gtsocial-umbx

link.go (24865B)

---

 // Derived from Inferno utils/6l/l.h and related files.
 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
 //
 //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
 //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
 //	Portions Copyright © 1997-1999 Vita Nuova Limited
 //	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
 //	Portions Copyright © 2004,2006 Bruce Ellis
 //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
 //	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
 //	Portions Copyright © 2009 The Go Authors. All rights reserved.
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
 // in the Software without restriction, including without limitation the rights
 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 // copies of the Software, and to permit persons to whom the Software is
 // furnished to do so, subject to the following conditions:
 //
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
 //
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
 package obj
 
 import (
 	"bufio"
 	"github.com/twitchyliquid64/golang-asm/dwarf"
 	"github.com/twitchyliquid64/golang-asm/goobj"
 	"github.com/twitchyliquid64/golang-asm/objabi"
 	"github.com/twitchyliquid64/golang-asm/src"
 	"github.com/twitchyliquid64/golang-asm/sys"
 	"fmt"
 	"sync"
 )
 
 // An Addr is an argument to an instruction.
 // The general forms and their encodings are:
 //
 //	sym±offset(symkind)(reg)(index*scale)
 //		Memory reference at address &sym(symkind) + offset + reg + index*scale.
 //		Any of sym(symkind), ±offset, (reg), (index*scale), and *scale can be omitted.
 //		If (reg) and *scale are both omitted, the resulting expression (index) is parsed as (reg).
 //		To force a parsing as index*scale, write (index*1).
 //		Encoding:
 //			type = TYPE_MEM
 //			name = symkind (NAME_AUTO, ...) or 0 (NAME_NONE)
 //			sym = sym
 //			offset = ±offset
 //			reg = reg (REG_*)
 //			index = index (REG_*)
 //			scale = scale (1, 2, 4, 8)
 //
 //	$<mem>
 //		Effective address of memory reference <mem>, defined above.
 //		Encoding: same as memory reference, but type = TYPE_ADDR.
 //
 //	$<±integer value>
 //		This is a special case of $<mem>, in which only ±offset is present.
 //		It has a separate type for easy recognition.
 //		Encoding:
 //			type = TYPE_CONST
 //			offset = ±integer value
 //
 //	*<mem>
 //		Indirect reference through memory reference <mem>, defined above.
 //		Only used on x86 for CALL/JMP *sym(SB), which calls/jumps to a function
 //		pointer stored in the data word sym(SB), not a function named sym(SB).
 //		Encoding: same as above, but type = TYPE_INDIR.
 //
 //	$*$<mem>
 //		No longer used.
 //		On machines with actual SB registers, $*$<mem> forced the
 //		instruction encoding to use a full 32-bit constant, never a
 //		reference relative to SB.
 //
 //	$<floating point literal>
 //		Floating point constant value.
 //		Encoding:
 //			type = TYPE_FCONST
 //			val = floating point value
 //
 //	$<string literal, up to 8 chars>
 //		String literal value (raw bytes used for DATA instruction).
 //		Encoding:
 //			type = TYPE_SCONST
 //			val = string
 //
 //	<register name>
 //		Any register: integer, floating point, control, segment, and so on.
 //		If looking for specific register kind, must check type and reg value range.
 //		Encoding:
 //			type = TYPE_REG
 //			reg = reg (REG_*)
 //
 //	x(PC)
 //		Encoding:
 //			type = TYPE_BRANCH
 //			val = Prog* reference OR ELSE offset = target pc (branch takes priority)
 //
 //	$±x-±y
 //		Final argument to TEXT, specifying local frame size x and argument size y.
 //		In this form, x and y are integer literals only, not arbitrary expressions.
 //		This avoids parsing ambiguities due to the use of - as a separator.
 //		The ± are optional.
 //		If the final argument to TEXT omits the -±y, the encoding should still
 //		use TYPE_TEXTSIZE (not TYPE_CONST), with u.argsize = ArgsSizeUnknown.
 //		Encoding:
 //			type = TYPE_TEXTSIZE
 //			offset = x
 //			val = int32(y)
 //
 //	reg<<shift, reg>>shift, reg->shift, reg@>shift
 //		Shifted register value, for ARM and ARM64.
 //		In this form, reg must be a register and shift can be a register or an integer constant.
 //		Encoding:
 //			type = TYPE_SHIFT
 //		On ARM:
 //			offset = (reg&15) | shifttype<<5 | count
 //			shifttype = 0, 1, 2, 3 for <<, >>, ->, @>
 //			count = (reg&15)<<8 | 1<<4 for a register shift count, (n&31)<<7 for an integer constant.
 //		On ARM64:
 //			offset = (reg&31)<<16 | shifttype<<22 | (count&63)<<10
 //			shifttype = 0, 1, 2 for <<, >>, ->
 //
 //	(reg, reg)
 //		A destination register pair. When used as the last argument of an instruction,
 //		this form makes clear that both registers are destinations.
 //		Encoding:
 //			type = TYPE_REGREG
 //			reg = first register
 //			offset = second register
 //
 //	[reg, reg, reg-reg]
 //		Register list for ARM, ARM64, 386/AMD64.
 //		Encoding:
 //			type = TYPE_REGLIST
 //		On ARM:
 //			offset = bit mask of registers in list; R0 is low bit.
 //		On ARM64:
 //			offset = register count (Q:size) | arrangement (opcode) | first register
 //		On 386/AMD64:
 //			reg = range low register
 //			offset = 2 packed registers + kind tag (see x86.EncodeRegisterRange)
 //
 //	reg, reg
 //		Register pair for ARM.
 //		TYPE_REGREG2
 //
 //	(reg+reg)
 //		Register pair for PPC64.
 //		Encoding:
 //			type = TYPE_MEM
 //			reg = first register
 //			index = second register
 //			scale = 1
 //
 //	reg.[US]XT[BHWX]
 //		Register extension for ARM64
 //		Encoding:
 //			type = TYPE_REG
 //			reg = REG_[US]XT[BHWX] + register + shift amount
 //			offset = ((reg&31) << 16) | (exttype << 13) | (amount<<10)
 //
 //	reg.<T>
 //		Register arrangement for ARM64 SIMD register
 //		e.g.: V1.S4, V2.S2, V7.D2, V2.H4, V6.B16
 //		Encoding:
 //			type = TYPE_REG
 //			reg = REG_ARNG + register + arrangement
 //
 //	reg.<T>[index]
 //		Register element for ARM64
 //		Encoding:
 //			type = TYPE_REG
 //			reg = REG_ELEM + register + arrangement
 //			index = element index
 
