/
obj6.go
1304 lines (1190 loc) · 33.8 KB
/
obj6.go
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// 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 (
"cmd/internal/obj"
"cmd/internal/objabi"
"cmd/internal/src"
"cmd/internal/sys"
"math"
"strings"
)
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.Family == sys.I386 {
switch ctxt.Headtype {
case objabi.Hlinux,
objabi.Hnacl,
objabi.Hplan9,
objabi.Hwindows:
return false
}
return true
}
switch ctxt.Headtype {
case objabi.Hplan9, objabi.Hwindows:
return false
case objabi.Hlinux, objabi.Hfreebsd:
return !ctxt.Flag_shared
}
return true
}
func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
// 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 != objabi.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(p, newprog)
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 == objabi.Hwindows && ctxt.Arch.Family == sys.AMD64 || ctxt.Headtype == objabi.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 == objabi.Hnacl && ctxt.Arch.Family == sys.AMD64 {
if p.GetFrom3() != nil {
nacladdr(ctxt, p, p.GetFrom3())
}
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))
p.From.Type = obj.TYPE_MEM
p.From.Name = obj.NAME_EXTERN
p.From.Sym = ctxt.Float32Sym(f32)
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 {
f64 := p.From.Val.(float64)
p.From.Type = obj.TYPE_MEM
p.From.Name = obj.NAME_EXTERN
p.From.Sym = ctxt.Float64Sym(f64)
p.From.Offset = 0
}
}
if ctxt.Flag_dynlink {
rewriteToUseGot(ctxt, p, newprog)
}
if ctxt.Flag_shared && ctxt.Arch.Family == sys.I386 {
rewriteToPcrel(ctxt, p, newprog)
}
}
// Rewrite p, if necessary, to access global data via the global offset table.
func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
var lea, mov obj.As
var reg int16
if ctxt.Arch.Family == sys.AMD64 {
lea = ALEAQ
mov = AMOVQ
reg = REG_R15
} else {
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
// $LEA $offset($reg), $reg
// CALL $reg
// (we use LEAx rather than ADDx because ADDx clobbers
// flags and duffzero on 386 does not otherwise do so).
var sym *obj.LSym
if p.As == obj.ADUFFZERO {
sym = ctxt.Lookup("runtime.duffzero")
} else {
sym = ctxt.Lookup("runtime.duffcopy")
}
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(p, newprog)
p1.As = lea
p1.From.Type = obj.TYPE_MEM
p1.From.Offset = offset
p1.From.Reg = reg
p1.To.Type = obj.TYPE_REG
p1.To.Reg = reg
p2 := obj.Appendp(p1, newprog)
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 ctxt.Arch.Family == sys.AMD64 {
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(p, newprog)
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(q, newprog)
q.As = pAs
q.To = dest
q.From.Type = obj.TYPE_REG
q.From.Reg = reg
}
}
if p.GetFrom3() != nil && p.GetFrom3().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 ctxt.Arch.Family == sys.AMD64 || (p.To.Sym != nil && p.To.Sym.Local()) || p.RegTo2 != 0 {
return
}
p1 := obj.Appendp(p, newprog)
p2 := obj.Appendp(p1, newprog)
p1.As = ALEAL
p1.From.Type = obj.TYPE_MEM
p1.From.Name = obj.NAME_STATIC
p1.From.Sym = ctxt.Lookup("_GLOBAL_OFFSET_TABLE_")
p1.To.Type = obj.TYPE_REG
p1.To.Reg = REG_BX
p2.As = p.As
p2.Scond = p.Scond
p2.From = p.From
if p.RestArgs != nil {
p2.RestArgs = append(p2.RestArgs, p.RestArgs...)
