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We use this logic to detect live ranges and then do plain renaming across the whole codebase. As such, to prevent WaW hazards, we have to treat a write as if it were also a read. For example, the following sequence was observed before this patch: 13: UIF TEMP[6].xxxx :0 14: ADD TEMP[6].x, CONST[6].xxxx, -IN[3].yyyy 15: RCP TEMP[7].x, TEMP[3].xxxx 16: MUL TEMP[3].x, TEMP[6].xxxx, TEMP[7].xxxx 17: ADD TEMP[6].x, CONST[7].xxxx, -IN[3].yyyy 18: RCP TEMP[7].x, TEMP[3].xxxx 19: MUL TEMP[4].x, TEMP[6].xxxx, TEMP[7].xxxx While after this patch it becomes: 13: UIF TEMP[7].xxxx :0 14: ADD TEMP[7].x, CONST[6].xxxx, -IN[3].yyyy 15: RCP TEMP[8].x, TEMP[3].xxxx 16: MUL TEMP[4].x, TEMP[7].xxxx, TEMP[8].xxxx 17: ADD TEMP[7].x, CONST[7].xxxx, -IN[3].yyyy 18: RCP TEMP[8].x, TEMP[3].xxxx 19: MUL TEMP[5].x, TEMP[7].xxxx, TEMP[8].xxxx Most importantly note that in the first example, the second RCP is done on the result of the MUL while in the second, the second RCP should have the same value as the first. Looking at the GLSL source, it is apparent that both of the RCP's should have had the same source. Looking at what's going on, the GLSL looks something like float tmin_8; float tmin_10; tmin_10 = tmin_8; ... lots of code ... tmin_8 = tmpvar_17; ... more code that never looks at tmin_8 ... And so we end up with a last_read somewhere at the beginning, and a first_write somewhere at the bottom. For some reason DCE doesn't remove it, but even if that were fixed, DCE doesn't handle 100% of cases, esp including loops. With the last_read somewhere high up, we overwrite the previously correct (and large) last_read with a low one, and then proceed to decide to merge all kinds of junk onto this temp. Even if that weren't the case, and there were just some writes after the last read, then we might still overwrite a merged value with one of those. As a result, we should treat a write as a last_read for the purpose of determining the live range. Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu> Reviewed-by: Dave Airlie <airlied@redhat.com> Cc: mesa-stable@lists.freedesktop.org |
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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.