1 files changed, 1481 insertions, 0 deletions
diff --git a/vendor/github.com/google/gops/internal/obj/x86/obj6.go b/vendor/github.com/google/gops/internal/obj/x86/obj6.go
new file mode 100644
index 00000000..aad950bb
--- /dev/null
+++ b/vendor/github.com/google/gops/internal/obj/x86/obj6.go
@@ -0,0 +1,1481 @@
+// Inferno utils/6l/pass.c
+// https://bitbucket.org/inferno-os/inferno-os/src/default/utils/6l/pass.c
+//
+//	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 x86
+
+import (
+	"fmt"
+	"log"
+	"math"
+	"strings"
+
+	"github.com/google/gops/internal/obj"
+	"github.com/google/gops/internal/sys"
+)
+
+func CanUse1InsnTLS(ctxt *obj.Link) bool {
+	if isAndroid {
+		// For android, we use a disgusting hack that assumes
+		// the thread-local storage slot for g is allocated
+		// using pthread_key_create with a fixed offset
+		// (see src/runtime/cgo/gcc_android_amd64.c).
+		// This makes access to the TLS storage (for g) doable
+		// with 1 instruction.
+		return true
+	}
+
+	if ctxt.Arch.RegSize == 4 {
+		switch ctxt.Headtype {
+		case obj.Hlinux,
+			obj.Hnacl,
+			obj.Hplan9,
+			obj.Hwindows,
+			obj.Hwindowsgui:
+			return false
+		}
+
+		return true
+	}
+
+	switch ctxt.Headtype {
+	case obj.Hplan9, obj.Hwindows, obj.Hwindowsgui:
+		return false
+	case obj.Hlinux:
+		return !ctxt.Flag_shared
+	}
+
+	return true
+}
+
+func progedit(ctxt *obj.Link, p *obj.Prog) {
+	// Maintain information about code generation mode.
+	if ctxt.Mode == 0 {
+		ctxt.Mode = ctxt.Arch.RegSize * 8
+	}
+	p.Mode = int8(ctxt.Mode)
+
+	switch p.As {
+	case AMODE:
+		if p.From.Type == obj.TYPE_CONST || (p.From.Type == obj.TYPE_MEM && p.From.Reg == REG_NONE) {
+			switch int(p.From.Offset) {
+			case 16, 32, 64:
+				ctxt.Mode = int(p.From.Offset)
+			}
+		}
+		obj.Nopout(p)
+	}
+
+	// Thread-local storage references use the TLS pseudo-register.
+	// As a register, TLS refers to the thread-local storage base, and it
+	// can only be loaded into another register:
+	//
+	//         MOVQ TLS, AX
+	//
+	// An offset from the thread-local storage base is written off(reg)(TLS*1).
+	// Semantically it is off(reg), but the (TLS*1) annotation marks this as
+	// indexing from the loaded TLS base. This emits a relocation so that
+	// if the linker needs to adjust the offset, it can. For example:
+	//
+	//         MOVQ TLS, AX
+	//         MOVQ 0(AX)(TLS*1), CX // load g into CX
+	//
+	// On systems that support direct access to the TLS memory, this
+	// pair of instructions can be reduced to a direct TLS memory reference:
+	//
+	//         MOVQ 0(TLS), CX // load g into CX
+	//
+	// The 2-instruction and 1-instruction forms correspond to the two code
+	// sequences for loading a TLS variable in the local exec model given in "ELF
+	// Handling For Thread-Local Storage".
+	//
+	// We apply this rewrite on systems that support the 1-instruction form.
+	// The decision is made using only the operating system and the -shared flag,
+	// not the link mode. If some link modes on a particular operating system
+	// require the 2-instruction form, then all builds for that operating system
+	// will use the 2-instruction form, so that the link mode decision can be
+	// delayed to link time.
+	//
+	// In this way, all supported systems use identical instructions to
+	// access TLS, and they are rewritten appropriately first here in
+	// liblink and then finally using relocations in the linker.
+	//
+	// When -shared is passed, we leave the code in the 2-instruction form but
+	// assemble (and relocate) them in different ways to generate the initial
+	// exec code sequence. It's a bit of a fluke that this is possible without
+	// rewriting the instructions more comprehensively, and it only does because
+	// we only support a single TLS variable (g).
+
+	if CanUse1InsnTLS(ctxt) {
+		// Reduce 2-instruction sequence to 1-instruction sequence.
+		// Sequences like
+		//	MOVQ TLS, BX
+		//	... off(BX)(TLS*1) ...
+		// become
+		//	NOP
+		//	... off(TLS) ...
+		//
+		// TODO(rsc): Remove the Hsolaris special case. It exists only to
+		// guarantee we are producing byte-identical binaries as before this code.
+		// But it should be unnecessary.
+		if (p.As == AMOVQ || p.As == AMOVL) && p.From.Type == obj.TYPE_REG && p.From.Reg == REG_TLS && p.To.Type == obj.TYPE_REG && REG_AX <= p.To.Reg && p.To.Reg <= REG_R15 && ctxt.Headtype != obj.Hsolaris {
+			obj.Nopout(p)
+		}
+		if p.From.Type == obj.TYPE_MEM && p.From.Index == REG_TLS && REG_AX <= p.From.Reg && p.From.Reg <= REG_R15 {
+			p.From.Reg = REG_TLS
+			p.From.Scale = 0
+			p.From.Index = REG_NONE
+		}
+
+		if p.To.Type == obj.TYPE_MEM && p.To.Index == REG_TLS && REG_AX <= p.To.Reg && p.To.Reg <= REG_R15 {
+			p.To.Reg = REG_TLS
+			p.To.Scale = 0
+			p.To.Index = REG_NONE
+		}
+	} else {
+		// load_g_cx, below, always inserts the 1-instruction sequence. Rewrite it
+		// as the 2-instruction sequence if necessary.
