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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"
"cmd/compile/internal/types"
)
// expr models evaluating an expression n and flowing the result into
// hole k.
func (e *escape) expr(k hole, n ir.Node) {
if n == nil {
return
}
e.stmts(n.Init())
e.exprSkipInit(k, n)
}
func (e *escape) exprSkipInit(k hole, n ir.Node) {
if n == nil {
return
}
lno := ir.SetPos(n)
defer func() {
base.Pos = lno
}()
if k.derefs >= 0 && !n.Type().IsUntyped() && !n.Type().HasPointers() {
k.dst = &e.blankLoc
}
switch n.Op() {
default:
base.Fatalf("unexpected expr: %s %v", n.Op().String(), n)
case ir.OLITERAL, ir.ONIL, ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP, ir.OTYPE, ir.OMETHEXPR, ir.OLINKSYMOFFSET:
// nop
case ir.ONAME:
n := n.(*ir.Name)
if n.Class == ir.PFUNC || n.Class == ir.PEXTERN {
return
}
e.flow(k, e.oldLoc(n))
case ir.OPLUS, ir.ONEG, ir.OBITNOT, ir.ONOT:
n := n.(*ir.UnaryExpr)
e.discard(n.X)
case ir.OADD, ir.OSUB, ir.OOR, ir.OXOR, ir.OMUL, ir.ODIV, ir.OMOD, ir.OLSH, ir.ORSH, ir.OAND, ir.OANDNOT, ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
n := n.(*ir.BinaryExpr)
e.discard(n.X)
e.discard(n.Y)
case ir.OANDAND, ir.OOROR:
n := n.(*ir.LogicalExpr)
e.discard(n.X)
e.discard(n.Y)
case ir.OADDR:
n := n.(*ir.AddrExpr)
e.expr(k.addr(n, "address-of"), n.X) // "address-of"
case ir.ODEREF:
n := n.(*ir.StarExpr)
e.expr(k.deref(n, "indirection"), n.X) // "indirection"
case ir.ODOT, ir.ODOTMETH, ir.ODOTINTER:
n := n.(*ir.SelectorExpr)
e.expr(k.note(n, "dot"), n.X)
case ir.ODOTPTR:
n := n.(*ir.SelectorExpr)
e.expr(k.deref(n, "dot of pointer"), n.X) // "dot of pointer"
case ir.ODOTTYPE, ir.ODOTTYPE2:
n := n.(*ir.TypeAssertExpr)
e.expr(k.dotType(n.Type(), n, "dot"), n.X)
case ir.ODYNAMICDOTTYPE, ir.ODYNAMICDOTTYPE2:
n := n.(*ir.DynamicTypeAssertExpr)
e.expr(k.dotType(n.Type(), n, "dot"), n.X)
// n.T doesn't need to be tracked; it always points to read-only storage.
case ir.OINDEX:
n := n.(*ir.IndexExpr)
if n.X.Type().IsArray() {
e.expr(k.note(n, "fixed-array-index-of"), n.X)
} else {
// TODO(mdempsky): Fix why reason text.
e.expr(k.deref(n, "dot of pointer"), n.X)
}
e.discard(n.Index)
case ir.OINDEXMAP:
n := n.(*ir.IndexExpr)
e.discard(n.X)
e.discard(n.Index)
case ir.OSLICE, ir.OSLICEARR, ir.OSLICE3, ir.OSLICE3ARR, ir.OSLICESTR:
n := n.(*ir.SliceExpr)
e.expr(k.note(n, "slice"), n.X)
e.discard(n.Low)
e.discard(n.High)
e.discard(n.Max)
case ir.OCONV, ir.OCONVNOP:
n := n.(*ir.ConvExpr)
if (ir.ShouldCheckPtr(e.curfn, 2) || ir.ShouldAsanCheckPtr(e.curfn)) && n.Type().IsUnsafePtr() && n.X.Type().IsPtr() {
// When -d=checkptr=2 or -asan is enabled,
// treat conversions to unsafe.Pointer as an
// escaping operation. This allows better
// runtime instrumentation, since we can more
// easily detect object boundaries on the heap
// than the stack.
