/
pgen.go
410 lines (354 loc) · 10.7 KB
/
pgen.go
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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gc
import (
"cmd/compile/internal/ssa"
"cmd/compile/internal/types"
"cmd/internal/dwarf"
"cmd/internal/obj"
"cmd/internal/src"
"cmd/internal/sys"
"fmt"
"sort"
)
// "Portable" code generation.
func makefuncdatasym(pp *Progs, nameprefix string, funcdatakind int64, curfn *Node) *types.Sym {
// This symbol requires a unique, reproducible name;
// unique to avoid duplicate symbols,
// and reproducible for reproducible builds and toolstash.
// The function name will usually suffice.
suffix := curfn.Func.Nname.Sym.Name
if suffix == "_" {
// It is possible to have multiple functions called _,
// so in this rare case, use instead the function's position.
// This formatted string will be meaningless gibberish, but that's ok.
// It will be unique and reproducible, and it is rare anyway.
// Note that we can't just always use the position;
// it is possible to have multiple autogenerated functions at the same position.
// Fortunately, no autogenerated functions are called _.
if curfn.Pos == autogeneratedPos {
Fatalf("autogenerated func _")
}
suffix = fmt.Sprintf("%v", curfn.Pos)
}
// Add in the package path as well.
// When generating wrappers, we can end up compiling a function belonging
// to other packages, which might have a name that collides with one in our package.
symname := nameprefix + curfn.Func.Nname.Sym.Pkg.Path + "." + suffix
sym := lookup(symname)
p := pp.Prog(obj.AFUNCDATA)
Addrconst(&p.From, funcdatakind)
p.To.Type = obj.TYPE_MEM
p.To.Name = obj.NAME_EXTERN
p.To.Sym = Linksym(sym)
return sym
}
// TODO(mdempsky): Update to reference OpVar{Def,Kill,Live} instead
// and move to plive.go.
// VARDEF is an annotation for the liveness analysis, marking a place
// where a complete initialization (definition) of a variable begins.
// Since the liveness analysis can see initialization of single-word
// variables quite easy, gvardef is usually only called for multi-word
// or 'fat' variables, those satisfying isfat(n->type).
// However, gvardef is also called when a non-fat variable is initialized
// via a block move; the only time this happens is when you have
// return f()
// for a function with multiple return values exactly matching the return
// types of the current function.
//
// A 'VARDEF x' annotation in the instruction stream tells the liveness
// analysis to behave as though the variable x is being initialized at that
// point in the instruction stream. The VARDEF must appear before the
// actual (multi-instruction) initialization, and it must also appear after
// any uses of the previous value, if any. For example, if compiling:
//
// x = x[1:]
//
// it is important to generate code like:
//
// base, len, cap = pieces of x[1:]
// VARDEF x
// x = {base, len, cap}
//
// If instead the generated code looked like:
//
// VARDEF x
// base, len, cap = pieces of x[1:]
// x = {base, len, cap}
//
// then the liveness analysis would decide the previous value of x was
// unnecessary even though it is about to be used by the x[1:] computation.
// Similarly, if the generated code looked like:
//
// base, len, cap = pieces of x[1:]
// x = {base, len, cap}
// VARDEF x
//
// then the liveness analysis will not preserve the new value of x, because
// the VARDEF appears to have "overwritten" it.
//
// VARDEF is a bit of a kludge to work around the fact that the instruction
// stream is working on single-word values but the liveness analysis
// wants to work on individual variables, which might be multi-word
// aggregates. It might make sense at some point to look into letting
// the liveness analysis work on single-word values as well, although
// there are complications around interface values, slices, and strings,
// all of which cannot be treated as individual words.
