golang dwarf 代码
文件路径：/src/cmd/internal/obj/dwarf.go
/ Copyright 2019 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
/ Writes dwarf information to object files.
package obj
import (
"cmd/internal/dwarf"
"cmd/internal/objabi"
"cmd/internal/src"
"fmt"
"sort"
"sync"
)
/ Generate a sequence of opcodes that is as short as possible.
/ See section 6.2.5
const (
LINE_BASE = -4
LINE_RANGE = 10
PC_RANGE = (255 - OPCODE_BASE) / LINE_RANGE
OPCODE_BASE = 11
)
/ generateDebugLinesSymbol fills the debug lines symbol of a given function.
/
/ It's worth noting that this function doesn't generate the full debug_lines
/ DWARF section, saving that for the linker. This function just generates the
/ state machine part of debug_lines. The full table is generated by the
/ linker. Also, we use the file numbers from the full package (not just the
/ function in question) when generating the state machine. We do this so we
/ don't have to do a fixup on the indices when writing the full section.
func (ctxt *Link) generateDebugLinesSymbol(s, lines *LSym) {
dctxt := dwCtxt{ctxt}
/ Emit a LNE_set_address extended opcode, so as to establish the
/ starting text address of this function.
dctxt.AddUint8(lines, 0)
dwarf.Uleb128put(dctxt, lines, 1+int64(ctxt.Arch.PtrSize))
dctxt.AddUint8(lines, dwarf.DW_LNE_set_address)
dctxt.AddAddress(lines, s, 0)
/ Set up the debug_lines state machine to the default values
/ we expect at the start of a new sequence.
stmt := true
line := int64(1)
pc := s.Func().Text.Pc
var lastpc int64 / last PC written to line table, not last PC in func
name := ""
prologue, wrotePrologue := false, false
/ Walk the progs, generating the DWARF table.
for p := s.Func().Text; p != nil; p = p.Link {
prologue = prologue || (p.Pos.Xlogue() == src.PosPrologueEnd)
/ If we're not at a real instruction, keep looping!
if p.Pos.Line() == 0 || (p.Link != nil && p.Link.Pc == p.Pc) {
continue
}
newStmt := p.Pos.IsStmt() != src.PosNotStmt
newName, newLine := linkgetlineFromPos(ctxt, p.Pos)
/ Output debug info.
wrote := false
if name != newName {
newFile := ctxt.PosTable.FileIndex(newName) + 1 / 1 indexing for the table.
dctxt.AddUint8(lines, dwarf.DW_LNS_set_file)
dwarf.Uleb128put(dctxt, lines, int64(newFile))
name = newName
wrote = true
}
if prologue && !wrotePrologue {
dctxt.AddUint8(lines, uint8(dwarf.DW_LNS_set_prologue_end))
wrotePrologue = true
wrote = true
}
if stmt != newStmt {
dctxt.AddUint8(lines, uint8(dwarf.DW_LNS_negate_stmt))
stmt = newStmt
wrote = true
}
if line != int64(newLine) || wrote {
pcdelta := p.Pc - pc
lastpc = p.Pc
putpclcdelta(ctxt, dctxt, lines, uint64(pcdelta), int64(newLine)-line)
line, pc = int64(newLine), p.Pc
}
}
/ Because these symbols will be concatenated together by the
/ linker, we need to reset the state machine that controls the
/ debug symbols. Do this using an end-of-sequence operator.
/
/ Note: at one point in time, Delve did not support multiple end
/ sequence ops within a compilation unit (bug for this:
/ https://github.com/go-delve/delve/issues/1694), however the bug
/ has since been fixed (Oct 2019).
