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// Copyright 2018 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 escape
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"fmt"
)
// stmt evaluates a single Go statement.
func (e *escape) stmt(n ir.Node) {
if n == nil {
return
}
lno := ir.SetPos(n)
defer func() {
base.Pos = lno
}()
if base.Flag.LowerM > 2 {
fmt.Printf("%v:[%d] %v stmt: %v\n", base.FmtPos(base.Pos), e.loopDepth, e.curfn, n)
}
e.stmts(n.Init())
switch n.Op() {
default:
base.Fatalf("unexpected stmt: %v", n)
case ir.OFALL, ir.OINLMARK:
// nop
case ir.OBREAK, ir.OCONTINUE, ir.OGOTO:
// TODO(mdempsky): Handle dead code?
case ir.OBLOCK:
n := n.(*ir.BlockStmt)
e.stmts(n.List)
case ir.ODCL:
// Record loop depth at declaration.
n := n.(*ir.Decl)
if !ir.IsBlank(n.X) {
e.dcl(n.X)
}
case ir.OLABEL:
n := n.(*ir.LabelStmt)
if n.Label.IsBlank() {
break
}
switch e.labels[n.Label] {
case nonlooping:
if base.Flag.LowerM > 2 {
fmt.Printf("%v:%v non-looping label\n", base.FmtPos(base.Pos), n)
}
case looping:
if base.Flag.LowerM > 2 {
fmt.Printf("%v: %v looping label\n", base.FmtPos(base.Pos), n)
}
e.loopDepth++
default:
base.Fatalf("label %v missing tag", n.Label)
}
delete(e.labels, n.Label)
case ir.OIF:
n := n.(*ir.IfStmt)
e.discard(n.Cond)
e.block(n.Body)
e.block(n.Else)
case ir.OCHECKNIL:
n := n.(*ir.UnaryExpr)
e.discard(n.X)
case ir.OFOR:
n := n.(*ir.ForStmt)
base.Assert(!n.DistinctVars) // Should all be rewritten before escape analysis
e.loopDepth++
e.discard(n.Cond)
e.stmt(n.Post)
e.block(n.Body)
e.loopDepth--
case ir.ORANGE:
// for Key, Value = range X { Body }
n := n.(*ir.RangeStmt)
base.Assert(!n.DistinctVars) // Should all be rewritten before escape analysis
// X is evaluated outside the loop and persists until the loop
// terminates.
tmp := e.newLoc(nil, true)
e.expr(tmp.asHole(), n.X)
e.loopDepth++
ks := e.addrs([]ir.Node{n.Key, n.Value})
if n.X.Type().IsArray() {
e.flow(ks[1].note(n, "range"), tmp)
} else {
e.flow(ks[1].deref(n, "range-deref"), tmp)
}
e.reassigned(ks, n)
e.block(n.Body)
e.loopDepth--
case ir.OSWITCH:
n := n.(*ir.SwitchStmt)
if guard, ok := n.Tag.(*ir.TypeSwitchGuard); ok {
var ks []hole
if guard.Tag != nil {
for _, cas := range n.Cases {
cv := cas.Var
k := e.dcl(cv) // type switch variables have no ODCL.
if cv.Type().HasPointers() {
ks = append(ks, k.dotType(cv.Type(), cas, "switch case"))
}
}
}
e.expr(e.teeHole(ks...), n.Tag.(*ir.TypeSwitchGuard).X)
} else {
e.discard(n.Tag)
}
for _, cas := range n.Cases {
e.discards(cas.List)
e.block(cas.Body)
}
case ir.OSELECT:
n := n.(*ir.SelectStmt)
for _, cas := range n.Cases {
e.stmt(cas.Comm)
e.block(cas.Body)
}
case ir.ORECV:
// TODO(mdempsky): Consider e.discard(n.Left).
n := n.(*ir.UnaryExpr)
e.exprSkipInit(e.discardHole(), n) // already visited n.Ninit
case ir.OSEND:
n := n.(*ir.SendStmt)
e.discard(n.Chan)
e.assignHeap(n.Value, "send", n)
case ir.OAS:
n := n.(*ir.AssignStmt)
e.assignList([]ir.Node{n.X}, []ir.Node{n.Y}, "assign", n)
case ir.OASOP:
n := n.(*ir.AssignOpStmt)
// TODO(mdempsky): Worry about OLSH/ORSH?
e.assignList([]ir.Node{n.X}, []ir.Node{n.Y}, "assign", n)
case ir.OAS2:
n := n.(*ir.AssignListStmt)
e.assignList(n.Lhs, n.Rhs, "assign-pair", n)
case ir.OAS2DOTTYPE: // v, ok = x.(type)
n := n.(*ir.AssignListStmt)
e.assignList(n.Lhs, n.Rhs, "assign-pair-dot-type", n)
case ir.OAS2MAPR: // v, ok = m[k]
n := n.(*ir.AssignListStmt)
e.assignList(n.Lhs, n.Rhs, "assign-pair-mapr", n)
case ir.OAS2RECV, ir.OSELRECV2: // v, ok = <-ch
n := n.(*ir.AssignListStmt)
e.assignList(n.Lhs, n.Rhs, "assign-pair-receive", n)
case ir.OAS2FUNC:
n := n.(*ir.AssignListStmt)
e.stmts(n.Rhs[0].Init())
ks := e.addrs(n.Lhs)
e.call(ks, n.Rhs[0])
e.reassigned(ks, n)
case ir.ORETURN:
n := n.(*ir.ReturnStmt)
results := e.curfn.Type().Results()
dsts := make([]ir.Node, len(results))
for i, res := range results {
dsts[i] = res.Nname.(*ir.Name)
}
e.assignList(dsts, n.Results, "return", n)
case ir.OCALLFUNC, ir.OCALLMETH, ir.OCALLINTER, ir.OINLCALL, ir.OCLEAR, ir.OCLOSE, ir.OCOPY, ir.ODELETE, ir.OPANIC, ir.OPRINT, ir.OPRINTLN, ir.ORECOVERFP:
e.call(nil, n)
case ir.OGO, ir.ODEFER:
n := n.(*ir.GoDeferStmt)
e.goDeferStmt(n)
case ir.OTAILCALL:
n := n.(*ir.TailCallStmt)
e.call(nil, n.Call)
}
}
func (e *escape) stmts(l ir.Nodes) {
for _, n := range l {
e.stmt(n)
}
}
// block is like stmts, but preserves loopDepth.
func (e *escape) block(l ir.Nodes) {
old := e.loopDepth
e.stmts(l)
e.loopDepth = old
}
func (e *escape) dcl(n *ir.Name) hole {
if n.Curfn != e.curfn || n.IsClosureVar() {
base.Fatalf("bad declaration of %v", n)
}
loc := e.oldLoc(n)
loc.loopDepth = e.loopDepth
return loc.asHole()
}
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