agx: add =spill debug option

to force spilling so we can exercise the new code.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27616>

src/asahi/compiler/agx_compile.c

@@ -36,6 +36,7 @@ static const struct debug_named_value agx_debug_options[] = {
    {"nopreamble",AGX_DBG_NOPREAMBLE,"Do not use shader preambles"},
    {"demand",    AGX_DBG_DEMAND,    "Bound tightly to register demand"},
    {"nosched",   AGX_DBG_NOSCHED,   "Do not schedule the shader"},
+   {"spill",     AGX_DBG_SPILL,     "Spill (almost) everything"},
    DEBUG_NAMED_VALUE_END
 };
 /* clang-format on */

src/asahi/compiler/agx_debug.h

@@ -26,6 +26,7 @@ enum agx_compiler_dbg {
    AGX_DBG_NOPREAMBLE  = BITFIELD_BIT(8),
    AGX_DBG_DEMAND      = BITFIELD_BIT(9),
    AGX_DBG_NOSCHED     = BITFIELD_BIT(10),
+   AGX_DBG_SPILL       = BITFIELD_BIT(11),
 };
 /* clang-format on */
 

src/asahi/compiler/agx_register_allocate.c

@@ -1148,6 +1148,7 @@ agx_ra(agx_context *ctx)
    agx_compute_liveness(ctx);
    unsigned effective_demand = agx_calc_register_demand(ctx);
    bool spilling = (effective_demand > max_possible_regs);
+   spilling |= ((agx_compiler_debug & AGX_DBG_SPILL) && ctx->key->has_scratch);
 
    if (spilling) {
       assert(ctx->key->has_scratch && "internal shaders are unspillable");