/
/ Issue 38192: the DWARF standard specifies that when you issue
/ an end-sequence op, the PC value should be one past the last
/ text address in the translation unit, so apply a delta to the
/ text address before the end sequence op. If this isn't done,
/ GDB will assign a line number of zero the last row in the line
/ table, which we don't want.
lastlen := uint64(s.Size - (lastpc - s.Func().Text.Pc))
dctxt.AddUint8(lines, dwarf.DW_LNS_advance_pc)
dwarf.Uleb128put(dctxt, lines, int64(lastlen))
dctxt.AddUint8(lines, 0) / start extended opcode
dwarf.Uleb128put(dctxt, lines, 1)
dctxt.AddUint8(lines, dwarf.DW_LNE_end_sequence)
}
func putpclcdelta(linkctxt *Link, dctxt dwCtxt, s *LSym, deltaPC uint64, deltaLC int64) {
/ Choose a special opcode that minimizes the number of bytes needed to
/ encode the remaining PC delta and LC delta.
var opcode int64
if deltaLC < LINE_BASE {
if deltaPC >= PC_RANGE {
opcode = OPCODE_BASE + (LINE_RANGE * PC_RANGE)
} else {
opcode = OPCODE_BASE + (LINE_RANGE * int64(deltaPC))
}
} else if deltaLC < LINE_BASE+LINE_RANGE {
if deltaPC >= PC_RANGE {
opcode = OPCODE_BASE + (deltaLC - LINE_BASE) + (LINE_RANGE * PC_RANGE)
if opcode > 255 {
opcode -= LINE_RANGE
}
} else {
opcode = OPCODE_BASE + (deltaLC - LINE_BASE) + (LINE_RANGE * int64(deltaPC))
}
} else {
if deltaPC <= PC_RANGE {
opcode = OPCODE_BASE + (LINE_RANGE - 1) + (LINE_RANGE * int64(deltaPC))
if opcode > 255 {
opcode = 255
}
} else {
/ Use opcode 249 (pc+=23, lc+=5) or 255 (pc+=24, lc+=1).
/
/ Let x=deltaPC-PC_RANGE. If we use opcode 255, x will be the remaining
/ deltaPC that we need to encode separately before emitting 255. If we
/ use opcode 249, we will need to encode x+1. If x+1 takes one more
/ byte to encode than x, then we use opcode 255.
/
/ In all other cases x and x+1 take the same number of bytes to encode,
/ so we use opcode 249, which may save us a byte in encoding deltaLC,
/ for similar reasons.
switch deltaPC - PC_RANGE {
/ PC_RANGE is the largest deltaPC we can encode in one byte, using
/ DW_LNS_const_add_pc.
/
/ (1<<16)-1 is the largest deltaPC we can encode in three bytes, using
/ DW_LNS_fixed_advance_pc.
/
/ (1<<(7n))-1 is the largest deltaPC we can encode in n+1 bytes for
/ n=1,3,4,5,..., using DW_LNS_advance_pc.
case PC_RANGE, (1 << 7) - 1, (1 << 16) - 1, (1 << 21) - 1, (1 << 28) - 1,
(1 << 35) - 1, (1 << 42) - 1, (1 << 49) - 1, (1 << 56) - 1, (1 << 63) - 1:
opcode = 255
default:
opcode = OPCODE_BASE + LINE_RANGE*PC_RANGE - 1 / 249
}
}
}
if opcode < OPCODE_BASE || opcode > 255 {
panic(fmt.Sprintf("produced invalid special opcode %d", opcode))
}
/ Subtract from deltaPC and deltaLC the amounts that the opcode will add.
deltaPC -= uint64((opcode - OPCODE_BASE) / LINE_RANGE)
deltaLC -= (opcode-OPCODE_BASE)%LINE_RANGE + LINE_BASE
/ Encode deltaPC.
if deltaPC != 0 {
if deltaPC <= PC_RANGE {
/ Adjust the opcode so that we can use the 1-byte DW_LNS_const_add_pc
/ instruction.
opcode -= LINE_RANGE * int64(PC_RANGE-deltaPC)
if opcode < OPCODE_BASE {
panic(fmt.Sprintf("produced invalid special opcode %d", opcode))
}
dctxt.AddUint8(s, dwarf.DW_LNS_const_add_pc)
} else if (1<<14) <= deltaPC && deltaPC < (1<<16) {
dctxt.AddUint8(s, dwarf.DW_LNS_fixed_advance_pc)
dctxt.AddUint16(s, uint16(deltaPC))
} else {
dctxt.AddUint8(s, dwarf.DW_LNS_advance_pc)
dwarf.Uleb128put(dctxt, s, int64(deltaPC))
}
}
/ Encode deltaLC.