 type Addr struct {
 	Reg    int16
 	Index  int16
 	Scale  int16 // Sometimes holds a register.
 	Type   AddrType
 	Name   AddrName
 	Class  int8
 	Offset int64
 	Sym    *LSym
 
 	// argument value:
 	//	for TYPE_SCONST, a string
 	//	for TYPE_FCONST, a float64
 	//	for TYPE_BRANCH, a *Prog (optional)
 	//	for TYPE_TEXTSIZE, an int32 (optional)
 	Val interface{}
 }
 
 type AddrName int8
 
 const (
 	NAME_NONE AddrName = iota
 	NAME_EXTERN
 	NAME_STATIC
 	NAME_AUTO
 	NAME_PARAM
 	// A reference to name@GOT(SB) is a reference to the entry in the global offset
 	// table for 'name'.
 	NAME_GOTREF
 	// Indicates that this is a reference to a TOC anchor.
 	NAME_TOCREF
 )
 
 //go:generate stringer -type AddrType
 
 type AddrType uint8
 
 const (
 	TYPE_NONE AddrType = iota
 	TYPE_BRANCH
 	TYPE_TEXTSIZE
 	TYPE_MEM
 	TYPE_CONST
 	TYPE_FCONST
 	TYPE_SCONST
 	TYPE_REG
 	TYPE_ADDR
 	TYPE_SHIFT
 	TYPE_REGREG
 	TYPE_REGREG2
 	TYPE_INDIR
 	TYPE_REGLIST
 )
 
 func (a *Addr) Target() *Prog {
 	if a.Type == TYPE_BRANCH && a.Val != nil {
 		return a.Val.(*Prog)
 	}
 	return nil
 }
 func (a *Addr) SetTarget(t *Prog) {
 	if a.Type != TYPE_BRANCH {
 		panic("setting branch target when type is not TYPE_BRANCH")
 	}
 	a.Val = t
 }
 
