == nil {
   918  		// Reduce x[:] to x.
   919  		if base.Debug.Slice > 0 {
   920  			base.Warn("slice: omit slice operation")
   921  		}
   922  		return n.X
   923  	}
   924  	return n
   925  }
   926  
   927  // walkSliceHeader walks an OSLICEHEADER node.
   928  func walkSliceHeader(n *ir.SliceHeaderExpr, init *ir.Nodes) ir.Node {
   929  	n.Ptr = walkExpr(n.Ptr, init)
   930  	n.Len = walkExpr(n.Len, init)
   931  	n.Cap = walkExpr(n.Cap, init)
   932  	return n
   933  }
   934  
   935  // walkStringHeader walks an OSTRINGHEADER node.
   936  func walkStringHeader(n *ir.StringHeaderExpr, init *ir.Nodes) ir.Node {
   937  	n.Ptr = walkExpr(n.Ptr, init)
   938  	n.Len = walkExpr(n.Len, init)
   939  	return n
   940  }
   941  
   942  // return 1 if integer n must be in range [0, max), 0 otherwise.
   943  func bounded(n ir.Node, max int64) bool {
   944  	if n.Type() == nil || !n.Type().IsInteger() {
   945  		return false
   946  	}
   947  
   948  	sign := n.Type().IsSigned()
   949  	bits := int32(8 * n.Type().Size())
   950  
   951  	if ir.IsSmallIntConst(n) {
   952  		v := ir.Int64Val(n)
   953  		return 0 <= v && v < max
   954  	}
   955  
   956  	switch n.Op() {
   957  	case ir.OAND, ir.OANDNOT:
   958  		n := n.(*ir.BinaryExpr)
   959  		v := int64(-1)
   960  		switch {
   961  		case ir.IsSmallIntConst(n.X):
   962  			v = ir.Int64Val(n.X)
   963  		case ir.IsSmallIntConst(n.Y):
   964  			v = ir.Int64Val(n.Y)
   965  			if n.Op() == ir.OANDNOT {
   966  				v = ^v
   967  				if !sign {
   968  					v &= 1<<uint(bits) - 1
   969  				}
   970  			}
   971  		}
   972  		if 0 <= v && v < max {
   973  			return true
   974  		}
   975  
   976  	case ir.OMOD:
   977  		n := n.(*ir.BinaryExpr)
   978  		if !sign && ir.IsSmallIntConst(n.Y) {
   979  			v := ir.Int64Val(n.Y)
   980  			if 0 <= v && v <= max {
   981  				return true
   982  			}
   983  		}
   984  
   985  	case ir.ODIV:
   986  		n := n.(*ir.BinaryExpr)
   987  		if !sign && ir.IsSmallIntConst(n.Y) {
   988  			v := ir.Int64Val(n.Y)
   989  			for bits > 0 && v >= 2 {
   990  				bits--
   991  				v >>= 1
   992  			}
   993  		}
   994  
   995  	case ir.ORSH:
   996  		n := n.(*ir.BinaryExpr)
   997  		if !sign && ir.IsSmallIntConst(n.Y) {
   998  			v := ir.Int64Val(n.Y)
   999  			if v > int64(bits) {
  1000  				return true
  1001  			}
  1002  			bits -= int32(v)
  1003  		}
  1004  	}
  1005  
  1006  	if !sign && bits <= 62 && 1<<uint(bits) <= max {
  1007  		return true
  1008  	}
  1009  
  1010  	return false
  1011  }
  1012  
  1013  // usemethod checks calls for uses of Method and MethodByName of reflect.Value,
  1014  // reflect.Type, reflect.(*rtype), and reflect.(*interfaceType).
  1015  func usemethod(n *ir.CallExpr) {
  1016  	// Don't mark reflect.(*rtype).Method, etc. themselves in the reflect package.
  1017  	// Those functions may be alive via the itab, which should not cause all methods
  1018  	// alive. We only want to mark their callers.
  1019  	if base.Ctxt.Pkgpath == "reflect" {
  1020  		// TODO: is there a better way than hardcoding the names?
