+<li>INTEL_NO_HW - if set to 1, prevents batches from being submitted to the hardware.
+ This is useful for debugging hangs, etc.</li>
+<li>INTEL_DEBUG - a comma-separated list of named flags, which do various things:
+<ul>
+ <li>ann - annotate IR in assembly dumps</li>
+ <li>aub - dump batches into an AUB trace for use with simulation tools</li>
+ <li>bat - emit batch information</li>
+ <li>blit - emit messages about blit operations</li>
+ <li>blorp - emit messages about the blorp operations (blits & clears)</li>
+ <li>buf - emit messages about buffer objects</li>
+ <li>clip - emit messages about the clip unit (for old gens, includes the CLIP program)</li>
+ <li>color - use color in output</li>
+ <li>cs - dump shader assembly for compute shaders</li>
+ <li>do32 - generate compute shader SIMD32 programs even if workgroup size doesn't exceed the SIMD16 limit</li>
+ <li>dri - emit messages about the DRI interface</li>
+ <li>fbo - emit messages about framebuffers</li>
+ <li>fs - dump shader assembly for fragment shaders</li>
+ <li>gs - dump shader assembly for geometry shaders</li>
+ <li>hex - print instruction hex dump with the disassembly</li>
+ <li>l3 - emit messages about the new L3 state during transitions</li>
+ <li>miptree - emit messages about miptrees</li>
+ <li>no8 - don't generate SIMD8 fragment shader</li>
+ <li>no16 - suppress generation of 16-wide fragment shaders. useful for debugging broken shaders</li>
+ <li>nocompact - disable instruction compaction</li>
+ <li>nodualobj - suppress generation of dual-object geometry shader code</li>
+ <li>norbc - disable single sampled render buffer compression</li>
+ <li>optimizer - dump shader assembly to files at each optimization pass and iteration that make progress</li>
+ <li>perf - emit messages about performance issues</li>
+ <li>perfmon - emit messages about AMD_performance_monitor</li>
+ <li>pix - emit messages about pixel operations</li>
+ <li>prim - emit messages about drawing primitives</li>
+ <li>sf - emit messages about the strips & fans unit (for old gens, includes the SF program)</li>
+ <li>shader_time - record how much GPU time is spent in each shader</li>
+ <li>spill_fs - force spilling of all registers in the scalar backend (useful to debug spilling code)</li>
+ <li>spill_vec4 - force spilling of all registers in the vec4 backend (useful to debug spilling code)</li>
+ <li>state - emit messages about state flag tracking</li>
+ <li>sync - after sending each batch, emit a message and wait for that batch to finish rendering</li>
+ <li>tcs - dump shader assembly for tessellation control shaders</li>
+ <li>tes - dump shader assembly for tessellation evaluation shaders</li>
+ <li>tex - emit messages about textures.</li>
+ <li>urb - emit messages about URB setup</li>
+ <li>vert - emit messages about vertex assembly</li>
+ <li>vs - dump shader assembly for vertex shaders</li>
+</ul>
+<li>INTEL_SCALAR_VS (or TCS, TES, GS) - force scalar/vec4 mode for a shader stage (Gen8-9 only)</li>
+<li>INTEL_PRECISE_TRIG - if set to 1, true or yes, then the driver prefers
+ accuracy over performance in trig functions.</li>