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-rw-r--r--src/cmd/compile/internal/ssa/debug.go1187
1 files changed, 1187 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/debug.go b/src/cmd/compile/internal/ssa/debug.go
new file mode 100644
index 0000000..6353f72
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/debug.go
@@ -0,0 +1,1187 @@
+// Copyright 2017 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 ssa
+
+import (
+ "cmd/internal/dwarf"
+ "cmd/internal/obj"
+ "encoding/hex"
+ "fmt"
+ "math/bits"
+ "sort"
+ "strings"
+)
+
+type SlotID int32
+type VarID int32
+
+// A FuncDebug contains all the debug information for the variables in a
+// function. Variables are identified by their LocalSlot, which may be the
+// result of decomposing a larger variable.
+type FuncDebug struct {
+ // Slots is all the slots used in the debug info, indexed by their SlotID.
+ Slots []LocalSlot
+ // The user variables, indexed by VarID.
+ Vars []GCNode
+ // The slots that make up each variable, indexed by VarID.
+ VarSlots [][]SlotID
+ // The location list data, indexed by VarID. Must be processed by PutLocationList.
+ LocationLists [][]byte
+
+ // Filled in by the user. Translates Block and Value ID to PC.
+ GetPC func(ID, ID) int64
+}
+
+type BlockDebug struct {
+ // Whether the block had any changes to user variables at all.
+ relevant bool
+ // State at the end of the block if it's fully processed. Immutable once initialized.
+ endState []liveSlot
+}
+
+// A liveSlot is a slot that's live in loc at entry/exit of a block.
+type liveSlot struct {
+ // An inlined VarLoc, so it packs into 16 bytes instead of 20.
+ Registers RegisterSet
+ StackOffset
+
+ slot SlotID
+}
+
+func (loc liveSlot) absent() bool {
+ return loc.Registers == 0 && !loc.onStack()
+}
+
+// StackOffset encodes whether a value is on the stack and if so, where. It is
+// a 31-bit integer followed by a presence flag at the low-order bit.
+type StackOffset int32
+
+func (s StackOffset) onStack() bool {
+ return s != 0
+}
+
+func (s StackOffset) stackOffsetValue() int32 {
+ return int32(s) >> 1
+}
+
+// stateAtPC is the current state of all variables at some point.
+type stateAtPC struct {
+ // The location of each known slot, indexed by SlotID.
+ slots []VarLoc
+ // The slots present in each register, indexed by register number.
+ registers [][]SlotID
+}
+
+// reset fills state with the live variables from live.
+func (state *stateAtPC) reset(live []liveSlot) {
+ slots, registers := state.slots, state.registers
+ for i := range slots {
+ slots[i] = VarLoc{}
+ }
+ for i := range registers {
+ registers[i] = registers[i][:0]
+ }
+ for _, live := range live {
+ slots[live.slot] = VarLoc{live.Registers, live.StackOffset}
+ if live.Registers == 0 {
+ continue
+ }
+
+ mask := uint64(live.Registers)
+ for {
+ if mask == 0 {
+ break
+ }
+ reg := uint8(bits.TrailingZeros64(mask))
+ mask &^= 1 << reg
+
+ registers[reg] = append(registers[reg], live.slot)
+ }
+ }
+ state.slots, state.registers = slots, registers
+}
+
+func (s *debugState) LocString(loc VarLoc) string {
+ if loc.absent() {
+ return "<nil>"
+ }
+
+ var storage []string
+ if loc.onStack() {
+ storage = append(storage, "stack")
+ }
+
+ mask := uint64(loc.Registers)
+ for {
+ if mask == 0 {
+ break
+ }
+ reg := uint8(bits.TrailingZeros64(mask))
+ mask &^= 1 << reg
+
+ storage = append(storage, s.registers[reg].String())
+ }
+ return strings.Join(storage, ",")
+}
+
+// A VarLoc describes the storage for part of a user variable.
+type VarLoc struct {
+ // The registers this variable is available in. There can be more than
+ // one in various situations, e.g. it's being moved between registers.
+ Registers RegisterSet
+
+ StackOffset
+}
+
+func (loc VarLoc) absent() bool {
+ return loc.Registers == 0 && !loc.onStack()
+}
+
+var BlockStart = &Value{
+ ID: -10000,
+ Op: OpInvalid,
+ Aux: "BlockStart",
+}
+
+var BlockEnd = &Value{
+ ID: -20000,
+ Op: OpInvalid,
+ Aux: "BlockEnd",
+}
+
+// RegisterSet is a bitmap of registers, indexed by Register.num.
+type RegisterSet uint64
+
+// logf prints debug-specific logging to stdout (always stdout) if the current
+// function is tagged by GOSSAFUNC (for ssa output directed either to stdout or html).
+func (s *debugState) logf(msg string, args ...interface{}) {
+ if s.f.PrintOrHtmlSSA {
+ fmt.Printf(msg, args...)
+ }
+}
+
+type debugState struct {
+ // See FuncDebug.
+ slots []LocalSlot
+ vars []GCNode
+ varSlots [][]SlotID
+ lists [][]byte
+
+ // The user variable that each slot rolls up to, indexed by SlotID.
+ slotVars []VarID
+
+ f *Func
+ loggingEnabled bool
+ registers []Register
+ stackOffset func(LocalSlot) int32
+ ctxt *obj.Link
+
+ // The names (slots) associated with each value, indexed by Value ID.
