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cmd/compile/internal/ssa: only store relevant slots in pendingEntries

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For functions with many local variables, keeping track of every
LocalSlot for every variable is very expensive. Only track the slots
that are actually used by a given variable.

Change-Id: Iaafbce030a782b8b8c4a0eb7cf025e59af899ea4
Reviewed-on: https://go-review.googlesource.com/92400
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Heschi Kreinick 2018-01-31 16:30:16 -05:00
parent a306341db7
commit 9c854d65a3
1 changed files with 22 additions and 15 deletions
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37
src/cmd/compile/internal/ssa/debug.go
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@ -214,10 +214,14 @@ func (state *debugState) initializeCache() {
state.changedVars = make([]bool, len(state.vars))
// A pending entry per user variable, with space to track each of its pieces.
if want := len(state.vars) * len(state.slots); cap(state.cache.pendingSlotLocs) < want {
state.cache.pendingSlotLocs = make([]VarLoc, want)
nPieces := 0
for i := range state.varSlots {
nPieces += len(state.varSlots[i])
}
psl := state.cache.pendingSlotLocs[:len(state.vars)*len(state.slots)]
if cap(state.cache.pendingSlotLocs) < nPieces {
state.cache.pendingSlotLocs = make([]VarLoc, nPieces)
}
psl := state.cache.pendingSlotLocs[:nPieces]
for i := range psl {
psl[i] = VarLoc{}
}
@ -225,10 +229,12 @@ func (state *debugState) initializeCache() {
state.cache.pendingEntries = make([]pendingEntry, len(state.vars))
}
pe := state.cache.pendingEntries[:len(state.vars)]
for varID := range pe {
freePieceIdx := 0
for varID, slots := range state.varSlots {
pe[varID] = pendingEntry{
pieces: state.cache.pendingSlotLocs[varID*len(state.slots) : (varID+1)*len(state.slots)],
pieces: state.cache.pendingSlotLocs[freePieceIdx : freePieceIdx+len(slots)],
}
freePieceIdx += len(slots)
}
}
@ -657,9 +663,8 @@ func (a partsByVarOffset) Swap(i, j int) { a.slotIDs[i], a.slotIDs[j] = a.slotID
type pendingEntry struct {
present bool
startBlock, startValue ID
// The location of each piece of the variable, indexed by *SlotID*,
// even though only a few slots are used in each entry. This could be
// improved by only storing the relevant slots.
// The location of each piece of the variable, in the same order as the
// SlotIDs in varParts.
pieces []VarLoc
}
@ -736,14 +741,14 @@ func (state *debugState) buildLocationLists(Ctxt *obj.Link, blockLocs []*BlockDe
if state.loggingEnabled {
var partStrs []string
for _, slot := range state.varSlots[varID] {
partStrs = append(partStrs, fmt.Sprintf("%v@%v", state.slots[slot], state.LocString(pending.pieces[slot])))
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 _, slotID := range state.varSlots[varID] {
loc := pending.pieces[slotID]
for i, slotID := range state.varSlots[varID] {
loc := pending.pieces[i]
slot := state.slots[slotID]
if !loc.absent() {
@ -795,8 +800,8 @@ func (state *debugState) buildLocationLists(Ctxt *obj.Link, blockLocs []*BlockDe
// Extend the previous entry if possible.
if pending.present {
merge := true
for _, slotID := range state.varSlots[varID] {
if !canMerge(pending.pieces[slotID], curLoc[slotID]) {
for i, slotID := range state.varSlots[varID] {
if !canMerge(pending.pieces[i], curLoc[slotID]) {
merge = false
break
}
@ -810,7 +815,9 @@ func (state *debugState) buildLocationLists(Ctxt *obj.Link, blockLocs []*BlockDe
pending.present = true
pending.startBlock = v.Block.ID
pending.startValue = v.ID
copy(pending.pieces, curLoc)
for i, slot := range state.varSlots[varID] {
pending.pieces[i] = curLoc[slot]
}
return
}