dwarf.go

Documentation: cmd/compile/internal/dwarfgen

     1  // Copyright 2011 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 dwarfgen
     6  
     7  import (
     8  	"bytes"
     9  	"flag"
    10  	"fmt"
    11  	"internal/buildcfg"
    12  	"sort"
    13  
    14  	"cmd/compile/internal/base"
    15  	"cmd/compile/internal/ir"
    16  	"cmd/compile/internal/reflectdata"
    17  	"cmd/compile/internal/ssa"
    18  	"cmd/compile/internal/ssagen"
    19  	"cmd/compile/internal/types"
    20  	"cmd/internal/dwarf"
    21  	"cmd/internal/obj"
    22  	"cmd/internal/objabi"
    23  	"cmd/internal/src"
    24  )
    25  
    26  func Info(fnsym *obj.LSym, infosym *obj.LSym, curfn obj.Func) (scopes []dwarf.Scope, inlcalls dwarf.InlCalls) {
    27  	fn := curfn.(*ir.Func)
    28  
    29  	if fn.Nname != nil {
    30  		expect := fn.Linksym()
    31  		if fnsym.ABI() == obj.ABI0 {
    32  			expect = fn.LinksymABI(obj.ABI0)
    33  		}
    34  		if fnsym != expect {
    35  			base.Fatalf("unexpected fnsym: %v != %v", fnsym, expect)
    36  		}
    37  	}
    38  
    39  	// Back when there were two different *Funcs for a function, this code
    40  	// was not consistent about whether a particular *Node being processed
    41  	// was an ODCLFUNC or ONAME node. Partly this is because inlined function
    42  	// bodies have no ODCLFUNC node, which was it's own inconsistency.
    43  	// In any event, the handling of the two different nodes for DWARF purposes
    44  	// was subtly different, likely in unintended ways. CL 272253 merged the
    45  	// two nodes' Func fields, so that code sees the same *Func whether it is
    46  	// holding the ODCLFUNC or the ONAME. This resulted in changes in the
    47  	// DWARF output. To preserve the existing DWARF output and leave an
    48  	// intentional change for a future CL, this code does the following when
    49  	// fn.Op == ONAME:
    50  	//
    51  	// 1. Disallow use of createComplexVars in createDwarfVars.
    52  	//    It was not possible to reach that code for an ONAME before,
    53  	//    because the DebugInfo was set only on the ODCLFUNC Func.
    54  	//    Calling into it in the ONAME case causes an index out of bounds panic.
    55  	//
    56  	// 2. Do not populate apdecls. fn.Func.Dcl was in the ODCLFUNC Func,
    57  	//    not the ONAME Func. Populating apdecls for the ONAME case results
    58  	//    in selected being populated after createSimpleVars is called in
    59  	//    createDwarfVars, and then that causes the loop to skip all the entries
    60  	//    in dcl, meaning that the RecordAutoType calls don't happen.
    61  	//
    62  	// These two adjustments keep toolstash -cmp working for now.
    63  	// Deciding the right answer is, as they say, future work.
    64  	//
    65  	// We can tell the difference between the old ODCLFUNC and ONAME
    66  	// cases by looking at the infosym.Name. If it's empty, DebugInfo is
    67  	// being called from (*obj.Link).populateDWARF, which used to use
    68  	// the ODCLFUNC. If it's non-empty (the name will end in $abstract),
    69  	// DebugInfo is being called from (*obj.Link).DwarfAbstractFunc,
    70  	// which used to use the ONAME form.
    71  	isODCLFUNC := infosym.Name == ""
    72  
    73  	var apdecls []*ir.Name
    74  	// Populate decls for fn.