+		//	MOVQ 0(TLS), BX
+		// becomes
+		//	MOVQ TLS, BX
+		//	MOVQ 0(BX)(TLS*1), BX
+		if (p.As == AMOVQ || p.As == AMOVL) && p.From.Type == obj.TYPE_MEM && p.From.Reg == REG_TLS && p.To.Type == obj.TYPE_REG && REG_AX <= p.To.Reg && p.To.Reg <= REG_R15 {
+			q := obj.Appendp(ctxt, p)
+			q.As = p.As
+			q.From = p.From
+			q.From.Type = obj.TYPE_MEM
+			q.From.Reg = p.To.Reg
+			q.From.Index = REG_TLS
+			q.From.Scale = 2 // TODO: use 1
+			q.To = p.To
+			p.From.Type = obj.TYPE_REG
+			p.From.Reg = REG_TLS
+			p.From.Index = REG_NONE
+			p.From.Offset = 0
+		}
+	}
+
+	// TODO: Remove.
+	if (ctxt.Headtype == obj.Hwindows || ctxt.Headtype == obj.Hwindowsgui) && p.Mode == 64 || ctxt.Headtype == obj.Hplan9 {
+		if p.From.Scale == 1 && p.From.Index == REG_TLS {
+			p.From.Scale = 2
+		}
+		if p.To.Scale == 1 && p.To.Index == REG_TLS {
+			p.To.Scale = 2
+		}
+	}
+
+	// Rewrite 0 to $0 in 3rd argument to CMPPS etc.
+	// That's what the tables expect.
+	switch p.As {
+	case ACMPPD, ACMPPS, ACMPSD, ACMPSS:
+		if p.To.Type == obj.TYPE_MEM && p.To.Name == obj.NAME_NONE && p.To.Reg == REG_NONE && p.To.Index == REG_NONE && p.To.Sym == nil {
+			p.To.Type = obj.TYPE_CONST
+		}
+	}
+
+	// Rewrite CALL/JMP/RET to symbol as TYPE_BRANCH.
+	switch p.As {
+	case obj.ACALL, obj.AJMP, obj.ARET:
+		if p.To.Type == obj.TYPE_MEM && (p.To.Name == obj.NAME_EXTERN || p.To.Name == obj.NAME_STATIC) && p.To.Sym != nil {
+			p.To.Type = obj.TYPE_BRANCH
+		}
+	}
+
+	// Rewrite MOVL/MOVQ $XXX(FP/SP) as LEAL/LEAQ.
+	if p.From.Type == obj.TYPE_ADDR && (ctxt.Arch.Family == sys.AMD64 || p.From.Name != obj.NAME_EXTERN && p.From.Name != obj.NAME_STATIC) {
+		switch p.As {
+		case AMOVL:
+			p.As = ALEAL
+			p.From.Type = obj.TYPE_MEM
+		case AMOVQ:
+			p.As = ALEAQ
+			p.From.Type = obj.TYPE_MEM
+		}
+	}
+
+	if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
+		if p.From3 != nil {
+			nacladdr(ctxt, p, p.From3)
+		}
+		nacladdr(ctxt, p, &p.From)
+		nacladdr(ctxt, p, &p.To)
+	}
+
+	// Rewrite float constants to values stored in memory.
+	switch p.As {
+	// Convert AMOVSS $(0), Xx to AXORPS Xx, Xx
+	case AMOVSS:
+		if p.From.Type == obj.TYPE_FCONST {
+			//  f == 0 can't be used here due to -0, so use Float64bits
+			if f := p.From.Val.(float64); math.Float64bits(f) == 0 {
+				if p.To.Type == obj.TYPE_REG && REG_X0 <= p.To.Reg && p.To.Reg <= REG_X15 {
+					p.As = AXORPS
+					p.From = p.To
+					break
+				}
+			}
+		}
+		fallthrough
+
+	case AFMOVF,
+		AFADDF,
+		AFSUBF,
+		AFSUBRF,
+		AFMULF,
+		AFDIVF,
+		AFDIVRF,
+		AFCOMF,
+		AFCOMFP,
+		AADDSS,
+		ASUBSS,
+		AMULSS,
+		ADIVSS,
+		ACOMISS,
+		AUCOMISS:
+		if p.From.Type == obj.TYPE_FCONST {
+			f32 := float32(p.From.Val.(float64))
+			i32 := math.Float32bits(f32)
+			literal := fmt.Sprintf("$f32.%08x", i32)
+			s := obj.Linklookup(ctxt, literal, 0)
+			p.From.Type = obj.TYPE_MEM
+			p.From.Name = obj.NAME_EXTERN
+			p.From.Sym = s
+			p.From.Sym.Set(obj.AttrLocal, true)
+			p.From.Offset = 0
+		}
+
+	case AMOVSD:
+		// Convert AMOVSD $(0), Xx to AXORPS Xx, Xx
+		if p.From.Type == obj.TYPE_FCONST {
+			//  f == 0 can't be used here due to -0, so use Float64bits
+			if f := p.From.Val.(float64); math.Float64bits(f) == 0 {
+				if p.To.Type == obj.TYPE_REG && REG_X0 <= p.To.Reg && p.To.Reg <= REG_X15 {
+					p.As = AXORPS
+					p.From = p.To
+					break
+				}
+			}
+		}
+		fallthrough
+
+	case AFMOVD,
+		AFADDD,
+		AFSUBD,
+		AFSUBRD,
+		AFMULD,
+		AFDIVD,
+		AFDIVRD,
+		AFCOMD,
+		AFCOMDP,
+		AADDSD,
+		ASUBSD,
+		AMULSD,
+		ADIVSD,
+		ACOMISD,
+		AUCOMISD:
+		if p.From.Type == obj.TYPE_FCONST {
+			i64 := math.Float64bits(p.From.Val.(float64))
+			literal := fmt.Sprintf("$f64.%016x", i64)
+			s := obj.Linklookup(ctxt, literal, 0)
+			p.From.Type = obj.TYPE_MEM
+			p.From.Name = obj.NAME_EXTERN
+			p.From.Sym = s
+			p.From.Sym.Set(obj.AttrLocal, true)
+			p.From.Offset = 0
+		}
+	}
+
+	if ctxt.Flag_dynlink {
+		rewriteToUseGot(ctxt, p)
+	}
+
+	if ctxt.Flag_shared && p.Mode == 32 {
+		rewriteToPcrel(ctxt, p)
+	}
+}
+
+// Rewrite p, if necessary, to access global data via the global offset table.
