go expr 源码

golang expr 代码

文件路径：/src/cmd/compile/internal/escape/expr.go

// 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.OIDATA, ir.OSPTR:
		n := n.(*ir.UnaryExpr)
		e.expr(k, 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:
		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()
}

相关信息

go 源码目录

相关文章

go assign 源码

go call 源码

go desugar 源码

go escape 源码

go graph 源码

go leaks 源码

go solve 源码

go stmt 源码

go utils 源码