broadcom/compiler: add V3D_DEBUG_RA option

To ask to debug a registr allocation failure
(V3D_DEBUG_REGISTER_ALLOCATION seemed too long to me).

When a fallback register allocation algorithm was added, if the
register allocation fails, it only dumpg the current vir with the
register pressure info with the failed fallback. But if we want do
debug the problem, we would be interested on both.

Additionally, it was strange that we got the full vir dump with the
failure even if no debug option was set.

Additionally we add shaderdb like stats for those failures, to make
easier to compare one and the other.

v2: keep a small warning message in case both register allocation
    algorithms fails (Neil)

Reviewed-by: Neil Roberts <nroberts@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6999>
5 files changed