+func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
+	var add, lea, mov obj.As
+	var reg int16
+	if p.Mode == 64 {
+		add = AADDQ
+		lea = ALEAQ
+		mov = AMOVQ
+		reg = REG_R15
+	} else {
+		add = AADDL
+		lea = ALEAL
+		mov = AMOVL
+		reg = REG_CX
+		if p.As == ALEAL && p.To.Reg != p.From.Reg && p.To.Reg != p.From.Index {
+			// Special case: clobber the destination register with
+			// the PC so we don't have to clobber CX.
+			// The SSA backend depends on CX not being clobbered across LEAL.
+			// See cmd/compile/internal/ssa/gen/386.rules (search for Flag_shared).
+			reg = p.To.Reg
+		}
+	}
+
+	if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
+		//     ADUFFxxx $offset
+		// becomes
+		//     $MOV runtime.duffxxx@GOT, $reg
+		//     $ADD $offset, $reg
+		//     CALL $reg
+		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 = mov
+		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 = reg
+		p.To.Offset = 0
+		p.To.Sym = nil
+		p1 := obj.Appendp(ctxt, p)
+		p1.As = add
+		p1.From.Type = obj.TYPE_CONST
+		p1.From.Offset = offset
+		p1.To.Type = obj.TYPE_REG
+		p1.To.Reg = reg
+		p2 := obj.Appendp(ctxt, p1)
+		p2.As = obj.ACALL
+		p2.To.Type = obj.TYPE_REG
+		p2.To.Reg = reg
+	}
+
+	// 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.As == lea && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
+		// $LEA sym, Rx becomes $MOV $sym, Rx which will be rewritten below
+		p.As = mov
+		p.From.Type = obj.TYPE_ADDR
+	}
+	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
+		// $MOV $sym, Rx becomes $MOV sym@GOT, Rx
+		// $MOV $sym+<off>, Rx becomes $MOV sym@GOT, Rx; $LEA <off>(Rx), Rx
+		// On 386 only, more complicated things like PUSHL $sym become $MOV sym@GOT, CX; PUSHL CX
+		cmplxdest := false
+		pAs := p.As
+		var dest obj.Addr
+		if p.To.Type != obj.TYPE_REG || pAs != mov {
+			if p.Mode == 64 {
+				ctxt.Diag("do not know how to handle LEA-type insn to non-register in %v with -dynlink", p)
+			}
+			cmplxdest = true
+			dest = p.To
+			p.As = mov
+			p.To.Type = obj.TYPE_REG
+			p.To.Reg = reg
+			p.To.Sym = nil
+			p.To.Name = obj.NAME_NONE
+		}
+		p.From.Type = obj.TYPE_MEM
+		p.From.Name = obj.NAME_GOTREF
+		q := p
+		if p.From.Offset != 0 {
+			q = obj.Appendp(ctxt, p)
+			q.As = lea
+			q.From.Type = obj.TYPE_MEM
+			q.From.Reg = p.To.Reg
+			q.From.Offset = p.From.Offset
+			q.To = p.To
+			p.From.Offset = 0
+		}
+		if cmplxdest {
+			q = obj.Appendp(ctxt, q)
+			q.As = pAs
+			q.To = dest
+			q.From.Type = obj.TYPE_REG
+			q.From.Reg = reg
+		}
+	}
+	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 $MOV sym@GOT, R15; MOVx (R15), Ry
+	// MOVx Ry, sym becomes $MOV sym@GOT, R15; MOVx Ry, (R15)
+	// 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.ACALL {
+		// When dynlinking on 386, almost any call might end up being a call
+		// to a PLT, so make sure the GOT pointer is loaded into BX.
+		// RegTo2 is set on the replacement call insn to stop it being
+		// processed when it is in turn passed to progedit.
+		if p.Mode == 64 || (p.To.Sym != nil && p.To.Sym.Local()) || p.RegTo2 != 0 {
+			return
+		}
+		p1 := obj.Appendp(ctxt, p)
+		p2 := obj.Appendp(ctxt, p1)
+
+		p1.As = ALEAL
+		p1.From.Type = obj.TYPE_MEM
+		p1.From.Name = obj.NAME_STATIC
+		p1.From.Sym = obj.Linklookup(ctxt, "_GLOBAL_OFFSET_TABLE_", 0)
+		p1.To.Type = obj.TYPE_REG
+		p1.To.Reg = REG_BX
+
+		p2.As = p.As
+		p2.Scond = p.Scond
+		p2.From = p.From
+		p2.From3 = p.From3
+		p2.Reg = p.Reg
+		p2.To = p.To
+		// p.To.Type was set to TYPE_BRANCH above, but that makes checkaddr
+		// in ../pass.go complain, so set it back to TYPE_MEM here, until p2
+		// itself gets passed to progedit.
