Golang ssa.Value类代码示例

// describePointer runs the pointer analysis of the selected SSA value.
func describePointer(o *Oracle, v ssa.Value, indirect bool) (ptrs []pointerResult, err error) {
	buildSSA(o)

	// TODO(adonovan): don't run indirect pointer analysis on non-ptr-ptrlike types.
	o.config.Queries = map[ssa.Value]pointer.Indirect{v: pointer.Indirect(indirect)}
	ptares := ptrAnalysis(o)

	// Combine the PT sets from all contexts.
	pointers := ptares.Queries[v]
	if pointers == nil {
		return nil, fmt.Errorf("PTA did not encounter this expression (dead code?)")
	}
	pts := pointer.PointsToCombined(pointers)

	if pointer.CanHaveDynamicTypes(v.Type()) {
		// Show concrete types for interface/reflect.Value expression.
		if concs := pts.DynamicTypes(); concs.Len() > 0 {
			concs.Iterate(func(conc types.Type, pta interface{}) {
				combined := pointer.PointsToCombined(pta.([]pointer.Pointer))
				labels := combined.Labels()
				sort.Sort(byPosAndString(labels)) // to ensure determinism
				ptrs = append(ptrs, pointerResult{conc, labels})
			})
		}
	} else {
		// Show labels for other expressions.
		labels := pts.Labels()
		sort.Sort(byPosAndString(labels)) // to ensure determinism
		ptrs = append(ptrs, pointerResult{v.Type(), labels})
	}
	sort.Sort(byTypeString(ptrs)) // to ensure determinism
	return ptrs, nil
}

// 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))
}

// 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.
//
// Nodes for locals are created en masse during genFunc and are
// implicitly contextualized by the function currently being analyzed
// (i.e. parameter to genFunc).
//
func (a *analysis) valueNode(v ssa.Value) nodeid {
	id, ok := a.valNode[v]
	if !ok {
		switch v := v.(type) {
		case *ssa.Function:
			id = a.makeFunction(v)

		case *ssa.Global:
			id = a.makeGlobal(v)

		case *ssa.Const:
			id = a.makeConstant(v)

		case *ssa.Capture:
			// TODO(adonovan): treat captures context-sensitively.
			id = a.addNodes(v.Type(), "capture")

		default:
			// *ssa.Parameters and ssa.Instruction values
			// are created by genFunc.
			// *Builtins are not true values.
			panic(v)
		}
		a.setValueNode(v, id)
	}
	return id
}

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()))
}

// runPTA runs the pointer analysis of the selected SSA value or address.
func runPTA(o *Oracle, v ssa.Value, isAddr bool) (ptrs []pointerResult, err error) {
	buildSSA(o)

	if isAddr {
		o.ptaConfig.AddIndirectQuery(v)
	} else {
		o.ptaConfig.AddQuery(v)
	}
	ptares := ptrAnalysis(o)

	// Combine the PT sets from all contexts.
	var pointers []pointer.Pointer
	if isAddr {
		pointers = ptares.IndirectQueries[v]
	} else {
		pointers = ptares.Queries[v]
	}
	if pointers == nil {
		return nil, fmt.Errorf("pointer analysis did not find expression (dead code?)")
	}
	pts := pointer.PointsToCombined(pointers)

	if pointer.CanHaveDynamicTypes(v.Type()) {
		// Show concrete types for interface/reflect.Value expression.
		if concs := pts.DynamicTypes(); concs.Len() > 0 {
			concs.Iterate(func(conc types.Type, pta interface{}) {
				combined := pointer.PointsToCombined(pta.([]pointer.Pointer))
				labels := combined.Labels()
				sort.Sort(byPosAndString(labels)) // to ensure determinism
				ptrs = append(ptrs, pointerResult{conc, labels})
			})
		}
	} else {
		// Show labels for other expressions.
		labels := pts.Labels()
		sort.Sort(byPosAndString(labels)) // to ensure determinism
		ptrs = append(ptrs, pointerResult{v.Type(), labels})
	}
	sort.Sort(byTypeString(ptrs)) // to ensure determinism
	return ptrs, nil
}

// 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.addOneNode(v.Type(), comment, nil)
		if obj := a.objectNode(nil, v); obj != 0 {
			a.addressOf(id, obj)
		}
		a.setValueNode(v, id, nil)
	}
	return id
}

// setValueNode associates node id with the value v.
// TODO(adonovan): disambiguate v by its CallGraphNode, if it's a local.
func (a *analysis) setValueNode(v ssa.Value, id nodeid) {
	a.valNode[v] = id
	if a.log != nil {
		fmt.Fprintf(a.log, "\tval[%s] = n%d  (%T)\n", v.Name(), id, v)
	}

	// Record the (v, id) relation if the client has queried v.
	if indirect, ok := a.config.Queries[v]; ok {
		if indirect {
			tmp := a.addNodes(v.Type(), "query.indirect")
			a.load(tmp, id, a.sizeof(v.Type()))
			id = tmp
		}
		a.queries[v] = append(a.queries[v], ptr{a, id})
	}
}