if deltaLC != 0 {
dctxt.AddUint8(s, dwarf.DW_LNS_advance_line)
dwarf.Sleb128put(dctxt, s, deltaLC)
}
/ Output the special opcode.
dctxt.AddUint8(s, uint8(opcode))
}
/ implement dwarf.Context
type dwCtxt struct{ *Link }
func (c dwCtxt) PtrSize() int {
return c.Arch.PtrSize
}
func (c dwCtxt) AddInt(s dwarf.Sym, size int, i int64) {
ls := s.(*LSym)
ls.WriteInt(c.Link, ls.Size, size, i)
}
func (c dwCtxt) AddUint16(s dwarf.Sym, i uint16) {
c.AddInt(s, 2, int64(i))
}
func (c dwCtxt) AddUint8(s dwarf.Sym, i uint8) {
b := []byte{byte(i)}
c.AddBytes(s, b)
}
func (c dwCtxt) AddBytes(s dwarf.Sym, b []byte) {
ls := s.(*LSym)
ls.WriteBytes(c.Link, ls.Size, b)
}
func (c dwCtxt) AddString(s dwarf.Sym, v string) {
ls := s.(*LSym)
ls.WriteString(c.Link, ls.Size, len(v), v)
ls.WriteInt(c.Link, ls.Size, 1, 0)
}
func (c dwCtxt) AddAddress(s dwarf.Sym, data interface{}, value int64) {
ls := s.(*LSym)
size := c.PtrSize()
if data != nil {
rsym := data.(*LSym)
ls.WriteAddr(c.Link, ls.Size, size, rsym, value)
} else {
ls.WriteInt(c.Link, ls.Size, size, value)
}
}
func (c dwCtxt) AddCURelativeAddress(s dwarf.Sym, data interface{}, value int64) {
ls := s.(*LSym)
rsym := data.(*LSym)
ls.WriteCURelativeAddr(c.Link, ls.Size, rsym, value)
}
func (c dwCtxt) AddSectionOffset(s dwarf.Sym, size int, t interface{}, ofs int64) {
panic("should be used only in the linker")
}
func (c dwCtxt) AddDWARFAddrSectionOffset(s dwarf.Sym, t interface{}, ofs int64) {
size := 4
if isDwarf64(c.Link) {
size = 8
}
ls := s.(*LSym)
rsym := t.(*LSym)
ls.WriteAddr(c.Link, ls.Size, size, rsym, ofs)
r := &ls.R[len(ls.R)-1]
r.Type = objabi.R_DWARFSECREF
}
func (c dwCtxt) AddFileRef(s dwarf.Sym, f interface{}) {
ls := s.(*LSym)
rsym := f.(*LSym)
fidx := c.Link.PosTable.FileIndex(rsym.Name)
/ Note the +1 here -- the value we're writing is going to be an
/ index into the DWARF line table file section, whose entries
/ are numbered starting at 1, not 0.
ls.WriteInt(c.Link, ls.Size, 4, int64(fidx+1))
}
func (c dwCtxt) CurrentOffset(s dwarf.Sym) int64 {
ls := s.(*LSym)
return ls.Size
}
/ Here "from" is a symbol corresponding to an inlined or concrete
/ function, "to" is the symbol for the corresponding abstract
/ function, and "dclIdx" is the index of the symbol of interest with
/ respect to the Dcl slice of the original pre-optimization version
/ of the inlined function.
func (c dwCtxt) RecordDclReference(from dwarf.Sym, to dwarf.Sym, dclIdx int, inlIndex int) {
ls := from.(*LSym)
tls := to.(*LSym)
ridx := len(ls.R) - 1
c.Link.DwFixups.ReferenceChildDIE(ls, ridx, tls, dclIdx, inlIndex)
}
func (c dwCtxt) RecordChildDieOffsets(s dwarf.Sym, vars []*dwarf.Var, offsets []int32) {
ls := s.(*LSym)
c.Link.DwFixups.RegisterChildDIEOffsets(ls, vars, offsets)
}
func (c dwCtxt) Logf(format string, args ...interface{}) {
c.Link.Logf(format, args...)