+		p2.To.Type = obj.TYPE_MEM
+		p2.RegTo2 = 1
+
+		obj.Nopout(p)
+		return
+
+	}
+	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ARET || p.As == obj.AJMP {
+		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 = mov
+	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 = reg
+
+	p2.As = p.As
+	p2.From = p.From
+	p2.To = p.To
+	if p.From.Name == obj.NAME_EXTERN {
+		p2.From.Reg = reg
+		p2.From.Name = obj.NAME_NONE
+		p2.From.Sym = nil
+	} else if p.To.Name == obj.NAME_EXTERN {
+		p2.To.Reg = reg
+		p2.To.Name = obj.NAME_NONE
+		p2.To.Sym = nil
+	} else {
+		return
+	}
+	obj.Nopout(p)
+}
+
+func rewriteToPcrel(ctxt *obj.Link, p *obj.Prog) {
+	// RegTo2 is set on the instructions we insert here so they don't get
+	// processed twice.
+	if p.RegTo2 != 0 {
+		return
+	}
+	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
+		return
+	}
+	// Any Prog (aside from the above special cases) with an Addr with Name ==
+	// NAME_EXTERN, NAME_STATIC or NAME_GOTREF has a CALL __x86.get_pc_thunk.XX
+	// inserted before it.
+	isName := func(a *obj.Addr) bool {
+		if a.Sym == nil || (a.Type != obj.TYPE_MEM && a.Type != obj.TYPE_ADDR) || a.Reg != 0 {
+			return false
+		}
+		if a.Sym.Type == obj.STLSBSS {
+			return false
+		}
+		return a.Name == obj.NAME_EXTERN || a.Name == obj.NAME_STATIC || a.Name == obj.NAME_GOTREF
+	}
+
+	if isName(&p.From) && p.From.Type == obj.TYPE_ADDR {
+		// Handle things like "MOVL $sym, (SP)" or "PUSHL $sym" by rewriting
+		// to "MOVL $sym, CX; MOVL CX, (SP)" or "MOVL $sym, CX; PUSHL CX"
+		// respectively.
+		if p.To.Type != obj.TYPE_REG {
+			q := obj.Appendp(ctxt, p)
+			q.As = p.As
+			q.From.Type = obj.TYPE_REG
+			q.From.Reg = REG_CX
+			q.To = p.To
+			p.As = AMOVL
+			p.To.Type = obj.TYPE_REG
+			p.To.Reg = REG_CX
+			p.To.Sym = nil
+			p.To.Name = obj.NAME_NONE
+		}
+	}
+
+	if !isName(&p.From) && !isName(&p.To) && (p.From3 == nil || !isName(p.From3)) {
+		return
+	}
+	var dst int16 = REG_CX
+	if (p.As == ALEAL || p.As == AMOVL) && p.To.Reg != p.From.Reg && p.To.Reg != p.From.Index {
+		dst = p.To.Reg
+		// Why?  See the comment near the top of rewriteToUseGot above.
+		// AMOVLs might be introduced by the GOT rewrites.
+	}
+	q := obj.Appendp(ctxt, p)
+	q.RegTo2 = 1
+	r := obj.Appendp(ctxt, q)
+	r.RegTo2 = 1
+	q.As = obj.ACALL
+	q.To.Sym = obj.Linklookup(ctxt, "__x86.get_pc_thunk."+strings.ToLower(Rconv(int(dst))), 0)
+	q.To.Type = obj.TYPE_MEM
+	q.To.Name = obj.NAME_EXTERN
+	q.To.Sym.Set(obj.AttrLocal, true)
+	r.As = p.As
+	r.Scond = p.Scond
+	r.From = p.From
+	r.From3 = p.From3
+	r.Reg = p.Reg
+	r.To = p.To
+	if isName(&p.From) {
+		r.From.Reg = dst
+	}
+	if isName(&p.To) {
+		r.To.Reg = dst
+	}
+	if p.From3 != nil && isName(p.From3) {
+		r.From3.Reg = dst
+	}
+	obj.Nopout(p)
+}
+
+func nacladdr(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) {
+	if p.As == ALEAL || p.As == ALEAQ {
+		return
+	}
+
+	if a.Reg == REG_BP {
+		ctxt.Diag("invalid address: %v", p)
+		return
+	}
+
+	if a.Reg == REG_TLS {
+		a.Reg = REG_BP
+	}
+	if a.Type == obj.TYPE_MEM && a.Name == obj.NAME_NONE {
+		switch a.Reg {
+		// all ok
+		case REG_BP, REG_SP, REG_R15:
+			break
+
+		default:
+			if a.Index != REG_NONE {
+				ctxt.Diag("invalid address %v", p)
+			}
+			a.Index = a.Reg
+			if a.Index != REG_NONE {
+				a.Scale = 1
+			}
+			a.Reg = REG_R15
+		}
+	}
+}
+
+func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
+	if ctxt.Headtype == obj.Hplan9 && ctxt.Plan9privates == nil {
+		ctxt.Plan9privates = obj.Linklookup(ctxt, "_privates", 0)
+	}
+
+	ctxt.Cursym = cursym
+
+	if cursym.Text == nil || cursym.Text.Link == nil {
+		return
+	}
+
+	p := cursym.Text
+	autoffset := int32(p.To.Offset)
+	if autoffset < 0 {
+		autoffset = 0
+	}
+
+	var bpsize int
+	if p.Mode == 64 && ctxt.Framepointer_enabled && autoffset > 0 && p.From3.Offset&obj.NOFRAME == 0 {
+		// Make room for to save a base pointer. If autoffset == 0,
+		// this might do something special like a tail jump to
+		// another function, so in that case we omit this.
+		bpsize = ctxt.Arch.PtrSize
+		autoffset += int32(bpsize)
+		p.To.Offset += int64(bpsize)
+	} else {
+		bpsize = 0
+	}
+
+	textarg := int64(p.To.Val.(int32))
+	cursym.Args = int32(textarg)
+	cursym.Locals = int32(p.To.Offset)
+
+	// TODO(rsc): Remove.
