src/cmd/internal/obj/arm64/obj7.go - go - Git at Google

 // cmd/7l/noop.c, cmd/7l/obj.c, cmd/ld/pass.c from Vita Nuova.
 // https://code.google.com/p/ken-cc/source/browse/
 //
 // 	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 arm64

 import (
 	"cmd/internal/obj"
 	"cmd/internal/sys"
 	"fmt"
 	"log"
 	"math"
 )

 var complements = []obj.As{
 	AADD:  ASUB,
 	AADDW: ASUBW,
 	ASUB:  AADD,
 	ASUBW: AADDW,
 	ACMP:  ACMN,
 	ACMPW: ACMNW,
 	ACMN:  ACMP,
 	ACMNW: ACMPW,
 }

 func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
 	// MOV	g_stackguard(g), R1
 	p = obj.Appendp(ctxt, p)

 	p.As = AMOVD
 	p.From.Type = obj.TYPE_MEM
 	p.From.Reg = REGG
 	p.From.Offset = 2 * int64(ctxt.Arch.PtrSize) // G.stackguard0
 	if ctxt.Cursym.CFunc() {
 		p.From.Offset = 3 * int64(ctxt.Arch.PtrSize) // G.stackguard1
 	}
 	p.To.Type = obj.TYPE_REG
 	p.To.Reg = REG_R1

 	q := (*obj.Prog)(nil)
 	if framesize <= obj.StackSmall {
 		// small stack: SP < stackguard
 		//	MOV	SP, R2
 		//	CMP	stackguard, R2
 		p = obj.Appendp(ctxt, p)

 		p.As = AMOVD
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REGSP
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2

 		p = obj.Appendp(ctxt, p)
 		p.As = ACMP
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REG_R1
 		p.Reg = REG_R2
 	} else if framesize <= obj.StackBig {
 		// large stack: SP-framesize < stackguard-StackSmall
 		//	SUB	$framesize, SP, R2
 		//	CMP	stackguard, R2
 		p = obj.Appendp(ctxt, p)

 		p.As = ASUB
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = int64(framesize)
 		p.Reg = REGSP
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2

 		p = obj.Appendp(ctxt, p)
 		p.As = ACMP
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REG_R1
 		p.Reg = REG_R2
 	} else {
 		// Such a large stack we need to protect against wraparound
 		// if SP is close to zero.
 		//	SP-stackguard+StackGuard < framesize + (StackGuard-StackSmall)
 		// The +StackGuard on both sides is required to keep the left side positive:
 		// SP is allowed to be slightly below stackguard. See stack.h.
 		//	CMP	$StackPreempt, R1
 		//	BEQ	label_of_call_to_morestack
 		//	ADD	$StackGuard, SP, R2
 		//	SUB	R1, R2
 		//	MOV	$(framesize+(StackGuard-StackSmall)), R3
 		//	CMP	R3, R2
 		p = obj.Appendp(ctxt, p)

 		p.As = ACMP
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = obj.StackPreempt
 		p.Reg = REG_R1

 		p = obj.Appendp(ctxt, p)
 		q = p
 		p.As = ABEQ
 		p.To.Type = obj.TYPE_BRANCH

 		p = obj.Appendp(ctxt, p)
 		p.As = AADD
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = obj.StackGuard
 		p.Reg = REGSP
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2

 		p = obj.Appendp(ctxt, p)
 		p.As = ASUB
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REG_R1
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2

 		p = obj.Appendp(ctxt, p)
 		p.As = AMOVD
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = int64(framesize) + (obj.StackGuard - obj.StackSmall)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R3

 		p = obj.Appendp(ctxt, p)
 		p.As = ACMP
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REG_R3
 		p.Reg = REG_R2
 	}

 	// BLS	do-morestack
 	bls := obj.Appendp(ctxt, p)
 	bls.As = ABLS
 	bls.To.Type = obj.TYPE_BRANCH

 	var last *obj.Prog
 	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
 	}

 	// Now we are at the end of the function, but logically
 	// we are still in function prologue. We need to fix the
 	// SP data and PCDATA.
 	spfix := obj.Appendp(ctxt, last)
 	spfix.As = obj.ANOP
 	spfix.Spadj = -framesize

 	pcdata := obj.Appendp(ctxt, spfix)
 	pcdata.Lineno = ctxt.Cursym.Text.Lineno
 	pcdata.Mode = ctxt.Cursym.Text.Mode
 	pcdata.As = obj.APCDATA
 	pcdata.From.Type = obj.TYPE_CONST
 	pcdata.From.Offset = obj.PCDATA_StackMapIndex
 	pcdata.To.Type = obj.TYPE_CONST
 	pcdata.To.Offset = -1 // pcdata starts at -1 at function entry

 	// MOV	LR, R3
 	movlr := obj.Appendp(ctxt, pcdata)
 	movlr.As = AMOVD
 	movlr.From.Type = obj.TYPE_REG
 	movlr.From.Reg = REGLINK
 	movlr.To.Type = obj.TYPE_REG
 	movlr.To.Reg = REG_R3
 	if q != nil {
 		q.Pcond = movlr
 	}
 	bls.Pcond = movlr

 	debug := movlr
 	if false {
 		debug = obj.Appendp(ctxt, debug)
 		debug.As = AMOVD
 		debug.From.Type = obj.TYPE_CONST
 		debug.From.Offset = int64(framesize)
 		debug.To.Type = obj.TYPE_REG
 		debug.To.Reg = REGTMP
 	}

 	// BL	runtime.morestack(SB)
 	call := obj.Appendp(ctxt, debug)
 	call.As = ABL
 	call.To.Type = obj.TYPE_BRANCH
 	morestack := "runtime.morestack"
 	switch {
 	case ctxt.Cursym.CFunc():
 		morestack = "runtime.morestackc"
 	case ctxt.Cursym.Text.From3.Offset&obj.NEEDCTXT == 0:
 		morestack = "runtime.morestack_noctxt"
 	}
 	call.To.Sym = obj.Linklookup(ctxt, morestack, 0)

 	// B	start
 	jmp := obj.Appendp(ctxt, call)
 	jmp.As = AB
 	jmp.To.Type = obj.TYPE_BRANCH
 	jmp.Pcond = ctxt.Cursym.Text.Link
 	jmp.Spadj = +framesize

 	// placeholder for bls's jump target
 	// p = obj.Appendp(ctxt, p)
 	// p.As = obj.ANOP

 	return bls
 }

 func progedit(ctxt *obj.Link, p *obj.Prog) {
 	p.From.Class = 0
 	p.To.Class = 0

 	// $0 results in C_ZCON, which matches both C_REG and various
 	// C_xCON, however the C_REG cases in asmout don't expect a
 	// constant, so they will use the register fields and assemble
 	// a R0. To prevent that, rewrite $0 as ZR.
 	if p.From.Type == obj.TYPE_CONST && p.From.Offset == 0 {
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REGZERO
 	}
 	if p.To.Type == obj.TYPE_CONST && p.To.Offset == 0 {
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REGZERO
 	}

 	// Rewrite BR/BL to symbol as TYPE_BRANCH.
 	switch p.As {
 	case AB,
 		ABL,
 		obj.ARET,
 		obj.ADUFFZERO,
 		obj.ADUFFCOPY:
 		if p.To.Sym != nil {
 			p.To.Type = obj.TYPE_BRANCH
 		}
 		break
 	}

