func xfol(ctxt *liblink.Link, p *liblink.Prog, last **liblink.Prog) {
var q *liblink.Prog
var r *liblink.Prog
var a int
var i int
loop:
if p == nil {
return
}
a = p.As
if a == AB {
q = p.Pcond
if q != nil && q.As != ATEXT {
p.Mark |= FOLL
p = q
if p.Mark&FOLL == 0 {
goto loop
}
}
}
if p.Mark&FOLL != 0 {
i = 0
q = p
for ; i < 4; (func() { i++; q = q.Link })() {
if q == *last || q == nil {
break
}
a = q.As
if a == ANOP {
i--
continue
}
if a == AB || (a == ARET && q.Scond == C_SCOND_NONE) || a == ARFE || a == AUNDEF {
goto copy
}
if q.Pcond == nil || (q.Pcond.Mark&FOLL != 0) {
continue
}
if a != ABEQ && a != ABNE {
continue
}
copy:
for {
r = ctxt.Prg()
*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 == ARET && q.Scond == C_SCOND_NONE) || a == ARFE || a == AUNDEF {
return
}
r.As = ABNE
if a == ABNE {
r.As = ABEQ
}
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.Prg()
q.As = a
q.Lineno = p.Lineno
q.To.Typ = D_BRANCH
q.To.Offset = p.Pc
q.Pcond = p
p = q
}
p.Mark |= FOLL
(*last).Link = p
*last = p
if a == AB || (a == ARET && p.Scond == C_SCOND_NONE) || a == ARFE || a == AUNDEF {
return
}
if p.Pcond != nil {
if a != ABL && a != ABX && p.Link != nil {
q = liblink.Brchain(ctxt, p.Link)
if a != ATEXT && a != ABCASE {
if q != nil && (q.Mark&FOLL != 0) {
p.As = relinv(a)
p.Link = p.Pcond
p.Pcond = q
}
}
xfol(ctxt, p.Link, last)
q = liblink.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 addstacksplit(ctxt *liblink.Link, cursym *liblink.LSym) {
var p *liblink.Prog
var q *liblink.Prog
var q1 *liblink.Prog
var autoffset int64
var deltasp int64
var a int
var pcsize int
var i uint32
var textstksiz int64
var textarg int64
if ctxt.Tlsg == nil {
ctxt.Tlsg = liblink.Linklookup(ctxt, "runtime.tlsg", 0)
}
if ctxt.Symmorestack[0] == nil {
if len(morename) > len(ctxt.Symmorestack) {
log.Fatalf("Link.symmorestack needs at least %d elements", len(morename))
}
for i = 0; i < uint32(len(morename)); i++ {
ctxt.Symmorestack[i] = liblink.Linklookup(ctxt, morename[i], 0)
}
}
if ctxt.Headtype == liblink.Hplan9 && ctxt.Plan9privates == nil {
ctxt.Plan9privates = liblink.Linklookup(ctxt, "_privates", 0)
}
ctxt.Cursym = cursym
if cursym.Text == nil || cursym.Text.Link == nil {
return
}
p = cursym.Text
parsetextconst(p.To.Offset, &textstksiz, &textarg)
autoffset = textstksiz
if autoffset < 0 {
autoffset = 0
}
cursym.Args = int(p.To.Offset >> 32)
cursym.Locals = textstksiz
if autoffset < liblink.StackSmall && p.From.Scale&liblink.NOSPLIT == 0 {
for q = p; q != nil; q = q.Link {
if q.As == ACALL {
goto noleaf
}
if (q.As == ADUFFCOPY || q.As == ADUFFZERO) && autoffset >= liblink.StackSmall-8 {
goto noleaf
}
}
p.From.Scale |= liblink.NOSPLIT
noleaf:
}
q = nil
if p.From.Scale&liblink.NOSPLIT == 0 || (p.From.Scale&liblink.WRAPPER != 0) {
p = liblink.Appendp(ctxt, p)
p = load_g_cx(ctxt, p) // load g into CX
}
if cursym.Text.From.Scale&liblink.NOSPLIT == 0 {
p = stacksplit(ctxt, p, autoffset, textarg, bool2int(cursym.Text.From.Scale&liblink.NEEDCTXT == 0), &q) // emit split check
}
if autoffset != 0 {
if autoffset%int64(ctxt.Arch.Regsize) != 0 {
ctxt.Diag("unaligned stack size %d", autoffset)
}
p = liblink.Appendp(ctxt, p)
p.As = AADJSP
p.From.Typ = D_CONST
p.From.Offset = autoffset
p.Spadj = autoffset
} else {
// zero-byte stack adjustment.