+ valueNames [][]SlotID
+
+ // The current state of whatever analysis is running.
+ currentState stateAtPC
+ liveCount []int
+ changedVars *sparseSet
+
+ // The pending location list entry for each user variable, indexed by VarID.
+ pendingEntries []pendingEntry
+
+ varParts map[GCNode][]SlotID
+ blockDebug []BlockDebug
+ pendingSlotLocs []VarLoc
+ liveSlots []liveSlot
+ liveSlotSliceBegin int
+ partsByVarOffset sort.Interface
+}
+
+func (state *debugState) initializeCache(f *Func, numVars, numSlots int) {
+ // One blockDebug per block. Initialized in allocBlock.
+ if cap(state.blockDebug) < f.NumBlocks() {
+ state.blockDebug = make([]BlockDebug, f.NumBlocks())
+ } else {
+ // This local variable, and the ones like it below, enable compiler
+ // optimizations. Don't inline them.
+ b := state.blockDebug[:f.NumBlocks()]
+ for i := range b {
+ b[i] = BlockDebug{}
+ }
+ }
+
+ // A list of slots per Value. Reuse the previous child slices.
+ if cap(state.valueNames) < f.NumValues() {
+ old := state.valueNames
+ state.valueNames = make([][]SlotID, f.NumValues())
+ copy(state.valueNames, old)
+ }
+ vn := state.valueNames[:f.NumValues()]
+ for i := range vn {
+ vn[i] = vn[i][:0]
+ }
+
+ // Slot and register contents for currentState. Cleared by reset().
+ if cap(state.currentState.slots) < numSlots {
+ state.currentState.slots = make([]VarLoc, numSlots)
+ } else {
+ state.currentState.slots = state.currentState.slots[:numSlots]
+ }
+ if cap(state.currentState.registers) < len(state.registers) {
+ state.currentState.registers = make([][]SlotID, len(state.registers))
+ } else {
+ state.currentState.registers = state.currentState.registers[:len(state.registers)]
+ }
+
+ // Used many times by mergePredecessors.
+ if cap(state.liveCount) < numSlots {
+ state.liveCount = make([]int, numSlots)
+ } else {
+ state.liveCount = state.liveCount[:numSlots]
+ }
+
+ // A relatively small slice, but used many times as the return from processValue.
+ state.changedVars = newSparseSet(numVars)
+
+ // A pending entry per user variable, with space to track each of its pieces.
+ numPieces := 0
+ for i := range state.varSlots {
+ numPieces += len(state.varSlots[i])
+ }
+ if cap(state.pendingSlotLocs) < numPieces {
+ state.pendingSlotLocs = make([]VarLoc, numPieces)
+ } else {
+ psl := state.pendingSlotLocs[:numPieces]
+ for i := range psl {
+ psl[i] = VarLoc{}
+ }
+ }
+ if cap(state.pendingEntries) < numVars {
+ state.pendingEntries = make([]pendingEntry, numVars)
+ }
+ pe := state.pendingEntries[:numVars]
+ freePieceIdx := 0
+ for varID, slots := range state.varSlots {
+ pe[varID] = pendingEntry{
+ pieces: state.pendingSlotLocs[freePieceIdx : freePieceIdx+len(slots)],
+ }
+ freePieceIdx += len(slots)
+ }
+ state.pendingEntries = pe
+
+ if cap(state.lists) < numVars {
+ state.lists = make([][]byte, numVars)
+ } else {
+ state.lists = state.lists[:numVars]
+ for i := range state.lists {
+ state.lists[i] = nil
+ }
+ }
+
+ state.liveSlots = state.liveSlots[:0]
+ state.liveSlotSliceBegin = 0
+}
+
+func (state *debugState) allocBlock(b *Block) *BlockDebug {
+ return &state.blockDebug[b.ID]
+}
+
+func (state *debugState) appendLiveSlot(ls liveSlot) {
+ state.liveSlots = append(state.liveSlots, ls)
+}
+
+func (state *debugState) getLiveSlotSlice() []liveSlot {
+ s := state.liveSlots[state.liveSlotSliceBegin:]
+ state.liveSlotSliceBegin = len(state.liveSlots)
+ return s
+}
+
+func (s *debugState) blockEndStateString(b *BlockDebug) string {
+ endState := stateAtPC{slots: make([]VarLoc, len(s.slots)), registers: make([][]SlotID, len(s.registers))}
+ endState.reset(b.endState)
+ return s.stateString(endState)
+}
+
+func (s *debugState) stateString(state stateAtPC) string {
+ var strs []string
+ for slotID, loc := range state.slots {
+ if !loc.absent() {
+ strs = append(strs, fmt.Sprintf("\t%v = %v\n", s.slots[slotID], s.LocString(loc)))
+ }
+ }
+
+ strs = append(strs, "\n")
+ for reg, slots := range state.registers {
+ if len(slots) != 0 {
+ var slotStrs []string
+ for _, slot := range slots {
+ slotStrs = append(slotStrs, s.slots[slot].String())
+ }
+ strs = append(strs, fmt.Sprintf("\t%v = %v\n", &s.registers[reg], slotStrs))
+ }
+ }
+
+ if len(strs) == 1 {
+ return "(no vars)\n"
+ }
+ return strings.Join(strs, "")
+}
+
+// BuildFuncDebug returns debug information for f.