    75  	if isODCLFUNC {
    76  		for _, n := range fn.Dcl {
    77  			if n.Op() != ir.ONAME { // might be OTYPE or OLITERAL
    78  				continue
    79  			}
    80  			switch n.Class {
    81  			case ir.PAUTO:
    82  				if !n.Used() {
    83  					// Text == nil -> generating abstract function
    84  					if fnsym.Func().Text != nil {
    85  						base.Fatalf("debuginfo unused node (AllocFrame should truncate fn.Func.Dcl)")
    86  					}
    87  					continue
    88  				}
    89  			case ir.PPARAM, ir.PPARAMOUT:
    90  			default:
    91  				continue
    92  			}
    93  			apdecls = append(apdecls, n)
    94  			if n.Type().Kind() == types.TSSA {
    95  				// Can happen for TypeInt128 types. This only happens for
    96  				// spill locations, so not a huge deal.
    97  				continue
    98  			}
    99  			fnsym.Func().RecordAutoType(reflectdata.TypeLinksym(n.Type()))
   100  		}
   101  	}
   102  
   103  	decls, dwarfVars := createDwarfVars(fnsym, isODCLFUNC, fn, apdecls)
   104  
   105  	// For each type referenced by the functions auto vars but not
   106  	// already referenced by a dwarf var, attach an R_USETYPE relocation to
   107  	// the function symbol to insure that the type included in DWARF
   108  	// processing during linking.
   109  	typesyms := []*obj.LSym{}
   110  	for t := range fnsym.Func().Autot {
   111  		typesyms = append(typesyms, t)
   112  	}
   113  	sort.Sort(obj.BySymName(typesyms))
   114  	for _, sym := range typesyms {
   115  		r := obj.Addrel(infosym)
   116  		r.Sym = sym
   117  		r.Type = objabi.R_USETYPE
   118  	}
   119  	fnsym.Func().Autot = nil
   120  
   121  	var varScopes []ir.ScopeID
   122  	for _, decl := range decls {
   123  		pos := declPos(decl)
   124  		varScopes = append(varScopes, findScope(fn.Marks, pos))
   125  	}
   126  
   127  	scopes = assembleScopes(fnsym, fn, dwarfVars, varScopes)
   128  	if base.Flag.GenDwarfInl > 0 {
   129  		inlcalls = assembleInlines(fnsym, dwarfVars)
   130  	}
   131  	return scopes, inlcalls
   132  }
   133  
   134  func declPos(decl *ir.Name) src.XPos {
   135  	return decl.Canonical().Pos()
   136  }
   137  
   138  // createDwarfVars process fn, returning a list of DWARF variables and the
   139  // Nodes they represent.
   140  func createDwarfVars(fnsym *obj.LSym, complexOK bool, fn *ir.Func, apDecls []*ir.Name) ([]*ir.Name, []*dwarf.Var) {
   141  	// Collect a raw list of DWARF vars.
   142  	var vars []*dwarf.Var
   143  	var decls []*ir.Name
   144  	var selected ir.NameSet
   145  
   146  	if base.Ctxt.Flag_locationlists && base.Ctxt.Flag_optimize && fn.DebugInfo != nil && complexOK {
   147  		decls, vars, selected = createComplexVars(fnsym, fn)
   148  	} else if fn.ABI == obj.ABIInternal && base.Flag.N != 0 && complexOK {
   149  		decls, vars, selected = createABIVars(fnsym, fn, apDecls)
   150  	} else {
   151  		decls, vars, selected = createSimpleVars(fnsym, apDecls)
   152  	}
   153  	if fn.DebugInfo != nil {
   154  		// Recover zero sized variables eliminated by the stackframe pass
   155  		for _, n := range fn.DebugInfo.(*ssa.FuncDebug).OptDcl {
   156  			if n.Class != ir.PAUTO {
   157  				continue
   158  			}
   159  			types.CalcSize(n.Type())
   160  			if n.Type().Size() == 0 {
   161  				decls = append(decls, n)
   162  				vars = append(vars, createSimpleVar(fnsym, n))
   163  				vars[len(vars)-1].StackOffset = 0
   164  				fnsym.Func().RecordAutoType(reflectdata.TypeLinksym(n.Type()))
   165  			}
   166  		}
   167  	}
   168  
   169  	dcl := apDecls
   170  	if fnsym.WasInlined() {
   171  		dcl = preInliningDcls(fnsym)
   172  	} else {
   173  		// The backend's stackframe pass prunes away entries from the
   174  		// fn's Dcl list, including PARAMOUT nodes that correspond to
   175  		// output params passed in registers. Add back in these
   176  		// entries here so that we can process them properly during
   177  		// DWARF-gen. See issue 48573 for more details.
