Golang ssa.Value类代码示例

// valueOffsetNode ascertains the node for tuple/struct value v,
// then returns the node for its subfield #index.
//
func (a *analysis) valueOffsetNode(v ssa.Value, index int) nodeid {
	id := a.valueNode(v)
	if id == 0 {
		panic(fmt.Sprintf("cannot offset within n0: %s = %s", v.Name(), v))
	}
	return id + nodeid(a.offsetOf(v.Type(), index))
}

// genOffsetAddr generates constraints for a 'v=ptr.field' (FieldAddr)
// or 'v=ptr[*]' (IndexAddr) instruction v.
func (a *analysis) genOffsetAddr(cgn *cgnode, v ssa.Value, ptr nodeid, offset uint32) {
	dst := a.valueNode(v)
	if obj := a.objectNode(cgn, v); obj != 0 {
		// Pre-apply offsetAddrConstraint.solve().
		a.addressOf(v.Type(), dst, obj)
	} else {
		a.offsetAddr(v.Type(), dst, ptr, offset)
	}
}

// AddQuery adds v to Config.IndirectQueries.
// Precondition: CanPoint(v.Type().Underlying().(*types.Pointer).Elem()).
func (c *Config) AddIndirectQuery(v ssa.Value) {
	if c.IndirectQueries == nil {
		c.IndirectQueries = make(map[ssa.Value]struct{})
	}
	if !CanPoint(mustDeref(v.Type())) {
		panic(fmt.Sprintf("%s is not the address of a pointer-like value: %s", v, v.Type()))
	}
	c.IndirectQueries[v] = struct{}{}
}

// AddQuery adds v to Config.Queries.
// Precondition: CanPoint(v.Type()).
// TODO(adonovan): consider returning a new Pointer for this query,
// which will be initialized during analysis.  That avoids the needs
// for the corresponding ssa.Value-keyed maps in Config and Result.
func (c *Config) AddQuery(v ssa.Value) {
	if !CanPoint(v.Type()) {
		panic(fmt.Sprintf("%s is not a pointer-like value: %s", v, v.Type()))
	}
	if c.Queries == nil {
		c.Queries = make(map[ssa.Value]struct{})
	}
	c.Queries[v] = struct{}{}
}

func (fr *frame) canAvoidElementLoad(ptr ssa.Value) bool {
	for _, ref := range *ptr.Referrers() {
		switch ref := ref.(type) {
		case *ssa.Field:
		case *ssa.Index:
			if ref.X != ptr {
				return false
			}
			// ok
		default:
			return false
		}
	}

	return true
}

func (fr *frame) get(key ssa.Value) value {
	switch key := key.(type) {
	case nil:
		// Hack; simplifies handling of optional attributes
		// such as ssa.Slice.{Low,High}.
		return nil
	case *ssa.Function, *ssa.Builtin:
		return key
	case *ssa.Const:
		return constValue(key)
	case *ssa.Global:
		if r, ok := fr.i.globals[key]; ok {
			return r
		}
	}
	if r, ok := fr.env[key]; ok {
		return r
	}
	panic(fmt.Sprintf("get: no value for %T: %v", key, key.Name()))
}

// setValueNode associates node id with the value v.
// cgn identifies the context iff v is a local variable.
//
func (a *analysis) setValueNode(v ssa.Value, id nodeid, cgn *cgnode) {
	if cgn != nil {
		a.localval[v] = id
	} else {
		a.globalval[v] = id
	}
	if a.log != nil {
		fmt.Fprintf(a.log, "\tval[%s] = n%d  (%T)\n", v.Name(), id, v)
	}

	// Due to context-sensitivity, we may encounter the same Value
	// in many contexts. We merge them to a canonical node, since
	// that's what all clients want.

