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 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
*/
ctxt.Bso.Flush()
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 {
fmt.Fprintf(ctxt.Bso, "save suppressed in: %s\n", cursym.Text.From.Sym.Name)
}
ctxt.Bso.Flush()
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.Leaf = true
if ctxt.Autosize == 0 {
break
}
aoffset = 0
}
q = p
if ctxt.Autosize > aoffset {
q = ctxt.NewProg()
q.As = ASUB
q.Lineno = p.Lineno
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.Spadj = int32(q.From.Offset)
q.Link = p.Link
p.Link = q
if cursym.Text.Mark&LEAF != 0 {
break
}
}
q1 = ctxt.NewProg()
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.Link = q.Link
q1.Spadj = aoffset
q.Link = q1
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
}
}
}