 // Prog describes a single machine instruction.
 //
 // The general instruction form is:
 //
 //	(1) As.Scond From [, ...RestArgs], To
 //	(2) As.Scond From, Reg [, ...RestArgs], To, RegTo2
 //
 // where As is an opcode and the others are arguments:
 // From, Reg are sources, and To, RegTo2 are destinations.
 // RestArgs can hold additional sources and destinations.
 // Usually, not all arguments are present.
 // For example, MOVL R1, R2 encodes using only As=MOVL, From=R1, To=R2.
 // The Scond field holds additional condition bits for systems (like arm)
 // that have generalized conditional execution.
 // (2) form is present for compatibility with older code,
 // to avoid too much changes in a single swing.
 // (1) scheme is enough to express any kind of operand combination.
 //
 // Jump instructions use the To.Val field to point to the target *Prog,
 // which must be in the same linked list as the jump instruction.
 //
 // The Progs for a given function are arranged in a list linked through the Link field.
 //
 // Each Prog is charged to a specific source line in the debug information,
 // specified by Pos.Line().
 // Every Prog has a Ctxt field that defines its context.
 // For performance reasons, Progs usually are usually bulk allocated, cached, and reused;
 // those bulk allocators should always be used, rather than new(Prog).
 //
 // The other fields not yet mentioned are for use by the back ends and should
 // be left zeroed by creators of Prog lists.
 type Prog struct {
 	Ctxt     *Link    // linker context
 	Link     *Prog    // next Prog in linked list
 	From     Addr     // first source operand
 	RestArgs []Addr   // can pack any operands that not fit into {Prog.From, Prog.To}
 	To       Addr     // destination operand (second is RegTo2 below)
 	Pool     *Prog    // constant pool entry, for arm,arm64 back ends
 	Forwd    *Prog    // for x86 back end
 	Rel      *Prog    // for x86, arm back ends
 	Pc       int64    // for back ends or assembler: virtual or actual program counter, depending on phase
 	Pos      src.XPos // source position of this instruction
 	Spadj    int32    // effect of instruction on stack pointer (increment or decrement amount)
 	As       As       // assembler opcode
 	Reg      int16    // 2nd source operand
 	RegTo2   int16    // 2nd destination operand
 	Mark     uint16   // bitmask of arch-specific items
 	Optab    uint16   // arch-specific opcode index
 	Scond    uint8    // bits that describe instruction suffixes (e.g. ARM conditions)
 	Back     uint8    // for x86 back end: backwards branch state
 	Ft       uint8    // for x86 back end: type index of Prog.From
 	Tt       uint8    // for x86 back end: type index of Prog.To
 	Isize    uint8    // for x86 back end: size of the instruction in bytes
 }
 
 // From3Type returns p.GetFrom3().Type, or TYPE_NONE when
 // p.GetFrom3() returns nil.
 //
 // Deprecated: for the same reasons as Prog.GetFrom3.
 func (p *Prog) From3Type() AddrType {
 	if p.RestArgs == nil {
 		return TYPE_NONE
 	}
 	return p.RestArgs[0].Type
 }
 
 // GetFrom3 returns second source operand (the first is Prog.From).
 // In combination with Prog.From and Prog.To it makes common 3 operand
 // case easier to use.
 //
 // Should be used only when RestArgs is set with SetFrom3.
 //
 // Deprecated: better use RestArgs directly or define backend-specific getters.
 // Introduced to simplify transition to []Addr.
 // Usage of this is discouraged due to fragility and lack of guarantees.
 func (p *Prog) GetFrom3() *Addr {
 	if p.RestArgs == nil {
 		return nil
 	}
 	return &p.RestArgs[0]
 }
 