 	// Rewrite float constants to values stored in memory.
 	switch p.As {
 	case AFMOVS:
 		if p.From.Type == obj.TYPE_FCONST {
 			f32 := float32(p.From.Val.(float64))
 			i32 := math.Float32bits(f32)
 			if i32 == 0 {
 				p.From.Type = obj.TYPE_REG
 				p.From.Reg = REGZERO
 				break
 			}
 			literal := fmt.Sprintf("$f32.%08x", i32)
 			s := obj.Linklookup(ctxt, literal, 0)
 			s.Size = 4
 			p.From.Type = obj.TYPE_MEM
 			p.From.Sym = s
 			p.From.Sym.Set(obj.AttrLocal, true)
 			p.From.Name = obj.NAME_EXTERN
 			p.From.Offset = 0
 		}

 	case AFMOVD:
 		if p.From.Type == obj.TYPE_FCONST {
 			i64 := math.Float64bits(p.From.Val.(float64))
 			if i64 == 0 {
 				p.From.Type = obj.TYPE_REG
 				p.From.Reg = REGZERO
 				break
 			}
 			literal := fmt.Sprintf("$f64.%016x", i64)
 			s := obj.Linklookup(ctxt, literal, 0)
 			s.Size = 8
 			p.From.Type = obj.TYPE_MEM
 			p.From.Sym = s
 			p.From.Sym.Set(obj.AttrLocal, true)
 			p.From.Name = obj.NAME_EXTERN
 			p.From.Offset = 0
 		}

 		break
 	}

 	// Rewrite negative immediates as positive immediates with
 	// complementary instruction.
 	switch p.As {
 	case AADD, ASUB, ACMP, ACMN:
 		if p.From.Type == obj.TYPE_CONST && p.From.Offset < 0 && p.From.Offset != -1<<63 {
 			p.From.Offset = -p.From.Offset
 			p.As = complements[p.As]
 		}
 	case AADDW, ASUBW, ACMPW, ACMNW:
 		if p.From.Type == obj.TYPE_CONST && p.From.Offset < 0 && int32(p.From.Offset) != -1<<31 {
 			p.From.Offset = -p.From.Offset
 			p.As = complements[p.As]
 		}
 	}

 	// For 32-bit logical instruction with constant,
 	// rewrite the high 32-bit to be a repetition of
 	// the low 32-bit, so that the BITCON test can be
 	// shared for both 32-bit and 64-bit. 32-bit ops
 	// will zero the high 32-bit of the destination
 	// register anyway.
 	switch p.As {
 	case AANDW, AORRW, AEORW, AANDSW:
 		if p.From.Type == obj.TYPE_CONST {
 			v := p.From.Offset & 0xffffffff
 			p.From.Offset = v | v<<32
 		}
 	}

 	if ctxt.Flag_dynlink {
 		rewriteToUseGot(ctxt, p)
 	}
 }

 // Rewrite p, if necessary, to access global data via the global offset table.
 func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
 	if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
 		//     ADUFFxxx $offset
 		// becomes
 		//     MOVD runtime.duffxxx@GOT, REGTMP
 		//     ADD $offset, REGTMP
 		//     CALL REGTMP
 		var sym *obj.LSym
 		if p.As == obj.ADUFFZERO {
 			sym = obj.Linklookup(ctxt, "runtime.duffzero", 0)
 		} else {
 			sym = obj.Linklookup(ctxt, "runtime.duffcopy", 0)
 		}
 		offset := p.To.Offset
 		p.As = AMOVD
 		p.From.Type = obj.TYPE_MEM
 		p.From.Name = obj.NAME_GOTREF
 		p.From.Sym = sym
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REGTMP
 		p.To.Name = obj.NAME_NONE
 		p.To.Offset = 0
 		p.To.Sym = nil
 		p1 := obj.Appendp(ctxt, p)
 		p1.As = AADD
 		p1.From.Type = obj.TYPE_CONST
 		p1.From.Offset = offset
 		p1.To.Type = obj.TYPE_REG
 		p1.To.Reg = REGTMP
 		p2 := obj.Appendp(ctxt, p1)
 		p2.As = obj.ACALL
 		p2.To.Type = obj.TYPE_REG
 		p2.To.Reg = REGTMP
 	}

 	// We only care about global data: NAME_EXTERN means a global
 	// symbol in the Go sense, and p.Sym.Local is true for a few
 	// internally defined symbols.
 	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
 		// MOVD $sym, Rx becomes MOVD sym@GOT, Rx
 		// MOVD $sym+<off>, Rx becomes MOVD sym@GOT, Rx; ADD <off>, Rx
 		if p.As != AMOVD {
 			ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
 		}
 		if p.To.Type != obj.TYPE_REG {
 			ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
 		}
 		p.From.Type = obj.TYPE_MEM
 		p.From.Name = obj.NAME_GOTREF
 		if p.From.Offset != 0 {
 			q := obj.Appendp(ctxt, p)
 			q.As = AADD
 			q.From.Type = obj.TYPE_CONST
 			q.From.Offset = p.From.Offset
 			q.To = p.To
 			p.From.Offset = 0
 		}
 	}
 	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
 		ctxt.Diag("don't know how to handle %v with -dynlink", p)
 	}
 	var source *obj.Addr
 	// MOVx sym, Ry becomes MOVD sym@GOT, REGTMP; MOVx (REGTMP), Ry
 	// MOVx Ry, sym becomes MOVD sym@GOT, REGTMP; MOVD Ry, (REGTMP)
 	// An addition may be inserted between the two MOVs if there is an offset.
 	if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
 		if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
 			ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
 		}
 		source = &p.From
 	} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
 		source = &p.To
 	} else {
 		return
 	}
 	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
 		return
 	}
 	if source.Sym.Type == obj.STLSBSS {
 		return
 	}
 	if source.Type != obj.TYPE_MEM {
 		ctxt.Diag("don't know how to handle %v with -dynlink", p)
 	}
 	p1 := obj.Appendp(ctxt, p)
 	p2 := obj.Appendp(ctxt, p1)
 	p1.As = AMOVD
 	p1.From.Type = obj.TYPE_MEM
 	p1.From.Sym = source.Sym
 	p1.From.Name = obj.NAME_GOTREF
 	p1.To.Type = obj.TYPE_REG
 	p1.To.Reg = REGTMP

 	p2.As = p.As
 	p2.From = p.From
 	p2.To = p.To
 	if p.From.Name == obj.NAME_EXTERN {
 		p2.From.Reg = REGTMP
 		p2.From.Name = obj.NAME_NONE
 		p2.From.Sym = nil
 	} else if p.To.Name == obj.NAME_EXTERN {
 		p2.To.Reg = REGTMP
 		p2.To.Name = obj.NAME_NONE
 		p2.To.Sym = nil
 	} else {
 		return
 	}
 	obj.Nopout(p)
 }

 func follow(ctxt *obj.Link, s *obj.LSym) {
 	ctxt.Cursym = s

 	firstp := ctxt.NewProg()
 	lastp := firstp
 	xfol(ctxt, s.Text, &lastp)
 	lastp.Link = nil
 	s.Text = firstp.Link
 }

