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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 walk
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
)
// The result of walkStmt MUST be assigned back to n, e.g.
// n.Left = walkStmt(n.Left)
func walkStmt(n ir.Node) ir.Node {
if n == nil {
return n
}
ir.SetPos(n)
walkStmtList(n.Init())
switch n.Op() {
default:
if n.Op() == ir.ONAME {
n := n.(*ir.Name)
base.Errorf("%v is not a top level statement", n.Sym())
} else {
base.Errorf("%v is not a top level statement", n.Op())
}
ir.Dump("nottop", n)
return n
case ir.OAS,
ir.OASOP,
ir.OAS2,
ir.OAS2DOTTYPE,
ir.OAS2RECV,
ir.OAS2FUNC,
ir.OAS2MAPR,
ir.OCLOSE,
ir.OCOPY,
ir.OCALLINTER,
ir.OCALL,
ir.OCALLFUNC,
ir.ODELETE,
ir.OSEND,
ir.OPRINT,
ir.OPRINTN,
ir.OPANIC,
ir.ORECOVERFP,
ir.OGETG:
if n.Typecheck() == 0 {
base.Fatalf("missing typecheck: %+v", n)
}
init := ir.TakeInit(n)
n = walkExpr(n, &init)
if n.Op() == ir.ONAME {
// copy rewrote to a statement list and a temp for the length.
// Throw away the temp to avoid plain values as statements.
n = ir.NewBlockStmt(n.Pos(), init)
init = nil
}
if len(init) > 0 {
switch n.Op() {
case ir.OAS, ir.OAS2, ir.OBLOCK:
n.(ir.InitNode).PtrInit().Prepend(init...)
default:
init.Append(n)
n = ir.NewBlockStmt(n.Pos(), init)
}
}
return n
// special case for a receive where we throw away
// the value received.
case ir.ORECV:
n := n.(*ir.UnaryExpr)
return walkRecv(n)
case ir.OBREAK,
ir.OCONTINUE,
ir.OFALL,
ir.OGOTO,
ir.OLABEL,
ir.ODCL,
ir.ODCLCONST,
ir.ODCLTYPE,
ir.OCHECKNIL,
ir.OVARDEF,
ir.OVARKILL,
ir.OVARLIVE:
return n
case ir.OBLOCK:
n := n.(*ir.BlockStmt)
walkStmtList(n.List)
return n
case ir.OCASE:
base.Errorf("case statement out of place")
panic("unreachable")
case ir.ODEFER:
n := n.(*ir.GoDeferStmt)
ir.CurFunc.SetHasDefer(true)
ir.CurFunc.NumDefers++
if ir.CurFunc.NumDefers > maxOpenDefers {
// Don't allow open-coded defers if there are more than
// 8 defers in the function, since we use a single
// byte to record active defers.
ir.CurFunc.SetOpenCodedDeferDisallowed(true)
}
if n.Esc() != ir.EscNever {
// If n.Esc is not EscNever, then this defer occurs in a loop,
// so open-coded defers cannot be used in this function.
ir.CurFunc.SetOpenCodedDeferDisallowed(true)
}
fallthrough
case ir.OGO:
n := n.(*ir.GoDeferStmt)
return walkGoDefer(n)
case ir.OFOR, ir.OFORUNTIL:
n := n.(*ir.ForStmt)
return walkFor(n)
case ir.OIF:
n := n.(*ir.IfStmt)
return walkIf(n)
case ir.ORETURN:
n := n.(*ir.ReturnStmt)
return walkReturn(n)
case ir.OTAILCALL:
n := n.(*ir.TailCallStmt)
var init ir.Nodes
n.Call.X = walkExpr(n.Call.X, &init)
if len(init) > 0 {
init.Append(n)
return ir.NewBlockStmt(n.Pos(), init)
}
return n
case ir.OINLMARK:
n := n.(*ir.InlineMarkStmt)
return n
case ir.OSELECT:
n := n.(*ir.SelectStmt)
walkSelect(n)
return n
case ir.OSWITCH:
n := n.(*ir.SwitchStmt)
walkSwitch(n)
return n
case ir.ORANGE:
n := n.(*ir.RangeStmt)
return walkRange(n)
}
// No return! Each case must return (or panic),
// to avoid confusion about what gets returned
// in the presence of type assertions.
}
func walkStmtList(s []ir.Node) {
for i := range s {
s[i] = walkStmt(s[i])
}
}
// walkFor walks an OFOR or OFORUNTIL node.
func walkFor(n *ir.ForStmt) ir.Node {
if n.Cond != nil {
init := ir.TakeInit(n.Cond)
walkStmtList(init)
n.Cond = walkExpr(n.Cond, &init)
n.Cond = ir.InitExpr(init, n.Cond)
}
n.Post = walkStmt(n.Post)
if n.Op() == ir.OFORUNTIL {
walkStmtList(n.Late)
}
walkStmtList(n.Body)
return n
}
// validGoDeferCall reports whether call is a valid call to appear in
// a go or defer statement; that is, whether it's a regular function
// call without arguments or results.
func validGoDeferCall(call ir.Node) bool {
if call, ok := call.(*ir.CallExpr); ok && call.Op() == ir.OCALLFUNC && len(call.KeepAlive) == 0 {
sig := call.X.Type()
return sig.NumParams()+sig.NumResults() == 0
}
return false
}
// walkGoDefer walks an OGO or ODEFER node.
func walkGoDefer(n *ir.GoDeferStmt) ir.Node {
if !validGoDeferCall(n.Call) {
base.FatalfAt(n.Pos(), "invalid %v call: %v", n.Op(), n.Call)
}
var init ir.Nodes
call := n.Call.(*ir.CallExpr)
call.X = walkExpr(call.X, &init)
if len(init) > 0 {
init.Append(n)
return ir.NewBlockStmt(n.Pos(), init)
}
return n
}
// walkIf walks an OIF node.
func walkIf(n *ir.IfStmt) ir.Node {
n.Cond = walkExpr(n.Cond, n.PtrInit())
walkStmtList(n.Body)
walkStmtList(n.Else)
return n
}
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