   178  		debugInfo := fn.DebugInfo.(*ssa.FuncDebug)
   179  		for _, n := range debugInfo.RegOutputParams {
   180  			if n.Class != ir.PPARAMOUT || !n.IsOutputParamInRegisters() {
   181  				panic("invalid ir.Name on debugInfo.RegOutputParams list")
   182  			}
   183  			dcl = append(dcl, n)
   184  		}
   185  	}
   186  
   187  	// If optimization is enabled, the list above will typically be
   188  	// missing some of the original pre-optimization variables in the
   189  	// function (they may have been promoted to registers, folded into
   190  	// constants, dead-coded away, etc).  Input arguments not eligible
   191  	// for SSA optimization are also missing.  Here we add back in entries
   192  	// for selected missing vars. Note that the recipe below creates a
   193  	// conservative location. The idea here is that we want to
   194  	// communicate to the user that "yes, there is a variable named X
   195  	// in this function, but no, I don't have enough information to
   196  	// reliably report its contents."
   197  	// For non-SSA-able arguments, however, the correct information
   198  	// is known -- they have a single home on the stack.
   199  	for _, n := range dcl {
   200  		if selected.Has(n) {
   201  			continue
   202  		}
   203  		c := n.Sym().Name[0]
   204  		if c == '.' || n.Type().IsUntyped() {
   205  			continue
   206  		}
   207  		if n.Class == ir.PPARAM && !ssa.CanSSA(n.Type()) {
   208  			// SSA-able args get location lists, and may move in and
   209  			// out of registers, so those are handled elsewhere.
   210  			// Autos and named output params seem to get handled
   211  			// with VARDEF, which creates location lists.
   212  			// Args not of SSA-able type are treated here; they
   213  			// are homed on the stack in a single place for the
   214  			// entire call.
   215  			vars = append(vars, createSimpleVar(fnsym, n))
   216  			decls = append(decls, n)
   217  			continue
   218  		}
   219  		typename := dwarf.InfoPrefix + types.TypeSymName(n.Type())
   220  		decls = append(decls, n)
   221  		abbrev := dwarf.DW_ABRV_AUTO_LOCLIST
   222  		isReturnValue := (n.Class == ir.PPARAMOUT)
   223  		if n.Class == ir.PPARAM || n.Class == ir.PPARAMOUT {
   224  			abbrev = dwarf.DW_ABRV_PARAM_LOCLIST
   225  		}
   226  		if n.Esc() == ir.EscHeap {
   227  			// The variable in question has been promoted to the heap.
   228  			// Its address is in n.Heapaddr.
   229  			// TODO(thanm): generate a better location expression
   230  		}
   231  		inlIndex := 0
   232  		if base.Flag.GenDwarfInl > 1 {
   233  			if n.InlFormal() || n.InlLocal() {
   234  				inlIndex = posInlIndex(n.Pos()) + 1
   235  				if n.InlFormal() {
   236  					abbrev = dwarf.DW_ABRV_PARAM_LOCLIST
   237  				}
   238  			}
   239  		}
   240  		declpos := base.Ctxt.InnermostPos(n.Pos())
   241  		vars = append(vars, &dwarf.Var{
   242  			Name:          n.Sym().Name,
   243  			IsReturnValue: isReturnValue,
   244  			Abbrev:        abbrev,
   245  			StackOffset:   int32(n.FrameOffset()),
   246  			Type:          base.Ctxt.Lookup(typename),
   247  			DeclFile:      declpos.RelFilename(),
   248  			DeclLine:      declpos.RelLine(),
   249  			DeclCol:       declpos.RelCol(),
   250  			InlIndex:      int32(inlIndex),
   251  			ChildIndex:    -1,
   252  			DictIndex:     n.DictIndex,
   253  		})
   254  		// Record go type of to insure that it gets emitted by the linker.