e.assignHeap(n.X, "conversion to unsafe.Pointer", n)
} else if n.Type().IsUnsafePtr() && n.X.Type().IsUintptr() {
e.unsafeValue(k, n.X)
} else {
e.expr(k, n.X)
}
case ir.OCONVIFACE, ir.OCONVIDATA:
n := n.(*ir.ConvExpr)
if !n.X.Type().IsInterface() && !types.IsDirectIface(n.X.Type()) {
k = e.spill(k, n)
}
e.expr(k.note(n, "interface-converted"), n.X)
case ir.OEFACE:
n := n.(*ir.BinaryExpr)
// Note: n.X is not needed because it can never point to memory that might escape.
e.expr(k, n.Y)
case ir.OITAB, ir.OIDATA, ir.OSPTR:
n := n.(*ir.UnaryExpr)
e.expr(k, n.X)
case ir.OSLICE2ARR:
// Converting a slice to array is effectively a deref.
n := n.(*ir.ConvExpr)
e.expr(k.deref(n, "slice-to-array"), n.X)
case ir.OSLICE2ARRPTR:
// the slice pointer flows directly to the result
n := n.(*ir.ConvExpr)
e.expr(k, n.X)
case ir.ORECV:
n := n.(*ir.UnaryExpr)
e.discard(n.X)
case ir.OCALLMETH, ir.OCALLFUNC, ir.OCALLINTER, ir.OINLCALL,
ir.OLEN, ir.OCAP, ir.OCOMPLEX, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.OCOPY, ir.ORECOVER,
ir.OUNSAFEADD, ir.OUNSAFESLICE, ir.OUNSAFESTRING, ir.OUNSAFESTRINGDATA, ir.OUNSAFESLICEDATA:
e.call([]hole{k}, n)
case ir.ONEW:
n := n.(*ir.UnaryExpr)
e.spill(k, n)
case ir.OMAKESLICE:
n := n.(*ir.MakeExpr)
e.spill(k, n)
e.discard(n.Len)
e.discard(n.Cap)
case ir.OMAKECHAN:
n := n.(*ir.MakeExpr)
e.discard(n.Len)
case ir.OMAKEMAP:
n := n.(*ir.MakeExpr)
e.spill(k, n)
e.discard(n.Len)
case ir.OMETHVALUE:
// Flow the receiver argument to both the closure and
// to the receiver parameter.
n := n.(*ir.SelectorExpr)
closureK := e.spill(k, n)
m := n.Selection
// We don't know how the method value will be called
// later, so conservatively assume the result
// parameters all flow to the heap.
//
// TODO(mdempsky): Change ks into a callback, so that
// we don't have to create this slice?
var ks []hole
for i := m.Type.NumResults(); i > 0; i-- {
ks = append(ks, e.heapHole())
}
name, _ := m.Nname.(*ir.Name)
paramK := e.tagHole(ks, name, m.Type.Recv())
e.expr(e.teeHole(paramK, closureK), n.X)
case ir.OPTRLIT:
n := n.(*ir.AddrExpr)
e.expr(e.spill(k, n), n.X)
case ir.OARRAYLIT:
n := n.(*ir.CompLitExpr)
for _, elt := range n.List {
if elt.Op() == ir.OKEY {
elt = elt.(*ir.KeyExpr).Value
}
e.expr(k.note(n, "array literal element"), elt)
}
case ir.OSLICELIT:
n := n.(*ir.CompLitExpr)
k = e.spill(k, n)
for _, elt := range n.List {
if elt.Op() == ir.OKEY {
elt = elt.(*ir.KeyExpr).Value
}
e.expr(k.note(n, "slice-literal-element"), elt)
}
case ir.OSTRUCTLIT:
n := n.(*ir.CompLitExpr)
for _, elt := range n.List {
e.expr(k.note(n, "struct literal element"), elt.(*ir.StructKeyExpr).Value)
}
case ir.OMAPLIT:
n := n.(*ir.CompLitExpr)
e.spill(k, n)
// Map keys and values are always stored in the heap.