// Insert a fake non-zero adjustment so that stkcheck can
// recognize the end of the stack-splitting prolog.
p = liblink.Appendp(ctxt, p)
p.As = ANOP
p.Spadj = -ctxt.Arch.Ptrsize
p = liblink.Appendp(ctxt, p)
p.As = ANOP
p.Spadj = ctxt.Arch.Ptrsize
}
if q != nil {
q.Pcond = p
}
deltasp = autoffset
if cursym.Text.From.Scale&liblink.WRAPPER != 0 {
// g->panicwrap += autoffset + ctxt->arch->regsize;
p = liblink.Appendp(ctxt, p)
p.As = AADDL
p.From.Typ = D_CONST
p.From.Offset = autoffset + int64(ctxt.Arch.Regsize)
indir_cx(ctxt, &p.To)
p.To.Offset = 2 * ctxt.Arch.Ptrsize
}
if ctxt.Debugstack > 1 && autoffset != 0 {
// 6l -K -K means double-check for stack overflow
// even after calling morestack and even if the
// function is marked as nosplit.
p = liblink.Appendp(ctxt, p)
p.As = AMOVQ
indir_cx(ctxt, &p.From)
p.From.Offset = 0
p.To.Typ = D_BX
p = liblink.Appendp(ctxt, p)
p.As = ASUBQ
p.From.Typ = D_CONST
p.From.Offset = liblink.StackSmall + 32
p.To.Typ = D_BX
p = liblink.Appendp(ctxt, p)
p.As = ACMPQ
p.From.Typ = D_SP
p.To.Typ = D_BX
p = liblink.Appendp(ctxt, p)
p.As = AJHI
p.To.Typ = D_BRANCH
q1 = p
p = liblink.Appendp(ctxt, p)
p.As = AINT
p.From.Typ = D_CONST
p.From.Offset = 3
p = liblink.Appendp(ctxt, p)
p.As = ANOP
q1.Pcond = p
}
if ctxt.Debugzerostack != 0 && autoffset != 0 && cursym.Text.From.Scale&liblink.NOSPLIT == 0 {
// 6l -Z means zero the stack frame on entry.
// This slows down function calls but can help avoid
// false positives in garbage collection.
