docs: convert articles to reructuredtext

This uses the previously added scripts to convert the documentation to
reStructuredText, which is both easier to read offline, and can be used
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No modification to the generated results have been done.

Acked-by: Eric Engestrom <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4630>

1 files changed, 724 insertions, 0 deletions

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+Environment Variables
+=====================
+
+Normally, no environment variables need to be set. Most of the
+environment variables used by Mesa/Gallium are for debugging purposes,
+but they can sometimes be useful for debugging end-user issues.
+
+LibGL environment variables
+---------------------------
+
+``LIBGL_DEBUG``
+   If defined debug information will be printed to stderr. If set to
+   ``verbose`` additional information will be printed.
+``LIBGL_DRIVERS_PATH``
+   colon-separated list of paths to search for DRI drivers
+``LIBGL_ALWAYS_INDIRECT``
+   if set to ``true``, forces an indirect rendering context/connection.
+``LIBGL_ALWAYS_SOFTWARE``
+   if set to ``true``, always use software rendering
+``LIBGL_NO_DRAWARRAYS``
+   if set to ``true``, do not use DrawArrays GLX protocol (for
+   debugging)
+``LIBGL_SHOW_FPS``
+   print framerate to stdout based on the number of ``glXSwapBuffers``
+   calls per second.
+``LIBGL_DRI3_DISABLE``
+   disable DRI3 if set to ``true``.
+
+Core Mesa environment variables
+-------------------------------
+
+``MESA_NO_ASM``
+   if set, disables all assembly language optimizations
+``MESA_NO_MMX``
+   if set, disables Intel MMX optimizations
+``MESA_NO_3DNOW``
+   if set, disables AMD 3DNow! optimizations
+``MESA_NO_SSE``
+   if set, disables Intel SSE optimizations
+``MESA_NO_ERROR``
+   if set to 1, error checking is disabled as per ``KHR_no_error``. This
+   will result in undefined behaviour for invalid use of the api, but
+   can reduce CPU use for apps that are known to be error free.
+``MESA_DEBUG``
+   if set, error messages are printed to stderr. For example, if the
+   application generates a ``GL_INVALID_ENUM`` error, a corresponding
+   error message indicating where the error occurred, and possibly why,
+   will be printed to stderr. For release builds, ``MESA_DEBUG``
+   defaults to off (no debug output). ``MESA_DEBUG`` accepts the
+   following comma-separated list of named flags, which adds extra
+   behaviour to just set ``MESA_DEBUG=1``:
+
+   ``silent``
+      turn off debug messages. Only useful for debug builds.
+   ``flush``
+      flush after each drawing command
+   ``incomplete_tex``
+      extra debug messages when a texture is incomplete
+   ``incomplete_fbo``
+      extra debug messages when a fbo is incomplete
+   ``context``
+      create a debug context (see ``GLX_CONTEXT_DEBUG_BIT_ARB``) and
+      print error and performance messages to stderr (or
+      ``MESA_LOG_FILE``).
+
+``MESA_LOG_FILE``
+   specifies a file name for logging all errors, warnings, etc., rather
+   than stderr
+``MESA_TEX_PROG``
+   if set, implement conventional texture env modes with fragment
+   programs (intended for developers only)
+``MESA_TNL_PROG``
+   if set, implement conventional vertex transformation operations with
+   vertex programs (intended for developers only). Setting this variable
+   automatically sets the ``MESA_TEX_PROG`` variable as well.
+``MESA_EXTENSION_OVERRIDE``
+   can be used to enable/disable extensions. A value such as
+   ``GL_EXT_foo -GL_EXT_bar`` will enable the ``GL_EXT_foo`` extension
+   and disable the ``GL_EXT_bar`` extension.