   255  		fnsym.Func().RecordAutoType(reflectdata.TypeLinksym(n.Type()))
   256  	}
   257  
   258  	// Sort decls and vars.
   259  	sortDeclsAndVars(fn, decls, vars)
   260  
   261  	return decls, vars
   262  }
   263  
   264  // sortDeclsAndVars sorts the decl and dwarf var lists according to
   265  // parameter declaration order, so as to insure that when a subprogram
   266  // DIE is emitted, its parameter children appear in declaration order.
   267  // Prior to the advent of the register ABI, sorting by frame offset
   268  // would achieve this; with the register we now need to go back to the
   269  // original function signature.
   270  func sortDeclsAndVars(fn *ir.Func, decls []*ir.Name, vars []*dwarf.Var) {
   271  	paramOrder := make(map[*ir.Name]int)
   272  	idx := 1
   273  	for _, f := range fn.Type().RecvParamsResults() {
   274  		if n, ok := f.Nname.(*ir.Name); ok {
   275  			paramOrder[n] = idx
   276  			idx++
   277  		}
   278  	}
   279  	sort.Stable(varsAndDecls{decls, vars, paramOrder})
   280  }
   281  
   282  type varsAndDecls struct {
   283  	decls      []*ir.Name
   284  	vars       []*dwarf.Var
   285  	paramOrder map[*ir.Name]int
   286  }
   287  
   288  func (v varsAndDecls) Len() int {
   289  	return len(v.decls)
   290  }
   291  
   292  func (v varsAndDecls) Less(i, j int) bool {
   293  	nameLT := func(ni, nj *ir.Name) bool {
   294  		oi, foundi := v.paramOrder[ni]
   295  		oj, foundj := v.paramOrder[nj]
   296  		if foundi {
   297  			if foundj {
   298  				return oi < oj
   299  			} else {
   300  				return true
   301  			}
   302  		}
   303  		return false
   304  	}
   305  	return nameLT(v.decls[i], v.decls[j])
   306  }
   307  
   308  func (v varsAndDecls) Swap(i, j int) {
   309  	v.vars[i], v.vars[j] = v.vars[j], v.vars[i]
   310  	v.decls[i], v.decls[j] = v.decls[j], v.decls[i]
   311  }
   312  
   313  // Given a function that was inlined at some point during the
   314  // compilation, return a sorted list of nodes corresponding to the
   315  // autos/locals in that function prior to inlining. If this is a
   316  // function that is not local to the package being compiled, then the
   317  // names of the variables may have been "versioned" to avoid conflicts
   318  // with local vars; disregard this versioning when sorting.
   319  func preInliningDcls(fnsym *obj.LSym) []*ir.Name {
   320  	fn := base.Ctxt.DwFixups.GetPrecursorFunc(fnsym).(*ir.Func)
   321  	var rdcl []*ir.Name
   322  	for _, n := range fn.Inl.Dcl {
   323  		c := n.Sym().Name[0]
   324  		// Avoid reporting "_" parameters, since if there are more than
   325  		// one, it can result in a collision later on, as in #23179.
   326  		if n.Sym().Name == "_" || c == '.' || n.Type().IsUntyped() {
   327  			continue
   328  		}
   329  		rdcl = append(rdcl, n)
   330  	}
   331  	return rdcl
   332  }
   333  
   334  // createSimpleVars creates a DWARF entry for every variable declared in the
   335  // function, claiming that they are permanently on the stack.