}
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(p, newprog)
p2 := obj.Appendp(p1, newprog)
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, newprog obj.ProgAlloc) {
// 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 == objabi.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(p, newprog)
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.GetFrom3() == nil || !isName(p.GetFrom3())) {
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(p, newprog)
q.RegTo2 = 1
r := obj.Appendp(q, newprog)
r.RegTo2 = 1
q.As = obj.ACALL
thunkname := "__x86.get_pc_thunk." + strings.ToLower(rconv(int(dst)))
q.To.Sym = ctxt.LookupInit(thunkname, func(s *obj.LSym) { s.Set(obj.AttrLocal, true) })
q.To.Type = obj.TYPE_MEM
q.To.Name = obj.NAME_EXTERN
r.As = p.As
r.Scond = p.Scond
r.From = p.From
r.RestArgs = p.RestArgs
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.GetFrom3() != nil && isName(p.GetFrom3()) {
r.GetFrom3().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, newprog obj.ProgAlloc) {
if cursym.Func.Text == nil || cursym.Func.Text.Link == nil {
return
}
p := cursym.Func.Text
autoffset := int32(p.To.Offset)
if autoffset < 0 {
autoffset = 0
}
hasCall := false
for q := p; q != nil; q = q.Link {
if q.As == obj.ACALL || q.As == obj.ADUFFCOPY || q.As == obj.ADUFFZERO {
hasCall = true
break
}
}
var bpsize int
if ctxt.Arch.Family == sys.AMD64 && ctxt.Framepointer_enabled &&
!p.From.Sym.NoFrame() && // (1) below
!(autoffset == 0 && p.From.Sym.NoSplit()) && // (2) below
!(autoffset == 0 && !hasCall) { // (3) below
// Make room to save a base pointer.
// There are 2 cases we must avoid:
// 1) If noframe is set (which we do for functions which tail call).
// 2) Scary runtime internals which would be all messed up by frame pointers.
// We detect these using a heuristic: frameless nosplit functions.
// TODO: Maybe someday we label them all with NOFRAME and get rid of this heuristic.
// For performance, we also want to avoid:
// 3) Frameless leaf functions
bpsize = ctxt.Arch.PtrSize
autoffset += int32(bpsize)
p.To.Offset += int64(bpsize)
} else {
bpsize = 0
}
textarg := int64(p.To.Val.(int32))
cursym.Func.Args = int32(textarg)
cursym.Func.Locals = int32(p.To.Offset)
// TODO(rsc): Remove.
if ctxt.Arch.Family == sys.I386 && cursym.Func.Locals < 0 {
cursym.Func.Locals = 0
}
// TODO(rsc): Remove 'ctxt.Arch.Family == sys.AMD64 &&'.
if ctxt.Arch.Family == sys.AMD64 && autoffset < objabi.StackSmall && !p.From.Sym.NoSplit() {
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 >= objabi.StackSmall-8 {
leaf = false
break LeafSearch
}
}
}
if leaf {
p.From.Sym.Set(obj.AttrNoSplit, true)
}
}
if !p.From.Sym.NoSplit() || p.From.Sym.Wrapper() {
p = obj.Appendp(p, newprog)
p = load_g_cx(ctxt, p, newprog) // load g into CX
}
if !cursym.Func.Text.From.Sym.NoSplit() {
p = stacksplit(ctxt, cursym, p, newprog, autoffset, int32(textarg)) // emit split check
}
// Delve debugger would like the next instruction to be noted as the end of the function prologue.
// TODO: are there other cases (e.g., wrapper functions) that need marking?
markedPrologue := false
if autoffset != 0 {
if autoffset%int32(ctxt.Arch.RegSize) != 0 {
ctxt.Diag("unaligned stack size %d", autoffset)
}
p = obj.Appendp(p, newprog)
p.As = AADJSP
p.From.Type = obj.TYPE_CONST
p.From.Offset = int64(autoffset)
p.Spadj = autoffset
p.Pos = p.Pos.WithXlogue(src.PosPrologueEnd)
markedPrologue = true
}
deltasp := autoffset
if bpsize > 0 {
// Save caller's BP
p = obj.Appendp(p, newprog)
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)
if !markedPrologue {
p.Pos = p.Pos.WithXlogue(src.PosPrologueEnd)
}
// Move current frame to BP
p = obj.Appendp(p, newprog)
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.Func.Text.From.Sym.Wrapper() {
// if g._panic != nil && g._panic.argp == FP {
// g._panic.argp = bottom-of-frame
// }
//
// MOVQ g_panic(CX), BX
// TESTQ BX, BX
// JNE checkargp
// end:
// NOP
// ... rest of function ...