 // SetFrom3 assigns []Addr{a} to p.RestArgs.
 // In pair with Prog.GetFrom3 it can help in emulation of Prog.From3.
 //
 // Deprecated: for the same reasons as Prog.GetFrom3.
 func (p *Prog) SetFrom3(a Addr) {
 	p.RestArgs = []Addr{a}
 }
 
 // An As denotes an assembler opcode.
 // There are some portable opcodes, declared here in package obj,
 // that are common to all architectures.
 // However, the majority of opcodes are arch-specific
 // and are declared in their respective architecture's subpackage.
 type As int16
 
 // These are the portable opcodes.
 const (
 	AXXX As = iota
 	ACALL
 	ADUFFCOPY
 	ADUFFZERO
 	AEND
 	AFUNCDATA
 	AJMP
 	ANOP
 	APCALIGN
 	APCDATA
 	ARET
 	AGETCALLERPC
 	ATEXT
 	AUNDEF
 	A_ARCHSPECIFIC
 )
 
 // Each architecture is allotted a distinct subspace of opcode values
 // for declaring its arch-specific opcodes.
 // Within this subspace, the first arch-specific opcode should be
 // at offset A_ARCHSPECIFIC.
 //
 // Subspaces are aligned to a power of two so opcodes can be masked
 // with AMask and used as compact array indices.
 const (
 	ABase386 = (1 + iota) << 11
 	ABaseARM
 	ABaseAMD64
 	ABasePPC64
 	ABaseARM64
 	ABaseMIPS
 	ABaseRISCV
 	ABaseS390X
 	ABaseWasm
 
 	AllowedOpCodes = 1 << 11            // The number of opcodes available for any given architecture.
 	AMask          = AllowedOpCodes - 1 // AND with this to use the opcode as an array index.
 )
 
 // An LSym is the sort of symbol that is written to an object file.
 // It represents Go symbols in a flat pkg+"."+name namespace.
 type LSym struct {
 	Name string
 	Type objabi.SymKind
 	Attribute
 
 	RefIdx int // Index of this symbol in the symbol reference list.
 	Size   int64
 	Gotype *LSym
 	P      []byte
 	R      []Reloc
 
 	Func *FuncInfo
 
 	Pkg    string
 	PkgIdx int32
 	SymIdx int32 // TODO: replace RefIdx
 }
 
 // A FuncInfo contains extra fields for STEXT symbols.
 type FuncInfo struct {
 	Args     int32
 	Locals   int32
 	Align    int32
 	FuncID   objabi.FuncID
 	Text     *Prog
 	Autot    map[*LSym]struct{}
 	Pcln     Pcln
 	InlMarks []InlMark
 
 	dwarfInfoSym       *LSym
 	dwarfLocSym        *LSym
 	dwarfRangesSym     *LSym
 	dwarfAbsFnSym      *LSym
 	dwarfDebugLinesSym *LSym
 
 	GCArgs             *LSym
 	GCLocals           *LSym
 	GCRegs             *LSym // Only if !go115ReduceLiveness
 	StackObjects       *LSym
 	OpenCodedDeferInfo *LSym
 
 	FuncInfoSym *LSym
 }
 
 type InlMark struct {
 	// When unwinding from an instruction in an inlined body, mark
 	// where we should unwind to.
 	// id records the global inlining id of the inlined body.
 	// p records the location of an instruction in the parent (inliner) frame.
 	p  *Prog
 	id int32
 }
 
 // Mark p as the instruction to set as the pc when
 // "unwinding" the inlining global frame id. Usually it should be
 // instruction with a file:line at the callsite, and occur
 // just before the body of the inlined function.
 func (fi *FuncInfo) AddInlMark(p *Prog, id int32) {
 	fi.InlMarks = append(fi.InlMarks, InlMark{p: p, id: id})
 }
 
 // Record the type symbol for an auto variable so that the linker
 // an emit DWARF type information for the type.
 func (fi *FuncInfo) RecordAutoType(gotype *LSym) {
 	if fi.Autot == nil {
 		fi.Autot = make(map[*LSym]struct{})
 	}
 	fi.Autot[gotype] = struct{}{}
 }
 