   336  func createSimpleVars(fnsym *obj.LSym, apDecls []*ir.Name) ([]*ir.Name, []*dwarf.Var, ir.NameSet) {
   337  	var vars []*dwarf.Var
   338  	var decls []*ir.Name
   339  	var selected ir.NameSet
   340  	for _, n := range apDecls {
   341  		if ir.IsAutoTmp(n) {
   342  			continue
   343  		}
   344  
   345  		decls = append(decls, n)
   346  		vars = append(vars, createSimpleVar(fnsym, n))
   347  		selected.Add(n)
   348  	}
   349  	return decls, vars, selected
   350  }
   351  
   352  func createSimpleVar(fnsym *obj.LSym, n *ir.Name) *dwarf.Var {
   353  	var abbrev int
   354  	var offs int64
   355  
   356  	localAutoOffset := func() int64 {
   357  		offs = n.FrameOffset()
   358  		if base.Ctxt.Arch.FixedFrameSize == 0 {
   359  			offs -= int64(types.PtrSize)
   360  		}
   361  		if buildcfg.FramePointerEnabled {
   362  			offs -= int64(types.PtrSize)
   363  		}
   364  		return offs
   365  	}
   366  
   367  	switch n.Class {
   368  	case ir.PAUTO:
   369  		offs = localAutoOffset()
   370  		abbrev = dwarf.DW_ABRV_AUTO
   371  	case ir.PPARAM, ir.PPARAMOUT:
   372  		abbrev = dwarf.DW_ABRV_PARAM
   373  		if n.IsOutputParamInRegisters() {
   374  			offs = localAutoOffset()
   375  		} else {
   376  			offs = n.FrameOffset() + base.Ctxt.Arch.FixedFrameSize
   377  		}
   378  
   379  	default:
   380  		base.Fatalf("createSimpleVar unexpected class %v for node %v", n.Class, n)
   381  	}
   382  
   383  	typename := dwarf.InfoPrefix + types.TypeSymName(n.Type())
   384  	delete(fnsym.Func().Autot, reflectdata.TypeLinksym(n.Type()))
   385  	inlIndex := 0
   386  	if base.Flag.GenDwarfInl > 1 {
   387  		if n.InlFormal() || n.InlLocal() {
   388  			inlIndex = posInlIndex(n.Pos()) + 1
   389  			if n.InlFormal() {
   390  				abbrev = dwarf.DW_ABRV_PARAM
   391  			}
   392  		}
   393  	}
   394  	declpos := base.Ctxt.InnermostPos(declPos(n))
   395  	return &dwarf.Var{
   396  		Name:          n.Sym().Name,
   397  		IsReturnValue: n.Class == ir.PPARAMOUT,
   398  		IsInlFormal:   n.InlFormal(),
   399  		Abbrev:        abbrev,
   400  		StackOffset:   int32(offs),
   401  		Type:          base.Ctxt.Lookup(typename),
   402  		DeclFile:      declpos.RelFilename(),
   403  		DeclLine:      declpos.RelLine(),
   404  		DeclCol:       declpos.RelCol(),
   405  		InlIndex:      int32(inlIndex),
   406  		ChildIndex:    -1,
   407  		DictIndex:     n.DictIndex,
   408  	}
   409  }
   410  
   411  // createABIVars creates DWARF variables for functions in which the
   412  // register ABI is enabled but optimization is turned off. It uses a
   413  // hybrid approach in which register-resident input params are
   414  // captured with location lists, and all other vars use the "simple"
   415  // strategy.
   416  func createABIVars(fnsym *obj.LSym, fn *ir.Func, apDecls []*ir.Name) ([]*ir.Name, []*dwarf.Var, ir.NameSet) {
   417  
   418  	// Invoke createComplexVars to generate dwarf vars for input parameters
   419  	// that are register-allocated according to the ABI rules.