}
func isDwarf64(ctxt *Link) bool {
return ctxt.Headtype == objabi.Haix
}
func (ctxt *Link) dwarfSym(s *LSym) (dwarfInfoSym, dwarfLocSym, dwarfRangesSym, dwarfAbsFnSym, dwarfDebugLines *LSym) {
if s.Type != objabi.STEXT {
ctxt.Diag("dwarfSym of non-TEXT %v", s)
}
fn := s.Func()
if fn.dwarfInfoSym == nil {
fn.dwarfInfoSym = &LSym{
Type: objabi.SDWARFFCN,
}
if ctxt.Flag_locationlists {
fn.dwarfLocSym = &LSym{
Type: objabi.SDWARFLOC,
}
}
fn.dwarfRangesSym = &LSym{
Type: objabi.SDWARFRANGE,
}
fn.dwarfDebugLinesSym = &LSym{
Type: objabi.SDWARFLINES,
}
if s.WasInlined() {
fn.dwarfAbsFnSym = ctxt.DwFixups.AbsFuncDwarfSym(s)
}
}
return fn.dwarfInfoSym, fn.dwarfLocSym, fn.dwarfRangesSym, fn.dwarfAbsFnSym, fn.dwarfDebugLinesSym
}
func (s *LSym) Length(dwarfContext interface{}) int64 {
return s.Size
}
/ fileSymbol returns a symbol corresponding to the source file of the
/ first instruction (prog) of the specified function. This will
/ presumably be the file in which the function is defined.
func (ctxt *Link) fileSymbol(fn *LSym) *LSym {
p := fn.Func().Text
if p != nil {
f, _ := linkgetlineFromPos(ctxt, p.Pos)
fsym := ctxt.Lookup(f)
return fsym
}
return nil
}
/ populateDWARF fills in the DWARF Debugging Information Entries for
/ TEXT symbol 's'. The various DWARF symbols must already have been
/ initialized in InitTextSym.
func (ctxt *Link) populateDWARF(curfn interface{}, s *LSym, myimportpath string) {
info, loc, ranges, absfunc, lines := ctxt.dwarfSym(s)
if info.Size != 0 {
ctxt.Diag("makeFuncDebugEntry double process %v", s)
}
var scopes []dwarf.Scope
var inlcalls dwarf.InlCalls
if ctxt.DebugInfo != nil {
scopes, inlcalls = ctxt.DebugInfo(s, info, curfn)
}
var err error
dwctxt := dwCtxt{ctxt}
filesym := ctxt.fileSymbol(s)
fnstate := &dwarf.FnState{
Name: s.Name,
Importpath: myimportpath,
Info: info,
Filesym: filesym,
Loc: loc,
Ranges: ranges,
Absfn: absfunc,
StartPC: s,
Size: s.Size,
External: !s.Static(),
Scopes: scopes,
InlCalls: inlcalls,
UseBASEntries: ctxt.UseBASEntries,
}
if absfunc != nil {
err = dwarf.PutAbstractFunc(dwctxt, fnstate)
if err != nil {
ctxt.Diag("emitting DWARF for %s failed: %v", s.Name, err)
}
err = dwarf.PutConcreteFunc(dwctxt, fnstate, s.Wrapper())
} else {
err = dwarf.PutDefaultFunc(dwctxt, fnstate, s.Wrapper())
}
if err != nil {
ctxt.Diag("emitting DWARF for %s failed: %v", s.Name, err)
}
/ Fill in the debug lines symbol.
ctxt.generateDebugLinesSymbol(s, lines)
}
/ DwarfIntConst creates a link symbol for an integer constant with the
/ given name, type and value.
