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Prior to this patch, in the Gen4 and Gen5 GS, we used GRF 0 (called
"R0" in the code) as a staging area to prepare the message header for
the FF_SYNC and URB_WRITE messages. This cleverly avoided an
unnecessary MOV operation (since the initial value of GRF 0 contains
data that needs to be included in the message header), but it made the
code confusing, since GRF 0 could no longer be relied upon to contain
its initial value once the GS started preparing its first message.
This patch avoids confusion by using a separate register ("header") as
the staging area, at the cost of one MOV instruction.
Worse yet, prior to this patch, the GS would completely overwrite the
contents of GRF 0 with the writeback data it received from a completed
FF_SYNC or URB_WRITE message. It did this because DWORD 0 of the
writeback data contains the new URB handle, and that neds to be
included in DWORD 0 of the next URB_WRITE message header. However,
that caused the rest of the message header to be corrupted either with
undefined data or zeros. Astonishingly, this did not produce any
known failures (probably by dumb luck). However, it seems really
dodgy--corrupting FFTID in particular seems likely to cause GPU hangs.
This patch avoids the corruption by storing the writeback data in a
temporary register and then copying just DWORD 0 to the header for the
next message. This costs one extra MOV instruction per message sent,
except for the final message.
Also, this patch moves the logic for overriding DWORD 2 of the header
(which contains PrimType, PrimStart, PrimEnd, and some other data that
we don't care about yet). This logic is now in the function
brw_gs_overwrite_header_dw2() rather than in brw_gs_emit_vue(). This
saves one MOV instruction in brw_gs_quads() and brw_gs_quad_strip(),
and paves the way for the Gen6 GS, which will need more complex logic
to override DWORD 2 of the header.
Finally, the function brw_gs_alloc_regs() contained a benign bug: it
neglected to increment the register counter when allocating space for
the "temp" register. This turned out not to have any effect because
the temp register wasn't used on Gen4 and Gen5, the only hardware
models (so far) to require a GS program. Now, all the registers
allocated by brw_gs_alloc_regs() are actually used, and properly
accounted for.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
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File: docs/README.WIN32 Last updated: 23 April 2011 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons osmesa mesagdi to build classic mesa Windows GDI drivers; or 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. 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.