//
// VARKILL is the opposite of VARDEF: it marks a value as no longer needed,
// even if its address has been taken. That is, a VARKILL annotation asserts
// that its argument is certainly dead, for use when the liveness analysis
// would not otherwise be able to deduce that fact.
func emitptrargsmap() {
if Curfn.Func.Nname.Sym.Name == "_" {
return
}
sym := lookup(fmt.Sprintf("%s.args_stackmap", Curfn.Func.Nname.Sym.Name))
nptr := int(Curfn.Type.ArgWidth() / int64(Widthptr))
bv := bvalloc(int32(nptr) * 2)
nbitmap := 1
if Curfn.Type.Results().NumFields() > 0 {
nbitmap = 2
}
off := duint32(sym, 0, uint32(nbitmap))
off = duint32(sym, off, uint32(bv.n))
var xoffset int64
if Curfn.IsMethod() {
xoffset = 0
onebitwalktype1(Curfn.Type.Recvs(), &xoffset, bv)
}
if Curfn.Type.Params().NumFields() > 0 {
xoffset = 0
onebitwalktype1(Curfn.Type.Params(), &xoffset, bv)
}
off = dbvec(sym, off, bv)
if Curfn.Type.Results().NumFields() > 0 {
xoffset = 0
onebitwalktype1(Curfn.Type.Results(), &xoffset, bv)
off = dbvec(sym, off, bv)
}
ggloblsym(sym, int32(off), obj.RODATA|obj.LOCAL)
}
// cmpstackvarlt reports whether the stack variable a sorts before b.
//
// Sort the list of stack variables. Autos after anything else,
// within autos, unused after used, within used, things with
// pointers first, zeroed things first, and then decreasing size.
// Because autos are laid out in decreasing addresses
// on the stack, pointers first, zeroed things first and decreasing size
// really means, in memory, things with pointers needing zeroing at
// the top of the stack and increasing in size.
// Non-autos sort on offset.
func cmpstackvarlt(a, b *Node) bool {
if (a.Class == PAUTO) != (b.Class == PAUTO) {
return b.Class == PAUTO
}
if a.Class != PAUTO {
return a.Xoffset < b.Xoffset
}
if a.Used() != b.Used() {
return a.Used()
}
ap := types.Haspointers(a.Type)
bp := types.Haspointers(b.Type)
if ap != bp {
return ap
}
ap = a.Name.Needzero()
bp = b.Name.Needzero()
if ap != bp {
return ap
}
if a.Type.Width != b.Type.Width {
return a.Type.Width > b.Type.Width
}
return a.Sym.Name < b.Sym.Name
}
// byStackvar implements sort.Interface for []*Node using cmpstackvarlt.
type byStackVar []*Node
func (s byStackVar) Len() int { return len(s) }
func (s byStackVar) Less(i, j int) bool { return cmpstackvarlt(s[i], s[j]) }
func (s byStackVar) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
func (s *ssafn) AllocFrame(f *ssa.Func) {
s.stksize = 0
s.stkptrsize = 0
fn := s.curfn.Func
// Mark the PAUTO's unused.
for _, ln := range fn.Dcl {
if ln.Class == PAUTO {
ln.SetUsed(false)
}
}
for _, l := range f.RegAlloc {
if ls, ok := l.(ssa.LocalSlot); ok {
ls.N.(*Node).SetUsed(true)
}
}
scratchUsed := false
for _, b := range f.Blocks {
for _, v := range b.Values {
switch a := v.Aux.(type) {
case *ssa.ArgSymbol:
n := a.Node.(*Node)
// Don't modify nodfp; it is a global.
if n != nodfp {
n.SetUsed(true)
}
case *ssa.AutoSymbol:
a.Node.(*Node).SetUsed(true)
}
if !scratchUsed {
scratchUsed = v.Op.UsesScratch()
}
}
}
if f.Config.NeedsFpScratch && scratchUsed {
s.scratchFpMem = tempAt(src.NoXPos, s.curfn, types.Types[TUINT64])
}
sort.Sort(byStackVar(fn.Dcl))
// Reassign stack offsets of the locals that are used.