// checkargp:
// LEAQ (autoffset+8)(SP), DI
// CMPQ panic_argp(BX), DI
// JNE end
// MOVQ SP, panic_argp(BX)
// JMP end
//
// 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.
//
// The layout is chosen to help static branch prediction:
// Both conditional jumps are unlikely, so they are arranged to be forward jumps.
// MOVQ g_panic(CX), BX
p = obj.Appendp(p, newprog)
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 == objabi.Hnacl && ctxt.Arch.Family == sys.AMD64 {
p.As = AMOVL
p.From.Type = obj.TYPE_MEM
p.From.Reg = REG_R15
p.From.Scale = 1
p.From.Index = REG_CX
}
if ctxt.Arch.Family == sys.I386 {
p.As = AMOVL
}
// TESTQ BX, BX
p = obj.Appendp(p, newprog)
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 == objabi.Hnacl || ctxt.Arch.Family == sys.I386 {
p.As = ATESTL
}
// JNE checkargp (checkargp to be resolved later)
jne := obj.Appendp(p, newprog)
jne.As = AJNE
jne.To.Type = obj.TYPE_BRANCH
// end:
// NOP
end := obj.Appendp(jne, newprog)
end.As = obj.ANOP
// Fast forward to end of function.
var last *obj.Prog
for last = end; last.Link != nil; last = last.Link {
}
// LEAQ (autoffset+8)(SP), DI
p = obj.Appendp(last, newprog)
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 == objabi.Hnacl || ctxt.Arch.Family == sys.I386 {
p.As = ALEAL
}
// Set jne branch target.
jne.Pcond = p
// CMPQ panic_argp(BX), DI
p = obj.Appendp(p, newprog)
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 == objabi.Hnacl && ctxt.Arch.Family == sys.AMD64 {
p.As = ACMPL
p.From.Type = obj.TYPE_MEM
p.From.Reg = REG_R15
p.From.Scale = 1
p.From.Index = REG_BX
}
if ctxt.Arch.Family == sys.I386 {
p.As = ACMPL
}
// JNE end
p = obj.Appendp(p, newprog)
p.As = AJNE
p.To.Type = obj.TYPE_BRANCH
p.Pcond = end
// MOVQ SP, panic_argp(BX)
p = obj.Appendp(p, newprog)
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 == objabi.Hnacl && ctxt.Arch.Family == sys.AMD64 {
p.As = AMOVL
p.To.Type = obj.TYPE_MEM
p.To.Reg = REG_R15
p.To.Scale = 1
p.To.Index = REG_BX
}
if ctxt.Arch.Family == sys.I386 {
p.As = AMOVL
}
// JMP end
p = obj.Appendp(p, newprog)
p.As = obj.AJMP
p.To.Type = obj.TYPE_BRANCH
p.Pcond = end
// Reset p for following code.
p = end
}
for ; p != nil; p = p.Link {
pcsize := ctxt.Arch.RegSize
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.GetFrom3() != nil {
switch p.GetFrom3().Name {
case obj.NAME_AUTO:
p.GetFrom3().Offset += int64(deltasp) - int64(bpsize)
case obj.NAME_PARAM:
p.GetFrom3().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 {
to := p.To // Keep To attached to RET for retjmp below
p.To = obj.Addr{}
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(p, newprog)
}
p.As = AADJSP
p.From.Type = obj.TYPE_CONST
p.From.Offset = int64(-autoffset)
p.Spadj = -autoffset
p = obj.Appendp(p, newprog)
p.As = obj.ARET
p.To = to
// 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", "runtime.panicwrap":
return true
}
return false
}
func indir_cx(ctxt *obj.Link, a *obj.Addr) {
if ctxt.Headtype == objabi.Hnacl && ctxt.Arch.Family == sys.AMD64 {
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, newprog obj.ProgAlloc) *obj.Prog {
p.As = AMOVQ
if ctxt.Arch.PtrSize == 4 {
p.As = AMOVL
}
p.From.Type = obj.TYPE_MEM