added support for trace regions (#984)

- Introduces a UE-trace Region primitive in `zencore/trace.{h,cpp}` for marking named, potentially long-running intervals of work that Unreal Insights render as banners in the timeline, separately from CPU scopes.
- New API:
  - `uint64_t TraceBeginRegion(RegionName, Category={})` / `void TraceEndRegion(RegionId)` for manual begin/end pairs.
  - `ScopedTraceRegion` RAII helper plus `ZEN_TRACE_REGION(name)` / `ZEN_TRACE_REGION_CAT(name, category)` macros for scope-based use.
  - Emits the `Misc.RegionBeginWithId` / `Misc.RegionEndWithId` trace events (paired by a `GetHifreqTimerValue()`-derived id).
  - Full no-op fallback under `#if !ZEN_WITH_TRACE` so callers compile in all configurations.
- Annotates `GcScheduler::CollectGarbage` with `ZEN_TRACE_REGION_CAT("GcScheduler::CollectGarbage", "gc")` as a first caller — makes GC passes visible as banners in Insights without relying on the existing `ZEN_TRACE_CPU` scope alone (which doesn't render as a region).

1 files changed, 44 insertions, 0 deletions

diff --git a/src/zencore/trace.cpp b/src/zencore/trace.cpp
index d7084bbd1..6e2eea1c7 100644
--- a/src/zencore/trace.cpp
+++ b/src/zencore/trace.cpp
@@ -8,6 +8,7 @@
 #	include <zencore/string.h>
 #	include <zencore/thread.h>
 #	include <zencore/logging.h>
+#	include <zencore/timer.h>
 
 #	define TRACE_IMPLEMENT 1
 #	undef _WINSOCK_DEPRECATED_NO_WARNINGS
@@ -25,6 +26,21 @@
 #	include <zencore/memory/fmalloc.h>
 #	include <zencore/memory/memorytrace.h>
 
+namespace {
+
+TRACE_EVENT_BEGIN(Misc, RegionBeginWithId, NoSync)
+TRACE_EVENT_FIELD(uint64, CycleAndId)
+TRACE_EVENT_FIELD(uint8[], RegionName)
+TRACE_EVENT_FIELD(uint8[], Category)
+TRACE_EVENT_END()
+
+TRACE_EVENT_BEGIN(Misc, RegionEndWithId, NoSync)
+TRACE_EVENT_FIELD(uint64, Cycle)
+TRACE_EVENT_FIELD(uint64, RegionId)
+TRACE_EVENT_END()
+
+}  // namespace
+
 namespace zen {
 
 void
@@ -164,6 +180,34 @@ TraceStop()
 	return false;
 }
 
+uint64_t
+TraceBeginRegion(std::string_view RegionName, std::string_view Category)
+{
+	uint64_t RegionId = GetHifreqTimerValue();
+	TRACE_LOG(Misc, RegionBeginWithId, true) << RegionBeginWithId.CycleAndId(RegionId)
+											 << RegionBeginWithId.RegionName(reinterpret_cast<const uint8*>(RegionName.data()),
+																			 int32_t(RegionName.size()))
+											 << RegionBeginWithId.Category(reinterpret_cast<const uint8*>(Category.data()),
+																		   int32_t(Category.size()));
+	return RegionId;
+}
+
+void
+TraceEndRegion(uint64_t RegionId)
+{
+	TRACE_LOG(Misc, RegionEndWithId, true) << RegionEndWithId.Cycle(GetHifreqTimerValue()) << RegionEndWithId.RegionId(RegionId);
+}
+
+ScopedTraceRegion::ScopedTraceRegion(std::string_view RegionName, std::string_view Category)
+: m_RegionId(TraceBeginRegion(RegionName, Category))
+{
+}
+
+ScopedTraceRegion::~ScopedTraceRegion()
+{
+	TraceEndRegion(m_RegionId);
+}
+
 bool
 GetTraceOptionsFromCommandline(TraceOptions& OutOptions)
 {