 //go:generate stringer -type ABI
 
 // ABI is the calling convention of a text symbol.
 type ABI uint8
 
 const (
 	// ABI0 is the stable stack-based ABI. It's important that the
 	// value of this is "0": we can't distinguish between
 	// references to data and ABI0 text symbols in assembly code,
 	// and hence this doesn't distinguish between symbols without
 	// an ABI and text symbols with ABI0.
 	ABI0 ABI = iota
 
 	// ABIInternal is the internal ABI that may change between Go
 	// versions. All Go functions use the internal ABI and the
 	// compiler generates wrappers for calls to and from other
 	// ABIs.
 	ABIInternal
 
 	ABICount
 )
 
 // Attribute is a set of symbol attributes.
 type Attribute uint32
 
 const (
 	AttrDuplicateOK Attribute = 1 << iota
 	AttrCFunc
 	AttrNoSplit
 	AttrLeaf
 	AttrWrapper
 	AttrNeedCtxt
 	AttrNoFrame
 	AttrOnList
 	AttrStatic
 
 	// MakeTypelink means that the type should have an entry in the typelink table.
 	AttrMakeTypelink
 
 	// ReflectMethod means the function may call reflect.Type.Method or
 	// reflect.Type.MethodByName. Matching is imprecise (as reflect.Type
 	// can be used through a custom interface), so ReflectMethod may be
 	// set in some cases when the reflect package is not called.
 	//
 	// Used by the linker to determine what methods can be pruned.
 	AttrReflectMethod
 
 	// Local means make the symbol local even when compiling Go code to reference Go
 	// symbols in other shared libraries, as in this mode symbols are global by
 	// default. "local" here means in the sense of the dynamic linker, i.e. not
 	// visible outside of the module (shared library or executable) that contains its
 	// definition. (When not compiling to support Go shared libraries, all symbols are
 	// local in this sense unless there is a cgo_export_* directive).
 	AttrLocal
 
 	// For function symbols; indicates that the specified function was the
 	// target of an inline during compilation
 	AttrWasInlined
 
 	// TopFrame means that this function is an entry point and unwinders should not
 	// keep unwinding beyond this frame.
 	AttrTopFrame
 
 	// Indexed indicates this symbol has been assigned with an index (when using the
 	// new object file format).
 	AttrIndexed
 
 	// Only applied on type descriptor symbols, UsedInIface indicates this type is
 	// converted to an interface.
 	//
 	// Used by the linker to determine what methods can be pruned.
 	AttrUsedInIface
 
 	// ContentAddressable indicates this is a content-addressable symbol.
 	AttrContentAddressable
 
 	// attrABIBase is the value at which the ABI is encoded in
 	// Attribute. This must be last; all bits after this are
 	// assumed to be an ABI value.
 	//
 	// MUST BE LAST since all bits above this comprise the ABI.
 	attrABIBase
 )
 
 func (a Attribute) DuplicateOK() bool        { return a&AttrDuplicateOK != 0 }
 func (a Attribute) MakeTypelink() bool       { return a&AttrMakeTypelink != 0 }
 func (a Attribute) CFunc() bool              { return a&AttrCFunc != 0 }
 func (a Attribute) NoSplit() bool            { return a&AttrNoSplit != 0 }
 func (a Attribute) Leaf() bool               { return a&AttrLeaf != 0 }
 func (a Attribute) OnList() bool             { return a&AttrOnList != 0 }
 func (a Attribute) ReflectMethod() bool      { return a&AttrReflectMethod != 0 }
 func (a Attribute) Local() bool              { return a&AttrLocal != 0 }
 func (a Attribute) Wrapper() bool            { return a&AttrWrapper != 0 }
 func (a Attribute) NeedCtxt() bool           { return a&AttrNeedCtxt != 0 }
 func (a Attribute) NoFrame() bool            { return a&AttrNoFrame != 0 }
 func (a Attribute) Static() bool             { return a&AttrStatic != 0 }
 func (a Attribute) WasInlined() bool         { return a&AttrWasInlined != 0 }
 func (a Attribute) TopFrame() bool           { return a&AttrTopFrame != 0 }
 func (a Attribute) Indexed() bool            { return a&AttrIndexed != 0 }
 func (a Attribute) UsedInIface() bool        { return a&AttrUsedInIface != 0 }
 func (a Attribute) ContentAddressable() bool { return a&AttrContentAddressable != 0 }
 
