func addstacksplit(ctxt *liblink.Link, cursym *liblink.LSym) {
var p *liblink.Prog
var q *liblink.Prog
var autoffset int64
var deltasp int64
var a int
if ctxt.Symmorestack[0] == nil {
ctxt.Symmorestack[0] = liblink.Linklookup(ctxt, "runtime.morestack", 0)
ctxt.Symmorestack[1] = liblink.Linklookup(ctxt, "runtime.morestack_noctxt", 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
autoffset = p.To.Offset
if autoffset < 0 {
autoffset = 0
}
cursym.Locals = autoffset
cursym.Args = p.To.Offset2
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, bool2int(cursym.Text.From.Scale&liblink.NEEDCTXT == 0), &q) // emit split check
}
if autoffset != 0 {
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->ptrsize;
p = liblink.Appendp(ctxt, p)
p.As = AADDL
p.From.Typ = D_CONST
p.From.Offset = autoffset + ctxt.Arch.Ptrsize
p.To.Typ = D_INDIR + D_CX
p.To.Offset = 2 * ctxt.Arch.Ptrsize
}
if ctxt.Debugzerostack != 0 && autoffset != 0 && cursym.Text.From.Scale&liblink.NOSPLIT == 0 {
// 8l -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 = AMOVL
p.From.Typ = D_SP
p.To.Typ = D_DI
p = liblink.Appendp(ctxt, p)
p.As = AMOVL
p.From.Typ = D_CONST
p.From.Offset = autoffset / 4
p.To.Typ = D_CX
p = liblink.Appendp(ctxt, p)
p.As = AMOVL
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 = ASTOSL
}
for ; p != nil; p = p.Link {
a = p.From.Typ
if a == D_AUTO {
p.From.Offset += deltasp
}
if a == D_PARAM {
p.From.Offset += deltasp + 4
}
a = p.To.Typ
if a == D_AUTO {
p.To.Offset += deltasp
}
if a == D_PARAM {
p.To.Offset += deltasp + 4
}
switch p.As {
default:
continue
case APUSHL,
APUSHFL:
deltasp += 4
p.Spadj = 4
continue
case APUSHW,
APUSHFW:
deltasp += 2
p.Spadj = 2
continue
case APOPL,
APOPFL:
deltasp -= 4
p.Spadj = -4
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->ptrsize;
p.As = ASUBL
p.From.Typ = D_CONST
p.From.Offset = autoffset + ctxt.Arch.Ptrsize
p.To.Typ = D_INDIR + D_CX
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
}
}
}