 func relinv(a obj.As) obj.As {
 	switch a {
 	case ABEQ:
 		return ABNE
 	case ABNE:
 		return ABEQ
 	case ABCS:
 		return ABCC
 	case ABHS:
 		return ABLO
 	case ABCC:
 		return ABCS
 	case ABLO:
 		return ABHS
 	case ABMI:
 		return ABPL
 	case ABPL:
 		return ABMI
 	case ABVS:
 		return ABVC
 	case ABVC:
 		return ABVS
 	case ABHI:
 		return ABLS
 	case ABLS:
 		return ABHI
 	case ABGE:
 		return ABLT
 	case ABLT:
 		return ABGE
 	case ABGT:
 		return ABLE
 	case ABLE:
 		return ABGT
 	case ACBZ:
 		return ACBNZ
 	case ACBNZ:
 		return ACBZ
 	case ACBZW:
 		return ACBNZW
 	case ACBNZW:
 		return ACBZW
 	}

 	log.Fatalf("unknown relation: %s", Anames[a-obj.ABaseARM64])
 	return 0
 }

 func xfol(ctxt *obj.Link, p *obj.Prog, last **obj.Prog) {
 	var q *obj.Prog
 	var r *obj.Prog
 	var i int

 loop:
 	if p == nil {
 		return
 	}
 	a := p.As
 	if a == AB {
 		q = p.Pcond
 		if q != nil {
 			p.Mark |= FOLL
 			p = q
 			if !(p.Mark&FOLL != 0) {
 				goto loop
 			}
 		}
 	}

 	if p.Mark&FOLL != 0 {
 		i = 0
 		q = p
 		for ; i < 4; i, q = i+1, q.Link {
 			if q == *last || q == nil {
 				break
 			}
 			a = q.As
 			if a == obj.ANOP {
 				i--
 				continue
 			}

 			if a == AB || a == obj.ARET || a == AERET {
 				goto copy
 			}
 			if q.Pcond == nil || (q.Pcond.Mark&FOLL != 0) {
 				continue
 			}
 			if a != ABEQ && a != ABNE {
 				continue
 			}

 		copy:
 			for {
 				r = ctxt.NewProg()
 				*r = *p
 				if !(r.Mark&FOLL != 0) {
 					fmt.Printf("can't happen 1\n")
 				}
 				r.Mark |= FOLL
 				if p != q {
 					p = p.Link
 					(*last).Link = r
 					*last = r
 					continue
 				}

 				(*last).Link = r
 				*last = r
 				if a == AB || a == obj.ARET || a == AERET {
 					return
 				}
 				if a == ABNE {
 					r.As = ABEQ
 				} else {
 					r.As = ABNE
 				}
 				r.Pcond = p.Link
 				r.Link = p.Pcond
 				if !(r.Link.Mark&FOLL != 0) {
 					xfol(ctxt, r.Link, last)
 				}
 				if !(r.Pcond.Mark&FOLL != 0) {
 					fmt.Printf("can't happen 2\n")
 				}
 				return
 			}
 		}

 		a = AB
 		q = ctxt.NewProg()
 		q.As = a
 		q.Lineno = p.Lineno
 		q.To.Type = obj.TYPE_BRANCH
 		q.To.Offset = p.Pc
 		q.Pcond = p
 		p = q
 	}

 	p.Mark |= FOLL
 	(*last).Link = p
 	*last = p
 	if a == AB || a == obj.ARET || a == AERET {
 		return
 	}
 	if p.Pcond != nil {
 		if a != ABL && p.Link != nil {
 			q = obj.Brchain(ctxt, p.Link)
 			if a != obj.ATEXT {
 				if q != nil && (q.Mark&FOLL != 0) {
 					p.As = relinv(a)
 					p.Link = p.Pcond
 					p.Pcond = q
 				}
 			}

 			xfol(ctxt, p.Link, last)
 			q = obj.Brchain(ctxt, p.Pcond)
 			if q == nil {
 				q = p.Pcond
 			}
 			if q.Mark&FOLL != 0 {
 				p.Pcond = q
 				return
 			}

 			p = q
 			goto loop
 		}
 	}

 	p = p.Link
 	goto loop
 }

 func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	ctxt.Cursym = cursym

 	if cursym.Text == nil || cursym.Text.Link == nil {
 		return
 	}

 	p := cursym.Text
 	textstksiz := p.To.Offset
 	aoffset := int32(textstksiz)

 	cursym.Args = p.To.Val.(int32)
 	cursym.Locals = int32(textstksiz)

 	/*
 	 * find leaf subroutines
 	 * strip NOPs
 	 * expand RET
 	 */
 	q := (*obj.Prog)(nil)
 	var q1 *obj.Prog
 	for p := cursym.Text; p != nil; p = p.Link {
 		switch p.As {
 		case obj.ATEXT:
 			p.Mark |= LEAF

 		case obj.ARET:
 			break

 		case obj.ANOP:
 			q1 = p.Link
 			q.Link = q1 /* q is non-nop */
 			q1.Mark |= p.Mark
 			continue

 		case ABL,
 			obj.ADUFFZERO,
 			obj.ADUFFCOPY:
 			cursym.Text.Mark &^= LEAF
 			fallthrough

 		case ACBNZ,
 			ACBZ,
 			ACBNZW,
 			ACBZW,
 			ATBZ,
 			ATBNZ,
 			AB,
 			ABEQ,
 			ABNE,
 			ABCS,
 			ABHS,
 			ABCC,
 			ABLO,
 			ABMI,
 			ABPL,
 			ABVS,
 			ABVC,
 			ABHI,
 			ABLS,
 			ABGE,
 			ABLT,
 			ABGT,
 			ABLE,
 			AADR, /* strange */
 			AADRP:
 			q1 = p.Pcond

 			if q1 != nil {
 				for q1.As == obj.ANOP {
 					q1 = q1.Link
 					p.Pcond = q1
 				}
 			}

 			break
 		}

 		q = p
 	}

 	var q2 *obj.Prog
 	var retjmp *obj.LSym
 	for p := cursym.Text; p != nil; p = p.Link {
 		o := p.As
 		switch o {
 		case obj.ATEXT:
 			cursym.Text = p
 			if textstksiz < 0 {
 				ctxt.Autosize = 0
 			} else {
 				ctxt.Autosize = int32(textstksiz + 8)
 			}
 			if (cursym.Text.Mark&LEAF != 0) && ctxt.Autosize <= 8 {
 				ctxt.Autosize = 0
 			} else if ctxt.Autosize&(16-1) != 0 {
 				// The frame includes an LR.
 				// If the frame size is 8, it's only an LR,
 				// so there's no potential for breaking references to
 				// local variables by growing the frame size,
 				// because there are no local variables.
 				// But otherwise, if there is a non-empty locals section,
 				// the author of the code is responsible for making sure
 				// that the frame size is 8 mod 16.
 				if ctxt.Autosize == 8 {
 					ctxt.Autosize += 8
 					cursym.Locals += 8
 				} else {
 					ctxt.Diag("%v: unaligned frame size %d - must be 8 mod 16 (or 0)", p, ctxt.Autosize-8)
 				}
 			}
 			p.To.Offset = int64(ctxt.Autosize) - 8
 			if ctxt.Autosize == 0 && !(cursym.Text.Mark&LEAF != 0) {
 				if ctxt.Debugvlog != 0 {
 					ctxt.Logf("save suppressed in: %s\n", cursym.Text.From.Sym.Name)
 				}
 				cursym.Text.Mark |= LEAF
 			}

 			if !(p.From3.Offset&obj.NOSPLIT != 0) {
 				p = stacksplit(ctxt, p, ctxt.Autosize) // emit split check
 			}

 			aoffset = ctxt.Autosize
 			if aoffset > 0xF0 {
 				aoffset = 0xF0
 			}
 			if cursym.Text.Mark&LEAF != 0 {
 				cursym.Set(obj.AttrLeaf, true)
 				if ctxt.Autosize == 0 {
 					break
 				}
 			}

