aco: fix target calculation when vgpr spilling introduces sgpr spilling

A shader might require vgpr spilling but not require sgpr spilling. In
that case, the spiller lowers the sgpr target by 5 which could mean sgpr
spilling is then required. Then the vgpr target has to be lowered to make
space for the linear vgprs. Previously, space wasn't make for the linear
vgprs.

Found while testing the spiller on the pipeline-db with a lowered limit

Fixes: a7ff1bb5b9a78cf57073b5e2e136daf0c85078d6
   ('aco: simplify calculation of target register pressure when spilling')

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3257>

diff --git a/src/amd/compiler/aco_spill.cpp b/src/amd/compiler/aco_spill.cpp
index 1c555db79ab605478a5abfbe0f8de3b6519d0a0a..e0c3ea955cd4312538d5ae95643b3ffec6932d8e 100644 (file)
--- a/src/amd/compiler/aco_spill.cpp
+++ b/src/amd/compiler/aco_spill.cpp
@@ -1750,9 +1750,8 @@ void spill(Program* program, live& live_vars, const struct radv_nir_compiler_opt
 
    if (register_target.vgpr > program->vgpr_limit)
       register_target.sgpr = program->sgpr_limit - 5;
-   register_target.vgpr = program->vgpr_limit - (register_target.vgpr - program->max_reg_demand.vgpr);
-
    int spills_to_vgpr = (program->max_reg_demand.sgpr - register_target.sgpr + program->wave_size - 1 + 32) / program->wave_size;
+   register_target.vgpr = program->vgpr_limit - spills_to_vgpr;
 
    /* initialize ctx */
    spill_ctx ctx(register_target, program, live_vars.register_demand);