+	if p.Mode == 32 && cursym.Locals < 0 {
+		cursym.Locals = 0
+	}
+
+	// TODO(rsc): Remove 'p.Mode == 64 &&'.
+	if p.Mode == 64 && autoffset < obj.StackSmall && p.From3Offset()&obj.NOSPLIT == 0 {
+		leaf := true
+	LeafSearch:
+		for q := p; q != nil; q = q.Link {
+			switch q.As {
+			case obj.ACALL:
+				// Treat common runtime calls that take no arguments
+				// the same as duffcopy and duffzero.
+				if !isZeroArgRuntimeCall(q.To.Sym) {
+					leaf = false
+					break LeafSearch
+				}
+				fallthrough
+			case obj.ADUFFCOPY, obj.ADUFFZERO:
+				if autoffset >= obj.StackSmall-8 {
+					leaf = false
+					break LeafSearch
+				}
+			}
+		}
+
+		if leaf {
+			p.From3.Offset |= obj.NOSPLIT
+		}
+	}
+
+	if p.From3Offset()&obj.NOSPLIT == 0 || p.From3Offset()&obj.WRAPPER != 0 {
+		p = obj.Appendp(ctxt, p)
+		p = load_g_cx(ctxt, p) // load g into CX
+	}
+
+	if cursym.Text.From3Offset()&obj.NOSPLIT == 0 {
+		p = stacksplit(ctxt, p, autoffset, int32(textarg)) // emit split check
+	}
+
+	if autoffset != 0 {
+		if autoffset%int32(ctxt.Arch.RegSize) != 0 {
+			ctxt.Diag("unaligned stack size %d", autoffset)
+		}
+		p = obj.Appendp(ctxt, p)
+		p.As = AADJSP
+		p.From.Type = obj.TYPE_CONST
+		p.From.Offset = int64(autoffset)
+		p.Spadj = autoffset
+	}
+
+	deltasp := autoffset
+
+	if bpsize > 0 {
+		// Save caller's BP
+		p = obj.Appendp(ctxt, p)
+
+		p.As = AMOVQ
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_BP
+		p.To.Type = obj.TYPE_MEM
+		p.To.Reg = REG_SP
+		p.To.Scale = 1
+		p.To.Offset = int64(autoffset) - int64(bpsize)
+
+		// Move current frame to BP
+		p = obj.Appendp(ctxt, p)
+
+		p.As = ALEAQ
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = REG_SP
+		p.From.Scale = 1
+		p.From.Offset = int64(autoffset) - int64(bpsize)
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_BP
+	}
+
+	if cursym.Text.From3Offset()&obj.WRAPPER != 0 {
+		// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
+		//
+		//	MOVQ g_panic(CX), BX
+		//	TESTQ BX, BX
+		//	JEQ end
+		//	LEAQ (autoffset+8)(SP), DI
+		//	CMPQ panic_argp(BX), DI
+		//	JNE end
+		//	MOVQ SP, panic_argp(BX)
+		// end:
+		//	NOP
+		//
+		// The NOP is needed to give the jumps somewhere to land.
+		// It is a liblink NOP, not an x86 NOP: it encodes to 0 instruction bytes.
+
+		p = obj.Appendp(ctxt, p)
+
+		p.As = AMOVQ
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = REG_CX
+		p.From.Offset = 4 * int64(ctxt.Arch.PtrSize) // G.panic
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_BX
+		if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
+			p.As = AMOVL
+			p.From.Type = obj.TYPE_MEM
+			p.From.Reg = REG_R15
+			p.From.Scale = 1
+			p.From.Index = REG_CX
+		}
+		if p.Mode == 32 {
+			p.As = AMOVL
+		}
+
+		p = obj.Appendp(ctxt, p)
+		p.As = ATESTQ
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_BX
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_BX
+		if ctxt.Headtype == obj.Hnacl || p.Mode == 32 {
+			p.As = ATESTL
+		}
+
+		p = obj.Appendp(ctxt, p)
+		p.As = AJEQ
+		p.To.Type = obj.TYPE_BRANCH
+		p1 := p
+
+		p = obj.Appendp(ctxt, p)
+		p.As = ALEAQ
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = REG_SP
+		p.From.Offset = int64(autoffset) + int64(ctxt.Arch.RegSize)
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_DI
+		if ctxt.Headtype == obj.Hnacl || p.Mode == 32 {
+			p.As = ALEAL
+		}
+
+		p = obj.Appendp(ctxt, p)
+		p.As = ACMPQ
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = REG_BX
+		p.From.Offset = 0 // Panic.argp
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_DI
+		if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
+			p.As = ACMPL
+			p.From.Type = obj.TYPE_MEM
+			p.From.Reg = REG_R15
+			p.From.Scale = 1
+			p.From.Index = REG_BX
+		}
+		if p.Mode == 32 {
+			p.As = ACMPL
+		}
+
+		p = obj.Appendp(ctxt, p)
+		p.As = AJNE
+		p.To.Type = obj.TYPE_BRANCH
+		p2 := p
+
+		p = obj.Appendp(ctxt, p)
+		p.As = AMOVQ
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_SP
+		p.To.Type = obj.TYPE_MEM
+		p.To.Reg = REG_BX
+		p.To.Offset = 0 // Panic.argp
+		if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
+			p.As = AMOVL
+			p.To.Type = obj.TYPE_MEM
+			p.To.Reg = REG_R15
+			p.To.Scale = 1
+			p.To.Index = REG_BX
+		}
+		if p.Mode == 32 {
+			p.As = AMOVL
+		}
+
+		p = obj.Appendp(ctxt, p)
+		p.As = obj.ANOP
+		p1.Pcond = p
+		p2.Pcond = p
+	}
+
+	for ; p != nil; p = p.Link {
+		pcsize := int(p.Mode) / 8
+		switch p.From.Name {
+		case obj.NAME_AUTO:
+			p.From.Offset += int64(deltasp) - int64(bpsize)