+// f must be fully processed, so that each Value is where it will be when
+// machine code is emitted.
+func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset func(LocalSlot) int32) *FuncDebug {
+ if f.RegAlloc == nil {
+ f.Fatalf("BuildFuncDebug on func %v that has not been fully processed", f)
+ }
+ state := &f.Cache.debugState
+ state.loggingEnabled = loggingEnabled
+ state.f = f
+ state.registers = f.Config.registers
+ state.stackOffset = stackOffset
+ state.ctxt = ctxt
+
+ if state.loggingEnabled {
+ state.logf("Generating location lists for function %q\n", f.Name)
+ }
+
+ if state.varParts == nil {
+ state.varParts = make(map[GCNode][]SlotID)
+ } else {
+ for n := range state.varParts {
+ delete(state.varParts, n)
+ }
+ }
+
+ // Recompose any decomposed variables, and establish the canonical
+ // IDs for each var and slot by filling out state.vars and state.slots.
+
+ state.slots = state.slots[:0]
+ state.vars = state.vars[:0]
+ for i, slot := range f.Names {
+ state.slots = append(state.slots, slot)
+ if slot.N.IsSynthetic() {
+ continue
+ }
+
+ topSlot := &slot
+ for topSlot.SplitOf != nil {
+ topSlot = topSlot.SplitOf
+ }
+ if _, ok := state.varParts[topSlot.N]; !ok {
+ state.vars = append(state.vars, topSlot.N)
+ }
+ state.varParts[topSlot.N] = append(state.varParts[topSlot.N], SlotID(i))
+ }
+
+ // Recreate the LocalSlot for each stack-only variable.
+ // This would probably be better as an output from stackframe.
+ for _, b := range f.Blocks {
+ for _, v := range b.Values {
+ if v.Op == OpVarDef || v.Op == OpVarKill {
+ n := v.Aux.(GCNode)
+ if n.IsSynthetic() {
+ continue
+ }
+
+ if _, ok := state.varParts[n]; !ok {
+ slot := LocalSlot{N: n, Type: v.Type, Off: 0}
+ state.slots = append(state.slots, slot)
+ state.varParts[n] = []SlotID{SlotID(len(state.slots) - 1)}
+ state.vars = append(state.vars, n)
+ }
+ }
+ }
+ }
+
+ // Fill in the var<->slot mappings.
+ if cap(state.varSlots) < len(state.vars) {
+ state.varSlots = make([][]SlotID, len(state.vars))
+ } else {
+ state.varSlots = state.varSlots[:len(state.vars)]
+ for i := range state.varSlots {
+ state.varSlots[i] = state.varSlots[i][:0]
+ }
+ }
+ if cap(state.slotVars) < len(state.slots) {
+ state.slotVars = make([]VarID, len(state.slots))
+ } else {
+ state.slotVars = state.slotVars[:len(state.slots)]
+ }
+
+ if state.partsByVarOffset == nil {
+ state.partsByVarOffset = &partsByVarOffset{}
+ }
+ for varID, n := range state.vars {
+ parts := state.varParts[n]
+ state.varSlots[varID] = parts
+ for _, slotID := range parts {
+ state.slotVars[slotID] = VarID(varID)
+ }
+ *state.partsByVarOffset.(*partsByVarOffset) = partsByVarOffset{parts, state.slots}
+ sort.Sort(state.partsByVarOffset)
+ }
+
+ state.initializeCache(f, len(state.varParts), len(state.slots))
+
+ for i, slot := range f.Names {
+ if slot.N.IsSynthetic() {
+ continue
+ }
+ for _, value := range f.NamedValues[slot] {
+ state.valueNames[value.ID] = append(state.valueNames[value.ID], SlotID(i))
+ }
+ }
+
+ blockLocs := state.liveness()
+ state.buildLocationLists(blockLocs)
+
+ return &FuncDebug{
+ Slots: state.slots,
+ VarSlots: state.varSlots,
+ Vars: state.vars,
+ LocationLists: state.lists,
+ }
+}
+
+// liveness walks the function in control flow order, calculating the start
+// and end state of each block.
+func (state *debugState) liveness() []*BlockDebug {
+ blockLocs := make([]*BlockDebug, state.f.NumBlocks())
+
+ // Reverse postorder: visit a block after as many as possible of its
+ // predecessors have been visited.
+ po := state.f.Postorder()
+ for i := len(po) - 1; i >= 0; i-- {
+ b := po[i]
+
+ // Build the starting state for the block from the final
+ // state of its predecessors.
+ startState, startValid := state.mergePredecessors(b, blockLocs, nil)
+ changed := false
+ if state.loggingEnabled {
+ state.logf("Processing %v, initial state:\n%v", b, state.stateString(state.currentState))
+ }
+
+ // Update locs/registers with the effects of each Value.
+ for _, v := range b.Values {
+ slots := state.valueNames[v.ID]
+
+ // Loads and stores inherit the names of their sources.
+ var source *Value
+ switch v.Op {
+ case OpStoreReg:
+ source = v.Args[0]
+ case OpLoadReg:
+ switch a := v.Args[0]; a.Op {
+ case OpArg, OpPhi:
+ source = a
+ case OpStoreReg:
+ source = a.Args[0]
+ default:
+ if state.loggingEnabled {
+ state.logf("at %v: load with unexpected source op: %v (%v)\n", v, a.Op, a)
+ }
+ }
+ }
+ // Update valueNames with the source so that later steps
+ // don't need special handling.