p = liblink.Appendp(ctxt, p)
p.As = AMOVQ
p.From.Typ = D_SP
p.To.Typ = D_DI
p = liblink.Appendp(ctxt, p)
p.As = AMOVQ
p.From.Typ = D_CONST
p.From.Offset = autoffset / 8
p.To.Typ = D_CX
p = liblink.Appendp(ctxt, p)
p.As = AMOVQ
p.From.Typ = D_CONST
p.From.Offset = 0
p.To.Typ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = AREP
p = liblink.Appendp(ctxt, p)
p.As = ASTOSQ
}
for ; p != nil; p = p.Link {
pcsize = p.Mode / 8
a = p.From.Typ
if a == D_AUTO {
p.From.Offset += deltasp
}
if a == D_PARAM {
p.From.Offset += deltasp + int64(pcsize)
}
a = p.To.Typ
if a == D_AUTO {
p.To.Offset += deltasp
}
if a == D_PARAM {
p.To.Offset += 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 ARET:
break
}
if autoffset != deltasp {
ctxt.Diag("unbalanced PUSH/POP")
}
if cursym.Text.From.Scale&liblink.WRAPPER != 0 {
p = load_g_cx(ctxt, p)
p = liblink.Appendp(ctxt, p)
// g->panicwrap -= autoffset + ctxt->arch->regsize;
p.As = ASUBL
p.From.Typ = D_CONST
p.From.Offset = autoffset + int64(ctxt.Arch.Regsize)
indir_cx(ctxt, &p.To)
p.To.Offset = 2 * ctxt.Arch.Ptrsize
p = liblink.Appendp(ctxt, p)
p.As = ARET
}
if autoffset != 0 {
p.As = AADJSP
p.From.Typ = D_CONST
p.From.Offset = -autoffset
p.Spadj = -autoffset
p = liblink.Appendp(ctxt, p)
p.As = 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 = AJMP
}
}
}
func indir_cx(ctxt *liblink.Link, a *liblink.Addr) {
if ctxt.Headtype == liblink.Hnacl {
a.Typ = D_INDIR + D_R15
a.Index = D_CX
a.Scale = 1
return
}
a.Typ = D_INDIR + D_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 *liblink.Link, p *liblink.Prog) *liblink.Prog {
var next *liblink.Prog
p.As = AMOVQ
if ctxt.Arch.Ptrsize == 4 {
p.As = AMOVL
}
p.From.Typ = D_INDIR + D_TLS
p.From.Offset = 0
p.To.Typ = D_CX
next = p.Link
progedit(ctxt, p)
for p.Link != next {
p = p.Link
}
if p.From.Index == D_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.
// On return, *jmpok is the instruction that should jump
// to the stack frame allocation if no split is needed.
func stacksplit(ctxt *liblink.Link, p *liblink.Prog, framesize int64, textarg int64, noctxt int, jmpok **liblink.Prog) *liblink.Prog {
var q *liblink.Prog
var q1 *liblink.Prog
var moreconst1 int64
var moreconst2 int64
var i uint32
var cmp int
var lea int
var mov int
var sub int
cmp = ACMPQ
lea = ALEAQ
mov = AMOVQ
sub = ASUBQ
if ctxt.Headtype == liblink.Hnacl {
cmp = ACMPL
lea = ALEAL
mov = AMOVL
sub = ASUBL
}
if ctxt.Debugstack != 0 {
// 6l -K means check not only for stack
// overflow but stack underflow.
// On underflow, INT 3 (breakpoint).
// Underflow itself is rare but this also
// catches out-of-sync stack guard info
p = liblink.Appendp(ctxt, p)
p.As = cmp
indir_cx(ctxt, &p.From)
p.From.Offset = 8
p.To.Typ = D_SP
p = liblink.Appendp(ctxt, p)
p.As = AJHI
p.To.Typ = D_BRANCH
p.To.Offset = 4
q1 = p
p = liblink.Appendp(ctxt, p)
p.As = AINT
p.From.Typ = D_CONST
p.From.Offset = 3
p = liblink.Appendp(ctxt, p)
p.As = ANOP
q1.Pcond = p
}
q1 = nil
if framesize <= liblink.StackSmall {
// small stack: SP <= stackguard
// CMPQ SP, stackguard
p = liblink.Appendp(ctxt, p)
p.As = cmp
p.From.Typ = D_SP
indir_cx(ctxt, &p.To)
} else if framesize <= liblink.StackBig {
// large stack: SP-framesize <= stackguard-StackSmall
// LEAQ -xxx(SP), AX
// CMPQ AX, stackguard
p = liblink.Appendp(ctxt, p)
p.As = lea
p.From.Typ = D_INDIR + D_SP
p.From.Offset = -(framesize - liblink.StackSmall)
p.To.Typ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = cmp
p.From.Typ = D_AX
indir_cx(ctxt, &p.To)
} 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 = liblink.Appendp(ctxt, p)
p.As = mov
indir_cx(ctxt, &p.From)
p.From.Offset = 0
p.To.Typ = D_SI
p = liblink.Appendp(ctxt, p)
p.As = cmp
p.From.Typ = D_SI
p.To.Typ = D_CONST
p.To.Offset = liblink.StackPreempt
p = liblink.Appendp(ctxt, p)
p.As = AJEQ
p.To.Typ = D_BRANCH
q1 = p
p = liblink.Appendp(ctxt, p)
p.As = lea
p.From.Typ = D_INDIR + D_SP
p.From.Offset = liblink.StackGuard
p.To.Typ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = sub
p.From.Typ = D_SI
p.To.Typ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = cmp
p.From.Typ = D_AX
p.To.Typ = D_CONST
p.To.Offset = framesize + (liblink.StackGuard - liblink.StackSmall)
}
// common
p = liblink.Appendp(ctxt, p)
p.As = AJHI
p.To.Typ = D_BRANCH
q = p
// If we ask for more stack, we'll get a minimum of StackMin bytes.
