aco: Don't store TCS outputs to LDS when we're sure that none are read.

This allows us not to write an output to LDS, even if it has
an indirect offset.

No pipeline DB changes.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3964>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3964>

diff --git a/src/amd/compiler/aco_instruction_selection.cpp b/src/amd/compiler/aco_instruction_selection.cpp
index 386616f52ef19be5ec88f4d42c2263946206d542..1de79f01da80570b0a76d45a48221df304ada281 100644 (file)
--- a/src/amd/compiler/aco_instruction_selection.cpp
+++ b/src/amd/compiler/aco_instruction_selection.cpp
@@ -3339,6 +3339,10 @@ bool should_write_tcs_patch_output_to_lds(isel_context *ctx, nir_intrinsic_instr
    unsigned off = nir_intrinsic_base(instr) * 4u;
    nir_src *off_src = nir_get_io_offset_src(instr);
 
+   /* When none of the appropriate outputs are read, we are OK to never write to LDS */
+   if (per_vertex ? ctx->shader->info.outputs_read == 0U : ctx->shader->info.patch_outputs_read == 0u)
+      return false;
+
    /* Indirect offset, we can't be sure if this is read or not, always write to LDS */
    if (!nir_src_is_const(*off_src))
       return true;