+``MESA_EXTENSION_MAX_YEAR``
+   The ``GL_EXTENSIONS`` string returned by Mesa is sorted by extension
+   year. If this variable is set to year X, only extensions defined on
+   or before year X will be reported. This is to work-around a bug in
+   some games where the extension string is copied into a fixed-size
+   buffer without truncating. If the extension string is too long, the
+   buffer overrun can cause the game to crash. This is a work-around for
+   that.
+``MESA_GL_VERSION_OVERRIDE``
+   changes the value returned by ``glGetString(GL_VERSION)`` and
+   possibly the GL API type.
+
+   -  The format should be ``MAJOR.MINOR[FC|COMPAT]``
+   -  ``FC`` is an optional suffix that indicates a forward compatible
+      context. This is only valid for versions >= 3.0.
+   -  ``COMPAT`` is an optional suffix that indicates a compatibility
+      context or ``GL_ARB_compatibility`` support. This is only valid
+      for versions >= 3.1.
+   -  GL versions <= 3.0 are set to a compatibility (non-Core) profile
+   -  GL versions = 3.1, depending on the driver, it may or may not have
+      the ``ARB_compatibility`` extension enabled.
+   -  GL versions >= 3.2 are set to a Core profile
+   -  Examples:
+
+      ``2.1``
+         select a compatibility (non-Core) profile with GL version 2.1.
+      ``3.0``
+         select a compatibility (non-Core) profile with GL version 3.0.
+      ``3.0FC``
+         select a Core+Forward Compatible profile with GL version 3.0.
+      ``3.1``
+         select GL version 3.1 with ``GL_ARB_compatibility`` enabled per
+         the driver default.
+      ``3.1FC``
+         select GL version 3.1 with forward compatibility and
+         ``GL_ARB_compatibility`` disabled.
+      ``3.1COMPAT``
+         select GL version 3.1 with ``GL_ARB_compatibility`` enabled.
+      ``X.Y``
+         override GL version to X.Y without changing the profile.
+      ``X.YFC``
+         select a Core+Forward Compatible profile with GL version X.Y.
+      ``X.YCOMPAT``
+         select a Compatibility profile with GL version X.Y.
+
+   -  Mesa may not really implement all the features of the given
+      version. (for developers only)
+
+``MESA_GLES_VERSION_OVERRIDE``
+   changes the value returned by ``glGetString(GL_VERSION)`` for OpenGL
+   ES.
+
+   -  The format should be ``MAJOR.MINOR``
+   -  Examples: ``2.0``, ``3.0``, ``3.1``
+   -  Mesa may not really implement all the features of the given
+      version. (for developers only)
+
+``MESA_GLSL_VERSION_OVERRIDE``
+   changes the value returned by
+   ``glGetString(GL_SHADING_LANGUAGE_VERSION)``. Valid values are
+   integers, such as ``130``. Mesa will not really implement all the
+   features of the given language version if it's higher than what's
+   normally reported. (for developers only)
+``MESA_GLSL_CACHE_DISABLE``
+   if set to ``true``, disables the GLSL shader cache
+``MESA_GLSL_CACHE_MAX_SIZE``
+   if set, determines the maximum size of the on-disk cache of compiled
+   GLSL programs. Should be set to a number optionally followed by
+   ``K``, ``M``, or ``G`` to specify a size in kilobytes, megabytes, or
+   gigabytes. By default, gigabytes will be assumed. And if unset, a
+   maximum size of 1GB will be used. Note: A separate cache might be
+   created for each architecture that Mesa is installed for on your
+   system. For example under the default settings you may end up with a
+   1GB cache for x86_64 and another 1GB cache for i386.
+``MESA_GLSL_CACHE_DIR``
+   if set, determines the directory to be used for the on-disk cache of
+   compiled GLSL programs. If this variable is not set, then the cache
+   will be stored in ``$XDG_CACHE_HOME/mesa_shader_cache`` (if that
+   variable is set), or else within ``.cache/mesa_shader_cache`` within
+   the user's home directory.
+``MESA_GLSL``
+   `shading language compiler options <shading.html#envvars>`__
+``MESA_NO_MINMAX_CACHE``
+   when set, the minmax index cache is globally disabled.
+``MESA_SHADER_CAPTURE_PATH``
+   see `Capturing Shaders <shading.html#capture>`__
+``MESA_SHADER_DUMP_PATH`` and ``MESA_SHADER_READ_PATH``
+   see `Experimenting with Shader
+   Replacements <shading.html#replacement>`__
+``MESA_VK_VERSION_OVERRIDE``
+   changes the Vulkan physical device version as returned in
+   ``VkPhysicalDeviceProperties::apiVersion``.
+
+   -  The format should be ``MAJOR.MINOR[.PATCH]``
+   -  This will not let you force a version higher than the driver's
+      instance version as advertised by ``vkEnumerateInstanceVersion``
+   -  This can be very useful for debugging but some features may not be
+      implemented correctly. (For developers only)
+
+NIR passes enviroment variables
+-------------------------------
+
+The following are only applicable for drivers that uses NIR, as they
+modify the behaviour for the common NIR_PASS and NIR_PASS_V macros, that
+wrap calls to NIR lowering/optimizations.
+
+``NIR_PRINT``
+   If defined, the resulting NIR shader will be printed out at each
+   succesful NIR lowering/optimization call.
+``NIR_TEST_CLONE``
+   If defined, cloning a NIR shader would be tested at each succesful
+   NIR lowering/optimization call.
+``NIR_TEST_SERIALIZE``
+   If defined, serialize and deserialize a NIR shader would be tested at
+   each succesful NIR lowering/optimization call.
+
+Mesa Xlib driver environment variables
+--------------------------------------
+
+The following are only applicable to the Mesa Xlib software driver. See
+the `Xlib software driver page <xlibdriver.html>`__ for details.
+
+``MESA_RGB_VISUAL``
+   specifies the X visual and depth for RGB mode
+``MESA_CI_VISUAL``
+   specifies the X visual and depth for CI mode
+``MESA_BACK_BUFFER``
+   specifies how to implement the back color buffer, either ``pixmap``
+   or ``ximage``
+``MESA_GAMMA``
+   gamma correction coefficients for red, green, blue channels
+``MESA_XSYNC``
+   enable synchronous X behavior (for debugging only)
+``MESA_GLX_FORCE_CI``
+   if set, force GLX to treat 8bpp visuals as CI visuals
+``MESA_GLX_FORCE_ALPHA``
+   if set, forces RGB windows to have an alpha channel.
+``MESA_GLX_DEPTH_BITS``
+   specifies default number of bits for depth buffer.
+``MESA_GLX_ALPHA_BITS``
+   specifies default number of bits for alpha channel.
+
+i945/i965 driver environment variables (non-Gallium)
+----------------------------------------------------
+
+``INTEL_NO_HW``
+   if set to 1, prevents batches from being submitted to the hardware.
+   This is useful for debugging hangs, etc.
+``INTEL_DEBUG``
+   a comma-separated list of named flags, which do various things:
+
+   ``ann``
+      annotate IR in assembly dumps
+   ``aub``
+      dump batches into an AUB trace for use with simulation tools
+   ``bat``
+      emit batch information
+   ``blit``
+      emit messages about blit operations
+   ``blorp``
+      emit messages about the blorp operations (blits & clears)
+   ``buf``
+      emit messages about buffer objects
+   ``clip``
+      emit messages about the clip unit (for old gens, includes the CLIP
+      program)
+   ``color``
+      use color in output
+   ``cs``
+      dump shader assembly for compute shaders
+   ``do32``
+      generate compute shader SIMD32 programs even if workgroup size
+      doesn't exceed the SIMD16 limit
+   ``dri``
+      emit messages about the DRI interface
+   ``fbo``
+      emit messages about framebuffers
+   ``fs``
+      dump shader assembly for fragment shaders
+   ``gs``
+      dump shader assembly for geometry shaders
+   ``hex``
+      print instruction hex dump with the disassembly
+   ``l3``
+      emit messages about the new L3 state during transitions
+   ``miptree``
+      emit messages about miptrees
+   ``no8``
+      don't generate SIMD8 fragment shader
+   ``no16``
+      suppress generation of 16-wide fragment shaders. useful for
+      debugging broken shaders
+   ``nocompact``
+      disable instruction compaction
+   ``nodualobj``
+      suppress generation of dual-object geometry shader code
+   ``nofc``
+      disable fast clears
+   ``norbc``
+      disable single sampled render buffer compression
+   ``optimizer``
+      dump shader assembly to files at each optimization pass and
+      iteration that make progress
+   ``perf``
+      emit messages about performance issues
+   ``perfmon``
+      emit messages about ``AMD_performance_monitor``
+   ``pix``
+      emit messages about pixel operations
+   ``prim``
+      emit messages about drawing primitives
+   ``reemit``
+      mark all state dirty on each draw call
+   ``sf``
+      emit messages about the strips & fans unit (for old gens, includes
+      the SF program)
+   ``shader_time``
+      record how much GPU time is spent in each shader
+   ``spill_fs``
+      force spilling of all registers in the scalar backend (useful to
+      debug spilling code)
+   ``spill_vec4``
+      force spilling of all registers in the vec4 backend (useful to
+      debug spilling code)
+   ``state``
+      emit messages about state flag tracking
+   ``submit``
+      emit batchbuffer usage statistics
+   ``sync``
+      after sending each batch, emit a message and wait for that batch
+      to finish rendering
+   ``tcs``
+      dump shader assembly for tessellation control shaders
+   ``tes``
+      dump shader assembly for tessellation evaluation shaders
+   ``tex``
+      emit messages about textures.
+   ``urb``
+      emit messages about URB setup
+   ``vert``
+      emit messages about vertex assembly
+   ``vs``
+      dump shader assembly for vertex shaders
+
+``INTEL_SCALAR_VS`` (or ``TCS``, ``TES``, ``GS``)
+   force scalar/vec4 mode for a shader stage (Gen8-9 only)
+``INTEL_PRECISE_TRIG``
+   if set to 1, true or yes, then the driver prefers accuracy over
+   performance in trig functions.
+
+Radeon driver environment variables (radeon, r200, and r300g)
+-------------------------------------------------------------
+
+``RADEON_NO_TCL``
+   if set, disable hardware-accelerated Transform/Clip/Lighting.
+
+EGL environment variables
+-------------------------
+
+Mesa EGL supports different sets of environment variables. See the `Mesa
+EGL <egl.html>`__ page for the details.
+
+Gallium environment variables
+-----------------------------
+
+``GALLIUM_HUD``
+   draws various information on the screen, like framerate, cpu load,
+   driver statistics, performance counters, etc. Set
+   ``GALLIUM_HUD=help`` and run e.g. ``glxgears`` for more info.
+``GALLIUM_HUD_PERIOD``
+   sets the hud update rate in seconds (float). Use zero to update every
+   frame. The default period is 1/2 second.
+``GALLIUM_HUD_VISIBLE``
+   control default visibility, defaults to true.
+``GALLIUM_HUD_TOGGLE_SIGNAL``
+   toggle visibility via user specified signal. Especially useful to
+   toggle hud at specific points of application and disable for
+   unencumbered viewing the rest of the time. For example, set
+   ``GALLIUM_HUD_VISIBLE`` to ``false`` and
+   ``GALLIUM_HUD_TOGGLE_SIGNAL`` to ``10`` (``SIGUSR1``). Use
+   ``kill -10 <pid>`` to toggle the hud as desired.
+``GALLIUM_HUD_SCALE``
+   Scale hud by an integer factor, for high DPI displays. Default is 1.
+``GALLIUM_HUD_DUMP_DIR``
+   specifies a directory for writing the displayed hud values into
+   files.
+``GALLIUM_DRIVER``
+   useful in combination with ``LIBGL_ALWAYS_SOFTWARE=true`` for
+   choosing one of the software renderers ``softpipe``, ``llvmpipe`` or
+   ``swr``.
+``GALLIUM_LOG_FILE``
+   specifies a file for logging all errors, warnings, etc. rather than
+   stderr.
+``GALLIUM_PRINT_OPTIONS``
+   if non-zero, print all the Gallium environment variables which are
+   used, and their current values.
+``GALLIUM_DUMP_CPU``
+   if non-zero, print information about the CPU on start-up
+``TGSI_PRINT_SANITY``
+   if set, do extra sanity checking on TGSI shaders and print any errors
+   to stderr.
+``DRAW_FSE``
+   ???
+``DRAW_NO_FSE``
+   ???
+``DRAW_USE_LLVM``
+   if set to zero, the draw module will not use LLVM to execute shaders,
+   vertex fetch, etc.
+``ST_DEBUG``
+   controls debug output from the Mesa/Gallium state tracker. Setting to
+   ``tgsi``, for example, will print all the TGSI shaders. See
+   ``src/mesa/state_tracker/st_debug.c`` for other options.
+
+Clover environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``CLOVER_EXTRA_BUILD_OPTIONS``
+   allows specifying additional compiler and linker options. Specified
+   options are appended after the options set by the OpenCL program in
+   ``clBuildProgram``.
+``CLOVER_EXTRA_COMPILE_OPTIONS``
+   allows specifying additional compiler options. Specified options are
+   appended after the options set by the OpenCL program in
+   ``clCompileProgram``.
+``CLOVER_EXTRA_LINK_OPTIONS``
+   allows specifying additional linker options. Specified options are
+   appended after the options set by the OpenCL program in
+   ``clLinkProgram``.
+
+Softpipe driver environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``SOFTPIPE_DUMP_FS``
+   if set, the softpipe driver will print fragment shaders to stderr
+``SOFTPIPE_DUMP_GS``
+   if set, the softpipe driver will print geometry shaders to stderr
+``SOFTPIPE_NO_RAST``
+   if set, rasterization is no-op'd. For profiling purposes.
+``SOFTPIPE_USE_LLVM``
+   if set, the softpipe driver will try to use LLVM JIT for vertex
+   shading processing.
+
+LLVMpipe driver environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``LP_NO_RAST``
+   if set LLVMpipe will no-op rasterization
+``LP_DEBUG``
+   a comma-separated list of debug options is accepted. See the source
+   code for details.
+``LP_PERF``
+   a comma-separated list of options to selectively no-op various parts
+   of the driver. See the source code for details.
+``LP_NUM_THREADS``
+   an integer indicating how many threads to use for rendering. Zero
+   turns off threading completely. The default value is the number of
+   CPU cores present.
+
+VMware SVGA driver environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``SVGA_FORCE_SWTNL``
+   force use of software vertex transformation
+``SVGA_NO_SWTNL``
+   don't allow software vertex transformation fallbacks (will often
+   result in incorrect rendering).
+``SVGA_DEBUG``
+   for dumping shaders, constant buffers, etc. See the code for details.
+``SVGA_EXTRA_LOGGING``
+   if set, enables extra logging to the ``vmware.log`` file, such as the
+   OpenGL program's name and command line arguments.
+``SVGA_NO_LOGGING``
+   if set, disables logging to the ``vmware.log`` file. This is useful
+   when using Valgrind because it otherwise crashes when initializing
+   the host log feature.
+
+See the driver code for other, lesser-used variables.
