On 11/18/2013 03:22 PM, Kenneth Graunke wrote: > On 11/18/2013 12:27 PM, Eric Anholt wrote: >> Kenneth Graunke <kenn...@whitecape.org> writes: >> >>> Broadwell significantly changes the EU instruction encoding. Many of >>> the fields got moved to different bit positions; some even got split >>> in two. >>> >>> With so many changes, it was infeasible to continue using struct >>> brw_instruction. We needed a new representation. >>> >>> This new approach is a bit different: rather than a struct, I created a >>> class that has four DWords, and helper functions that read/write various >>> bits. This has several advantages: >>> >>> 1. We can create several different names for the same bits. For >>> example, conditional modifiers, SFID for SEND instructions, and the >>> MATH instruction's function opcode are all stored in bits 27:24. >>> >>> In each situation, we can use the appropriate setter function: >>> set_sfid(), set_math_function(), or set_cond_modifier(). This >>> is much easier to follow. >>> >>> 2. Since the fields are expressed using the original 128-bit numbers, >>> the code to create the getter/setter functions follows the table in >>> the documentation very closely. >>> >>> To aid in debugging, I've enabled -fkeep-inline-functions when building >>> gen8_instruction.cpp. Otherwise, these functions cannot be called by >>> gdb, making it insanely difficult to print out anything. >> >> I dislike C++ creep. > > I wrote this in C++ because all of the compiler infrastructure which > uses it is already in C++. It seemed natural. > > However, Damien requested that we write it in C so it could be easily > copied to xf86-video-intel, intel-gpu-tools, gen4asm/disasm, etc. Which > is probably a good thing. He actually already ported it to C.
For reference, Damien's C port of this code is in the public intel-gpu-tools repo as assember/gen8_instruction.[ch]: http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/plain/assembler/gen8_instruction.h http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/plain/assembler/gen8_instruction.c So I guess we have some options: 1. Use the C++ version of my bitfield approach. 2. Use Damien's C port of my bitfield approach. 3. Rewrite it as a struct of union of structs again. Having a system that Eric likes is important to me. I'm interested to hear other opinions as well... --Ken _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