for i, n := range fn.Dcl {
if n.Op != ONAME || n.Class != PAUTO {
continue
}
if !n.Used() {
fn.Dcl = fn.Dcl[:i]
break
}
dowidth(n.Type)
w := n.Type.Width
if w >= thearch.MAXWIDTH || w < 0 {
Fatalf("bad width")
}
s.stksize += w
s.stksize = Rnd(s.stksize, int64(n.Type.Align))
if types.Haspointers(n.Type) {
s.stkptrsize = s.stksize
}
if thearch.LinkArch.InFamily(sys.MIPS, sys.MIPS64, sys.ARM, sys.ARM64, sys.PPC64, sys.S390X) {
s.stksize = Rnd(s.stksize, int64(Widthptr))
}
n.Xoffset = -s.stksize
}
s.stksize = Rnd(s.stksize, int64(Widthreg))
s.stkptrsize = Rnd(s.stkptrsize, int64(Widthreg))
}
func compile(fn *Node) {
Curfn = fn
dowidth(fn.Type)
if fn.Nbody.Len() == 0 {
emitptrargsmap()
return
}
saveerrors()
order(fn)
if nerrors != 0 {
return
}
walk(fn)
if nerrors != 0 {
return
}
checkcontrolflow(fn)
if nerrors != 0 {
return
}
if instrumenting {
instrument(fn)
}
// From this point, there should be no uses of Curfn. Enforce that.
Curfn = nil
// Set up the function's LSym early to avoid data races with the assemblers.
fn.Func.initLSym()
// Build an SSA backend function.
ssafn := buildssa(fn)
pp := newProgs(fn)
genssa(ssafn, pp)
fieldtrack(pp.Text.From.Sym, fn.Func.FieldTrack)
if pp.Text.To.Offset < 1<<31 {
pp.Flush()
} else {
largeStackFrames = append(largeStackFrames, fn.Pos)
}
pp.Free()
}
func debuginfo(fnsym *obj.LSym, curfn interface{}) []*dwarf.Var {
fn := curfn.(*Node)
if expect := Linksym(fn.Func.Nname.Sym); fnsym != expect {
Fatalf("unexpected fnsym: %v != %v", fnsym, expect)
}
var vars []*dwarf.Var
for _, n := range fn.Func.Dcl {
if n.Op != ONAME { // might be OTYPE or OLITERAL
continue
}
var name obj.AddrName
var abbrev int
offs := n.Xoffset
switch n.Class {
case PAUTO:
if !n.Used() {
Fatalf("debuginfo unused node (AllocFrame should truncate fn.Func.Dcl)")
}
name = obj.NAME_AUTO
abbrev = dwarf.DW_ABRV_AUTO
if Ctxt.FixedFrameSize() == 0 {
offs -= int64(Widthptr)
}
if obj.Framepointer_enabled(obj.GOOS, obj.GOARCH) {
offs -= int64(Widthptr)
}
case PPARAM, PPARAMOUT:
name = obj.NAME_PARAM
abbrev = dwarf.DW_ABRV_PARAM
offs += Ctxt.FixedFrameSize()
default:
continue
}
gotype := Linksym(ngotype(n))
fnsym.Autom = append(fnsym.Autom, &obj.Auto{
Asym: Ctxt.Lookup(n.Sym.Name, 0),
Aoffset: int32(n.Xoffset),
Name: name,
Gotype: gotype,
})
if n.IsAutoTmp() {
continue
}
typename := dwarf.InfoPrefix + gotype.Name[len("type."):]
vars = append(vars, &dwarf.Var{
Name: n.Sym.Name,
Abbrev: abbrev,
Offset: int32(offs),
Type: Ctxt.Lookup(typename, 0),
})
}
// Stable sort so that ties are broken with declaration order.
sort.Stable(dwarf.VarsByOffset(vars))
return vars
}
// fieldtrack adds R_USEFIELD relocations to fnsym to record any
// struct fields that it used.
func fieldtrack(fnsym *obj.LSym, tracked map[*types.Sym]struct{}) {
if fnsym == nil {
return
}
if obj.Fieldtrack_enabled == 0 || len(tracked) == 0 {
return
}
trackSyms := make([]*types.Sym, 0, len(tracked))
for sym := range tracked {
trackSyms = append(trackSyms, sym)
}
sort.Sort(symByName(trackSyms))
for _, sym := range trackSyms {
r := obj.Addrel(fnsym)
r.Sym = Linksym(sym)
r.Type = obj.R_USEFIELD
}
}
type symByName []*types.Sym
func (a symByName) Len() int { return len(a) }
func (a symByName) Less(i, j int) bool { return a[i].Name < a[j].Name }
func (a symByName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }