Thomas Helland
90dfcc6b32
Use our knowledge that pointers are at least 4 byte aligned to remove the useless digits. Then shift by 6, 10, and 14 bits and add this to the original pointer, effectively folding in the entropy of the higher bits of the pointer into a 4-bit section. Stopping at 14 means we can add the entropy from 18 bits, or at least a 600Kbyte section of memory. Assuming that ralloc allocates from a linearly allocated heap less than this we can make a very efficient pointer hashing function for our usecase. Even if we are not on an architecture that is 4 byte aligned, there is still a high big chance that the thing we are allocating is at least 8 bytes in size, so even then we will have entropy into the third bit. The 4 bit increment on the shifts is chosen rather arbitrarily; if we had chosen a 3 bit increment we would need to add another xor to cover a decently sized memorypool. Increasing it to 5 bits would spread our entropy more, possibly hurting us with more collisions on hash tables of size less than 32. With a hash table of size 16 there are a max of 11 entries, and we can assume that with such a small table collisions are not that painfull. This allows us to hash the whole 32 or 64 bit pointer at once, instead of running FNV1a, looping through each byte and doing increments, decrements, muls, and xors on every byte. This cuts _mesa_hash_data from 1.5 % on profiles, to making _mesa_hash_pointer show up with a 0.09% share. Collisions on insertion actually seems to be ever so slightly lower with this hash function, as found by printing a loop counter and sorting the data. perf stat shows a 1.5% reduction in instruction count, and a 5% reduction in stalled cycles. Shader-db runtime goes from 225 to 220 seconds. No instruction-count changes in shader-db, but there are some minor changes in cycle-count that is likely caused by nir walking a set in some of its passes, and this causing a different ordering. That might eventually lead to a difference in register allocation. However, the effect is a net positive; total cycles in shared programs: 24739550 -> 24738482 (-0.00%) cycles in affected programs: 374468 -> 373400 (-0.29%) helped: 178 HURT: 49 Reviewed-by: Marek Olšák <marek.olsak@amd.com> Reviewed-by: Eric Anholt <eric@anholt.net>
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 https://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.