 func (a *Attribute) Set(flag Attribute, value bool) {
 	if value {
 		*a |= flag
 	} else {
 		*a &^= flag
 	}
 }
 
 func (a Attribute) ABI() ABI { return ABI(a / attrABIBase) }
 func (a *Attribute) SetABI(abi ABI) {
 	const mask = 1 // Only one ABI bit for now.
 	*a = (*a &^ (mask * attrABIBase)) | Attribute(abi)*attrABIBase
 }
 
 var textAttrStrings = [...]struct {
 	bit Attribute
 	s   string
 }{
 	{bit: AttrDuplicateOK, s: "DUPOK"},
 	{bit: AttrMakeTypelink, s: ""},
 	{bit: AttrCFunc, s: "CFUNC"},
 	{bit: AttrNoSplit, s: "NOSPLIT"},
 	{bit: AttrLeaf, s: "LEAF"},
 	{bit: AttrOnList, s: ""},
 	{bit: AttrReflectMethod, s: "REFLECTMETHOD"},
 	{bit: AttrLocal, s: "LOCAL"},
 	{bit: AttrWrapper, s: "WRAPPER"},
 	{bit: AttrNeedCtxt, s: "NEEDCTXT"},
 	{bit: AttrNoFrame, s: "NOFRAME"},
 	{bit: AttrStatic, s: "STATIC"},
 	{bit: AttrWasInlined, s: ""},
 	{bit: AttrTopFrame, s: "TOPFRAME"},
 	{bit: AttrIndexed, s: ""},
 	{bit: AttrContentAddressable, s: ""},
 }
 
 // TextAttrString formats a for printing in as part of a TEXT prog.
 func (a Attribute) TextAttrString() string {
 	var s string
 	for _, x := range textAttrStrings {
 		if a&x.bit != 0 {
 			if x.s != "" {
 				s += x.s + "|"
 			}
 			a &^= x.bit
 		}
 	}
 	switch a.ABI() {
 	case ABI0:
 	case ABIInternal:
 		s += "ABIInternal|"
 		a.SetABI(0) // Clear ABI so we don't print below.
 	}
 	if a != 0 {
 		s += fmt.Sprintf("UnknownAttribute(%d)|", a)
 	}
 	// Chop off trailing |, if present.
 	if len(s) > 0 {
 		s = s[:len(s)-1]
 	}
 	return s
 }
 
 func (s *LSym) String() string {
 	return s.Name
 }
 
 // The compiler needs *LSym to be assignable to cmd/compile/internal/ssa.Sym.
 func (s *LSym) CanBeAnSSASym() {
 }
 
 type Pcln struct {
 	Pcsp        Pcdata
 	Pcfile      Pcdata
 	Pcline      Pcdata
 	Pcinline    Pcdata
 	Pcdata      []Pcdata
 	Funcdata    []*LSym
 	Funcdataoff []int64
 	UsedFiles   map[goobj.CUFileIndex]struct{} // file indices used while generating pcfile
 	InlTree     InlTree                        // per-function inlining tree extracted from the global tree
 }
 
 type Reloc struct {
 	Off  int32
 	Siz  uint8
 	Type objabi.RelocType
 	Add  int64
 	Sym  *LSym
 }
 
 type Auto struct {
 	Asym    *LSym
 	Aoffset int32
 	Name    AddrName
 	Gotype  *LSym
 }
 