  1021  		switch fn := ir.CurFunc.Nname.Sym().Name; {
  1022  		case fn == "(*rtype).Method", fn == "(*rtype).MethodByName":
  1023  			return
  1024  		case fn == "(*interfaceType).Method", fn == "(*interfaceType).MethodByName":
  1025  			return
  1026  		case fn == "Value.Method", fn == "Value.MethodByName":
  1027  			return
  1028  		}
  1029  	}
  1030  
  1031  	dot, ok := n.Fun.(*ir.SelectorExpr)
  1032  	if !ok {
  1033  		return
  1034  	}
  1035  
  1036  	// looking for either direct method calls and interface method calls of:
  1037  	//	reflect.Type.Method        - func(int) reflect.Method
  1038  	//	reflect.Type.MethodByName  - func(string) (reflect.Method, bool)
  1039  	//
  1040  	//	reflect.Value.Method       - func(int) reflect.Value
  1041  	//	reflect.Value.MethodByName - func(string) reflect.Value
  1042  	methodName := dot.Sel.Name
  1043  	t := dot.Selection.Type
  1044  
  1045  	// Check the number of arguments and return values.
  1046  	if t.NumParams() != 1 || (t.NumResults() != 1 && t.NumResults() != 2) {
  1047  		return
  1048  	}
  1049  
  1050  	// Check the type of the argument.
  1051  	switch pKind := t.Param(0).Type.Kind(); {
  1052  	case methodName == "Method" && pKind == types.TINT,
  1053  		methodName == "MethodByName" && pKind == types.TSTRING:
  1054  
  1055  	default:
  1056  		// not a call to Method or MethodByName of reflect.{Type,Value}.
  1057  		return
  1058  	}
  1059  
  1060  	// Check that first result type is "reflect.Method" or "reflect.Value".
  1061  	// Note that we have to check sym name and sym package separately, as
  1062  	// we can't check for exact string "reflect.Method" reliably
  1063  	// (e.g., see #19028 and #38515).
  1064  	switch s := t.Result(0).Type.Sym(); {
  1065  	case s != nil && types.ReflectSymName(s) == "Method",
  1066  		s != nil && types.ReflectSymName(s) == "Value":
  1067  
  1068  	default:
  1069  		// not a call to Method or MethodByName of reflect.{Type,Value}.
  1070  		return
  1071  	}
  1072  
  1073  	var targetName ir.Node
  1074  	switch dot.Op() {
  1075  	case ir.ODOTINTER:
  1076  		if methodName == "MethodByName" {
  1077  			targetName = n.Args[0]
  1078  		}
  1079  	case ir.OMETHEXPR:
  1080  		if methodName == "MethodByName" {
  1081  			targetName = n.Args[1]
  1082  		}
  1083  	default:
  1084  		base.FatalfAt(dot.Pos(), "usemethod: unexpected dot.Op() %s", dot.Op())
  1085  	}
  1086  
  1087  	if ir.IsConst(targetName, constant.String) {
  1088  		name := constant.StringVal(targetName.Val())
  1089  		ir.CurFunc.LSym.AddRel(base.Ctxt, obj.Reloc{
  1090  			Type: objabi.R_USENAMEDMETHOD,
  1091  			Sym:  staticdata.StringSymNoCommon(name),
  1092  		})
  1093  	} else {
  1094  		ir.CurFunc.LSym.Set(obj.AttrReflectMethod, true)
  1095  	}
  1096  }
  1097  
  1098  func usefield(n *ir.SelectorExpr) {
  1099  	if !buildcfg.Experiment.FieldTrack {
  1100  		return
  1101  	}
  1102  
  1103  	switch n.Op() {
  1104  	default:
  1105  		base.Fatalf("usefield %v", n.Op())
  1106  
  1107  	case ir.ODOT, ir.ODOTPTR:
  1108  		break
  1109  	}
  1110  
  1111  	field := n.Selection
  1112  	if field == nil {
  1113  		base.Fatalf("usefield %v %v without paramfld", n.X.Type(), n.Sel)
  1114  	}
  1115  	if field.Sym != n.Sel {
  1116  		base.Fatalf("field inconsistency: %v != %v", field.Sym, n.Sel)
  1117  	}
  1118  	if !strings.Contains(field.Note, "go:\"track\"") {
  1119  		return
  1120  	}
  1121  
  1122  	outer := n.X.Type()
  1123  	if outer.IsPtr() {
  1124  		outer = outer.Elem()
  1125  	}
  1126  	if outer.Sym() == nil {
  1127  		base.Errorf("tracked field must be in named struct type")
  1128  	}
  1129  
  1130  	sym := reflectdata.TrackSym(outer, field)
  1131  	if ir.CurFunc.FieldTrack == nil {
  1132  		ir.CurFunc.FieldTrack = make(map[*obj.LSym]struct{})
  1133  	}
  1134  	ir.CurFunc.FieldTrack[sym] = struct{}{}
  1135  }
  1136
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