	// Record the (v, id) relation if the client has queried pts(v).
	if _, ok := a.config.Queries[v]; ok {
		t := v.Type()
		ptr, ok := a.result.Queries[v]
		if !ok {
			// First time?  Create the canonical query node.
			ptr = Pointer{a, a.addNodes(t, "query")}
			a.result.Queries[v] = ptr
		}
		a.result.Queries[v] = ptr
		a.copy(ptr.n, id, a.sizeof(t))
	}

	// Record the (*v, id) relation if the client has queried pts(*v).
	if _, ok := a.config.IndirectQueries[v]; ok {
		t := v.Type()
		ptr, ok := a.result.IndirectQueries[v]
		if !ok {
			// First time? Create the canonical indirect query node.
			ptr = Pointer{a, a.addNodes(v.Type(), "query.indirect")}
			a.result.IndirectQueries[v] = ptr
		}
		a.genLoad(cgn, ptr.n, v, 0, a.sizeof(t))
	}
}

// valueNode returns the id of the value node for v, creating it (and
// the association) as needed.  It may return zero for uninteresting
// values containing no pointers.
//
func (a *analysis) valueNode(v ssa.Value) nodeid {
	// Value nodes for locals are created en masse by genFunc.
	if id, ok := a.localval[v]; ok {
		return id
	}

	// Value nodes for globals are created on demand.
	id, ok := a.globalval[v]
	if !ok {
		var comment string
		if a.log != nil {
			comment = v.String()
		}
		id = a.addNodes(v.Type(), comment)
		if obj := a.objectNode(nil, v); obj != 0 {
			a.addressOf(v.Type(), id, obj)
		}
		a.setValueNode(v, id, nil)
	}
	return id
}

// Declare creates an llvm.dbg.declare call for the specified function
// parameter or local variable.
func (d *DIBuilder) Declare(b llvm.Builder, v ssa.Value, llv llvm.Value, paramIndex int) {
	tag := tagAutoVariable
	if paramIndex >= 0 {
		tag = tagArgVariable
	}
	var diFile llvm.Metadata
	var line int
	if file := d.fset.File(v.Pos()); file != nil {
		line = file.Line(v.Pos())
		diFile = d.getFile(file)
	}
	localVar := d.builder.CreateLocalVariable(d.scope(), llvm.DILocalVariable{
		Tag:   tag,
		Name:  llv.Name(),
		File:  diFile,
		Line:  line,
		ArgNo: paramIndex + 1,
		Type:  d.DIType(v.Type()),
	})
	expr := d.builder.CreateExpression(nil)
	d.builder.InsertDeclareAtEnd(llv, localVar, expr, b.GetInsertBlock())
}

// objectNode returns the object to which v points, if known.
// In other words, if the points-to set of v is a singleton, it
// returns the sole label, zero otherwise.
//
// We exploit this information to make the generated constraints less
// dynamic.  For example, a complex load constraint can be replaced by
// a simple copy constraint when the sole destination is known a priori.
//
// Some SSA instructions always have singletons points-to sets:
// 	Alloc, Function, Global, MakeChan, MakeClosure,  MakeInterface,  MakeMap,  MakeSlice.
// Others may be singletons depending on their operands:
// 	FreeVar, Const, Convert, FieldAddr, IndexAddr, Slice.
//
// Idempotent.  Objects are created as needed, possibly via recursion
// down the SSA value graph, e.g IndexAddr(FieldAddr(Alloc))).
//
func (a *analysis) objectNode(cgn *cgnode, v ssa.Value) nodeid {
	switch v.(type) {
	case *ssa.Global, *ssa.Function, *ssa.Const, *ssa.FreeVar:
		// Global object.
		obj, ok := a.globalobj[v]
		if !ok {
			switch v := v.(type) {
			case *ssa.Global:
				obj = a.nextNode()
				a.addNodes(mustDeref(v.Type()), "global")
				a.endObject(obj, nil, v)

			case *ssa.Function:
				obj = a.makeFunctionObject(v, nil)

			case *ssa.Const:
				// not addressable

			case *ssa.FreeVar:
				// not addressable
			}

			if a.log != nil {
				fmt.Fprintf(a.log, "\tglobalobj[%s] = n%d\n", v, obj)
			}
			a.globalobj[v] = obj
		}
		return obj
	}

	// Local object.
	obj, ok := a.localobj[v]
	if !ok {
		switch v := v.(type) {
		case *ssa.Alloc:
			obj = a.nextNode()
			a.addNodes(mustDeref(v.Type()), "alloc")
			a.endObject(obj, cgn, v)

		case *ssa.MakeSlice:
			obj = a.nextNode()
			a.addNodes(sliceToArray(v.Type()), "makeslice")
			a.endObject(obj, cgn, v)

		case *ssa.MakeChan:
			obj = a.nextNode()
			a.addNodes(v.Type().Underlying().(*types.Chan).Elem(), "makechan")
			a.endObject(obj, cgn, v)

		case *ssa.MakeMap:
			obj = a.nextNode()
			tmap := v.Type().Underlying().(*types.Map)
			a.addNodes(tmap.Key(), "makemap.key")
			elem := a.addNodes(tmap.Elem(), "makemap.value")