+		case obj.NAME_PARAM:
+			p.From.Offset += int64(deltasp) + int64(pcsize)
+		}
+		if p.From3 != nil {
+			switch p.From3.Name {
+			case obj.NAME_AUTO:
+				p.From3.Offset += int64(deltasp) - int64(bpsize)
+			case obj.NAME_PARAM:
+				p.From3.Offset += int64(deltasp) + int64(pcsize)
+			}
+		}
+		switch p.To.Name {
+		case obj.NAME_AUTO:
+			p.To.Offset += int64(deltasp) - int64(bpsize)
+		case obj.NAME_PARAM:
+			p.To.Offset += int64(deltasp) + int64(pcsize)
+		}
+
+		switch p.As {
+		default:
+			continue
+
+		case APUSHL, APUSHFL:
+			deltasp += 4
+			p.Spadj = 4
+			continue
+
+		case APUSHQ, APUSHFQ:
+			deltasp += 8
+			p.Spadj = 8
+			continue
+
+		case APUSHW, APUSHFW:
+			deltasp += 2
+			p.Spadj = 2
+			continue
+
+		case APOPL, APOPFL:
+			deltasp -= 4
+			p.Spadj = -4
+			continue
+
+		case APOPQ, APOPFQ:
+			deltasp -= 8
+			p.Spadj = -8
+			continue
+
+		case APOPW, APOPFW:
+			deltasp -= 2
+			p.Spadj = -2
+			continue
+
+		case obj.ARET:
+			// do nothing
+		}
+
+		if autoffset != deltasp {
+			ctxt.Diag("unbalanced PUSH/POP")
+		}
+
+		if autoffset != 0 {
+			if bpsize > 0 {
+				// Restore caller's BP
+				p.As = AMOVQ
+
+				p.From.Type = obj.TYPE_MEM
+				p.From.Reg = REG_SP
+				p.From.Scale = 1
+				p.From.Offset = int64(autoffset) - int64(bpsize)
+				p.To.Type = obj.TYPE_REG
+				p.To.Reg = REG_BP
+				p = obj.Appendp(ctxt, p)
+			}
+
+			p.As = AADJSP
+			p.From.Type = obj.TYPE_CONST
+			p.From.Offset = int64(-autoffset)
+			p.Spadj = -autoffset
+			p = obj.Appendp(ctxt, p)
+			p.As = obj.ARET
+
+			// If there are instructions following
+			// this ARET, they come from a branch
+			// with the same stackframe, so undo
+			// the cleanup.
+			p.Spadj = +autoffset
+		}
+
+		if p.To.Sym != nil { // retjmp
+			p.As = obj.AJMP
+		}
+	}
+}
+
+func isZeroArgRuntimeCall(s *obj.LSym) bool {
+	if s == nil {
+		return false
+	}
+	switch s.Name {
+	case "runtime.panicindex", "runtime.panicslice", "runtime.panicdivide":
+		return true
+	}
+	return false
+}
+
+func indir_cx(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) {
+	if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
+		a.Type = obj.TYPE_MEM
+		a.Reg = REG_R15
+		a.Index = REG_CX
+		a.Scale = 1
+		return
+	}
+
+	a.Type = obj.TYPE_MEM
+	a.Reg = REG_CX
+}
+
+// Append code to p to load g into cx.
+// Overwrites p with the first instruction (no first appendp).
+// Overwriting p is unusual but it lets use this in both the
+// prologue (caller must call appendp first) and in the epilogue.
+// Returns last new instruction.
+func load_g_cx(ctxt *obj.Link, p *obj.Prog) *obj.Prog {
+	p.As = AMOVQ
+	if ctxt.Arch.PtrSize == 4 {
+		p.As = AMOVL
+	}
+	p.From.Type = obj.TYPE_MEM
+	p.From.Reg = REG_TLS
+	p.From.Offset = 0
+	p.To.Type = obj.TYPE_REG
+	p.To.Reg = REG_CX
+
+	next := p.Link
+	progedit(ctxt, p)
+	for p.Link != next {
+		p = p.Link
+	}
+
+	if p.From.Index == REG_TLS {
+		p.From.Scale = 2
+	}
+
+	return p
+}
+
+// Append code to p to check for stack split.
+// Appends to (does not overwrite) p.
+// Assumes g is in CX.
+// Returns last new instruction.
+func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32, textarg int32) *obj.Prog {
+	cmp := ACMPQ
+	lea := ALEAQ
+	mov := AMOVQ
+	sub := ASUBQ
+
+	if ctxt.Headtype == obj.Hnacl || p.Mode == 32 {
+		cmp = ACMPL
+		lea = ALEAL
+		mov = AMOVL
+		sub = ASUBL
+	}
+
+	var q1 *obj.Prog
+	if framesize <= obj.StackSmall {
+		// small stack: SP <= stackguard
+		//	CMPQ SP, stackguard
+		p = obj.Appendp(ctxt, p)
+
+		p.As = cmp
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_SP
+		indir_cx(ctxt, p, &p.To)
+		p.To.Offset = 2 * int64(ctxt.Arch.PtrSize) // G.stackguard0
+		if ctxt.Cursym.CFunc() {
+			p.To.Offset = 3 * int64(ctxt.Arch.PtrSize) // G.stackguard1
+		}
+	} else if framesize <= obj.StackBig {
+		// large stack: SP-framesize <= stackguard-StackSmall
+		//	LEAQ -xxx(SP), AX
+		//	CMPQ AX, stackguard
+		p = obj.Appendp(ctxt, p)
+
+		p.As = lea
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = REG_SP
+		p.From.Offset = -(int64(framesize) - obj.StackSmall)
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_AX
+
+		p = obj.Appendp(ctxt, p)
+		p.As = cmp
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_AX
+		indir_cx(ctxt, p, &p.To)
+		p.To.Offset = 2 * int64(ctxt.Arch.PtrSize) // G.stackguard0
+		if ctxt.Cursym.CFunc() {
+			p.To.Offset = 3 * int64(ctxt.Arch.PtrSize) // G.stackguard1
+		}
+	} 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.