 			// Frame is non-empty. Make sure to save link register, even if
 			// it is a leaf function, so that traceback works.
 			q = p
 			if ctxt.Autosize > aoffset {
 				// Frame size is too large for a MOVD.W instruction.
 				// Store link register before decrementing SP, so if a signal comes
 				// during the execution of the function prologue, the traceback
 				// code will not see a half-updated stack frame.
 				q = obj.Appendp(ctxt, q)
 				q.Lineno = p.Lineno
 				q.As = ASUB
 				q.From.Type = obj.TYPE_CONST
 				q.From.Offset = int64(ctxt.Autosize)
 				q.Reg = REGSP
 				q.To.Type = obj.TYPE_REG
 				q.To.Reg = REGTMP

 				q = obj.Appendp(ctxt, q)
 				q.Lineno = p.Lineno
 				q.As = AMOVD
 				q.From.Type = obj.TYPE_REG
 				q.From.Reg = REGLINK
 				q.To.Type = obj.TYPE_MEM
 				q.To.Reg = REGTMP

 				q1 = obj.Appendp(ctxt, q)
 				q1.Lineno = p.Lineno
 				q1.As = AMOVD
 				q1.From.Type = obj.TYPE_REG
 				q1.From.Reg = REGTMP
 				q1.To.Type = obj.TYPE_REG
 				q1.To.Reg = REGSP
 				q1.Spadj = ctxt.Autosize
 			} else {
 				// small frame, update SP and save LR in a single MOVD.W instruction
 				q1 = obj.Appendp(ctxt, q)
 				q1.As = AMOVD
 				q1.Lineno = p.Lineno
 				q1.From.Type = obj.TYPE_REG
 				q1.From.Reg = REGLINK
 				q1.To.Type = obj.TYPE_MEM
 				q1.Scond = C_XPRE
 				q1.To.Offset = int64(-aoffset)
 				q1.To.Reg = REGSP
 				q1.Spadj = aoffset
 			}

 			if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
 				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
 				//
 				//	MOV g_panic(g), R1
 				//	CMP ZR, R1
 				//	BEQ end
 				//	MOV panic_argp(R1), R2
 				//	ADD $(autosize+8), RSP, R3
 				//	CMP R2, R3
 				//	BNE end
 				//	ADD $8, RSP, R4
 				//	MOVD R4, panic_argp(R1)
 				// end:
 				//	NOP
 				//
 				// The NOP is needed to give the jumps somewhere to land.
 				// It is a liblink NOP, not a ARM64 NOP: it encodes to 0 instruction bytes.
 				q = q1

 				q = obj.Appendp(ctxt, q)
 				q.As = AMOVD
 				q.From.Type = obj.TYPE_MEM
 				q.From.Reg = REGG
 				q.From.Offset = 4 * int64(ctxt.Arch.PtrSize) // G.panic
 				q.To.Type = obj.TYPE_REG
 				q.To.Reg = REG_R1

 				q = obj.Appendp(ctxt, q)
 				q.As = ACMP
 				q.From.Type = obj.TYPE_REG
 				q.From.Reg = REGZERO
 				q.Reg = REG_R1

 				q = obj.Appendp(ctxt, q)
 				q.As = ABEQ
 				q.To.Type = obj.TYPE_BRANCH
 				q1 = q

 				q = obj.Appendp(ctxt, q)
 				q.As = AMOVD
 				q.From.Type = obj.TYPE_MEM
 				q.From.Reg = REG_R1
 				q.From.Offset = 0 // Panic.argp
 				q.To.Type = obj.TYPE_REG
 				q.To.Reg = REG_R2

 				q = obj.Appendp(ctxt, q)
 				q.As = AADD
 				q.From.Type = obj.TYPE_CONST
 				q.From.Offset = int64(ctxt.Autosize) + 8
 				q.Reg = REGSP
 				q.To.Type = obj.TYPE_REG
 				q.To.Reg = REG_R3

 				q = obj.Appendp(ctxt, q)
 				q.As = ACMP
 				q.From.Type = obj.TYPE_REG
 				q.From.Reg = REG_R2
 				q.Reg = REG_R3

 				q = obj.Appendp(ctxt, q)
 				q.As = ABNE
 				q.To.Type = obj.TYPE_BRANCH
 				q2 = q

 				q = obj.Appendp(ctxt, q)
 				q.As = AADD
 				q.From.Type = obj.TYPE_CONST
 				q.From.Offset = 8
 				q.Reg = REGSP
 				q.To.Type = obj.TYPE_REG
 				q.To.Reg = REG_R4

 				q = obj.Appendp(ctxt, q)
 				q.As = AMOVD
 				q.From.Type = obj.TYPE_REG
 				q.From.Reg = REG_R4
 				q.To.Type = obj.TYPE_MEM
 				q.To.Reg = REG_R1
 				q.To.Offset = 0 // Panic.argp

 				q = obj.Appendp(ctxt, q)

 				q.As = obj.ANOP
 				q1.Pcond = q
 				q2.Pcond = q
 			}

 		case obj.ARET:
 			nocache(p)
 			if p.From.Type == obj.TYPE_CONST {
 				ctxt.Diag("using BECOME (%v) is not supported!", p)
 				break
 			}

 			retjmp = p.To.Sym
 			p.To = obj.Addr{}
 			if cursym.Text.Mark&LEAF != 0 {
 				if ctxt.Autosize != 0 {
 					p.As = AADD
 					p.From.Type = obj.TYPE_CONST
 					p.From.Offset = int64(ctxt.Autosize)
 					p.To.Type = obj.TYPE_REG
 					p.To.Reg = REGSP
 					p.Spadj = -ctxt.Autosize
 				}
 			} else {
 				/* want write-back pre-indexed SP+autosize -> SP, loading REGLINK*/
 				aoffset = ctxt.Autosize

 				if aoffset > 0xF0 {
 					aoffset = 0xF0
 				}
 				p.As = AMOVD
 				p.From.Type = obj.TYPE_MEM
 				p.Scond = C_XPOST
 				p.From.Offset = int64(aoffset)
 				p.From.Reg = REGSP
 				p.To.Type = obj.TYPE_REG
 				p.To.Reg = REGLINK
 				p.Spadj = -aoffset
 				if ctxt.Autosize > aoffset {
 					q = ctxt.NewProg()
 					q.As = AADD
 					q.From.Type = obj.TYPE_CONST
 					q.From.Offset = int64(ctxt.Autosize) - int64(aoffset)
 					q.To.Type = obj.TYPE_REG
 					q.To.Reg = REGSP
 					q.Link = p.Link
 					q.Spadj = int32(-q.From.Offset)
 					q.Lineno = p.Lineno
 					p.Link = q
 					p = q
 				}
 			}

 			if p.As != obj.ARET {
 				q = ctxt.NewProg()
 				q.Lineno = p.Lineno
 				q.Link = p.Link
 				p.Link = q
 				p = q
 			}

 			if retjmp != nil { // retjmp
 				p.As = AB
 				p.To.Type = obj.TYPE_BRANCH
 				p.To.Sym = retjmp
 				p.Spadj = +ctxt.Autosize
 				break
 			}

 			p.As = obj.ARET
 			p.To.Type = obj.TYPE_MEM
 			p.To.Offset = 0
 			p.To.Reg = REGLINK
 			p.Spadj = +ctxt.Autosize