			// To update the value field, MapUpdate
			// generates store-with-offset constraints which
			// the presolver can't model, so we must mark
			// those nodes indirect.
			for id, end := elem, elem+nodeid(a.sizeof(tmap.Elem())); id < end; id++ {
				a.mapValues = append(a.mapValues, id)
			}
			a.endObject(obj, cgn, v)

		case *ssa.MakeInterface:
			tConc := v.X.Type()
			obj = a.makeTagged(tConc, cgn, v)

			// Copy the value into it, if nontrivial.
			if x := a.valueNode(v.X); x != 0 {
				a.copy(obj+1, x, a.sizeof(tConc))
			}

		case *ssa.FieldAddr:
			if xobj := a.objectNode(cgn, v.X); xobj != 0 {
				obj = xobj + nodeid(a.offsetOf(mustDeref(v.X.Type()), v.Field))
			}

		case *ssa.IndexAddr:
			if xobj := a.objectNode(cgn, v.X); xobj != 0 {
				obj = xobj + 1
			}

		case *ssa.Slice:
//.........这里部分代码省略.........

func escapes(val ssa.Value, bb *ssa.BasicBlock, pending []ssa.Value) bool {
	for _, p := range pending {
		if val == p {
			return false
		}
	}

	for _, ref := range *val.Referrers() {
		switch ref := ref.(type) {
		case *ssa.Phi:
			// We must consider the variable to have escaped if it is
			// possible for the program to see more than one "version"
			// of the variable at once, as this requires the program
			// to use heap allocation for the multiple versions.
			//
			// I (pcc) think that this is only possible (without stores)
			// in the case where a phi node that (directly or indirectly)
			// refers to the allocation dominates the allocation.
			if ref.Block().Dominates(bb) {
				return true
			}
			if escapes(ref, bb, append(pending, val)) {
				return true
			}

		case *ssa.BinOp, *ssa.ChangeType, *ssa.Convert, *ssa.ChangeInterface, *ssa.MakeInterface, *ssa.Slice, *ssa.FieldAddr, *ssa.IndexAddr, *ssa.TypeAssert, *ssa.Extract:
			if escapes(ref.(ssa.Value), bb, append(pending, val)) {
				return true
			}

		case *ssa.Range, *ssa.DebugRef:
			continue

		case *ssa.UnOp:
			if ref.Op == token.MUL || ref.Op == token.ARROW {
				continue
			}
			if escapes(ref, bb, append(pending, val)) {
				return true
			}

		case *ssa.Store:
			if val == ref.Val {
				return true
			}

		case *ssa.Call:
			if builtin, ok := ref.Call.Value.(*ssa.Builtin); ok {
				switch builtin.Name() {
				case "cap", "len", "copy", "ssa:wrapnilchk":
					continue
				case "append":
					if ref.Call.Args[0] == val && escapes(ref, bb, append(pending, val)) {
						return true
					}
				default:
					return true
				}
			} else {
				return true
			}

		default:
			return true
		}
	}

	return false
}

func (fr *frame) value(v ssa.Value) (result *govalue) {
	switch v := v.(type) {
	case nil:
		return nil
	case *ssa.Function:
		return fr.resolveFunctionDescriptor(v)
	case *ssa.Const:
		return fr.newValueFromConst(v.Value, v.Type())
	case *ssa.Global:
		if g, ok := fr.globals[v]; ok {
			return newValue(g, v.Type())
		}
		// Create an external global. Globals for this package are defined
		// on entry to translatePackage, and have initialisers.
		llelemtyp := fr.llvmtypes.ToLLVM(deref(v.Type()))
		vname := fr.types.mc.mangleGlobalName(v)
		llglobal := llvm.AddGlobal(fr.module.Module, llelemtyp, vname)
		llglobal = llvm.ConstBitCast(llglobal, fr.llvmtypes.ToLLVM(v.Type()))
		fr.globals[v] = llglobal
		return newValue(llglobal, v.Type())
	}
	if value, ok := fr.env[v]; ok {
		return value
	}

	panic(fmt.Errorf("Instruction %q not visited yet", v.Name()))
}