Change existing TRACE_DISABLE preprocessor define to TRACE_ENABLE.

Tracing remains enabled by default.

(adapted from github pull request #3645)

Closes #3645

(Internal change: 2379816)

Author: cvj

pxr/base/trace/overview.dox

@@ -174,7 +174,7 @@ Adding trace instrumentation macros has the following overhead:
     The dynamic versions of the macros TRACE_FUNCTION_DYNAMIC(), TRACE_SCOPE_DYNAMIC() have a much higher overhead than the static versions. The reason for this is that for the static versions, the names of the scopes are compiled as constexpr data, but the dynamic versions construct strings at runtime. This overhead of dynamic macros is true whether tracing is enabled or not. Because of this, the static versions should be preferred whenever possible.
     </li>
 </ul>
-It is possible to disable TRACE macros from generating code by defining TRACE_DISABLE in the preprocessor.
+It is possible to disable TRACE macros from generating code by defining TRACE_ENABLE to 0 in the preprocessor.  TRACE macros are enabled by default.
 
 The TraceCollector class and TRACE macros are thread-safe.
 

pxr/base/trace/trace.h

@@ -19,7 +19,11 @@
 
 #include <atomic>
 
-#if !defined(TRACE_DISABLE)
+#if !defined(TRACE_ENABLE)
+    #define TRACE_ENABLE 1
+#endif
+
+#if TRACE_ENABLE
 
 /// Records a timestamp when constructed and a timespan event when destructed,
 /// using the name of the function or method as the key.
@@ -166,7 +170,7 @@ PXR_NS::TraceAuto TF_PP_CAT(TraceAuto_, instance)(str)
 #define _TRACE_MARKER_DYNAMIC_INSTANCE(instance, name) \
     TraceCollector::GetInstance().MarkerEvent(name);
 
-#else // TRACE_DISABLE
+#else // TRACE_ENABLE
 
 #define TRACE_FUNCTION()
 #define TRACE_FUNCTION_DYNAMIC(name)
@@ -175,8 +179,10 @@ PXR_NS::TraceAuto TF_PP_CAT(TraceAuto_, instance)(str)
 #define TRACE_FUNCTION_SCOPE(name)
 #define TRACE_MARKER(name)
 #define TRACE_MARKER_DYNAMIC(name)
+#define TRACE_COUNTER_DELTA(name, delta)
+#define TRACE_COUNTER_VALUE(name, value)
 
-#endif // TRACE_DISABLE
+#endif // TRACE_ENABLE
 
 PXR_NAMESPACE_OPEN_SCOPE