broadcom/compiler: disable TMU pipelining if we fail to register allocate

TMU pipelining can severely reduce our capacity to emit TMU spills,
causing us to fail to compile a shader we may otherwise be able to
compile. This is because pipelining extends the liveness of TMU
sequences by posponing the thread switch and LDTMU until a result
is needed, and we can't emit TMU spills while in the middle of a
TMU sequence.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8825>

src/broadcom/compiler/v3d_compiler.h

@@ -627,6 +627,12 @@ struct v3d_compile {
          */
         bool fallback_scheduler;
 
+        /* Disable TMU pipelining. This may increase the chances of being able
+         * to compile shaders with high register pressure that require to emit
+         * TMU spills.
+         */
+        bool disable_tmu_pipelining;
+
         /* State for whether we're executing on each channel currently.  0 if
          * yes, otherwise a block number + 1 that the channel jumped to.
          */