+		//
+		// Preemption sets stackguard to StackPreempt, a very large value.
+		// That breaks the math above, so we have to check for that explicitly.
+		//	MOVQ	stackguard, CX
+		//	CMPQ	CX, $StackPreempt
+		//	JEQ	label-of-call-to-morestack
+		//	LEAQ	StackGuard(SP), AX
+		//	SUBQ	CX, AX
+		//	CMPQ	AX, $(framesize+(StackGuard-StackSmall))
+
+		p = obj.Appendp(ctxt, p)
+
+		p.As = mov
+		indir_cx(ctxt, p, &p.From)
+		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_SI
+
+		p = obj.Appendp(ctxt, p)
+		p.As = cmp
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_SI
+		p.To.Type = obj.TYPE_CONST
+		p.To.Offset = obj.StackPreempt
+		if p.Mode == 32 {
+			p.To.Offset = int64(uint32(obj.StackPreempt & (1<<32 - 1)))
+		}
+
+		p = obj.Appendp(ctxt, p)
+		p.As = AJEQ
+		p.To.Type = obj.TYPE_BRANCH
+		q1 = p
+
+		p = obj.Appendp(ctxt, p)
+		p.As = lea
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = REG_SP
+		p.From.Offset = obj.StackGuard
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_AX
+
+		p = obj.Appendp(ctxt, p)
+		p.As = sub
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_SI
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_AX
+
+		p = obj.Appendp(ctxt, p)
+		p.As = cmp
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_AX
+		p.To.Type = obj.TYPE_CONST
+		p.To.Offset = int64(framesize) + (obj.StackGuard - obj.StackSmall)
+	}
+
+	// common
+	jls := obj.Appendp(ctxt, p)
+	jls.As = AJLS
+	jls.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
+
+	call := obj.Appendp(ctxt, pcdata)
+	call.Lineno = ctxt.Cursym.Text.Lineno
+	call.Mode = ctxt.Cursym.Text.Mode
+	call.As = obj.ACALL
+	call.To.Type = obj.TYPE_BRANCH
+	call.To.Name = obj.NAME_EXTERN
+	morestack := "runtime.morestack"
+	switch {
+	case ctxt.Cursym.CFunc():
+		morestack = "runtime.morestackc"
+	case ctxt.Cursym.Text.From3Offset()&obj.NEEDCTXT == 0:
+		morestack = "runtime.morestack_noctxt"
+	}
+	call.To.Sym = obj.Linklookup(ctxt, morestack, 0)
+	// When compiling 386 code for dynamic linking, the call needs to be adjusted
+	// to follow PIC rules. This in turn can insert more instructions, so we need
+	// to keep track of the start of the call (where the jump will be to) and the
+	// end (which following instructions are appended to).
+	callend := call
+	progedit(ctxt, callend)
+	for ; callend.Link != nil; callend = callend.Link {
+		progedit(ctxt, callend.Link)
+	}
+
+	jmp := obj.Appendp(ctxt, callend)
+	jmp.As = obj.AJMP
+	jmp.To.Type = obj.TYPE_BRANCH
+	jmp.Pcond = ctxt.Cursym.Text.Link
+	jmp.Spadj = +framesize
+
+	jls.Pcond = call
+	if q1 != nil {
+		q1.Pcond = call
+	}
+
+	return jls
+}
+
+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 nofollow(a obj.As) bool {
+	switch a {
+	case obj.AJMP,
+		obj.ARET,
+		AIRETL,
+		AIRETQ,
+		AIRETW,
+		ARETFL,
+		ARETFQ,
+		ARETFW,
+		obj.AUNDEF:
+		return true
+	}
+
+	return false
+}
+
+func pushpop(a obj.As) bool {
+	switch a {
+	case APUSHL,
+		APUSHFL,
+		APUSHQ,
+		APUSHFQ,
+		APUSHW,
+		APUSHFW,
+		APOPL,
+		APOPFL,
+		APOPQ,
+		APOPFQ,
+		APOPW,
+		APOPFW:
+		return true
+	}
+
+	return false
+}
+
+func relinv(a obj.As) obj.As {
+	switch a {
+	case AJEQ:
+		return AJNE
+	case AJNE:
+		return AJEQ
+	case AJLE:
+		return AJGT
+	case AJLS:
+		return AJHI
+	case AJLT:
+		return AJGE
+	case AJMI:
+		return AJPL
+	case AJGE:
+		return AJLT
+	case AJPL:
+		return AJMI
+	case AJGT:
+		return AJLE
+	case AJHI:
+		return AJLS
+	case AJCS:
+		return AJCC
+	case AJCC:
+		return AJCS
+	case AJPS:
+		return AJPC
+	case AJPC:
+		return AJPS
+	case AJOS:
+		return AJOC
+	case AJOC:
+		return AJOS
+	}
+
+	log.Fatalf("unknown relation: %s", a)
+	return 0
+}
+
+func xfol(ctxt *obj.Link, p *obj.Prog, last **obj.Prog) {
+	var q *obj.Prog
+	var i int
+	var a obj.As
+
+loop:
+	if p == nil {
+		return
+	}
+	if p.As == obj.AJMP {
+		q = p.Pcond
+		if q != nil && q.As != obj.ATEXT {
+			/* mark instruction as done and continue layout at target of jump */
+			p.Mark |= DONE
+
+			p = q
+			if p.Mark&DONE == 0 {
+				goto loop
+			}
+		}
+	}
+
+	if p.Mark&DONE != 0 {
+		/*
+		 * p goes here, but already used it elsewhere.