func (ctxt *Link) DwarfIntConst(myimportpath, name, typename string, val int64) {
if myimportpath == "" {
return
}
s := ctxt.LookupInit(dwarf.ConstInfoPrefix+myimportpath, func(s *LSym) {
s.Type = objabi.SDWARFCONST
ctxt.Data = append(ctxt.Data, s)
})
dwarf.PutIntConst(dwCtxt{ctxt}, s, ctxt.Lookup(dwarf.InfoPrefix+typename), myimportpath+"."+name, val)
}
/ DwarfGlobal creates a link symbol containing a DWARF entry for
/ a global variable.
func (ctxt *Link) DwarfGlobal(myimportpath, typename string, varSym *LSym) {
if myimportpath == "" || varSym.Local() {
return
}
varname := varSym.Name
dieSymName := dwarf.InfoPrefix + varname
dieSym := ctxt.LookupInit(dieSymName, func(s *LSym) {
s.Type = objabi.SDWARFVAR
s.Set(AttrDuplicateOK, true) / needed for shared linkage
ctxt.Data = append(ctxt.Data, s)
})
typeSym := ctxt.Lookup(dwarf.InfoPrefix + typename)
dwarf.PutGlobal(dwCtxt{ctxt}, dieSym, typeSym, varSym, varname)
}
func (ctxt *Link) DwarfAbstractFunc(curfn interface{}, s *LSym, myimportpath string) {
absfn := ctxt.DwFixups.AbsFuncDwarfSym(s)
if absfn.Size != 0 {
ctxt.Diag("internal error: DwarfAbstractFunc double process %v", s)
}
if s.Func() == nil {
s.NewFuncInfo()
}
scopes, _ := ctxt.DebugInfo(s, absfn, curfn)
dwctxt := dwCtxt{ctxt}
filesym := ctxt.fileSymbol(s)
fnstate := dwarf.FnState{
Name: s.Name,
Importpath: myimportpath,
Info: absfn,
Filesym: filesym,
Absfn: absfn,
External: !s.Static(),
Scopes: scopes,
UseBASEntries: ctxt.UseBASEntries,
}
if err := dwarf.PutAbstractFunc(dwctxt, &fnstate); err != nil {
ctxt.Diag("emitting DWARF for %s failed: %v", s.Name, err)
}
}
/ This table is designed to aid in the creation of references between
/ DWARF subprogram DIEs.
/
/ In most cases when one DWARF DIE has to refer to another DWARF DIE,
/ the target of the reference has an LSym, which makes it easy to use
/ the existing relocation mechanism. For DWARF inlined routine DIEs,
/ however, the subprogram DIE has to refer to a child
/ parameter/variable DIE of the abstract subprogram. This child DIE
/ doesn't have an LSym, and also of interest is the fact that when
/ DWARF generation is happening for inlined function F within caller
/ G, it's possible that DWARF generation hasn't happened yet for F,
/ so there is no way to know the offset of a child DIE within F's
/ abstract function. Making matters more complex, each inlined
/ instance of F may refer to a subset of the original F's variables
/ (depending on what happens with optimization, some vars may be
/ eliminated).
/
/ The fixup table below helps overcome this hurdle. At the point
/ where a parameter/variable reference is made (via a call to
/ "ReferenceChildDIE"), a fixup record is generate that records
/ the relocation that is targeting that child variable. At a later
/ point when the abstract function DIE is emitted, there will be
/ a call to "RegisterChildDIEOffsets", at which point the offsets
/ needed to apply fixups are captured. Finally, once the parallel
/ portion of the compilation is done, fixups can actually be applied
/ during the "Finalize" method (this can't be done during the
/ parallel portion of the compile due to the possibility of data
/ races).