// We need a stack frame large enough to hold the top-of-stack data,
// the function arguments+results, our caller's PC, our frame,
// a word for the return PC of the next call, and then the StackLimit bytes
// that must be available on entry to any function called from a function
// that did a stack check. If StackMin is enough, don't ask for a specific
// amount: then we can use the custom functions and save a few
// instructions.
moreconst1 = 0
if liblink.StackTop+textarg+ctxt.Arch.Ptrsize+framesize+ctxt.Arch.Ptrsize+liblink.StackLimit >= liblink.StackMin {
moreconst1 = framesize
}
moreconst2 = textarg
if moreconst2 == 1 { // special marker
moreconst2 = 0
}
if moreconst2&7 != 0 {
ctxt.Diag("misaligned argument size in stack split")
}
// 4 varieties varieties (const1==0 cross const2==0)
// and 6 subvarieties of (const1==0 and const2!=0)
p = liblink.Appendp(ctxt, p)
if moreconst1 == 0 && moreconst2 == 0 {
p.As = ACALL
p.To.Typ = D_BRANCH
p.To.Sym = ctxt.Symmorestack[0*2+noctxt]
} else if moreconst1 != 0 && moreconst2 == 0 {
p.As = AMOVL
p.From.Typ = D_CONST
p.From.Offset = moreconst1
p.To.Typ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = ACALL
p.To.Typ = D_BRANCH
p.To.Sym = ctxt.Symmorestack[1*2+noctxt]
} else if moreconst1 == 0 && moreconst2 <= 48 && moreconst2%8 == 0 {
i = uint32(moreconst2/8 + 3)
p.As = ACALL
p.To.Typ = D_BRANCH
p.To.Sym = ctxt.Symmorestack[i*2+uint32(noctxt)]
} else if moreconst1 == 0 && moreconst2 != 0 {
p.As = AMOVL
p.From.Typ = D_CONST
p.From.Offset = moreconst2
p.To.Typ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = ACALL
p.To.Typ = D_BRANCH
p.To.Sym = ctxt.Symmorestack[2*2+noctxt]
} else {
// Pass framesize and argsize.
