- Faster include dependency caching (ToLowerInvariant() is faster than StringComparer.InvariantCultureIgnoreCase on all platforms)
- Cached off the list of FileInfos when requesting cached include dependencies (reduces string hash lookup spam)
- Moved an object lookup out of an inner loop
[CL 2399988 by Mike Fricker in Main branch]
- Adds experimental super-fast C++ outdated file checking
- This feature is turned off for now as we continue to test and improve it
- You can try it out by enabling "bUseExperimentalFastDependencyScan" option in your BuildConfiguration.xml
- Here is the basic idea:
- We no longer exhaustively scan all includes and build up a big graph every invocation
- Instead, source files whose build products are missing have their includes scanned asynchronously while being compiled
- The flat list of dependent includes for every outdated C++ is saved into a new cache file ("FlatCPPIncludes.bin")
- On the next run, we quickly load that up and "just know" which files to check timestamps on to determine what is out of date
- Lots of "@todo fastubt" comments were added to UnrealBuildTool for potential performance optimizations and further improvements on this feature.
UnrealBuildTool: Determination of which modules have UObjects is now faster
- We now cache which modules have UObjects and load those for the next session
UnrealBuildTool: Module "shared" precompiled header determination is now much faster
- We no longer scan all C++ includes for a module to figure out which "shared" PCH to use
- Instead, we use the module dependencies specified in the module's *.Build.cs file
- For example, if your module depends on "Engine" and "UnrealEd", we choose "UnrealEd"'s shared PCH
Other UBT optimizations:
- Reduced calls to string formatting functions when setting up API definitions for all modules
- Added new performance diagnostics when bPrintPerformanceInfo is enabled in BuildConfiguration.xml
- We no longer check for "external" headers when scanning includes (this code didn't work at all)
- Optimized CleanDirectorySeparators() utility function to avoid string copies
Fixed UnrealBuildTool not saving DependencyCache under a platform-named folder
[CL 2238266 by Mike Fricker in Main branch]