+ if source != nil {
+ slots = append(slots, state.valueNames[source.ID]...)
+ state.valueNames[v.ID] = slots
+ }
+
+ reg, _ := state.f.getHome(v.ID).(*Register)
+ c := state.processValue(v, slots, reg)
+ changed = changed || c
+ }
+
+ if state.loggingEnabled {
+ state.f.Logf("Block %v done, locs:\n%v", b, state.stateString(state.currentState))
+ }
+
+ locs := state.allocBlock(b)
+ locs.relevant = changed
+ if !changed && startValid {
+ locs.endState = startState
+ } else {
+ for slotID, slotLoc := range state.currentState.slots {
+ if slotLoc.absent() {
+ continue
+ }
+ state.appendLiveSlot(liveSlot{slot: SlotID(slotID), Registers: slotLoc.Registers, StackOffset: slotLoc.StackOffset})
+ }
+ locs.endState = state.getLiveSlotSlice()
+ }
+ blockLocs[b.ID] = locs
+ }
+ return blockLocs
+}
+
+// mergePredecessors takes the end state of each of b's predecessors and
+// intersects them to form the starting state for b. It puts that state in
+// blockLocs, and fills state.currentState with it. If convenient, it returns
+// a reused []liveSlot, true that represents the starting state.
+// If previousBlock is non-nil, it registers changes vs. that block's end
+// state in state.changedVars. Note that previousBlock will often not be a
+// predecessor.
+func (state *debugState) mergePredecessors(b *Block, blockLocs []*BlockDebug, previousBlock *Block) ([]liveSlot, bool) {
+ // Filter out back branches.
+ var predsBuf [10]*Block
+ preds := predsBuf[:0]
+ for _, pred := range b.Preds {
+ if blockLocs[pred.b.ID] != nil {
+ preds = append(preds, pred.b)
+ }
+ }
+
+ if state.loggingEnabled {
+ // The logf below would cause preds to be heap-allocated if
+ // it were passed directly.
+ preds2 := make([]*Block, len(preds))
+ copy(preds2, preds)
+ state.logf("Merging %v into %v\n", preds2, b)
+ }
+
+ // TODO all the calls to this are overkill; only need to do this for slots that are not present in the merge.
+ markChangedVars := func(slots []liveSlot) {
+ for _, live := range slots {
+ state.changedVars.add(ID(state.slotVars[live.slot]))
+ }
+ }
+
+ if len(preds) == 0 {
+ if previousBlock != nil {
+ // Mark everything in previous block as changed because it is not a predecessor.
+ markChangedVars(blockLocs[previousBlock.ID].endState)
+ }
+ state.currentState.reset(nil)
+ return nil, true
+ }
+
+ p0 := blockLocs[preds[0].ID].endState
+ if len(preds) == 1 {
+ if previousBlock != nil && preds[0].ID != previousBlock.ID {
+ // Mark everything in previous block as changed because it is not a predecessor.
+ markChangedVars(blockLocs[previousBlock.ID].endState)
+ }
+ state.currentState.reset(p0)
+ return p0, true
+ }
+
+ baseID := preds[0].ID
+ baseState := p0
+
+ // If previous block is not a predecessor, its location information changes at boundary with this block.
+ previousBlockIsNotPredecessor := previousBlock != nil // If it's nil, no info to change.
+
+ if previousBlock != nil {
+ // Try to use previousBlock as the base state
+ // if possible.
+ for _, pred := range preds[1:] {
+ if pred.ID == previousBlock.ID {
+ baseID = pred.ID
+ baseState = blockLocs[pred.ID].endState
+ previousBlockIsNotPredecessor = false
+ break
+ }
+ }
+ }
+
+ if state.loggingEnabled {
+ state.logf("Starting %v with state from b%v:\n%v", b, baseID, state.blockEndStateString(blockLocs[baseID]))
+ }
+
+ slotLocs := state.currentState.slots
+ for _, predSlot := range baseState {
+ slotLocs[predSlot.slot] = VarLoc{predSlot.Registers, predSlot.StackOffset}
+ state.liveCount[predSlot.slot] = 1
+ }
+ for _, pred := range preds {
+ if pred.ID == baseID {
+ continue
+ }
+ if state.loggingEnabled {
+ state.logf("Merging in state from %v:\n%v", pred, state.blockEndStateString(blockLocs[pred.ID]))
+ }
+ for _, predSlot := range blockLocs[pred.ID].endState {
+ state.liveCount[predSlot.slot]++
+ liveLoc := slotLocs[predSlot.slot]
+ if !liveLoc.onStack() || !predSlot.onStack() || liveLoc.StackOffset != predSlot.StackOffset {
+ liveLoc.StackOffset = 0
+ }
+ liveLoc.Registers &= predSlot.Registers
+ slotLocs[predSlot.slot] = liveLoc
+ }
+ }
+
+ // Check if the final state is the same as the first predecessor's
+ // final state, and reuse it if so. In principle it could match any,
+ // but it's probably not worth checking more than the first.
+ unchanged := true
+ for _, predSlot := range baseState {
+ if state.liveCount[predSlot.slot] != len(preds) ||
+ slotLocs[predSlot.slot].Registers != predSlot.Registers ||
+ slotLocs[predSlot.slot].StackOffset != predSlot.StackOffset {
+ unchanged = false
+ break
+ }
+ }
+ if unchanged {
+ if state.loggingEnabled {
+ state.logf("After merge, %v matches b%v exactly.\n", b, baseID)
+ }
+ if previousBlockIsNotPredecessor {
+ // Mark everything in previous block as changed because it is not a predecessor.