 		case AADD, ASUB:
 			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
 				if p.As == AADD {
 					p.Spadj = int32(-p.From.Offset)
 				} else {
 					p.Spadj = int32(+p.From.Offset)
 				}
 			}
 			break
 		}
 	}
 }

 func nocache(p *obj.Prog) {
 	p.Optab = 0
 	p.From.Class = 0
 	p.To.Class = 0
 }

 var unaryDst = map[obj.As]bool{
 	AWORD:  true,
 	ADWORD: true,
 	ABL:    true,
 	AB:     true,
 	ASVC:   true,
 }

 var Linkarm64 = obj.LinkArch{
 	Arch:       sys.ArchARM64,
 	Preprocess: preprocess,
 	Assemble:   span7,
 	Follow:     follow,
 	Progedit:   progedit,
 	UnaryDst:   unaryDst,
 }
	// cmd/7l/noop.c, cmd/7l/obj.c, cmd/ld/pass.c from Vita Nuova.
	// https://code.google.com/p/ken-cc/source/browse/
	//
	// 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 arm64

	import (
	"cmd/internal/obj"
	"cmd/internal/sys"
	"fmt"
	"log"
	"math"
	)

	var complements = []obj.As{
	AADD: ASUB,
	AADDW: ASUBW,
	ASUB: AADD,
	ASUBW: AADDW,
	ACMP: ACMN,
	ACMPW: ACMNW,
	ACMN: ACMP,
	ACMNW: ACMPW,
	}

	func stacksplit(ctxt obj.Link, p obj.Prog, framesize int32) *obj.Prog {
	// MOV g_stackguard(g), R1
	p = obj.Appendp(ctxt, p)

	p.As = AMOVD
	p.From.Type = obj.TYPE_MEM
	p.From.Reg = REGG
	p.From.Offset = 2 * int64(ctxt.Arch.PtrSize) // G.stackguard0
	if ctxt.Cursym.CFunc() {
	p.From.Offset = 3 * int64(ctxt.Arch.PtrSize) // G.stackguard1
	}
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R1

	q := (*obj.Prog)(nil)
	if framesize <= obj.StackSmall {
	// small stack: SP < stackguard
	// MOV SP, R2
	// CMP stackguard, R2
	p = obj.Appendp(ctxt, p)

	p.As = AMOVD
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REGSP
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R2

	p = obj.Appendp(ctxt, p)
	p.As = ACMP
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REG_R1
	p.Reg = REG_R2
	} else if framesize <= obj.StackBig {
	// large stack: SP-framesize < stackguard-StackSmall
	// SUB $framesize, SP, R2
	// CMP stackguard, R2
	p = obj.Appendp(ctxt, p)

	p.As = ASUB
	p.From.Type = obj.TYPE_CONST
	p.From.Offset = int64(framesize)
	p.Reg = REGSP
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R2

	p = obj.Appendp(ctxt, p)
	p.As = ACMP
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REG_R1
	p.Reg = REG_R2
	} else {
	// Such a large stack we need to protect against wraparound
	// if SP is close to zero.
	// SP-stackguard+StackGuard < framesize + (StackGuard-StackSmall)
	// The +StackGuard on both sides is required to keep the left side positive:
	// SP is allowed to be slightly below stackguard. See stack.h.
	// CMP $StackPreempt, R1
	// BEQ label_of_call_to_morestack
	// ADD $StackGuard, SP, R2
	// SUB R1, R2
	// MOV $(framesize+(StackGuard-StackSmall)), R3
	// CMP R3, R2
	p = obj.Appendp(ctxt, p)

	p.As = ACMP
	p.From.Type = obj.TYPE_CONST
	p.From.Offset = obj.StackPreempt
	p.Reg = REG_R1

	p = obj.Appendp(ctxt, p)
	q = p
	p.As = ABEQ
	p.To.Type = obj.TYPE_BRANCH

	p = obj.Appendp(ctxt, p)
	p.As = AADD
	p.From.Type = obj.TYPE_CONST
	p.From.Offset = obj.StackGuard
	p.Reg = REGSP
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R2

	p = obj.Appendp(ctxt, p)
	p.As = ASUB
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REG_R1
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R2

	p = obj.Appendp(ctxt, p)
	p.As = AMOVD
	p.From.Type = obj.TYPE_CONST
	p.From.Offset = int64(framesize) + (obj.StackGuard - obj.StackSmall)
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R3

	p = obj.Appendp(ctxt, p)
	p.As = ACMP
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REG_R3
	p.Reg = REG_R2
	}

	// BLS do-morestack
	bls := obj.Appendp(ctxt, p)
	bls.As = ABLS
	bls.To.Type = obj.TYPE_BRANCH

	var last *obj.Prog
	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
	}

	// Now we are at the end of the function, but logically
	// we are still in function prologue. We need to fix the
	// SP data and PCDATA.
	spfix := obj.Appendp(ctxt, last)
	spfix.As = obj.ANOP
	spfix.Spadj = -framesize

	pcdata := obj.Appendp(ctxt, spfix)
	pcdata.Lineno = ctxt.Cursym.Text.Lineno
	pcdata.Mode = ctxt.Cursym.Text.Mode
	pcdata.As = obj.APCDATA
	pcdata.From.Type = obj.TYPE_CONST
	pcdata.From.Offset = obj.PCDATA_StackMapIndex
	pcdata.To.Type = obj.TYPE_CONST
	pcdata.To.Offset = -1 // pcdata starts at -1 at function entry

	// MOV LR, R3
	movlr := obj.Appendp(ctxt, pcdata)
	movlr.As = AMOVD
	movlr.From.Type = obj.TYPE_REG
	movlr.From.Reg = REGLINK
	movlr.To.Type = obj.TYPE_REG
	movlr.To.Reg = REG_R3
	if q != nil {
	q.Pcond = movlr
	}
	bls.Pcond = movlr

	debug := movlr
	if false {
	debug = obj.Appendp(ctxt, debug)
	debug.As = AMOVD
	debug.From.Type = obj.TYPE_CONST
	debug.From.Offset = int64(framesize)
	debug.To.Type = obj.TYPE_REG
	debug.To.Reg = REGTMP
	}

	// BL runtime.morestack(SB)
	call := obj.Appendp(ctxt, debug)
	call.As = ABL
	call.To.Type = obj.TYPE_BRANCH
	morestack := "runtime.morestack"
	switch {
	case ctxt.Cursym.CFunc():
	morestack = "runtime.morestackc"
	case ctxt.Cursym.Text.From3.Offset&obj.NEEDCTXT == 0:
	morestack = "runtime.morestack_noctxt"
	}
	call.To.Sym = obj.Linklookup(ctxt, morestack, 0)

	// B start
	jmp := obj.Appendp(ctxt, call)
	jmp.As = AB
	jmp.To.Type = obj.TYPE_BRANCH
	jmp.Pcond = ctxt.Cursym.Text.Link
	jmp.Spadj = +framesize

	// placeholder for bls's jump target
	// p = obj.Appendp(ctxt, p)
	// p.As = obj.ANOP

	return bls
	}

	func progedit(ctxt obj.Link, p obj.Prog) {
	p.From.Class = 0
	p.To.Class = 0

	// $0 results in C_ZCON, which matches both C_REG and various
	// C_xCON, however the C_REG cases in asmout don't expect a
	// constant, so they will use the register fields and assemble
	// a R0. To prevent that, rewrite $0 as ZR.
	if p.From.Type == obj.TYPE_CONST && p.From.Offset == 0 {
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REGZERO
	}
	if p.To.Type == obj.TYPE_CONST && p.To.Offset == 0 {
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REGZERO
	}