// 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)
	}

	// Record the (v, id) relation if the client has queried v.
	if indirect, ok := a.config.Queries[v]; ok {
		if indirect {
			tmp := a.addNodes(v.Type(), "query.indirect")
			a.genLoad(cgn, tmp, v, 0, a.sizeof(v.Type()))
			id = tmp
		}
		a.result.Queries[v] = append(a.result.Queries[v], ptr{a, cgn, id})
	}
}

func (fr *frame) value(v ssa.Value) (result *LLVMValue) {
	switch v := v.(type) {
	case nil:
		return nil
	case *ssa.Function:
		result, ok := fr.funcvals[v]
		if ok {
			return result
		}
		// fr.globals[v] has the function in raw pointer form;
		// we must convert it to <f,ctx> form. If the function
		// does not have a receiver, then create a wrapper
		// function that has an additional "context" parameter.
		f := fr.resolveFunction(v)
		if v.Signature.Recv() == nil && len(v.FreeVars) == 0 {
			f = contextFunction(fr.compiler, f)
		}
		pair := llvm.ConstNull(fr.llvmtypes.ToLLVM(f.Type()))
		fnptr := llvm.ConstBitCast(f.LLVMValue(), pair.Type().StructElementTypes()[0])
		pair = llvm.ConstInsertValue(pair, fnptr, []uint32{0})
		result = fr.NewValue(pair, f.Type())
		fr.funcvals[v] = result
		return result
	case *ssa.Const:
		return fr.NewConstValue(v.Value, v.Type())
	case *ssa.Global:
		if g, ok := fr.globals[v]; ok {
			return g
		}
		// Create an external global. Globals for this package are defined
		// on entry to translatePackage, and have initialisers.
		llelemtyp := fr.llvmtypes.ToLLVM(deref(v.Type()))
		llglobal := llvm.AddGlobal(fr.module.Module, llelemtyp, v.String())
		global := fr.NewValue(llglobal, v.Type())
		fr.globals[v] = global
		return global
	}
	if value, ok := fr.env[v]; ok {
		return value
	}

	// Instructions are not necessarily visited before they are used (e.g. Phi
	// edges) so we must "backpatch": create a value with the resultant type,
	// and then replace it when we visit the instruction.
	if b, ok := fr.backpatch[v]; ok {
		return b
	}
	if fr.backpatch == nil {
		fr.backpatch = make(map[ssa.Value]*LLVMValue)
	}
	// Note: we must not create a constant here (e.g. Undef/ConstNull), as
	// it is not permissible to replace a constant with a non-constant.
	// We must create the value in its own standalone basic block, so we can
	// dispose of it after replacing.
	currBlock := fr.builder.GetInsertBlock()
	fr.builder.SetInsertPointAtEnd(llvm.AddBasicBlock(currBlock.Parent(), ""))
	placeholder := fr.compiler.builder.CreatePHI(fr.llvmtypes.ToLLVM(v.Type()), "")
	fr.builder.SetInsertPointAtEnd(currBlock)
	value := fr.NewValue(placeholder, v.Type())
	fr.backpatch[v] = value
	return value
}

func describeValue(o *Oracle, qpos *QueryPos, path []ast.Node) (*describeValueResult, error) {
	var expr ast.Expr
	var obj types.Object
	switch n := path[0].(type) {
	case *ast.ValueSpec:
		// ambiguous ValueSpec containing multiple names
		return nil, fmt.Errorf("multiple value specification")
	case *ast.Ident:
		obj = qpos.info.ObjectOf(n)
		expr = n
	case ast.Expr:
		expr = n
	default:
		// Is this reachable?
		return nil, fmt.Errorf("unexpected AST for expr: %T", n)
	}

	typ := qpos.info.TypeOf(expr)
	constVal := qpos.info.ValueOf(expr)

	// From this point on, we cannot fail with an error.
	// Failure to run the pointer analysis will be reported later.
	//
	// Our disposition to pointer analysis may be one of the following:
	// - ok:    ssa.Value was const or func.
	// - error: no ssa.Value for expr (e.g. trivially dead code)
	// - ok:    ssa.Value is non-pointerlike
	// - error: no Pointer for ssa.Value (e.g. analytically unreachable)
	// - ok:    Pointer has empty points-to set
	// - ok:    Pointer has non-empty points-to set
	// ptaErr is non-nil only in the "error:" cases.

	var ptaErr error
	var ptrs []pointerResult

	// Only run pointer analysis on pointerlike expression types.
	if pointer.CanPoint(typ) {
		// Determine the ssa.Value for the expression.
		var value ssa.Value
		if obj != nil {
			// def/ref of func/var/const object
			value, ptaErr = ssaValueForIdent(o.prog, qpos.info, obj, path)
		} else {
			// any other expression
			if qpos.info.ValueOf(path[0].(ast.Expr)) == nil { // non-constant?
				value, ptaErr = ssaValueForExpr(o.prog, qpos.info, path)
			}
		}
		if value != nil {
			// TODO(adonovan): IsIdentical may be too strict;
			// perhaps we need is-assignable or even
			// has-same-underlying-representation?
			indirect := types.IsIdentical(types.NewPointer(typ), value.Type())

			ptrs, ptaErr = describePointer(o, value, indirect)
		}
	}

	return &describeValueResult{
		qpos:     qpos,
		expr:     expr,
		typ:      typ,
		constVal: constVal,
		obj:      obj,
		ptaErr:   ptaErr,
		ptrs:     ptrs,
	}, nil
}

// 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:
// 	Capture, 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 {
	if cgn == nil {
		// 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:
				if t, ok := v.Type().Underlying().(*types.Slice); ok && !v.IsNil() {
					// Non-nil []byte or []rune constant.
					obj = a.nextNode()
					a.addNodes(sliceToArray(t), "array in slice constant")
					a.endObject(obj, nil, v)
				}

			case *ssa.Capture:
				// For now, Captures have the same cardinality as globals.
				// TODO(adonovan): treat captures context-sensitively.
			}

			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")
			a.addNodes(tmap.Elem(), "makemap.value")
			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:
			obj = a.objectNode(cgn, v.X)

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