+ markChangedVars(blockLocs[previousBlock.ID].endState)
+ }
+ state.currentState.reset(baseState)
+ return baseState, true
+ }
+
+ for reg := range state.currentState.registers {
+ state.currentState.registers[reg] = state.currentState.registers[reg][:0]
+ }
+
+ // A slot is live if it was seen in all predecessors, and they all had
+ // some storage in common.
+ for _, predSlot := range baseState {
+ slotLoc := slotLocs[predSlot.slot]
+
+ if state.liveCount[predSlot.slot] != len(preds) {
+ // Seen in only some predecessors. Clear it out.
+ slotLocs[predSlot.slot] = VarLoc{}
+ continue
+ }
+
+ // Present in all predecessors.
+ mask := uint64(slotLoc.Registers)
+ for {
+ if mask == 0 {
+ break
+ }
+ reg := uint8(bits.TrailingZeros64(mask))
+ mask &^= 1 << reg
+ state.currentState.registers[reg] = append(state.currentState.registers[reg], predSlot.slot)
+ }
+ }
+
+ if previousBlockIsNotPredecessor {
+ // Mark everything in previous block as changed because it is not a predecessor.
+ markChangedVars(blockLocs[previousBlock.ID].endState)
+
+ }
+ return nil, false
+}
+
+// processValue updates locs and state.registerContents to reflect v, a value with
+// the names in vSlots and homed in vReg. "v" becomes visible after execution of
+// the instructions evaluating it. It returns which VarIDs were modified by the
+// Value's execution.
+func (state *debugState) processValue(v *Value, vSlots []SlotID, vReg *Register) bool {
+ locs := state.currentState
+ changed := false
+ setSlot := func(slot SlotID, loc VarLoc) {
+ changed = true
+ state.changedVars.add(ID(state.slotVars[slot]))
+ state.currentState.slots[slot] = loc
+ }
+
+ // Handle any register clobbering. Call operations, for example,
+ // clobber all registers even though they don't explicitly write to
+ // them.
+ clobbers := uint64(opcodeTable[v.Op].reg.clobbers)
+ for {
+ if clobbers == 0 {
+ break
+ }
+ reg := uint8(bits.TrailingZeros64(clobbers))
+ clobbers &^= 1 << reg
+
+ for _, slot := range locs.registers[reg] {
+ if state.loggingEnabled {
+ state.logf("at %v: %v clobbered out of %v\n", v, state.slots[slot], &state.registers[reg])
+ }
+
+ last := locs.slots[slot]
+ if last.absent() {
+ state.f.Fatalf("at %v: slot %v in register %v with no location entry", v, state.slots[slot], &state.registers[reg])
+ continue
+ }
+ regs := last.Registers &^ (1 << reg)
+ setSlot(slot, VarLoc{regs, last.StackOffset})
+ }
+
+ locs.registers[reg] = locs.registers[reg][:0]
+ }
+
+ switch {
+ case v.Op == OpVarDef, v.Op == OpVarKill:
+ n := v.Aux.(GCNode)
+ if n.IsSynthetic() {
+ break
+ }
+
+ slotID := state.varParts[n][0]
+ var stackOffset StackOffset
+ if v.Op == OpVarDef {
+ stackOffset = StackOffset(state.stackOffset(state.slots[slotID])<<1 | 1)
+ }
+ setSlot(slotID, VarLoc{0, stackOffset})
+ if state.loggingEnabled {
+ if v.Op == OpVarDef {
+ state.logf("at %v: stack-only var %v now live\n", v, state.slots[slotID])
+ } else {
+ state.logf("at %v: stack-only var %v now dead\n", v, state.slots[slotID])
+ }
+ }
+
+ case v.Op == OpArg:
+ home := state.f.getHome(v.ID).(LocalSlot)
+ stackOffset := state.stackOffset(home)<<1 | 1
+ for _, slot := range vSlots {
+ if state.loggingEnabled {
+ state.logf("at %v: arg %v now on stack in location %v\n", v, state.slots[slot], home)
+ if last := locs.slots[slot]; !last.absent() {
+ state.logf("at %v: unexpected arg op on already-live slot %v\n", v, state.slots[slot])
+ }
+ }
+
+ setSlot(slot, VarLoc{0, StackOffset(stackOffset)})
+ }
+
+ case v.Op == OpStoreReg:
+ home := state.f.getHome(v.ID).(LocalSlot)
+ stackOffset := state.stackOffset(home)<<1 | 1
+ for _, slot := range vSlots {
+ last := locs.slots[slot]
+ if last.absent() {
+ if state.loggingEnabled {
+ state.logf("at %v: unexpected spill of unnamed register %s\n", v, vReg)
+ }
+ break
+ }
+
+ setSlot(slot, VarLoc{last.Registers, StackOffset(stackOffset)})
+ if state.loggingEnabled {
+ state.logf("at %v: %v spilled to stack location %v\n", v, state.slots[slot], home)
+ }
+ }
+
+ case vReg != nil:
+ if state.loggingEnabled {
+ newSlots := make([]bool, len(state.slots))
+ for _, slot := range vSlots {
+ newSlots[slot] = true
+ }
+
+ for _, slot := range locs.registers[vReg.num] {
+ if !newSlots[slot] {
+ state.logf("at %v: overwrote %v in register %v\n", v, state.slots[slot], vReg)
+ }
+ }
+ }
+
+ for _, slot := range locs.registers[vReg.num] {
+ last := locs.slots[slot]
+ setSlot(slot, VarLoc{last.Registers &^ (1 << uint8(vReg.num)), last.StackOffset})
+ }
+ locs.registers[vReg.num] = locs.registers[vReg.num][:0]
+ locs.registers[vReg.num] = append(locs.registers[vReg.num], vSlots...)