	// Rewrite BR/BL to symbol as TYPE_BRANCH.
	switch p.As {
	case AB,
	ABL,
	obj.ARET,
	obj.ADUFFZERO,
	obj.ADUFFCOPY:
	if p.To.Sym != nil {
	p.To.Type = obj.TYPE_BRANCH
	}
	break
	}

	// Rewrite float constants to values stored in memory.
	switch p.As {
	case AFMOVS:
	if p.From.Type == obj.TYPE_FCONST {
	f32 := float32(p.From.Val.(float64))
	i32 := math.Float32bits(f32)
	if i32 == 0 {
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REGZERO
	break
	}
	literal := fmt.Sprintf("$f32.%08x", i32)
	s := obj.Linklookup(ctxt, literal, 0)
	s.Size = 4
	p.From.Type = obj.TYPE_MEM
	p.From.Sym = s
	p.From.Sym.Set(obj.AttrLocal, true)
	p.From.Name = obj.NAME_EXTERN
	p.From.Offset = 0
	}

	case AFMOVD:
	if p.From.Type == obj.TYPE_FCONST {
	i64 := math.Float64bits(p.From.Val.(float64))
	if i64 == 0 {
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REGZERO
	break
	}
	literal := fmt.Sprintf("$f64.%016x", i64)
	s := obj.Linklookup(ctxt, literal, 0)
	s.Size = 8
	p.From.Type = obj.TYPE_MEM
	p.From.Sym = s
	p.From.Sym.Set(obj.AttrLocal, true)
	p.From.Name = obj.NAME_EXTERN
	p.From.Offset = 0
	}

	break
	}

	// Rewrite negative immediates as positive immediates with
	// complementary instruction.
	switch p.As {
	case AADD, ASUB, ACMP, ACMN:
	if p.From.Type == obj.TYPE_CONST && p.From.Offset < 0 && p.From.Offset != -1<<63 {
	p.From.Offset = -p.From.Offset
	p.As = complements[p.As]
	}
	case AADDW, ASUBW, ACMPW, ACMNW:
	if p.From.Type == obj.TYPE_CONST && p.From.Offset < 0 && int32(p.From.Offset) != -1<<31 {
	p.From.Offset = -p.From.Offset
	p.As = complements[p.As]
	}
	}

	// For 32-bit logical instruction with constant,
	// rewrite the high 32-bit to be a repetition of
	// the low 32-bit, so that the BITCON test can be
	// shared for both 32-bit and 64-bit. 32-bit ops
	// will zero the high 32-bit of the destination
	// register anyway.
	switch p.As {
	case AANDW, AORRW, AEORW, AANDSW:
	if p.From.Type == obj.TYPE_CONST {
	v := p.From.Offset & 0xffffffff
	p.From.Offset = v \| v<<32
	}
	}

	if ctxt.Flag_dynlink {
	rewriteToUseGot(ctxt, p)
	}
	}

	// Rewrite p, if necessary, to access global data via the global offset table.
	func rewriteToUseGot(ctxt obj.Link, p obj.Prog) {
	if p.As == obj.ADUFFCOPY \|\| p.As == obj.ADUFFZERO {
	// ADUFFxxx $offset
	// becomes
	// MOVD runtime.duffxxx@GOT, REGTMP
	// ADD $offset, REGTMP
	// CALL REGTMP
	var sym *obj.LSym
	if p.As == obj.ADUFFZERO {
	sym = obj.Linklookup(ctxt, "runtime.duffzero", 0)
	} else {
	sym = obj.Linklookup(ctxt, "runtime.duffcopy", 0)
	}
	offset := p.To.Offset
	p.As = AMOVD
	p.From.Type = obj.TYPE_MEM
	p.From.Name = obj.NAME_GOTREF
	p.From.Sym = sym
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REGTMP
	p.To.Name = obj.NAME_NONE
	p.To.Offset = 0
	p.To.Sym = nil
	p1 := obj.Appendp(ctxt, p)
	p1.As = AADD
	p1.From.Type = obj.TYPE_CONST
	p1.From.Offset = offset
	p1.To.Type = obj.TYPE_REG
	p1.To.Reg = REGTMP
	p2 := obj.Appendp(ctxt, p1)
	p2.As = obj.ACALL
	p2.To.Type = obj.TYPE_REG
	p2.To.Reg = REGTMP
	}

	// We only care about global data: NAME_EXTERN means a global
	// symbol in the Go sense, and p.Sym.Local is true for a few
	// internally defined symbols.
	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
	// MOVD $sym, Rx becomes MOVD sym@GOT, Rx
	// MOVD $sym+<off>, Rx becomes MOVD sym@GOT, Rx; ADD <off>, Rx
	if p.As != AMOVD {
	ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
	}
	if p.To.Type != obj.TYPE_REG {
	ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
	}
	p.From.Type = obj.TYPE_MEM
	p.From.Name = obj.NAME_GOTREF
	if p.From.Offset != 0 {
	q := obj.Appendp(ctxt, p)
	q.As = AADD
	q.From.Type = obj.TYPE_CONST
	q.From.Offset = p.From.Offset
	q.To = p.To
	p.From.Offset = 0
	}
	}
	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
	ctxt.Diag("don't know how to handle %v with -dynlink", p)
	}
	var source *obj.Addr
	// MOVx sym, Ry becomes MOVD sym@GOT, REGTMP; MOVx (REGTMP), Ry
	// MOVx Ry, sym becomes MOVD sym@GOT, REGTMP; MOVD Ry, (REGTMP)
	// An addition may be inserted between the two MOVs if there is an offset.
	if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
	if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
	ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
	}
	source = &p.From
	} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
	source = &p.To
	} else {
	return
	}
	if p.As == obj.ATEXT \|\| p.As == obj.AFUNCDATA \|\| p.As == obj.ACALL \|\| p.As == obj.ARET \|\| p.As == obj.AJMP {
	return
	}
	if source.Sym.Type == obj.STLSBSS {
	return
	}
	if source.Type != obj.TYPE_MEM {
	ctxt.Diag("don't know how to handle %v with -dynlink", p)
	}
	p1 := obj.Appendp(ctxt, p)
	p2 := obj.Appendp(ctxt, p1)
	p1.As = AMOVD
	p1.From.Type = obj.TYPE_MEM
	p1.From.Sym = source.Sym
	p1.From.Name = obj.NAME_GOTREF
	p1.To.Type = obj.TYPE_REG
	p1.To.Reg = REGTMP

	p2.As = p.As
	p2.From = p.From
	p2.To = p.To
	if p.From.Name == obj.NAME_EXTERN {
	p2.From.Reg = REGTMP
	p2.From.Name = obj.NAME_NONE
	p2.From.Sym = nil
	} else if p.To.Name == obj.NAME_EXTERN {
	p2.To.Reg = REGTMP
	p2.To.Name = obj.NAME_NONE
	p2.To.Sym = nil
	} else {
	return
	}
	obj.Nopout(p)
	}

	func follow(ctxt obj.Link, s obj.LSym) {
	ctxt.Cursym = s

	firstp := ctxt.NewProg()
	lastp := firstp
	xfol(ctxt, s.Text, &lastp)
	lastp.Link = nil
	s.Text = firstp.Link
	}

