Why do this:
Currently when compiling a cpp file with MSVC, it compiles across multiple cores while clang does not. This means that while we support limiting the number of cores(using ProcessorCountMultiplier), MSVC will use more cores than we specify. It also means that MSVC will always be faster when compiling because clang does not support compiling a cpp over multiple cores. To get similiar results when compiling with clang, we set the weight of MSVC to 1.5 and the weight of clang to 1.0. We then set the ProcessorCountMultiplier to 1.5. This results in MSVC and clang taking roughly the same amount of CPU utilization and clang compiles to be much faster.
Old Timing(secs) Old CPU Utilization New Timing New CPU Utilization(secs)
PlatformA AncientGame 590.94 51 431.47 73
MSVC AncientGameEditor 1016.96 94 1026.08 95
Clang AncientGameEditor 1543.72 63 1270.4 84
PlatformB AncientGame 494 52 396.95 74
Old = without weight path
New = with weight path
#jira
#rb christopher.waters, joe.kirchoff
#preflight 6409026c8832f48a4dc72025
[CL 24567859 by bryan sefcik in ue5-main branch]
* Fixed so -SingleFile includes running prereq actions if they are not up to date.
#preflight skipped
#rb joe.kirchoff
#jira none
[CL 24239919 by henrik karlsson in ue5-main branch]
* Changed so clang single file placeholder action is not having any produced items.. this means that ubt modes that looks for produced items won't find anything on the placeholder actions
#preflight skipped
#rb joe.kirchoff
[CL 24136526 by henrik karlsson in ue5-main branch]
* Disabled -SingleFile option when building for multiple architectures at once... this can be implemented if someone needs it but require a bit of work
* Enabled -SingleFile option for apple platforms
#preflight skipped
#rb zach.neyland
#jira none
[CL 24129855 by henrik karlsson in ue5-main branch]
-SingleFile=... will not work for the time being, but this at least resolves horde build failures.
#jira UE-176814
#preflight na
[CL 24128134 by zack neyland in ue5-main branch]
Changed how single files are built. We don't want to invalidate makefile everytime we build single files since it destroys turnaround times. With this change a single file compile can take 2s (+ the actual compile time).
The new behavior injects a special action per module when creating the makefile. These actions can be used to on-the-fly create a proper compile action that follows the rules of the module that the specific file belongs to.. In a normal build these actions are ignored since the logic deciding which actions to build is backtraced from which binaries we want to create.
When a specific file compile is triggered, the logic deciding which files to build search up all these special actions and create a lookup based on which folders the special actions handle. It then try to find the special action that handles the specific file. The matching special action then creates a compile action that can handle that specific file and then queue up the action for execution. If no special action is found it falls back to try to use actions that have this specific file as input (ispc files for example)
Details:
* Removed lots of custom code for "specific files" handling
* Changed so pch (both private and shared) always use definition file. Added #pragma once and change so pch wrapper file include definition file. This made the adaptive path and specific file easy to implement (just disable pch in compile environment and it will just work)
* Added SingleFileAction for both VCToolChain and ClangToolChain. It now works to compile specific headers and cpp files. (It creates wrapper files on the fly to be able to compile all header files (compiling headers directly blow up if there are circular includes)
* Fixed so GenerateClangDatabase mode works with new changes
* Moved the logic that makes sure all (directly) depending cpp files are recompiled when .h are included in the singlefile option
#preflight 63dcc46f78716a01e8069649
#rb joe.kirchoff
[CL 24094027 by henrik karlsson in ue5-main branch]
* Turned off shared response file for apple platforms to fix compile errors. Need to be revisited
#preflight skipped
#rb none
#jira none
[CL 23943727 by henrik karlsson in ue5-main branch]
* Added support for additional response files (will be used by header units)
* Added support for shared response files and changed so normal cpp/h build path uses it if toolchain supports it.
* Enabled shared response files on all platforms but android (which doesnt seem to support reponse files including response files)
* Some cleanup in the iwyu toolchain related to shared rsp files
#preflight 63d9af169b3bb6a66cec9a8e
#rb joe.kirchoff
[CL 23943501 by henrik karlsson in ue5-main branch]
* Fixed so only colliding headers gets hash suffix for files in immediate folder
#preflight 63d86e11f626715201a3daa5
#rb joe.kirchoff
[CL 23924099 by henrik karlsson in ue5-main branch]
* Submitted binaries and tps
* Changed so iwyu toolchain is using this new path
#preflight skipped
#rb none
[CL 23898321 by henrik karlsson in ue5-main branch]
- Creates the UnrealArchitectures class, which wraps a list of UnrealArch objects
- UnrealArch is a single architecture, expandable enum-like struct
- There is no more concept of "no/default architecture", there is always a valid active architecture when building
- Most uses of "string Architecture" are replaced with one of the two above, depending if multiple architectures are supported or not
- UnrealArch has some platform-extensions for platform-specific naming (like Linux adds in LinuxName that turns, for instance, Arm64 -> aarch64-unknown-linux-gnueabi, which is used in folder names, etc)
- UnrealArch has bIsX64 which can be used determine intel instruction set (as opposed to arm)
- TargetRules class has an "Architecture" accessor that will return a single architecture if the active architectures is a single architecture, or throw an exception if multiple. This is useful in a majority of the cases where a paltform can only have a single architecture active in TargetRules (microsoft platforms, for instance, will create separate targets when compiling multiple architectures at once)
- Added UnrealArchitectureConfig class, which contains all the architecture information for a platform (what architectures are supported, what ones are currently active for given project, etc)
#preflight 63c81fb5b065224750a1759e
#rb mike.fricker,roman.dzieciol,joe.kirchoff,dmytro.vovk,brandon.schaefer [various parts]
#p4v-preflight-copy 23562471
[CL 23829977 by josh adams in ue5-main branch]