+ for _, slot := range vSlots {
+ if state.loggingEnabled {
+ state.logf("at %v: %v now in %s\n", v, state.slots[slot], vReg)
+ }
+
+ last := locs.slots[slot]
+ setSlot(slot, VarLoc{1<<uint8(vReg.num) | last.Registers, last.StackOffset})
+ }
+ }
+ return changed
+}
+
+// varOffset returns the offset of slot within the user variable it was
+// decomposed from. This has nothing to do with its stack offset.
+func varOffset(slot LocalSlot) int64 {
+ offset := slot.Off
+ s := &slot
+ for ; s.SplitOf != nil; s = s.SplitOf {
+ offset += s.SplitOffset
+ }
+ return offset
+}
+
+type partsByVarOffset struct {
+ slotIDs []SlotID
+ slots []LocalSlot
+}
+
+func (a partsByVarOffset) Len() int { return len(a.slotIDs) }
+func (a partsByVarOffset) Less(i, j int) bool {
+ return varOffset(a.slots[a.slotIDs[i]]) < varOffset(a.slots[a.slotIDs[j]])
+}
+func (a partsByVarOffset) Swap(i, j int) { a.slotIDs[i], a.slotIDs[j] = a.slotIDs[j], a.slotIDs[i] }
+
+// A pendingEntry represents the beginning of a location list entry, missing
+// only its end coordinate.
+type pendingEntry struct {
+ present bool
+ startBlock, startValue ID
+ // The location of each piece of the variable, in the same order as the
+ // SlotIDs in varParts.
+ pieces []VarLoc
+}
+
+func (e *pendingEntry) clear() {
+ e.present = false
+ e.startBlock = 0
+ e.startValue = 0
+ for i := range e.pieces {
+ e.pieces[i] = VarLoc{}
+ }
+}
+
+// canMerge reports whether the location description for new is the same as
+// pending.
+func canMerge(pending, new VarLoc) bool {
+ if pending.absent() && new.absent() {
+ return true
+ }
+ if pending.absent() || new.absent() {
+ return false
+ }
+ if pending.onStack() {
+ return pending.StackOffset == new.StackOffset
+ }
+ if pending.Registers != 0 && new.Registers != 0 {
+ return firstReg(pending.Registers) == firstReg(new.Registers)
+ }
+ return false
+}
+
+// firstReg returns the first register in set that is present.
+func firstReg(set RegisterSet) uint8 {
+ if set == 0 {
+ // This is wrong, but there seem to be some situations where we
+ // produce locations with no storage.
+ return 0
+ }
+ return uint8(bits.TrailingZeros64(uint64(set)))
+}
+
+// buildLocationLists builds location lists for all the user variables in
+// state.f, using the information about block state in blockLocs.
+// The returned location lists are not fully complete. They are in terms of
+// SSA values rather than PCs, and have no base address/end entries. They will
+// be finished by PutLocationList.
+func (state *debugState) buildLocationLists(blockLocs []*BlockDebug) {
+ // Run through the function in program text order, building up location
+ // lists as we go. The heavy lifting has mostly already been done.
+
+ var prevBlock *Block
+ for _, b := range state.f.Blocks {
+ state.mergePredecessors(b, blockLocs, prevBlock)
+
+ if !blockLocs[b.ID].relevant {
+ // Handle any differences among predecessor blocks and previous block (perhaps not a predecessor)
+ for _, varID := range state.changedVars.contents() {
+ state.updateVar(VarID(varID), b, BlockStart)
+ }
+ continue
+ }
+
+ zeroWidthPending := false
+ apcChangedSize := 0 // size of changedVars for leading Args, Phi, ClosurePtr
+ // expect to see values in pattern (apc)* (zerowidth|real)*
+ for _, v := range b.Values {
+ slots := state.valueNames[v.ID]
+ reg, _ := state.f.getHome(v.ID).(*Register)
+ changed := state.processValue(v, slots, reg) // changed == added to state.changedVars
+
+ if opcodeTable[v.Op].zeroWidth {
+ if changed {
+ if v.Op == OpArg || v.Op == OpPhi || v.Op.isLoweredGetClosurePtr() {
+ // These ranges begin at true beginning of block, not after first instruction
+ if zeroWidthPending {
+ b.Func.Fatalf("Unexpected op mixed with OpArg/OpPhi/OpLoweredGetClosurePtr at beginning of block %s in %s\n%s", b, b.Func.Name, b.Func)
+ }
+ apcChangedSize = len(state.changedVars.contents())
+ continue
+ }
+ // Other zero-width ops must wait on a "real" op.
+ zeroWidthPending = true
+ }
+ continue
+ }
+
+ if !changed && !zeroWidthPending {
+ continue
+ }
+ // Not zero-width; i.e., a "real" instruction.