	func relinv(a obj.As) obj.As {
	switch a {
	case ABEQ:
	return ABNE
	case ABNE:
	return ABEQ
	case ABCS:
	return ABCC
	case ABHS:
	return ABLO
	case ABCC:
	return ABCS
	case ABLO:
	return ABHS
	case ABMI:
	return ABPL
	case ABPL:
	return ABMI
	case ABVS:
	return ABVC
	case ABVC:
	return ABVS
	case ABHI:
	return ABLS
	case ABLS:
	return ABHI
	case ABGE:
	return ABLT
	case ABLT:
	return ABGE
	case ABGT:
	return ABLE
	case ABLE:
	return ABGT
	case ACBZ:
	return ACBNZ
	case ACBNZ:
	return ACBZ
	case ACBZW:
	return ACBNZW
	case ACBNZW:
	return ACBZW
	}

	log.Fatalf("unknown relation: %s", Anames[a-obj.ABaseARM64])
	return 0
	}

	func xfol(ctxt obj.Link, p obj.Prog, last **obj.Prog) {
	var q *obj.Prog
	var r *obj.Prog
	var i int

	loop:
	if p == nil {
	return
	}
	a := p.As
	if a == AB {
	q = p.Pcond
	if q != nil {
	p.Mark \|= FOLL
	p = q
	if !(p.Mark&FOLL != 0) {
	goto loop
	}
	}
	}

	if p.Mark&FOLL != 0 {
	i = 0
	q = p
	for ; i < 4; i, q = i+1, q.Link {
	if q == *last \|\| q == nil {
	break
	}
	a = q.As
	if a == obj.ANOP {
	i--
	continue
	}

	if a == AB \|\| a == obj.ARET \|\| a == AERET {
	goto copy
	}
	if q.Pcond == nil \|\| (q.Pcond.Mark&FOLL != 0) {
	continue
	}
	if a != ABEQ && a != ABNE {
	continue
	}

	copy:
	for {
	r = ctxt.NewProg()
	r = p
	if !(r.Mark&FOLL != 0) {
	fmt.Printf("can't happen 1\n")
	}
	r.Mark \|= FOLL
	if p != q {
	p = p.Link
	(*last).Link = r
	*last = r
	continue
	}

	(*last).Link = r
	*last = r
	if a == AB \|\| a == obj.ARET \|\| a == AERET {
	return
	}
	if a == ABNE {
	r.As = ABEQ
	} else {
	r.As = ABNE
	}
	r.Pcond = p.Link
	r.Link = p.Pcond
	if !(r.Link.Mark&FOLL != 0) {
	xfol(ctxt, r.Link, last)
	}
	if !(r.Pcond.Mark&FOLL != 0) {
	fmt.Printf("can't happen 2\n")
	}
	return
	}
	}

	a = AB
	q = ctxt.NewProg()
	q.As = a
	q.Lineno = p.Lineno
	q.To.Type = obj.TYPE_BRANCH
	q.To.Offset = p.Pc
	q.Pcond = p
	p = q
	}

	p.Mark \|= FOLL
	(*last).Link = p
	*last = p
	if a == AB \|\| a == obj.ARET \|\| a == AERET {
	return
	}
	if p.Pcond != nil {
	if a != ABL && p.Link != nil {
	q = obj.Brchain(ctxt, p.Link)
	if a != obj.ATEXT {
	if q != nil && (q.Mark&FOLL != 0) {
	p.As = relinv(a)
	p.Link = p.Pcond
	p.Pcond = q
	}
	}

	xfol(ctxt, p.Link, last)
	q = obj.Brchain(ctxt, p.Pcond)
	if q == nil {
	q = p.Pcond
	}
	if q.Mark&FOLL != 0 {
	p.Pcond = q
	return
	}

	p = q
	goto loop
	}
	}

	p = p.Link
	goto loop
	}

	func preprocess(ctxt obj.Link, cursym obj.LSym) {
	ctxt.Cursym = cursym

	if cursym.Text == nil \|\| cursym.Text.Link == nil {
	return
	}

	p := cursym.Text
	textstksiz := p.To.Offset
	aoffset := int32(textstksiz)

	cursym.Args = p.To.Val.(int32)
	cursym.Locals = int32(textstksiz)

	/*
	* find leaf subroutines
	* strip NOPs
	* expand RET
	*/
	q := (*obj.Prog)(nil)
	var q1 *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
	switch p.As {
	case obj.ATEXT:
	p.Mark \|= LEAF

	case obj.ARET:
	break

	case obj.ANOP:
	q1 = p.Link
	q.Link = q1 /* q is non-nop */
	q1.Mark \|= p.Mark
	continue

	case ABL,
	obj.ADUFFZERO,
	obj.ADUFFCOPY:
	cursym.Text.Mark &^= LEAF
	fallthrough

	case ACBNZ,
	ACBZ,
	ACBNZW,
	ACBZW,
	ATBZ,
	ATBNZ,
	AB,
	ABEQ,
	ABNE,
	ABCS,
	ABHS,
	ABCC,
	ABLO,
	ABMI,
	ABPL,
	ABVS,
	ABVC,
	ABHI,
	ABLS,
	ABGE,
	ABLT,
	ABGT,
	ABLE,
	AADR, /* strange */
	AADRP:
	q1 = p.Pcond

	if q1 != nil {
	for q1.As == obj.ANOP {
	q1 = q1.Link
	p.Pcond = q1
	}
	}

	break
	}

	q = p
	}

	var q2 *obj.Prog
	var retjmp *obj.LSym
	for p := cursym.Text; p != nil; p = p.Link {
	o := p.As
	switch o {
	case obj.ATEXT:
	cursym.Text = p
	if textstksiz < 0 {
	ctxt.Autosize = 0
	} else {
	ctxt.Autosize = int32(textstksiz + 8)
	}
	if (cursym.Text.Mark&LEAF != 0) && ctxt.Autosize <= 8 {
	ctxt.Autosize = 0
	} else if ctxt.Autosize&(16-1) != 0 {
	// The frame includes an LR.
	// If the frame size is 8, it's only an LR,
	// so there's no potential for breaking references to
	// local variables by growing the frame size,
	// because there are no local variables.
	// But otherwise, if there is a non-empty locals section,
	// the author of the code is responsible for making sure
	// that the frame size is 8 mod 16.
	if ctxt.Autosize == 8 {
	ctxt.Autosize += 8
	cursym.Locals += 8
	} else {
	ctxt.Diag("%v: unaligned frame size %d - must be 8 mod 16 (or 0)", p, ctxt.Autosize-8)
	}
	}
	p.To.Offset = int64(ctxt.Autosize) - 8
	if ctxt.Autosize == 0 && !(cursym.Text.Mark&LEAF != 0) {
	if ctxt.Debugvlog != 0 {
	ctxt.Logf("save suppressed in: %s\n", cursym.Text.From.Sym.Name)
	}
	cursym.Text.Mark \|= LEAF
	}

	if !(p.From3.Offset&obj.NOSPLIT != 0) {
	p = stacksplit(ctxt, p, ctxt.Autosize) // emit split check
	}

	aoffset = ctxt.Autosize
	if aoffset > 0xF0 {
	aoffset = 0xF0
	}
	if cursym.Text.Mark&LEAF != 0 {
	cursym.Set(obj.AttrLeaf, true)
	if ctxt.Autosize == 0 {
	break
	}
	}