p.As = AMOVQ
p.From.Typ = D_CONST
p.From.Offset = int64(uint64(moreconst2) << 32)
p.From.Offset |= moreconst1
p.To.Typ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = ACALL
p.To.Typ = D_BRANCH
p.To.Sym = ctxt.Symmorestack[3*2+noctxt]
}
p = liblink.Appendp(ctxt, p)
p.As = AJMP
p.To.Typ = D_BRANCH
p.Pcond = ctxt.Cursym.Text.Link
if q != nil {
q.Pcond = p.Link
}
if q1 != nil {
q1.Pcond = q.Link
}
*jmpok = q
return p
}
func follow(ctxt *liblink.Link, s *liblink.LSym) {
var firstp *liblink.Prog
var lastp *liblink.Prog
ctxt.Cursym = s
firstp = ctxt.Prg()
lastp = firstp
xfol(ctxt, s.Text, &lastp)
lastp.Link = nil
s.Text = firstp.Link
}
func nofollow(a int) bool {
switch a {
case AJMP,
ARET,
AIRETL,
AIRETQ,
AIRETW,
ARETFL,
ARETFQ,
ARETFW,
AUNDEF:
return true
}
return false
}
func pushpop(a int) int {
switch a {
case APUSHL,
APUSHFL,
APUSHQ,
APUSHFQ,
APUSHW,
APUSHFW,
APOPL,
APOPFL,
APOPQ,
APOPFQ,
APOPW,
APOPFW:
return 1
}
return 0
}
func relinv(a int) int {
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", Anames6[a])
return 0
}
func xfol(ctxt *liblink.Link, p *liblink.Prog, last **liblink.Prog) {
var q *liblink.Prog
var i int
var a int
loop:
if p == nil {
return
}
if p.As == AJMP {
q = p.Pcond
if q != nil && q.As != ATEXT {
/* mark instruction as done and continue layout at target of jump */
p.Mark = 1
p = q
if p.Mark == 0 {
goto loop
}
}
}
if p.Mark != 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; (func() { i++; q = q.Link })() {
if q == nil {
break
}
if q == *last {
break
}
a = q.As
if a == ANOP {
i--
continue
}
if nofollow(a) || pushpop(a) != 0 {
break // NOTE(rsc): arm does goto copy
}
if q.Pcond == nil || q.Pcond.Mark != 0 {
continue
}
if a == ACALL || a == ALOOP {
continue
}
for {
if p.As == ANOP {
p = p.Link
continue
}
q = liblink.Copyp(ctxt, p)
p = p.Link
q.Mark = 1
(*last).Link = q
*last = q
if q.As != a || q.Pcond == nil || q.Pcond.Mark != 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 != 0 {
return
}
goto loop /* */
}
}
q = ctxt.Prg()
q.As = AJMP
q.Lineno = p.Lineno
q.To.Typ = D_BRANCH
q.To.Offset = p.Pc
q.Pcond = p
p = q
}
/* emit p */
p.Mark = 1
(*last).Link = p
*last = p
a = p.As
/* continue loop with what comes after p */
if nofollow(a) {
return
}
if p.Pcond != nil && a != ACALL {
/*
* some kind of conditional branch.
* recurse to follow one path.
* continue loop on the other.
*/
q = liblink.Brchain(ctxt, p.Pcond)
if q != nil {
p.Pcond = q
}
q = liblink.Brchain(ctxt, p.Link)
if q != nil {
p.Link = q
}
if p.From.Typ == D_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 != 0 {
if a != ALOOP {
p.As = relinv(a)
p.Link = p.Pcond
p.Pcond = q
}
}
}
xfol(ctxt, p.Link, last)
if p.Pcond.Mark != 0 {
return
}
p = p.Pcond
goto loop
}
p = p.Link
goto loop
}
func prg() *liblink.Prog {
var p *liblink.Prog
p = new(liblink.Prog)
*p = zprg
return p
}
var Linkamd64 = liblink.LinkArch{
Name: "amd64",
Thechar: '6',
ByteOrder: binary.LittleEndian,
Pconv: Pconv,
Addstacksplit: addstacksplit,
Assemble: span6,
