| // Copyright 2013 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 pointer |
| |
| // This file defines a naive Andersen-style solver for the inclusion |
| // constraint system. |
| |
| import ( |
| "fmt" |
| |
| "code.google.com/p/go.tools/go/types" |
| ) |
| |
| func (a *analysis) solve() { |
| // Solver main loop. |
| for round := 1; ; round++ { |
| if a.log != nil { |
| fmt.Fprintf(a.log, "Solving, round %d\n", round) |
| } |
| |
| // Add new constraints to the graph: |
| // static constraints from SSA on round 1, |
| // dynamic constraints from reflection thereafter. |
| a.processNewConstraints() |
| |
| id := a.work.take() |
| if id == empty { |
| break |
| } |
| if a.log != nil { |
| fmt.Fprintf(a.log, "\tnode n%d\n", id) |
| } |
| |
| n := a.nodes[id] |
| |
| // Difference propagation. |
| delta := n.pts.diff(n.prevPts) |
| if delta == nil { |
| continue |
| } |
| n.prevPts = n.pts.clone() |
| |
| // Apply all resolution rules attached to n. |
| a.solveConstraints(n, delta) |
| |
| if a.log != nil { |
| fmt.Fprintf(a.log, "\t\tpts(n%d) = %s\n", id, n.pts) |
| } |
| } |
| |
| if a.log != nil { |
| fmt.Fprintf(a.log, "Solver done\n") |
| } |
| } |
| |
| // processNewConstraints takes the new constraints from a.constraints |
| // and adds them to the graph, ensuring |
| // that new constraints are applied to pre-existing labels and |
| // that pre-existing constraints are applied to new labels. |
| // |
| func (a *analysis) processNewConstraints() { |
| // Take the slice of new constraints. |
| // (May grow during call to solveConstraints.) |
| constraints := a.constraints |
| a.constraints = nil |
| |
| // Initialize points-to sets from addr-of (base) constraints. |
| for _, c := range constraints { |
| if c, ok := c.(*addrConstraint); ok { |
| dst := a.nodes[c.dst] |
| dst.pts.add(c.src) |
| |
| // Populate the worklist with nodes that point to |
| // something initially (due to addrConstraints) and |
| // have other constraints attached. |
| // (A no-op in round 1.) |
| if dst.copyTo != nil || dst.complex != nil { |
| a.addWork(c.dst) |
| } |
| } |
| } |
| |
| // Attach simple (copy) and complex constraints to nodes. |
| var stale nodeset |
| for _, c := range constraints { |
| var id nodeid |
| switch c := c.(type) { |
| case *addrConstraint: |
| // base constraints handled in previous loop |
| continue |
| case *copyConstraint: |
| // simple (copy) constraint |
| id = c.src |
| a.nodes[id].copyTo.add(c.dst) |
| default: |
| // complex constraint |
| id = c.ptr() |
| a.nodes[id].complex.add(c) |
| } |
| |
| if n := a.nodes[id]; len(n.pts) > 0 { |
| if len(n.prevPts) > 0 { |
| stale.add(id) |
| } |
| a.addWork(id) |
| } |
| } |
| // Apply new constraints to pre-existing PTS labels. |
| for id := range stale { |
| n := a.nodes[id] |
| a.solveConstraints(n, n.prevPts) |
| } |
| } |
| |
| // solveConstraints applies each resolution rule attached to node n to |
| // the set of labels delta. It may generate new constraints in |
| // a.constraints. |
| // |
| func (a *analysis) solveConstraints(n *node, delta nodeset) { |
| if delta == nil { |
| return |
| } |
| |
| // Process complex constraints dependent on n. |
| for c := range n.complex { |
| if a.log != nil { |
| fmt.Fprintf(a.log, "\t\tconstraint %s\n", c) |
| } |
| // TODO(adonovan): parameter n is never used. Remove? |