 type Pcdata struct {
 	P []byte
 }
 
 // Link holds the context for writing object code from a compiler
 // to be linker input or for reading that input into the linker.
 type Link struct {
 	Headtype           objabi.HeadType
 	Arch               *LinkArch
 	Debugasm           int
 	Debugvlog          bool
 	Debugpcln          string
 	Flag_shared        bool
 	Flag_dynlink       bool
 	Flag_linkshared    bool
 	Flag_optimize      bool
 	Flag_locationlists bool
 	Retpoline          bool // emit use of retpoline stubs for indirect jmp/call
 	Bso                *bufio.Writer
 	Pathname           string
 	Pkgpath            string           // the current package's import path, "" if unknown
 	hashmu             sync.Mutex       // protects hash, funchash
 	hash               map[string]*LSym // name -> sym mapping
 	funchash           map[string]*LSym // name -> sym mapping for ABIInternal syms
 	statichash         map[string]*LSym // name -> sym mapping for static syms
 	PosTable           src.PosTable
 	InlTree            InlTree // global inlining tree used by gc/inl.go
 	DwFixups           *DwarfFixupTable
 	Imports            []goobj.ImportedPkg
 	DiagFunc           func(string, ...interface{})
 	DiagFlush          func()
 	DebugInfo          func(fn *LSym, info *LSym, curfn interface{}) ([]dwarf.Scope, dwarf.InlCalls) // if non-nil, curfn is a *gc.Node
 	GenAbstractFunc    func(fn *LSym)
 	Errors             int
 
 	InParallel    bool // parallel backend phase in effect
 	UseBASEntries bool // use Base Address Selection Entries in location lists and PC ranges
 	IsAsm         bool // is the source assembly language, which may contain surprising idioms (e.g., call tables)
 
 	// state for writing objects
 	Text []*LSym
 	Data []*LSym
 
 	// ABIAliases are text symbols that should be aliased to all
 	// ABIs. These symbols may only be referenced and not defined
 	// by this object, since the need for an alias may appear in a
 	// different object than the definition. Hence, this
 	// information can't be carried in the symbol definition.
 	//
 	// TODO(austin): Replace this with ABI wrappers once the ABIs
 	// actually diverge.
 	ABIAliases []*LSym
 
 	// Constant symbols (e.g. $i64.*) are data symbols created late
 	// in the concurrent phase. To ensure a deterministic order, we
 	// add them to a separate list, sort at the end, and append it
 	// to Data.
 	constSyms []*LSym
 
 	// pkgIdx maps package path to index. The index is used for
 	// symbol reference in the object file.
 	pkgIdx map[string]int32
 
 	defs         []*LSym // list of defined symbols in the current package
 	hashed64defs []*LSym // list of defined short (64-bit or less) hashed (content-addressable) symbols
 	hasheddefs   []*LSym // list of defined hashed (content-addressable) symbols
 	nonpkgdefs   []*LSym // list of defined non-package symbols
 	nonpkgrefs   []*LSym // list of referenced non-package symbols
 
 	Fingerprint goobj.FingerprintType // fingerprint of symbol indices, to catch index mismatch
 }
 
 func (ctxt *Link) Diag(format string, args ...interface{}) {
 	ctxt.Errors++
 	ctxt.DiagFunc(format, args...)
 }
 
 func (ctxt *Link) Logf(format string, args ...interface{}) {
 	fmt.Fprintf(ctxt.Bso, format, args...)
 	ctxt.Bso.Flush()
 }
 
 // The smallest possible offset from the hardware stack pointer to a local
 // variable on the stack. Architectures that use a link register save its value
 // on the stack in the function prologue and so always have a pointer between
 // the hardware stack pointer and the local variable area.
 func (ctxt *Link) FixedFrameSize() int64 {
 	switch ctxt.Arch.Family {
 	case sys.AMD64, sys.I386, sys.Wasm:
 		return 0
 	case sys.PPC64:
 		// PIC code on ppc64le requires 32 bytes of stack, and it's easier to
 		// just use that much stack always on ppc64x.
 		return int64(4 * ctxt.Arch.PtrSize)
 	default:
 		return int64(ctxt.Arch.PtrSize)
 	}
 }
 
 // LinkArch is the definition of a single architecture.
 type LinkArch struct {
 	*sys.Arch
 	Init           func(*Link)
 	Preprocess     func(*Link, *LSym, ProgAlloc)
 	Assemble       func(*Link, *LSym, ProgAlloc)
 	Progedit       func(*Link, *Prog, ProgAlloc)
 	UnaryDst       map[As]bool // Instruction takes one operand, a destination.
 	DWARFRegisters map[int16]int16
 }