cmd/trace/v2: emit regions in the goroutine-oriented task view

This change emits regions in the goroutine-oriented task view (the
/trace endpoint with the taskid query variable set) in the same way the
old cmd/trace does.

For #60773.
Fixes #63960.

Change-Id: If6c3e7072c694c84a7d2d6c34df668f48d3acc2a
Reviewed-on: https://go-review.googlesource.com/c/go/+/543995
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/trace/v2/gen.go

@@ -73,6 +73,11 @@ func runGenerator(ctx *traceContext, g generator, parsed *parsedTrace, opts *gen
 	}
 	for i, task := range opts.tasks {
 		emitTask(ctx, task, i)
+		if opts.mode&traceviewer.ModeGoroutineOriented != 0 {
+			for _, region := range task.Regions {
+				emitRegion(ctx, region)
+			}
+		}
 	}
 	g.Finish(ctx)
 }
@@ -130,6 +135,54 @@ func emitTask(ctx *traceContext, task *trace.UserTaskSummary, sortIndex int) {
 	}
 }
 
+// emitRegion emits goroutine-based slice events to the UI. The caller
+// must be emitting for a goroutine-oriented trace.
+//
+// TODO(mknyszek): Make regions part of the regular generator loop and
+// treat them like ranges so that we can emit regions in traces oriented
+// by proc or thread.
+func emitRegion(ctx *traceContext, region *trace.UserRegionSummary) {
+	if region.Name == "" {
+		return
+	}
+	// Collect information about the region.
+	var startStack, endStack tracev2.Stack
+	goroutine := tracev2.NoGoroutine
+	startTime, endTime := ctx.startTime, ctx.endTime
+	if region.Start != nil {
+		startStack = region.Start.Stack()
+		startTime = region.Start.Time()
+		goroutine = region.Start.Goroutine()
+	}
+	if region.End != nil {
+		endStack = region.End.Stack()
+		endTime = region.End.Time()
+		goroutine = region.End.Goroutine()
+	}
+	if goroutine == tracev2.NoGoroutine {
+		return
+	}
+	arg := struct {
+		TaskID uint64 `json:"taskid"`
+	}{
+		TaskID: uint64(region.TaskID),
+	}
+	ctx.AsyncSlice(traceviewer.AsyncSliceEvent{
+		SliceEvent: traceviewer.SliceEvent{
+			Name:     region.Name,
+			Ts:       ctx.elapsed(startTime),
+			Dur:      endTime.Sub(startTime),
+			Resource: uint64(goroutine),
+			Stack:    ctx.Stack(viewerFrames(startStack)),
+			EndStack: ctx.Stack(viewerFrames(endStack)),
+			Arg:      arg,
+		},
+		Category:       "Region",
+		Scope:          fmt.Sprintf("%x", region.TaskID),
+		TaskColorIndex: uint64(region.TaskID),
+	})
+}
+
 // Building blocks for generators.
 
 // stackSampleGenerator implements a generic handler for stack sample events.

src/internal/trace/traceviewer/emitter.go

@@ -317,6 +317,7 @@ type Emitter struct {
 	resources                    map[uint64]string
 	focusResource                uint64
 	tasks                        map[uint64]task
+	asyncSliceSeq                uint64
 }
 
 type task struct {
@@ -376,7 +377,6 @@ func (e *Emitter) slice(s SliceEvent, sectionID uint64, cname string) {
 		Arg:      s.Arg,
 		Cname:    cname,
 	})
-
 }
 
 type SliceEvent struct {
@@ -389,6 +389,50 @@ type SliceEvent struct {
 	Arg      any
 }
 
+func (e *Emitter) AsyncSlice(s AsyncSliceEvent) {
+	if !e.tsWithinRange(s.Ts) && !e.tsWithinRange(s.Ts+s.Dur) {
+		return
+	}
+	if e.filter != nil && !e.filter(s.Resource) {
+		return
+	}
+	cname := ""
+	if s.TaskColorIndex != 0 {
+		cname = pickTaskColor(s.TaskColorIndex)
+	}
+	e.asyncSliceSeq++
+	e.OptionalEvent(&format.Event{
+		Category: s.Category,
+		Name:     s.Name,
+		Phase:    "b",
+		Time:     viewerTime(s.Ts),
+		TID:      s.Resource,
+		ID:       e.asyncSliceSeq,
+		Scope:    s.Scope,
+		Stack:    s.Stack,
+		Cname:    cname,
+	})
+	e.OptionalEvent(&format.Event{
+		Category: s.Category,
+		Name:     s.Name,
+		Phase:    "e",
+		Time:     viewerTime(s.Ts + s.Dur),
+		TID:      s.Resource,
+		ID:       e.asyncSliceSeq,
+		Scope:    s.Scope,
+		Stack:    s.EndStack,
+		Arg:      s.Arg,
+		Cname:    cname,
+	})
+}
+
+type AsyncSliceEvent struct {
+	SliceEvent
+	Category       string
+	Scope          string
+	TaskColorIndex uint64 // Take on the same color as the task with this ID.
+}
+
 func (e *Emitter) Instant(i InstantEvent) {
 	if !e.tsWithinRange(i.Ts) {
 		return