+
+WGL environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``WGL_SWAP_INTERVAL``
+   to set a swap interval, equivalent to calling
+   ``wglSwapIntervalEXT()`` in an application. If this environment
+   variable is set, application calls to ``wglSwapIntervalEXT()`` will
+   have no effect.
+
+VA-API environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``VAAPI_MPEG4_ENABLED``
+   enable MPEG4 for VA-API, disabled by default.
+
+VC4 driver environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``VC4_DEBUG``
+   a comma-separated list of named flags, which do various things:
+
+   ``cl``
+      dump command list during creation
+   ``qpu``
+      dump generated QPU instructions
+   ``qir``
+      dump QPU IR during program compile
+   ``nir``
+      dump NIR during program compile
+   ``tgsi``
+      dump TGSI during program compile
+   ``shaderdb``
+      dump program compile information for shader-db analysis
+   ``perf``
+      print during performance-related events
+   ``norast``
+      skip actual hardware execution of commands
+   ``always_flush``
+      flush after each draw call
+   ``always_sync``
+      wait for finish after each flush
+   ``dump``
+      write a GPU command stream trace file (VC4 simulator only)
+
+RADV driver environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``RADV_DEBUG``
+   a comma-separated list of named flags, which do various things:
+
+   ``allbos``
+      force all allocated buffers to be referenced in submissions
+   ``allentrypoints``
+      enable all device/instance entrypoints
+   ``checkir``
+      validate the LLVM IR before LLVM compiles the shader
+   ``errors``
+      display more info about errors
+   ``info``
+      show GPU-related information
+   ``metashaders``
+      dump internal meta shaders
+   ``nobinning``
+      disable primitive binning
+   ``nocache``
+      disable shaders cache
+   ``nocompute``
+      disable compute queue
+   ``nodcc``
+      disable Delta Color Compression (DCC) on images
+   ``nodynamicbounds``
+      do not check OOB access for dynamic descriptors
+   ``nofastclears``
+      disable fast color/depthstencil clears
+   ``nohiz``
+      disable HIZ for depthstencil images
+   ``noibs``
+      disable directly recording command buffers in GPU-visible memory
+   ``noloadstoreopt``
+      disable LLVM SILoadStoreOptimizer pass
+   ``nomemorycache``
+      disable memory shaders cache
+   ``nongg``
+      disable NGG for GFX10+
+   ``nooutoforder``
+      disable out-of-order rasterization
+   ``noshaderballot``
+      disable shader ballot
+   ``nothreadllvm``
+      disable LLVM threaded compilation
+   ``preoptir``
+      dump LLVM IR before any optimizations
+   ``shaders``
+      dump shaders
+   ``shaderstats``
+      dump shader statistics
+   ``spirv``
+      dump SPIR-V
+   ``startup``
+      display info at startup
+   ``syncshaders``
+      synchronize shaders after all draws/dispatches
+   ``vmfaults``
+      check for VM memory faults via dmesg
+   ``zerovram``
+      initialize all memory allocated in VRAM as zero
+
+``RADV_FORCE_FAMILY``
+   create a null device to compile shaders without a AMD GPU (eg.
