Attila CPU Performance Fix

Source code for the Total War: ATTILA CPU performance mod: a dinput8.dll that the game loads at startup and that patches the engine in memory. No game files are changed.

Download the ready-made DLL:

• Nexus Mods: https://www.nexusmods.com/totalwarattila/mods/168
• Steam Workshop: https://steamcommunity.com/sharedfiles/filedetails/?id=3824249154 (after subscribing, run install.bat in the mod's folder)

Created with the help of AI (Claude by Anthropic). Tested in game by JGdaCaesar.

What each file does

File	Fix
heapfix.c	Entry point (DllMain, or a DLL load notification when something loaded dinput8.dll before the game DLL), dinput8 forwarding, heapfix.log, and the main fix: replaces the game's single-lock dlmalloc heap with mimalloc for blocks up to 16 KB (its own 512-768 MB reservation); larger blocks stay on the game's dlmalloc
pool.c	Faster free lookup for the engine's small-object pools
sortfix.c	The two render-list sorts (by +0x6C/+0x68 and +0x4C/+0x48): key extraction plus radix sort, same order as the game's sorts
batchfix.c	Battle draw batching: items with the same material and equal variant values share a batch
campfix.c	Campaign map: four x87 rounding-mode blocks (fog of war, terrain height, curve table)
x87fix.c	The same x87 rounding idiom at the ~1,280 other sites in the engine (fisttp / SSE4.1 roundss)
heightcache.c	Cache for repeated terrain height queries on the main thread
memfast.c	Fast path for the engine's memcpy on copies of 64 bytes or less
loopfetch.c	Six battle render loops prefetch the field the loop reads next, four items ahead (prefetch only, never a load through an item pointer)
fileio.c	Loading: .pack files opened without FILE_FLAG_NO_BUFFERING; small reads of read-only files in the game's user folder (the unpacked save) served from a 64 KB buffer, file position kept exactly
attrcache.c	Loading: cache of missing loose-file folders behind the game's GetFileAttributesW and read-only CreateFileW calls. Every folder above a cached name is watched (FindFirstChangeNotification); any change clears the cache. Answers and last-error values are the same as Windows'
texfix.c	Battle loading: the DXT1 compressor for unit imposters (FUN_118e8390 / FUN_1192eee0) redone with SSE2, byte-identical output
fps.c	Hook on the per-frame function that runs the rounding-mode safety checks of campfix.c and x87fix.c
diag.c	Diagnostics in heapfix.log: mod version, game build, system, settings, other hook DLLs, and crash records (a vectored exception handler that only logs and never handles the exception)
dinput8.def	The exports a dinput8.dll must have

Every patch first compares the game's bytes at its address with what it expects, and skips itself (and says so in heapfix.log) if they differ. So on another game version it does nothing.

Building

You need:

• llvm-mingw (the release used: 20261006, UCRT, x86_64 host), with its bin folder on PATH
• the mimalloc v3.5.3 source, in a folder named mimalloc next to build.bat (or set MIMALLOC to its path)

Then run:

build.bat

The DLL lands in build\dinput8.dll. The build is reproducible: with the same llvm-mingw and mimalloc versions you should get exactly the same file as the one on Nexus. Compare the SHA-256 (certutil -hashfile build\dinput8.dll SHA256) with the one given for each release.

Automated builds

Every commit is also built on GitHub's own machines by .github/workflows/build.yml, with the compiler and mimalloc downloaded from their official releases (checksums pinned). Open the latest run under Actions: its summary shows the SHA-256 of the DLL, which matches the Nexus download for the same version, and the DLL itself can be downloaded there. Builds also carry a signed build attestation (gh attestation verify dinput8.dll -R JSa25/AttilaCPUPerfFix).

Tests

The tests run the game's own code next to the replacements on millions of inputs and check the results are identical (diag_test instead checks the crash records on deliberate faults; lateload_test loads the built DLL before the game DLL, as an overlay can, and checks every fix still installs from Windows' load notification; loopfetch_test runs each prefetch stub over arrays that end at a no-access page, with stale pointers in the slots a loop never reaches, and checks every register matches the original instructions; fileio_test and attrcache_test compare against plain Windows calls on a temporary folder tree while files and folders are created, renamed and deleted, and attrcache_test also runs with the folder watches ignored to show it catches a stale cache). They read your copy of the game's empire.retail.dll (it is not included here):

build.bat test "C:\...\steamapps\common\Total War Attila\empire.retail.dll"

License

See LICENSE. mimalloc is (c) Microsoft Corporation and Daan Leijen, MIT license (third_party/mimalloc-LICENSE.txt).