+
+ zeroWidthPending = false
+ for i, varID := range state.changedVars.contents() {
+ if i < apcChangedSize { // buffered true start-of-block changes
+ state.updateVar(VarID(varID), v.Block, BlockStart)
+ } else {
+ state.updateVar(VarID(varID), v.Block, v)
+ }
+ }
+ state.changedVars.clear()
+ apcChangedSize = 0
+ }
+ for i, varID := range state.changedVars.contents() {
+ if i < apcChangedSize { // buffered true start-of-block changes
+ state.updateVar(VarID(varID), b, BlockStart)
+ } else {
+ state.updateVar(VarID(varID), b, BlockEnd)
+ }
+ }
+
+ prevBlock = b
+ }
+
+ if state.loggingEnabled {
+ state.logf("location lists:\n")
+ }
+
+ // Flush any leftover entries live at the end of the last block.
+ for varID := range state.lists {
+ state.writePendingEntry(VarID(varID), state.f.Blocks[len(state.f.Blocks)-1].ID, BlockEnd.ID)
+ list := state.lists[varID]
+ if state.loggingEnabled {
+ if len(list) == 0 {
+ state.logf("\t%v : empty list\n", state.vars[varID])
+ } else {
+ state.logf("\t%v : %q\n", state.vars[varID], hex.EncodeToString(state.lists[varID]))
+ }
+ }
+ }
+}
+
+// updateVar updates the pending location list entry for varID to
+// reflect the new locations in curLoc, beginning at v in block b.
+// v may be one of the special values indicating block start or end.
+func (state *debugState) updateVar(varID VarID, b *Block, v *Value) {
+ curLoc := state.currentState.slots
+ // Assemble the location list entry with whatever's live.
+ empty := true
+ for _, slotID := range state.varSlots[varID] {
+ if !curLoc[slotID].absent() {
+ empty = false
+ break
+ }
+ }
+ pending := &state.pendingEntries[varID]
+ if empty {
+ state.writePendingEntry(varID, b.ID, v.ID)
+ pending.clear()
+ return
+ }
+
+ // Extend the previous entry if possible.
+ if pending.present {
+ merge := true
+ for i, slotID := range state.varSlots[varID] {
+ if !canMerge(pending.pieces[i], curLoc[slotID]) {
+ merge = false
+ break
+ }
+ }
+ if merge {
+ return
+ }
+ }
+
+ state.writePendingEntry(varID, b.ID, v.ID)
+ pending.present = true
+ pending.startBlock = b.ID
+ pending.startValue = v.ID
+ for i, slot := range state.varSlots[varID] {
+ pending.pieces[i] = curLoc[slot]
+ }
+}
+
+// writePendingEntry writes out the pending entry for varID, if any,
+// terminated at endBlock/Value.
+func (state *debugState) writePendingEntry(varID VarID, endBlock, endValue ID) {
+ pending := state.pendingEntries[varID]
+ if !pending.present {
+ return
+ }
+
+ // Pack the start/end coordinates into the start/end addresses
+ // of the entry, for decoding by PutLocationList.
+ start, startOK := encodeValue(state.ctxt, pending.startBlock, pending.startValue)
+ end, endOK := encodeValue(state.ctxt, endBlock, endValue)
+ if !startOK || !endOK {
+ // If someone writes a function that uses >65K values,
+ // they get incomplete debug info on 32-bit platforms.
+ return
+ }
+ if start == end {
+ if state.loggingEnabled {
+ // Printf not logf so not gated by GOSSAFUNC; this should fire very rarely.
+ fmt.Printf("Skipping empty location list for %v in %s\n", state.vars[varID], state.f.Name)
+ }
+ return
+ }
+
+ list := state.lists[varID]
+ list = appendPtr(state.ctxt, list, start)
+ list = appendPtr(state.ctxt, list, end)
+ // Where to write the length of the location description once
+ // we know how big it is.
+ sizeIdx := len(list)
+ list = list[:len(list)+2]
+
+ if state.loggingEnabled {
+ var partStrs []string
+ for i, slot := range state.varSlots[varID] {
+ partStrs = append(partStrs, fmt.Sprintf("%v@%v", state.slots[slot], state.LocString(pending.pieces[i])))
+ }
+ state.logf("Add entry for %v: \tb%vv%v-b%vv%v = \t%v\n", state.vars[varID], pending.startBlock, pending.startValue, endBlock, endValue, strings.Join(partStrs, " "))
+ }
+
+ for i, slotID := range state.varSlots[varID] {
+ loc := pending.pieces[i]
+ slot := state.slots[slotID]
+
+ if !loc.absent() {
+ if loc.onStack() {
+ if loc.stackOffsetValue() == 0 {
+ list = append(list, dwarf.DW_OP_call_frame_cfa)
+ } else {
+ list = append(list, dwarf.DW_OP_fbreg)
+ list = dwarf.AppendSleb128(list, int64(loc.stackOffsetValue()))
+ }
+ } else {
+ regnum := state.ctxt.Arch.DWARFRegisters[state.registers[firstReg(loc.Registers)].ObjNum()]
+ if regnum < 32 {
+ list = append(list, dwarf.DW_OP_reg0+byte(regnum))
+ } else {
+ list = append(list, dwarf.DW_OP_regx)
+ list = dwarf.AppendUleb128(list, uint64(regnum))
+ }
+ }
+ }
+
+ if len(state.varSlots[varID]) > 1 {
+ list = append(list, dwarf.DW_OP_piece)
+ list = dwarf.AppendUleb128(list, uint64(slot.Type.Size()))
+ }
+ }
+ state.ctxt.Arch.ByteOrder.PutUint16(list[sizeIdx:], uint16(len(list)-sizeIdx-2))
+ state.lists[varID] = list
+}
+
+// PutLocationList adds list (a location list in its intermediate representation) to listSym.
