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The hardware documentation relating to the UAV HW-assisted coherency mechanism and UAV access enable bits is scarce and sometimes contradictory, and there's quite some guesswork behind this commit, so let me summarize the background first: HSW and later hardware have infrastructure to support a stricter form of data coherency between shader invocations from separate primitives. The mechanism is controlled by the "Accesses UAV" bits on 3DSTATE_VS, _HS, _DS, _GS and _PS (or _PS_EXTRA on BDW+), and the "UAV Coherency Required" bit on the 3DPRIMITIVE command. Regardless of whether "UAV Coherency Required" is set, the hardware fixed-function units will increment a per-stage semaphore for each request received if "Accesses UAV" is set for the same or any lower stage. An implicit DC flush is emitted by the lowermost stage with "Accesses UAV" set once it's done processing the request, this also happens regardless of the value of "UAV Coherency Required". The completion of the DC flush will cause the same stage and all previous ones to decrement the semaphore, marking the UAV accesses for the primitive as coherent with L3. The "UAV Coherency Required" 3DPRIMITIVE bit will cause a pipeline stall before any threads are dispatched for the first FF stage with "Accesses UAV" set until the semaphore is cleared for the same stage. Effectively this guarantees that UAV memory accesses performed by previous primitives from any stage will be strictly ordered (and thanks to the implicit DC flush visible in memory) with UAV accesses from the following primitives. None of this is required by the usual image, atomic counter and SSBO GL APIs which have very relaxed cross-primitive coherency and ordering requirements, so we don't actually ever set the "UAV Coherency Required" bit -- Ordering with respect to shader invocations from previous stages on the same primitive where there is a data dependency is of course already guaranteed as the spec requires, regardless of this mechanism being enabled. We do set the "Accesses UAV" bits though since my commit |
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File: docs/README.WIN32 Last updated: 21 June 2013 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons libgl-gdi to build gallium based GDI driver. This will work both with MSVS or Mingw. Windows Drivers ------- ------- At this time, only the gallium GDI driver is known to work. Source code also exists in the tree for other drivers in src/mesa/drivers/windows, but the status of this code is unknown. Recipe ------ Building on windows requires several open-source packages. These are steps that work as of this writing. - install python 2.7 - install scons (latest) - install mingw, flex, and bison - install pywin32 from here: http://www.lfd.uci.edu/~gohlke/pythonlibs get pywin32-218.4.win-amd64-py2.7.exe - install git - download mesa from git see http://www.mesa3d.org/repository.html - run scons General ------- After building, you can copy the above DLL files to a place in your PATH such as $SystemRoot/SYSTEM32. If you don't like putting things in a system directory, place them in the same directory as the executable(s). Be careful about accidentially overwriting files of the same name in the SYSTEM32 directory. The DLL files are built so that the external entry points use the stdcall calling convention. Static LIB files are not built. The LIB files that are built with are the linker import files associated with the DLL files. The si-glu sources are used to build the GLU libs. This was done mainly to get the better tessellator code. If you have a Windows-related build problem or question, please post to the mesa-dev or mesa-users list.