for _, elt := range n.List {
elt := elt.(*ir.KeyExpr)
e.assignHeap(elt.Key, "map literal key", n)
e.assignHeap(elt.Value, "map literal value", n)
}
case ir.OCLOSURE:
n := n.(*ir.ClosureExpr)
k = e.spill(k, n)
e.closures = append(e.closures, closure{k, n})
if fn := n.Func; fn.IsHiddenClosure() {
for _, cv := range fn.ClosureVars {
if loc := e.oldLoc(cv); !loc.captured {
loc.captured = true
// Ignore reassignments to the variable in straightline code
// preceding the first capture by a closure.
if loc.loopDepth == e.loopDepth {
loc.reassigned = false
}
}
}
for _, n := range fn.Dcl {
// Add locations for local variables of the
// closure, if needed, in case we're not including
// the closure func in the batch for escape
// analysis (happens for escape analysis called
// from reflectdata.methodWrapper)
if n.Op() == ir.ONAME && n.Opt == nil {
e.with(fn).newLoc(n, false)
}
}
e.walkFunc(fn)
}
case ir.ORUNES2STR, ir.OBYTES2STR, ir.OSTR2RUNES, ir.OSTR2BYTES, ir.ORUNESTR:
n := n.(*ir.ConvExpr)
e.spill(k, n)
e.discard(n.X)
case ir.OADDSTR:
n := n.(*ir.AddStringExpr)
e.spill(k, n)
// Arguments of OADDSTR never escape;
// runtime.concatstrings makes sure of that.
e.discards(n.List)
case ir.ODYNAMICTYPE:
// Nothing to do - argument is a *runtime._type (+ maybe a *runtime.itab) pointing to static data section
}
}
// unsafeValue evaluates a uintptr-typed arithmetic expression looking
// for conversions from an unsafe.Pointer.
func (e *escape) unsafeValue(k hole, n ir.Node) {
if n.Type().Kind() != types.TUINTPTR {
base.Fatalf("unexpected type %v for %v", n.Type(), n)
}
if k.addrtaken {
base.Fatalf("unexpected addrtaken")
}
e.stmts(n.Init())
switch n.Op() {
case ir.OCONV, ir.OCONVNOP:
n := n.(*ir.ConvExpr)
if n.X.Type().IsUnsafePtr() {
e.expr(k, n.X)
} else {
e.discard(n.X)
}
case ir.ODOTPTR:
n := n.(*ir.SelectorExpr)
if ir.IsReflectHeaderDataField(n) {
e.expr(k.deref(n, "reflect.Header.Data"), n.X)
} else {
e.discard(n.X)
}
case ir.OPLUS, ir.ONEG, ir.OBITNOT:
n := n.(*ir.UnaryExpr)
e.unsafeValue(k, n.X)
case ir.OADD, ir.OSUB, ir.OOR, ir.OXOR, ir.OMUL, ir.ODIV, ir.OMOD, ir.OAND, ir.OANDNOT:
n := n.(*ir.BinaryExpr)
e.unsafeValue(k, n.X)
e.unsafeValue(k, n.Y)
case ir.OLSH, ir.ORSH:
n := n.(*ir.BinaryExpr)
e.unsafeValue(k, n.X)
// RHS need not be uintptr-typed (#32959) and can't meaningfully
// flow pointers anyway.
e.discard(n.Y)
default:
e.exprSkipInit(e.discardHole(), n)
}
}
// discard evaluates an expression n for side-effects, but discards
// its value.
func (e *escape) discard(n ir.Node) {
e.expr(e.discardHole(), n)
}
func (e *escape) discards(l ir.Nodes) {
for _, n := range l {
e.discard(n)
}
}
// spill allocates a new location associated with expression n, flows
// its address to k, and returns a hole that flows values to it. It's
// intended for use with most expressions that allocate storage.
func (e *escape) spill(k hole, n ir.Node) hole {
loc := e.newLoc(n, true)
e.flow(k.addr(n, "spill"), loc)
return loc.asHole()
}