+func (debugInfo *FuncDebug) PutLocationList(list []byte, ctxt *obj.Link, listSym, startPC *obj.LSym) {
+ getPC := debugInfo.GetPC
+
+ if ctxt.UseBASEntries {
+ listSym.WriteInt(ctxt, listSym.Size, ctxt.Arch.PtrSize, ^0)
+ listSym.WriteAddr(ctxt, listSym.Size, ctxt.Arch.PtrSize, startPC, 0)
+ }
+
+ // Re-read list, translating its address from block/value ID to PC.
+ for i := 0; i < len(list); {
+ begin := getPC(decodeValue(ctxt, readPtr(ctxt, list[i:])))
+ end := getPC(decodeValue(ctxt, readPtr(ctxt, list[i+ctxt.Arch.PtrSize:])))
+
+ // Horrible hack. If a range contains only zero-width
+ // instructions, e.g. an Arg, and it's at the beginning of the
+ // function, this would be indistinguishable from an
+ // end entry. Fudge it.
+ if begin == 0 && end == 0 {
+ end = 1
+ }
+
+ if ctxt.UseBASEntries {
+ listSym.WriteInt(ctxt, listSym.Size, ctxt.Arch.PtrSize, int64(begin))
+ listSym.WriteInt(ctxt, listSym.Size, ctxt.Arch.PtrSize, int64(end))
+ } else {
+ listSym.WriteCURelativeAddr(ctxt, listSym.Size, startPC, int64(begin))
+ listSym.WriteCURelativeAddr(ctxt, listSym.Size, startPC, int64(end))
+ }
+
+ i += 2 * ctxt.Arch.PtrSize
+ datalen := 2 + int(ctxt.Arch.ByteOrder.Uint16(list[i:]))
+ listSym.WriteBytes(ctxt, listSym.Size, list[i:i+datalen]) // copy datalen and location encoding
+ i += datalen
+ }
+
+ // Location list contents, now with real PCs.
+ // End entry.
+ listSym.WriteInt(ctxt, listSym.Size, ctxt.Arch.PtrSize, 0)
+ listSym.WriteInt(ctxt, listSym.Size, ctxt.Arch.PtrSize, 0)
+}
+
+// Pack a value and block ID into an address-sized uint, returning ~0 if they
+// don't fit.
+func encodeValue(ctxt *obj.Link, b, v ID) (uint64, bool) {
+ if ctxt.Arch.PtrSize == 8 {
+ result := uint64(b)<<32 | uint64(uint32(v))
+ //ctxt.Logf("b %#x (%d) v %#x (%d) -> %#x\n", b, b, v, v, result)
+ return result, true
+ }
+ if ctxt.Arch.PtrSize != 4 {
+ panic("unexpected pointer size")
+ }
+ if ID(int16(b)) != b || ID(int16(v)) != v {
+ return 0, false
+ }
+ return uint64(b)<<16 | uint64(uint16(v)), true
+}
+
+// Unpack a value and block ID encoded by encodeValue.
+func decodeValue(ctxt *obj.Link, word uint64) (ID, ID) {
+ if ctxt.Arch.PtrSize == 8 {
+ b, v := ID(word>>32), ID(word)
+ //ctxt.Logf("%#x -> b %#x (%d) v %#x (%d)\n", word, b, b, v, v)
+ return b, v
+ }
+ if ctxt.Arch.PtrSize != 4 {
+ panic("unexpected pointer size")
+ }
+ return ID(word >> 16), ID(int16(word))
+}
+
+// Append a pointer-sized uint to buf.
+func appendPtr(ctxt *obj.Link, buf []byte, word uint64) []byte {
+ if cap(buf) < len(buf)+20 {
+ b := make([]byte, len(buf), 20+cap(buf)*2)
+ copy(b, buf)
+ buf = b
+ }
+ writeAt := len(buf)
+ buf = buf[0 : len(buf)+ctxt.Arch.PtrSize]
+ writePtr(ctxt, buf[writeAt:], word)
+ return buf
+}
+
+// Write a pointer-sized uint to the beginning of buf.
+func writePtr(ctxt *obj.Link, buf []byte, word uint64) {
+ switch ctxt.Arch.PtrSize {
+ case 4:
+ ctxt.Arch.ByteOrder.PutUint32(buf, uint32(word))
+ case 8:
+ ctxt.Arch.ByteOrder.PutUint64(buf, word)
+ default:
+ panic("unexpected pointer size")
+ }
+
+}
+
+// Read a pointer-sized uint from the beginning of buf.
+func readPtr(ctxt *obj.Link, buf []byte) uint64 {
+ switch ctxt.Arch.PtrSize {
+ case 4:
+ return uint64(ctxt.Arch.ByteOrder.Uint32(buf))
+ case 8:
+ return ctxt.Arch.ByteOrder.Uint64(buf)
+ default:
+ panic("unexpected pointer size")
+ }
+
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-15 11:15:11 +0000