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// Copyright 2009 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/types"
)
// A function named init is a special case.
// It is called by the initialization before main is run.
// To make it unique within a package and also uncallable,
// the name, normally "pkg.init", is altered to "pkg.init.0".
var renameinitgen int
func renameinit() *types.Sym {
s := lookupN("init.", renameinitgen)
renameinitgen++
return s
}
// anyinit reports whether there any interesting init statements.
func anyinit(n []*Node) bool {
for _, ln := range n {
switch ln.Op {
case ODCLFUNC, ODCLCONST, ODCLTYPE, OEMPTY:
case OAS:
if !isblank(ln.Left) || !candiscard(ln.Right) {
return true
}
default:
return true
}
}
// is this main
if localpkg.Name == "main" {
return true
}
// is there an explicit init function
if renameinitgen > 0 {
return true
}
// are there any imported init functions
for _, s := range types.InitSyms {
if s.Def != nil {
return true
}
}
// then none
return false
}
// fninit hand-crafts package initialization code.
//
// var initdone· uint8 (1)
// func init() { (2)
// if initdone· > 1 { (3)
// return (3a)
// }
// if initdone· == 1 { (4)
// throw() (4a)
// }
// initdone· = 1 (5)
// // over all matching imported symbols
// <pkg>.init() (6)
// { <init stmts> } (7)
// init.<n>() // if any (8)
// initdone· = 2 (9)
// return (10)
// }
func fninit(n []*Node) {
lineno = autogeneratedPos
nf := initfix(n)
if !anyinit(nf) {
return
}
var r []*Node
// (1)
gatevar := newname(lookup("initdone·"))
addvar(gatevar, types.Types[TUINT8], PEXTERN)
// (2)
initsym := lookup("init")
fn := dclfunc(initsym, nod(OTFUNC, nil, nil))
// (3)
a := nod(OIF, nil, nil)
a.Left = nod(OGT, gatevar, nodintconst(1))
a.SetLikely(true)
r = append(r, a)
// (3a)
a.Nbody.Set1(nod(ORETURN, nil, nil))
// (4)
b := nod(OIF, nil, nil)
b.Left = nod(OEQ, gatevar, nodintconst(1))
// this actually isn't likely, but code layout is better
// like this: no JMP needed after the call.
b.SetLikely(true)
r = append(r, b)
// (4a)
b.Nbody.Set1(nod(OCALL, syslook("throwinit"), nil))
// (5)
a = nod(OAS, gatevar, nodintconst(1))
r = append(r, a)
// (6)
for _, s := range types.InitSyms {
if s.Def != nil && s != initsym {
n := asNode(s.Def)
n.checkInitFuncSignature()
a = nod(OCALL, n, nil)
r = append(r, a)
}
}
// (7)
r = append(r, nf...)
// (8)
// maxInlineInitCalls is the threshold at which we switch
// from generating calls inline to generating a static array
// of functions and calling them in a loop.
// See CL 41500 for more discussion.
const maxInlineInitCalls = 500
if renameinitgen < maxInlineInitCalls {
// Not many init functions. Just call them all directly.
for i := 0; i < renameinitgen; i++ {
s := lookupN("init.", i)
n := asNode(s.Def)
n.checkInitFuncSignature()
a = nod(OCALL, n, nil)
r = append(r, a)
}
} else {
// Lots of init functions.
// Set up an array of functions and loop to call them.
// This is faster to compile and similar at runtime.
// Build type [renameinitgen]func().
typ := types.NewArray(functype(nil, nil, nil), int64(renameinitgen))
// Make and fill array.
fnarr := staticname(typ)
fnarr.Name.SetReadonly(true)
for i := 0; i < renameinitgen; i++ {
s := lookupN("init.", i)
lhs := nod(OINDEX, fnarr, nodintconst(int64(i)))
rhs := asNode(s.Def)
rhs.checkInitFuncSignature()
as := nod(OAS, lhs, rhs)
as = typecheck(as, Etop)
genAsStatic(as)
}
// Generate a loop that calls each function in turn.
// for i := 0; i < renameinitgen; i++ {
// fnarr[i]()
// }
i := temp(types.Types[TINT])
fnidx := nod(OINDEX, fnarr, i)
fnidx.SetBounded(true)
zero := nod(OAS, i, nodintconst(0))
cond := nod(OLT, i, nodintconst(int64(renameinitgen)))
incr := nod(OAS, i, nod(OADD, i, nodintconst(1)))
body := nod(OCALL, fnidx, nil)
loop := nod(OFOR, cond, incr)
loop.Nbody.Set1(body)
loop.Ninit.Set1(zero)
loop = typecheck(loop, Etop)
r = append(r, loop)
}
// (9)
a = nod(OAS, gatevar, nodintconst(2))
r = append(r, a)
// (10)
a = nod(ORETURN, nil, nil)
r = append(r, a)
exportsym(fn.Func.Nname)
fn.Nbody.Set(r)
funcbody()
Curfn = fn
fn = typecheck(fn, Etop)
typecheckslice(r, Etop)
Curfn = nil
funccompile(fn)
}
func (n *Node) checkInitFuncSignature() {
if n.Type.NumRecvs()+n.Type.NumParams()+n.Type.NumResults() > 0 {
Fatalf("init function cannot have receiver, params, or results: %v (%v)", n, n.Type)
}
}
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