   420  	decls, vars, selected := createComplexVars(fnsym, fn)
   421  
   422  	// Now fill in the remainder of the variables: input parameters
   423  	// that are not register-resident, output parameters, and local
   424  	// variables.
   425  	for _, n := range apDecls {
   426  		if ir.IsAutoTmp(n) {
   427  			continue
   428  		}
   429  		if _, ok := selected[n]; ok {
   430  			// already handled
   431  			continue
   432  		}
   433  
   434  		decls = append(decls, n)
   435  		vars = append(vars, createSimpleVar(fnsym, n))
   436  		selected.Add(n)
   437  	}
   438  
   439  	return decls, vars, selected
   440  }
   441  
   442  // createComplexVars creates recomposed DWARF vars with location lists,
   443  // suitable for describing optimized code.
   444  func createComplexVars(fnsym *obj.LSym, fn *ir.Func) ([]*ir.Name, []*dwarf.Var, ir.NameSet) {
   445  	debugInfo := fn.DebugInfo.(*ssa.FuncDebug)
   446  
   447  	// Produce a DWARF variable entry for each user variable.
   448  	var decls []*ir.Name
   449  	var vars []*dwarf.Var
   450  	var ssaVars ir.NameSet
   451  
   452  	for varID, dvar := range debugInfo.Vars {
   453  		n := dvar
   454  		ssaVars.Add(n)
   455  		for _, slot := range debugInfo.VarSlots[varID] {
   456  			ssaVars.Add(debugInfo.Slots[slot].N)
   457  		}
   458  
   459  		if dvar := createComplexVar(fnsym, fn, ssa.VarID(varID)); dvar != nil {
   460  			decls = append(decls, n)
   461  			vars = append(vars, dvar)
   462  		}
   463  	}
   464  
   465  	return decls, vars, ssaVars
   466  }
   467  
   468  // createComplexVar builds a single DWARF variable entry and location list.
   469  func createComplexVar(fnsym *obj.LSym, fn *ir.Func, varID ssa.VarID) *dwarf.Var {
   470  	debug := fn.DebugInfo.(*ssa.FuncDebug)
   471  	n := debug.Vars[varID]
   472  
   473  	var abbrev int
   474  	switch n.Class {
   475  	case ir.PAUTO:
   476  		abbrev = dwarf.DW_ABRV_AUTO_LOCLIST
   477  	case ir.PPARAM, ir.PPARAMOUT:
   478  		abbrev = dwarf.DW_ABRV_PARAM_LOCLIST
   479  	default:
   480  		return nil
   481  	}
   482  
   483  	gotype := reflectdata.TypeLinksym(n.Type())
   484  	delete(fnsym.Func().Autot, gotype)
   485  	typename := dwarf.InfoPrefix + gotype.Name[len("type:"):]
   486  	inlIndex := 0
   487  	if base.Flag.GenDwarfInl > 1 {
   488  		if n.InlFormal() || n.InlLocal() {
   489  			inlIndex = posInlIndex(n.Pos()) + 1
   490  			if n.InlFormal() {
   491  				abbrev = dwarf.DW_ABRV_PARAM_LOCLIST
   492  			}
   493  		}
   494  	}
   495  	declpos := base.Ctxt.InnermostPos(n.Pos())
   496  	dvar := &dwarf.Var{
   497  		Name:          n.Sym().Name,
   498  		IsReturnValue: n.Class == ir.PPARAMOUT,
   499  		IsInlFormal:   n.InlFormal(),
   500  		Abbrev:        abbrev,
   501  		Type:          base.Ctxt.Lookup(typename),
   502  		// The stack offset is used as a sorting key, so for decomposed
   503  		// variables just give it the first one. It's not used otherwise.
   504  		// This won't work well if the first slot hasn't been assigned a stack
   505  		// location, but it's not obvious how to do better.