| c.solve(a, n, delta) |
| } |
| |
| // Process copy constraints. |
| var copySeen nodeset |
| for mid := range n.copyTo { |
| if copySeen.add(mid) { |
| if a.nodes[mid].pts.addAll(delta) { |
| a.addWork(mid) |
| } |
| } |
| } |
| } |
| |
| // addLabel adds label to the points-to set of ptr and reports whether the set grew. |
| func (a *analysis) addLabel(ptr, label nodeid) bool { |
| return a.nodes[ptr].pts.add(label) |
| } |
| |
| func (a *analysis) addWork(id nodeid) { |
| a.work.add(id) |
| if a.log != nil { |
| fmt.Fprintf(a.log, "\t\twork: n%d\n", id) |
| } |
| } |
| |
| func (c *addrConstraint) ptr() nodeid { |
| panic("addrConstraint: not a complex constraint") |
| } |
| func (c *copyConstraint) ptr() nodeid { |
| panic("addrConstraint: not a complex constraint") |
| } |
| |
| // Complex constraints attach themselves to the relevant pointer node. |
| |
| func (c *storeConstraint) ptr() nodeid { |
| return c.dst |
| } |
| func (c *loadConstraint) ptr() nodeid { |
| return c.src |
| } |
| func (c *offsetAddrConstraint) ptr() nodeid { |
| return c.src |
| } |
| func (c *typeFilterConstraint) ptr() nodeid { |
| return c.src |
| } |
| func (c *untagConstraint) ptr() nodeid { |
| return c.src |
| } |
| func (c *invokeConstraint) ptr() nodeid { |
| return c.iface |
| } |
| |
| // onlineCopy adds a copy edge. It is called online, i.e. during |
| // solving, so it adds edges and pts members directly rather than by |
| // instantiating a 'constraint'. |
| // |
| // The size of the copy is implicitly 1. |
| // It returns true if pts(dst) changed. |
| // |
| func (a *analysis) onlineCopy(dst, src nodeid) bool { |
| if dst != src { |
| if nsrc := a.nodes[src]; nsrc.copyTo.add(dst) { |
| if a.log != nil { |
| fmt.Fprintf(a.log, "\t\t\tdynamic copy n%d <- n%d\n", dst, src) |
| } |
| // TODO(adonovan): most calls to onlineCopy |
| // are followed by addWork, possibly batched |
| // via a 'changed' flag; see if there's a |
| // noticeable penalty to calling addWork here. |
| return a.nodes[dst].pts.addAll(nsrc.pts) |
| } |
| } |
| return false |
| } |
| |
| // Returns sizeof. |
| // Implicitly adds nodes to worklist. |
| // |
| // TODO(adonovan): now that we support a.copy() during solving, we |
| // could eliminate onlineCopyN, but it's much slower. Investigate. |
| // |
| func (a *analysis) onlineCopyN(dst, src nodeid, sizeof uint32) uint32 { |
| for i := uint32(0); i < sizeof; i++ { |
| if a.onlineCopy(dst, src) { |
| a.addWork(dst) |
| } |
| src++ |
| dst++ |
| } |
| return sizeof |
| } |
| |
| func (c *loadConstraint) solve(a *analysis, n *node, delta nodeset) { |
| var changed bool |
| for k := range delta { |
| koff := k + nodeid(c.offset) |
| if a.onlineCopy(c.dst, koff) { |
| changed = true |
| } |
| } |
| if changed { |
| a.addWork(c.dst) |
| } |
| } |
| |
| func (c *storeConstraint) solve(a *analysis, n *node, delta nodeset) { |
| for k := range delta { |
| koff := k + nodeid(c.offset) |
| if a.onlineCopy(koff, c.src) { |
| a.addWork(koff) |
| } |
| } |
| } |
| |
| func (c *offsetAddrConstraint) solve(a *analysis, n *node, delta nodeset) { |
| dst := a.nodes[c.dst] |
| for k := range delta { |
| if dst.pts.add(k + nodeid(c.offset)) { |
| a.addWork(c.dst) |
| } |
| } |
| } |
| |
| func (c *typeFilterConstraint) solve(a *analysis, n *node, delta nodeset) { |
| for ifaceObj := range delta { |
