cmd/compile/internal: use sparseSet, optimize isSynthetic

changedVars was functionally a set, but couldn't be iterated over
efficiently. In functions with many variables, the wasted iteration was
costly. Use a sparseSet instead.

(*gc.Node).String() is very expensive: it calls Sprintf, which does
reflection, etc, etc. Instead, just look at .Sym.Name, which is all we
care about.

Change-Id: Ib61cd7b5c796e1813b8859135e85da5bfe2ac686
Reviewed-on: https://go-review.googlesource.com/92402
Reviewed-by: David Chase <drchase@google.com>

diff --git a/src/cmd/compile/internal/gc/syntax.go b/src/cmd/compile/internal/gc/syntax.go
index 5e301b6271fe2aff3c3f6ad272ce3c6946324536..e120dccabfcb66ebd064c2c37637e0222b15d7b6 100644 (file)
--- a/src/cmd/compile/internal/gc/syntax.go
+++ b/src/cmd/compile/internal/gc/syntax.go
@@ -59,6 +59,11 @@ type Node struct {
        Etype types.EType // op for OASOP, etype for OTYPE, exclam for export, 6g saved reg, ChanDir for OTCHAN, for OINDEXMAP 1=LHS,0=RHS
 }
 
+func (n *Node) IsSynthetic() bool {
+       name := n.Sym.Name
+       return name[0] == '.' || name[0] == '~'
+}
+
 // IsAutoTmp indicates if n was created by the compiler as a temporary,
 // based on the setting of the .AutoTemp flag in n's Name.
 func (n *Node) IsAutoTmp() bool {

diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index b4fee75b745ab525c889203f1ceace966427b670..9bf4ef5968b04b597f5a1324ad4dac859b1eb4e1 100644 (file)
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -142,6 +142,7 @@ type Frontend interface {
 type GCNode interface {
        Typ() *types.Type
        String() string
+       IsSynthetic() bool
        StorageClass() StorageClass
 }
 

diff --git a/src/cmd/compile/internal/ssa/debug.go b/src/cmd/compile/internal/ssa/debug.go
index b58a90be5fadf2759a653ccbac8f4143faddee0e..95f7e092319ade2298815c753df49a6585012619 100644 (file)
--- a/src/cmd/compile/internal/ssa/debug.go
+++ b/src/cmd/compile/internal/ssa/debug.go
@@ -183,7 +183,7 @@ type debugState struct {
        // The current state of whatever analysis is running.
        currentState stateAtPC
        liveCount    []int
-       changedVars  []bool
+       changedVars  *sparseSet
 }
 
 func (state *debugState) initializeCache() {
@@ -226,7 +226,7 @@ func (state *debugState) initializeCache() {
        state.liveCount = make([]int, len(state.slots))
 
        // A relatively small slice, but used many times as the return from processValue.
-       state.changedVars = make([]bool, len(state.vars))
+       state.changedVars = newSparseSet(len(state.vars))
 
        // A pending entry per user variable, with space to track each of its pieces.
        nPieces := 0
@@ -310,7 +310,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset fu
        for i, slot := range f.Names {
                slot := slot
                state.slots[i] = &slot
-               if isSynthetic(&slot) {
+               if slot.N.IsSynthetic() {
                        continue
                }
 
@@ -338,7 +338,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset fu
 
        state.initializeCache()
        for i, slot := range f.Names {
-               if isSynthetic(&slot) {
+               if slot.N.IsSynthetic() {
                        continue
                }
                for _, value := range f.NamedValues[slot] {
@@ -357,13 +357,6 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset fu
        }
 }
 
-// isSynthetic reports whether if slot represents a compiler-inserted variable,
-// e.g. an autotmp or an anonymous return value that needed a stack slot.
-func isSynthetic(slot *LocalSlot) bool {
-       c := slot.N.String()[0]
-       return c == '.' || c == '~'
-}
-
 // liveness walks the function in control flow order, calculating the start
 // and end state of each block.
 func (state *debugState) liveness() []*BlockDebug {
@@ -519,16 +512,15 @@ func (state *debugState) mergePredecessors(b *Block, blockLocs []*BlockDebug) ([
 
        // A slot is live if it was seen in all predecessors, and they all had
        // some storage in common.
-       for slotID, slotLoc := range slotLocs {
-               // Not seen in any predecessor.
-               if slotLoc.absent() {
-                       continue
-               }
-               // Seen in only some predecessors. Clear it out.
+       for slotID := range p0 {
+               slotLoc := slotLocs[slotID]
+
                if state.liveCount[slotID] != len(preds) {
+                       // Seen in only some predecessors. Clear it out.
                        slotLocs[slotID] = VarLoc{}
                        continue
                }
+
                // Present in all predecessors.
                mask := uint64(slotLoc.Registers)
                for {
@@ -553,7 +545,7 @@ func (state *debugState) processValue(v *Value, vSlots []SlotID, vReg *Register)
        changed := false
        setSlot := func(slot SlotID, loc VarLoc) {
                changed = true
-               state.changedVars[state.slotVars[slot]] = true
+               state.changedVars.add(ID(state.slotVars[slot]))
                state.currentState.slots[slot] = loc
        }
 
@@ -860,13 +852,10 @@ func (state *debugState) buildLocationLists(Ctxt *obj.Link, blockLocs []*BlockDe
                        }
 
                        phisPending = false
-                       for varID := range state.changedVars {
-                               if !state.changedVars[varID] {
-                                       continue
-                               }
-                               state.changedVars[varID] = false
+                       for _, varID := range state.changedVars.contents() {
                                updateVar(VarID(varID), v, state.currentState.slots)
                        }
+                       state.changedVars.clear()
                }
 
        }

diff --git a/src/cmd/compile/internal/ssa/export_test.go b/src/cmd/compile/internal/ssa/export_test.go
index d1d6831eb3b813fd532e286ab7586d953b28a813..ac7a1b00e045bb1fc424a9caf9b846007c3a3214 100644 (file)
--- a/src/cmd/compile/internal/ssa/export_test.go
+++ b/src/cmd/compile/internal/ssa/export_test.go
@@ -79,6 +79,10 @@ func (d *DummyAuto) StorageClass() StorageClass {
        return ClassAuto
 }
 
+func (d *DummyAuto) IsSynthetic() bool {
+       return false
+}
+
 func (DummyFrontend) StringData(s string) interface{} {
        return nil
 }