Paul Berry
a33ce665a5
This patch is a band-aid fix for a bug in commit 5fd67fa (i965/blorp:
Reduce alignment restrictions for stencil blits), which causes
multisampled stencil blits to work incorrectly on Sandy Bridge.
When blitting to or from a normal stencil buffer, we have to use a
coordinate transformation that swizzles coordinates to account for the
fact that stencil buffers use W tiling, but the most similar tiling
format available for textures and render targets is Y tiling. The
differences between W and Y tiling cause pixels to be scrambled within
a block of size 8x4 (width x height) as measured relative to a W tile,
or 16x2 as measured relative to a Y tile. So in order to make sure
that pixels at the edges of the blit aren't lost, we need to align the
rendering rectangle (and the buffer sizes) to multiples of the 8x4
block size. This alignment happens in the brw_blorp_blit_params
constructor, whereas the determination of how to swizzle the
coordinates happens during code generation, in the
brw_blorp_blit_program class.
When blitting to or from a multisampled stencil buffer, the coordinate
swizzling is more complex, because it has to account for the
interleaving pattern of samples, which uses 4x4 blocks for 4x MSAA and
8x4 blocks for 8x MSAA. The end result is that if multisampling is in
use, the 16x2 block size (relative so a Y tile) needs to be expanded
to 16x4, and the corresponding size relative to a W tile expands to
8x8.
The problem doesn't affect Ivy Bridge severely enough to crop up in
Piglit tests because on Ivy Bridge we have to disable multisampling
when blitting *to* a multisampled stencil buffer (the blorp compiler
generates code to compensate for the fact that multisampling is
disabled). However I suspect a bug is still present because we don't
disable multisampling when blitting *from* a multisampled stencil
buffer.
This patch fixes the problem by doubling the vertical alignment
requirement when blitting to or from a multisampled stencil buffer,
and multisampling has not been disabled.
In the long run I would like to rework the brw_blorp_blit_params
constructor--it's difficult to follow and has had several subtle bugs
like this one. However this band-aid fix should be suitable for
cherry-picking to release branches.
Fixes Piglit tests "unaligned-blit {2,4} stencil {msaa,upsample}" on
Sandy Bridge.
NOTE: This is a candidate for stable release branches.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
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.