| tDyn, _, indirect := a.taggedValue(ifaceObj) |
| if tDyn == nil { |
| panic("not a tagged value") |
| } |
| if indirect { |
| // TODO(adonovan): we'll need to implement this |
| // when we start creating indirect tagged objects. |
| panic("indirect tagged object") |
| } |
| |
| if types.IsAssignableTo(tDyn, c.typ) { |
| if a.addLabel(c.dst, ifaceObj) { |
| a.addWork(c.dst) |
| } |
| } |
| } |
| } |
| |
| func (c *untagConstraint) solve(a *analysis, n *node, delta nodeset) { |
| predicate := types.IsAssignableTo |
| if c.exact { |
| predicate = types.IsIdentical |
| } |
| for ifaceObj := range delta { |
| tDyn, v, indirect := a.taggedValue(ifaceObj) |
| if tDyn == nil { |
| panic("not a tagged value") |
| } |
| if indirect { |
| // TODO(adonovan): we'll need to implement this |
| // when we start creating indirect tagged objects. |
| panic("indirect tagged object") |
| } |
| |
| if predicate(tDyn, c.typ) { |
| // Copy payload sans tag to dst. |
| // |
| // TODO(adonovan): opt: if tConc is |
| // nonpointerlike we can skip this entire |
| // constraint, perhaps. We only care about |
| // pointers among the fields. |
| a.onlineCopyN(c.dst, v, a.sizeof(tDyn)) |
| } |
| } |
| } |
| |
| func (c *invokeConstraint) solve(a *analysis, n *node, delta nodeset) { |
| for ifaceObj := range delta { |
| tDyn, v, indirect := a.taggedValue(ifaceObj) |
| if tDyn == nil { |
| panic("not a tagged value") |
| } |
| if indirect { |
| // TODO(adonovan): we may need to implement this if |
| // we ever apply invokeConstraints to reflect.Value PTSs, |
| // e.g. for (reflect.Value).Call. |
| panic("indirect tagged object") |
| } |
| |
| // Look up the concrete method. |
| meth := tDyn.MethodSet().Lookup(c.method.Pkg(), c.method.Name()) |
| if meth == nil { |
| panic(fmt.Sprintf("n%d: type %s has no method %s (iface=n%d)", |
| c.iface, tDyn, c.method, ifaceObj)) |
| } |
| fn := a.prog.Method(meth) |
| if fn == nil { |
| panic(fmt.Sprintf("n%d: no ssa.Function for %s", c.iface, meth)) |
| } |
| sig := fn.Signature |
| |
| fnObj := a.globalobj[fn] // dynamic calls use shared contour |
| if fnObj == 0 { |
| // a.objectNode(fn) was not called during gen phase. |
| panic(fmt.Sprintf("a.globalobj[%s]==nil", fn)) |
| } |
| |
| // Make callsite's fn variable point to identity of |
| // concrete method. (There's no need to add it to |
| // worklist since it never has attached constraints.) |
| a.addLabel(c.params, fnObj) |
| |
| // Extract value and connect to method's receiver. |
| // Copy payload to method's receiver param (arg0). |
| arg0 := a.funcParams(fnObj) |
| recvSize := a.sizeof(sig.Recv().Type()) |
| a.onlineCopyN(arg0, v, recvSize) |
| |
| src := c.params + 1 // skip past identity |
| dst := arg0 + nodeid(recvSize) |
| |
| // Copy caller's argument block to method formal parameters. |
| paramsSize := a.sizeof(sig.Params()) |
| a.onlineCopyN(dst, src, paramsSize) |
| src += nodeid(paramsSize) |
| dst += nodeid(paramsSize) |
| |
| // Copy method results to caller's result block. |
| resultsSize := a.sizeof(sig.Results()) |
| a.onlineCopyN(src, dst, resultsSize) |
| } |
| } |
| |
| func (c *addrConstraint) solve(a *analysis, n *node, delta nodeset) { |
| panic("addr is not a complex constraint") |
| } |
| |
| func (c *copyConstraint) solve(a *analysis, n *node, delta nodeset) { |
| panic("copy is not a complex constraint") |
| } |