Datasize: datasize,
Follow: follow,
Iscall: iscall,
Isdata: isdata,
Prg: prg,
Progedit: progedit,
Settextflag: settextflag,
Symtype: symtype,
Textflag: textflag,
Minlc: 1,
Ptrsize: 8,
Regsize: 8,
D_ADDR: D_ADDR,
D_AUTO: D_AUTO,
D_BRANCH: D_BRANCH,
D_CONST: D_CONST,
D_EXTERN: D_EXTERN,
D_FCONST: D_FCONST,
D_NONE: D_NONE,
D_PARAM: D_PARAM,
D_SCONST: D_SCONST,
D_STATIC: D_STATIC,
ACALL: ACALL,
ADATA: ADATA,
AEND: AEND,
AFUNCDATA: AFUNCDATA,
AGLOBL: AGLOBL,
AJMP: AJMP,
ANOP: ANOP,
APCDATA: APCDATA,
ARET: ARET,
ATEXT: ATEXT,
ATYPE: ATYPE,
AUSEFIELD: AUSEFIELD,
}
var Linkamd64p32 = liblink.LinkArch{
Name: "amd64p32",
Thechar: '6',
ByteOrder: binary.LittleEndian,
Pconv: Pconv,
Addstacksplit: addstacksplit,
Assemble: span6,
Datasize: datasize,
Follow: follow,
Iscall: iscall,
Isdata: isdata,
Prg: prg,
Progedit: progedit,
Settextflag: settextflag,
Symtype: symtype,
Textflag: textflag,
Minlc: 1,
Ptrsize: 4,
Regsize: 8,
D_ADDR: D_ADDR,
D_AUTO: D_AUTO,
D_BRANCH: D_BRANCH,
D_CONST: D_CONST,
D_EXTERN: D_EXTERN,
D_FCONST: D_FCONST,
D_NONE: D_NONE,
D_PARAM: D_PARAM,
D_SCONST: D_SCONST,
D_STATIC: D_STATIC,
ACALL: ACALL,
ADATA: ADATA,
AEND: AEND,
AFUNCDATA: AFUNCDATA,
AGLOBL: AGLOBL,
AJMP: AJMP,
ANOP: ANOP,
APCDATA: APCDATA,
ARET: ARET,
ATEXT: ATEXT,
ATYPE: ATYPE,
AUSEFIELD: AUSEFIELD,
}
func xfol(ctxt *liblink.Link, p *liblink.Prog, last **liblink.Prog) {
var q *liblink.Prog
var i int
var a int
loop:
if p == nil {
return
}
if p.As == AJMP {
q = p.Pcond
if q != nil && q.As != ATEXT {
/* mark instruction as done and continue layout at target of jump */
p.Mark = 1
p = q
if p.Mark == 0 {
goto loop
}
}
}
if p.Mark != 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; (func() { i++; q = q.Link })() {
if q == nil {
break
}
if q == *last {
break
}
a = q.As
if a == ANOP {
i--
continue
}
if nofollow(a) || pushpop(a) != 0 {
break // NOTE(rsc): arm does goto copy
}
if q.Pcond == nil || q.Pcond.Mark != 0 {
continue
}
if a == ACALL || a == ALOOP {
continue
}
for {
if p.As == ANOP {
p = p.Link
continue
}
q = liblink.Copyp(ctxt, p)
p = p.Link
q.Mark = 1
(*last).Link = q
*last = q
if q.As != a || q.Pcond == nil || q.Pcond.Mark != 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 != 0 {
return
}
goto loop /* */
}
}
q = ctxt.Prg()
q.As = AJMP
q.Lineno = p.Lineno
q.To.Typ = D_BRANCH
q.To.Offset = p.Pc
q.Pcond = p
p = q
}
/* emit p */
p.Mark = 1
(*last).Link = p
*last = p
a = p.As
/* continue loop with what comes after p */
if nofollow(a) {
return
}
if p.Pcond != nil && a != ACALL {
/*
* some kind of conditional branch.
* recurse to follow one path.
* continue loop on the other.
*/
q = liblink.Brchain(ctxt, p.Pcond)
if q != nil {
p.Pcond = q
}
q = liblink.Brchain(ctxt, p.Link)
if q != nil {
p.Link = q
}
if p.From.Typ == D_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 != 0 {
if a != ALOOP {
p.As = relinv(a)
p.Link = p.Pcond
p.Pcond = q
}
}
}
xfol(ctxt, p.Link, last)
if p.Pcond.Mark != 0 {
return
}
p = p.Pcond
goto loop
}
p = p.Link
goto loop
}