	// Frame is non-empty. Make sure to save link register, even if
	// it is a leaf function, so that traceback works.
	q = p
	if ctxt.Autosize > aoffset {
	// Frame size is too large for a MOVD.W instruction.
	// Store link register before decrementing SP, so if a signal comes
	// during the execution of the function prologue, the traceback
	// code will not see a half-updated stack frame.
	q = obj.Appendp(ctxt, q)
	q.Lineno = p.Lineno
	q.As = ASUB
	q.From.Type = obj.TYPE_CONST
	q.From.Offset = int64(ctxt.Autosize)
	q.Reg = REGSP
	q.To.Type = obj.TYPE_REG
	q.To.Reg = REGTMP

	q = obj.Appendp(ctxt, q)
	q.Lineno = p.Lineno
	q.As = AMOVD
	q.From.Type = obj.TYPE_REG
	q.From.Reg = REGLINK
	q.To.Type = obj.TYPE_MEM
	q.To.Reg = REGTMP

	q1 = obj.Appendp(ctxt, q)
	q1.Lineno = p.Lineno
	q1.As = AMOVD
	q1.From.Type = obj.TYPE_REG
	q1.From.Reg = REGTMP
	q1.To.Type = obj.TYPE_REG
	q1.To.Reg = REGSP
	q1.Spadj = ctxt.Autosize
	} else {
	// small frame, update SP and save LR in a single MOVD.W instruction
	q1 = obj.Appendp(ctxt, q)
	q1.As = AMOVD
	q1.Lineno = p.Lineno
	q1.From.Type = obj.TYPE_REG
	q1.From.Reg = REGLINK
	q1.To.Type = obj.TYPE_MEM
	q1.Scond = C_XPRE
	q1.To.Offset = int64(-aoffset)
	q1.To.Reg = REGSP
	q1.Spadj = aoffset
	}

	if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
	// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
	//
	// MOV g_panic(g), R1
	// CMP ZR, R1
	// BEQ end
	// MOV panic_argp(R1), R2
	// ADD $(autosize+8), RSP, R3
	// CMP R2, R3
	// BNE end
	// ADD $8, RSP, R4
	// MOVD R4, panic_argp(R1)
	// end:
	// NOP
	//
	// The NOP is needed to give the jumps somewhere to land.
	// It is a liblink NOP, not a ARM64 NOP: it encodes to 0 instruction bytes.
	q = q1

	q = obj.Appendp(ctxt, q)
	q.As = AMOVD
	q.From.Type = obj.TYPE_MEM
	q.From.Reg = REGG
	q.From.Offset = 4 * int64(ctxt.Arch.PtrSize) // G.panic
	q.To.Type = obj.TYPE_REG
	q.To.Reg = REG_R1

	q = obj.Appendp(ctxt, q)
	q.As = ACMP
	q.From.Type = obj.TYPE_REG
	q.From.Reg = REGZERO
	q.Reg = REG_R1

	q = obj.Appendp(ctxt, q)
	q.As = ABEQ
	q.To.Type = obj.TYPE_BRANCH
	q1 = q

	q = obj.Appendp(ctxt, q)
	q.As = AMOVD
	q.From.Type = obj.TYPE_MEM
	q.From.Reg = REG_R1
	q.From.Offset = 0 // Panic.argp
	q.To.Type = obj.TYPE_REG
	q.To.Reg = REG_R2

	q = obj.Appendp(ctxt, q)
	q.As = AADD
	q.From.Type = obj.TYPE_CONST
	q.From.Offset = int64(ctxt.Autosize) + 8
	q.Reg = REGSP
	q.To.Type = obj.TYPE_REG
	q.To.Reg = REG_R3

	q = obj.Appendp(ctxt, q)
	q.As = ACMP
	q.From.Type = obj.TYPE_REG
	q.From.Reg = REG_R2
	q.Reg = REG_R3

	q = obj.Appendp(ctxt, q)
	q.As = ABNE
	q.To.Type = obj.TYPE_BRANCH
	q2 = q

	q = obj.Appendp(ctxt, q)
	q.As = AADD
	q.From.Type = obj.TYPE_CONST
	q.From.Offset = 8
	q.Reg = REGSP
	q.To.Type = obj.TYPE_REG
	q.To.Reg = REG_R4

	q = obj.Appendp(ctxt, q)
	q.As = AMOVD
	q.From.Type = obj.TYPE_REG
	q.From.Reg = REG_R4
	q.To.Type = obj.TYPE_MEM
	q.To.Reg = REG_R1
	q.To.Offset = 0 // Panic.argp

	q = obj.Appendp(ctxt, q)

	q.As = obj.ANOP
	q1.Pcond = q
	q2.Pcond = q
	}

	case obj.ARET:
	nocache(p)
	if p.From.Type == obj.TYPE_CONST {
	ctxt.Diag("using BECOME (%v) is not supported!", p)
	break
	}

	retjmp = p.To.Sym
	p.To = obj.Addr{}
	if cursym.Text.Mark&LEAF != 0 {
	if ctxt.Autosize != 0 {
	p.As = AADD
	p.From.Type = obj.TYPE_CONST
	p.From.Offset = int64(ctxt.Autosize)
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REGSP
	p.Spadj = -ctxt.Autosize
	}
	} else {
	/* want write-back pre-indexed SP+autosize -> SP, loading REGLINK*/
	aoffset = ctxt.Autosize

	if aoffset > 0xF0 {
	aoffset = 0xF0
	}
	p.As = AMOVD
	p.From.Type = obj.TYPE_MEM
	p.Scond = C_XPOST
	p.From.Offset = int64(aoffset)
	p.From.Reg = REGSP
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REGLINK
	p.Spadj = -aoffset
	if ctxt.Autosize > aoffset {
	q = ctxt.NewProg()
	q.As = AADD
	q.From.Type = obj.TYPE_CONST
	q.From.Offset = int64(ctxt.Autosize) - int64(aoffset)
	q.To.Type = obj.TYPE_REG
	q.To.Reg = REGSP
	q.Link = p.Link
	q.Spadj = int32(-q.From.Offset)
	q.Lineno = p.Lineno
	p.Link = q
	p = q
	}
	}

	if p.As != obj.ARET {
	q = ctxt.NewProg()
	q.Lineno = p.Lineno
	q.Link = p.Link
	p.Link = q
	p = q
	}

	if retjmp != nil { // retjmp
	p.As = AB
	p.To.Type = obj.TYPE_BRANCH
	p.To.Sym = retjmp
	p.Spadj = +ctxt.Autosize
	break
	}

	p.As = obj.ARET
	p.To.Type = obj.TYPE_MEM
	p.To.Offset = 0
	p.To.Reg = REGLINK
	p.Spadj = +ctxt.Autosize

	case AADD, ASUB:
	if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
	if p.As == AADD {
	p.Spadj = int32(-p.From.Offset)
	} else {
	p.Spadj = int32(+p.From.Offset)
	}
	}
	break
	}
	}
	}

	func nocache(p *obj.Prog) {
	p.Optab = 0
	p.From.Class = 0
	p.To.Class = 0
	}

	var unaryDst = map[obj.As]bool{
	AWORD: true,
	ADWORD: true,
	ABL: true,
	AB: true,
	ASVC: true,
	}

	var Linkarm64 = obj.LinkArch{
	Arch: sys.ArchARM64,
	Preprocess: preprocess,
	Assemble: span7,
	Follow: follow,
	Progedit: progedit,
	UnaryDst: unaryDst,
	}