/
/ This table is also used to record the "precursor" function node for
/ each function that is the target of an inline -- child DIE references
/ have to be made with respect to the original pre-optimization
/ version of the function (to allow for the fact that each inlined
/ body may be optimized differently).
type DwarfFixupTable struct {
ctxt *Link
mu sync.Mutex
symtab map[*LSym]int / maps abstract fn LSYM to index in svec
svec []symFixups
precursor map[*LSym]fnState / maps fn Lsym to precursor Node, absfn sym
}
type symFixups struct {
fixups []relFixup
doffsets []declOffset
inlIndex int32
defseen bool
}
type declOffset struct {
/ Index of variable within DCL list of pre-optimization function
dclIdx int32
/ Offset of var's child DIE with respect to containing subprogram DIE
offset int32
}
type relFixup struct {
refsym *LSym
relidx int32
dclidx int32
}
type fnState struct {
/ precursor function (really *gc.Node)
precursor interface{}
/ abstract function symbol
absfn *LSym
}
func NewDwarfFixupTable(ctxt *Link) *DwarfFixupTable {
return &DwarfFixupTable{
ctxt: ctxt,
symtab: make(map[*LSym]int),
precursor: make(map[*LSym]fnState),
}
}
func (ft *DwarfFixupTable) GetPrecursorFunc(s *LSym) interface{} {
if fnstate, found := ft.precursor[s]; found {
return fnstate.precursor
}
return nil
}
func (ft *DwarfFixupTable) SetPrecursorFunc(s *LSym, fn interface{}) {
if _, found := ft.precursor[s]; found {
ft.ctxt.Diag("internal error: DwarfFixupTable.SetPrecursorFunc double call on %v", s)
}
/ initialize abstract function symbol now. This is done here so
/ as to avoid data races later on during the parallel portion of
/ the back end.
absfn := ft.ctxt.LookupDerived(s, dwarf.InfoPrefix+s.Name+dwarf.AbstractFuncSuffix)
absfn.Set(AttrDuplicateOK, true)
absfn.Type = objabi.SDWARFABSFCN
ft.ctxt.Data = append(ft.ctxt.Data, absfn)
/ In the case of "late" inlining (inlines that happen during
/ wrapper generation as opposed to the main inlining phase) it's
/ possible that we didn't cache the abstract function sym for the
/ text symbol -- do so now if needed. See issue 38068.
if fn := s.Func(); fn != nil && fn.dwarfAbsFnSym == nil {
fn.dwarfAbsFnSym = absfn
}
ft.precursor[s] = fnState{precursor: fn, absfn: absfn}
}
/ Make a note of a child DIE reference: relocation 'ridx' within symbol 's'
/ is targeting child 'c' of DIE with symbol 'tgt'.
func (ft *DwarfFixupTable) ReferenceChildDIE(s *LSym, ridx int, tgt *LSym, dclidx int, inlIndex int) {
/ Protect against concurrent access if multiple backend workers
ft.mu.Lock()
defer ft.mu.Unlock()
/ Create entry for symbol if not already present.
idx, found := ft.symtab[tgt]
if !found {
ft.svec = append(ft.svec, symFixups{inlIndex: int32(inlIndex)})
idx = len(ft.svec) - 1
ft.symtab[tgt] = idx
}
/ Do we have child DIE offsets available? If so, then apply them,
/ otherwise create a fixup record.
sf := &ft.svec[idx]
if len(sf.doffsets) > 0 {
found := false
for _, do := range sf.doffsets {
if do.dclIdx == int32(dclidx) {
off := do.offset
s.R[ridx].Add += int64(off)
found = true
break
}
}
if !found {
ft.ctxt.Diag("internal error: DwarfFixupTable.ReferenceChildDIE unable to locate child DIE offset for dclIdx=%d src=%v tgt=%v", dclidx, s, tgt)
}
} else {
sf.fixups = append(sf.fixups, relFixup{s, int32(ridx), int32(dclidx)})
}
}
/ Called once DWARF generation is complete for a given abstract function,
/ whose children might have been referenced via a call above. Stores
/ the offsets for any child DIEs (vars, params) so that they can be
/ consumed later in on DwarfFixupTable.Finalize, which applies any
/ outstanding fixups.