+   gfx900)
+``RADV_PERFTEST``
+   a comma-separated list of named flags, which do various things:
+
+   ``aco``
+      enable ACO experimental compiler
+   ``bolist``
+      enable the global BO list
+   ``cswave32``
+      enable wave32 for compute shaders (GFX10+)
+   ``dccmsaa``
+      enable DCC for MSAA images
+   ``dfsm``
+      enable dfsm
+   ``gewave32``
+      enable wave32 for vertex/tess/geometry shaders (GFX10+)
+   ``localbos``
+      enable local BOs
+   ``pswave32``
+      enable wave32 for pixel shaders (GFX10+)
+   ``shader_ballot``
+      enable shader ballot
+   ``tccompatcmask``
+      enable TC-compat cmask for MSAA images
+
+``RADV_SECURE_COMPILE_THREADS``
+   maximum number of secure compile threads (up to 32)
+``RADV_TEX_ANISO``
+   force anisotropy filter (up to 16)
+``RADV_TRACE_FILE``
+   generate cmdbuffer tracefiles when a GPU hang is detected
+``ACO_DEBUG``
+   a comma-separated list of named flags, which do various things:
+
+   ``validateir``
+      validate the ACO IR at various points of compilation (enabled by
+      default for debug/debugoptimized builds)
+   ``validatera``
+      validate register assignment of ACO IR and catches many RA bugs
+   ``perfwarn``
+      abort on some suboptimal code generation
+
+radeonsi driver environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``AMD_DEBUG``
+   a comma-separated list of named flags, which do various things:
+``nodma``
+   Disable SDMA
+``nodmaclear``
+   Disable SDMA clears
+``nodmacopyimage``
+   Disable SDMA image copies
+``zerovram``
+   Clear VRAM allocations.
+``nodcc``
+   Disable DCC.
+``nodccclear``
+   Disable DCC fast clear.
+``nodccfb``
+   Disable separate DCC on the main framebuffer
+``nodccmsaa``
+   Disable DCC for MSAA
+``nodpbb``
+   Disable DPBB.
+``nodfsm``
+   Disable DFSM.
+``notiling``
+   Disable tiling
+``nofmask``
+   Disable MSAA compression
+``nohyperz``
+   Disable Hyper-Z
+``norbplus``
+   Disable RB+.
+``no2d``
+   Disable 2D tiling
+``info``
+   Print driver information
+``tex``
+   Print texture info
+``compute``
+   Print compute info
+``vm``
+   Print virtual addresses when creating resources
+``vs``
+   Print vertex shaders
+``ps``
+   Print pixel shaders
+``gs``
+   Print geometry shaders
+``tcs``
+   Print tessellation control shaders
+``tes``
+   Print tessellation evaluation shaders
+``cs``
+   Print compute shaders
+``noir``
+   Don't print the LLVM IR
+``nonir``
+   Don't print NIR when printing shaders
+``noasm``
+   Don't print disassembled shaders
+``preoptir``
+   Print the LLVM IR before initial optimizations
+``gisel``
+   Enable LLVM global instruction selector.
+``w32ge``
+   Use Wave32 for vertex, tessellation, and geometry shaders.
+``w32ps``
+   Use Wave32 for pixel shaders.
+``w32cs``
+   Use Wave32 for computes shaders.
+``w64ge``
+   Use Wave64 for vertex, tessellation, and geometry shaders.
+``w64ps``
+   Use Wave64 for pixel shaders.
+``w64cs``
+   Use Wave64 for computes shaders.
+``checkir``
+   Enable additional sanity checks on shader IR
+``mono``
+   Use old-style monolithic shaders compiled on demand
+``nooptvariant``
+   Disable compiling optimized shader variants.
+``forcedma``
+   Use SDMA for all operations when possible.
+``nowc``
+   Disable GTT write combining
+``check_vm``
+   Check VM faults and dump debug info.
+``reserve_vmid``
+   Force VMID reservation per context.
+``nogfx``
+   Disable graphics. Only multimedia compute paths can be used.
+``nongg``
+   Disable NGG and use the legacy pipeline.
+``nggc``
+   Always use NGG culling even when it can hurt.
+``nonggc``
+   Disable NGG culling.
+``alwayspd``
+   Always enable the primitive discard compute shader.
+``pd``
+   Enable the primitive discard compute shader for large draw calls.
+``nopd``
+   Disable the primitive discard compute shader.
+``switch_on_eop``
+   Program WD/IA to switch on end-of-packet.
+``nooutoforder``
+   Disable out-of-order rasterization
+``dpbb``
+   Enable DPBB.
+``dfsm``
+   Enable DFSM.
+
+Other Gallium drivers have their own environment variables. These may
+change frequently so the source code should be consulted for details.