+		 * copy up to 4 instructions or else branch to other copy.
+		 */
+		i = 0
+		q = p
+		for ; i < 4; i, q = i+1, q.Link {
+			if q == nil {
+				break
+			}
+			if q == *last {
+				break
+			}
+			a = q.As
+			if a == obj.ANOP {
+				i--
+				continue
+			}
+
+			if nofollow(a) || pushpop(a) {
+				break // NOTE(rsc): arm does goto copy
+			}
+			if q.Pcond == nil || q.Pcond.Mark&DONE != 0 {
+				continue
+			}
+			if a == obj.ACALL || a == ALOOP {
+				continue
+			}
+			for {
+				if p.As == obj.ANOP {
+					p = p.Link
+					continue
+				}
+
+				q = obj.Copyp(ctxt, p)
+				p = p.Link
+				q.Mark |= DONE
+				(*last).Link = q
+				*last = q
+				if q.As != a || q.Pcond == nil || q.Pcond.Mark&DONE != 0 {
+					continue
+				}
+
+				q.As = relinv(q.As)
+				p = q.Pcond
+				q.Pcond = q.Link
+				q.Link = p
+				xfol(ctxt, q.Link, last)
+				p = q.Link
+				if p.Mark&DONE != 0 {
+					return
+				}
+				goto loop
+				/* */
+			}
+		}
+		q = ctxt.NewProg()
+		q.As = obj.AJMP
+		q.Lineno = p.Lineno
+		q.To.Type = obj.TYPE_BRANCH
+		q.To.Offset = p.Pc
+		q.Pcond = p
+		p = q
+	}
+
+	/* emit p */
+	p.Mark |= DONE
+
+	(*last).Link = p
+	*last = p
+	a = p.As
+
+	/* continue loop with what comes after p */
+	if nofollow(a) {
+		return
+	}
+	if p.Pcond != nil && a != obj.ACALL {
+		/*
+		 * some kind of conditional branch.
+		 * recurse to follow one path.
+		 * continue loop on the other.
+		 */
+		q = obj.Brchain(ctxt, p.Pcond)
+		if q != nil {
+			p.Pcond = q
+		}
+		q = obj.Brchain(ctxt, p.Link)
+		if q != nil {
+			p.Link = q
+		}
+		if p.From.Type == obj.TYPE_CONST {
+			if p.From.Offset == 1 {
+				/*
+				 * expect conditional jump to be taken.
+				 * rewrite so that's the fall-through case.
+				 */
+				p.As = relinv(a)
+
+				q = p.Link
+				p.Link = p.Pcond
+				p.Pcond = q
+			}
+		} else {
+			q = p.Link
+			if q.Mark&DONE != 0 {
+				if a != ALOOP {
+					p.As = relinv(a)
+					p.Link = p.Pcond
+					p.Pcond = q
+				}
+			}
+		}
+
+		xfol(ctxt, p.Link, last)
+		if p.Pcond.Mark&DONE != 0 {
+			return
+		}
+		p = p.Pcond
+		goto loop
+	}
+
+	p = p.Link
+	goto loop
+}
+
+var unaryDst = map[obj.As]bool{
+	ABSWAPL:    true,
+	ABSWAPQ:    true,
+	ACMPXCHG8B: true,
+	ADECB:      true,
+	ADECL:      true,
+	ADECQ:      true,
+	ADECW:      true,
+	AINCB:      true,
+	AINCL:      true,
+	AINCQ:      true,
+	AINCW:      true,
+	ANEGB:      true,
+	ANEGL:      true,
+	ANEGQ:      true,
+	ANEGW:      true,
+	ANOTB:      true,
+	ANOTL:      true,
+	ANOTQ:      true,
+	ANOTW:      true,
+	APOPL:      true,
+	APOPQ:      true,
+	APOPW:      true,
+	ASETCC:     true,
+	ASETCS:     true,
+	ASETEQ:     true,
+	ASETGE:     true,
+	ASETGT:     true,
+	ASETHI:     true,
+	ASETLE:     true,
+	ASETLS:     true,
+	ASETLT:     true,
+	ASETMI:     true,
+	ASETNE:     true,
+	ASETOC:     true,
+	ASETOS:     true,
+	ASETPC:     true,
+	ASETPL:     true,
+	ASETPS:     true,
+	AFFREE:     true,
+	AFLDENV:    true,
+	AFSAVE:     true,
+	AFSTCW:     true,
+	AFSTENV:    true,
+	AFSTSW:     true,
+	AFXSAVE:    true,
+	AFXSAVE64:  true,
+	ASTMXCSR:   true,
+}
+
+var Linkamd64 = obj.LinkArch{
+	Arch:       sys.ArchAMD64,
+	Preprocess: preprocess,
+	Assemble:   span6,
+	Follow:     follow,
+	Progedit:   progedit,
+	UnaryDst:   unaryDst,
+}
+
+var Linkamd64p32 = obj.LinkArch{
+	Arch:       sys.ArchAMD64P32,
+	Preprocess: preprocess,
+	Assemble:   span6,
+	Follow:     follow,
+	Progedit:   progedit,
+	UnaryDst:   unaryDst,
+}
+
+var Link386 = obj.LinkArch{
+	Arch:       sys.Arch386,
+	Preprocess: preprocess,
+	Assemble:   span6,
+	Follow:     follow,
+	Progedit:   progedit,
+	UnaryDst:   unaryDst,
+}