   506  		StackOffset: ssagen.StackOffset(debug.Slots[debug.VarSlots[varID][0]]),
   507  		DeclFile:    declpos.RelFilename(),
   508  		DeclLine:    declpos.RelLine(),
   509  		DeclCol:     declpos.RelCol(),
   510  		InlIndex:    int32(inlIndex),
   511  		ChildIndex:  -1,
   512  		DictIndex:   n.DictIndex,
   513  	}
   514  	list := debug.LocationLists[varID]
   515  	if len(list) != 0 {
   516  		dvar.PutLocationList = func(listSym, startPC dwarf.Sym) {
   517  			debug.PutLocationList(list, base.Ctxt, listSym.(*obj.LSym), startPC.(*obj.LSym))
   518  		}
   519  	}
   520  	return dvar
   521  }
   522  
   523  // RecordFlags records the specified command-line flags to be placed
   524  // in the DWARF info.
   525  func RecordFlags(flags ...string) {
   526  	if base.Ctxt.Pkgpath == "" {
   527  		panic("missing pkgpath")
   528  	}
   529  
   530  	type BoolFlag interface {
   531  		IsBoolFlag() bool
   532  	}
   533  	type CountFlag interface {
   534  		IsCountFlag() bool
   535  	}
   536  	var cmd bytes.Buffer
   537  	for _, name := range flags {
   538  		f := flag.Lookup(name)
   539  		if f == nil {
   540  			continue
   541  		}
   542  		getter := f.Value.(flag.Getter)
   543  		if getter.String() == f.DefValue {
   544  			// Flag has default value, so omit it.
   545  			continue
   546  		}
   547  		if bf, ok := f.Value.(BoolFlag); ok && bf.IsBoolFlag() {
   548  			val, ok := getter.Get().(bool)
   549  			if ok && val {
   550  				fmt.Fprintf(&cmd, " -%s", f.Name)
   551  				continue
   552  			}
   553  		}
   554  		if cf, ok := f.Value.(CountFlag); ok && cf.IsCountFlag() {
   555  			val, ok := getter.Get().(int)
   556  			if ok && val == 1 {
   557  				fmt.Fprintf(&cmd, " -%s", f.Name)
   558  				continue
   559  			}
   560  		}
   561  		fmt.Fprintf(&cmd, " -%s=%v", f.Name, getter.Get())
   562  	}
   563  
   564  	// Adds flag to producer string signaling whether regabi is turned on or
   565  	// off.
   566  	// Once regabi is turned on across the board and the relative GOEXPERIMENT
   567  	// knobs no longer exist this code should be removed.
   568  	if buildcfg.Experiment.RegabiArgs {
   569  		cmd.Write([]byte(" regabi"))
   570  	}
   571  
   572  	if cmd.Len() == 0 {
   573  		return
   574  	}
   575  	s := base.Ctxt.Lookup(dwarf.CUInfoPrefix + "producer." + base.Ctxt.Pkgpath)
   576  	s.Type = objabi.SDWARFCUINFO
   577  	// Sometimes (for example when building tests) we can link
   578  	// together two package main archives. So allow dups.
   579  	s.Set(obj.AttrDuplicateOK, true)
   580  	base.Ctxt.Data = append(base.Ctxt.Data, s)
   581  	s.P = cmd.Bytes()[1:]
   582  }
   583  
   584  // RecordPackageName records the name of the package being
   585  // compiled, so that the linker can save it in the compile unit's DIE.
   586  func RecordPackageName() {
   587  	s := base.Ctxt.Lookup(dwarf.CUInfoPrefix + "packagename." + base.Ctxt.Pkgpath)
   588  	s.Type = objabi.SDWARFCUINFO
   589  	// Sometimes (for example when building tests) we can link
   590  	// together two package main archives. So allow dups.
   591  	s.Set(obj.AttrDuplicateOK, true)
   592  	base.Ctxt.Data = append(base.Ctxt.Data, s)
   593  	s.P = []byte(types.LocalPkg.Name)
   594  }
   595
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