func (ft *DwarfFixupTable) RegisterChildDIEOffsets(s *LSym, vars []*dwarf.Var, coffsets []int32) {
/ Length of these two slices should agree
if len(vars) != len(coffsets) {
ft.ctxt.Diag("internal error: RegisterChildDIEOffsets vars/offsets length mismatch")
return
}
/ Generate the slice of declOffset's based in vars/coffsets
doffsets := make([]declOffset, len(coffsets))
for i := range coffsets {
doffsets[i].dclIdx = vars[i].ChildIndex
doffsets[i].offset = coffsets[i]
}
ft.mu.Lock()
defer ft.mu.Unlock()
/ Store offsets for this symbol.
idx, found := ft.symtab[s]
if !found {
sf := symFixups{inlIndex: -1, defseen: true, doffsets: doffsets}
ft.svec = append(ft.svec, sf)
ft.symtab[s] = len(ft.svec) - 1
} else {
sf := &ft.svec[idx]
sf.doffsets = doffsets
sf.defseen = true
}
}
func (ft *DwarfFixupTable) processFixups(slot int, s *LSym) {
sf := &ft.svec[slot]
for _, f := range sf.fixups {
dfound := false
for _, doffset := range sf.doffsets {
if doffset.dclIdx == f.dclidx {
f.refsym.R[f.relidx].Add += int64(doffset.offset)
dfound = true
break
}
}
if !dfound {
ft.ctxt.Diag("internal error: DwarfFixupTable has orphaned fixup on %v targeting %v relidx=%d dclidx=%d", f.refsym, s, f.relidx, f.dclidx)
}
}
}
/ return the LSym corresponding to the 'abstract subprogram' DWARF
/ info entry for a function.
func (ft *DwarfFixupTable) AbsFuncDwarfSym(fnsym *LSym) *LSym {
/ Protect against concurrent access if multiple backend workers
ft.mu.Lock()
defer ft.mu.Unlock()
if fnstate, found := ft.precursor[fnsym]; found {
return fnstate.absfn
}
ft.ctxt.Diag("internal error: AbsFuncDwarfSym requested for %v, not seen during inlining", fnsym)
return nil
}
/ Called after all functions have been compiled; the main job of this
/ function is to identify cases where there are outstanding fixups.
/ This scenario crops up when we have references to variables of an
/ inlined routine, but that routine is defined in some other package.
/ This helper walks through and locate these fixups, then invokes a
/ helper to create an abstract subprogram DIE for each one.
func (ft *DwarfFixupTable) Finalize(myimportpath string, trace bool) {
if trace {
ft.ctxt.Logf("DwarfFixupTable.Finalize invoked for %s\n", myimportpath)
}
/ Collect up the keys from the precursor map, then sort the
/ resulting list (don't want to rely on map ordering here).
fns := make([]*LSym, len(ft.precursor))
idx := 0
for fn := range ft.precursor {
fns[idx] = fn
idx++
}
sort.Sort(BySymName(fns))
/ Should not be called during parallel portion of compilation.
if ft.ctxt.InParallel {
ft.ctxt.Diag("internal error: DwarfFixupTable.Finalize call during parallel backend")
}
/ Generate any missing abstract functions.
for _, s := range fns {
absfn := ft.AbsFuncDwarfSym(s)
slot, found := ft.symtab[absfn]
if !found || !ft.svec[slot].defseen {
ft.ctxt.GenAbstractFunc(s)
}
}
/ Apply fixups.
for _, s := range fns {
absfn := ft.AbsFuncDwarfSym(s)
slot, found := ft.symtab[absfn]
if !found {
ft.ctxt.Diag("internal error: DwarfFixupTable.Finalize orphan abstract function for %v", s)
} else {
ft.processFixups(slot, s)
}
}
}
type BySymName []*LSym
func (s BySymName) Len() int { return len(s) }
func (s BySymName) Less(i, j int) bool { return s[i].Name < s[j].Name }
func (s BySymName) Swap(i, j int) { s[i], s[j] = s[j], s[i] }