Mesa (main): ac/nir: add pass_tessfactors_by_reg param to hs output lower

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Module: Mesa
Branch: main
Commit: 18d51831a8a2ccdb5263511fa09888a94108bff3
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=18d51831a8a2ccdb5263511fa09888a94108bff3

Author: Qiang Yu <yuq825 at gmail.com>
Date:   Mon May 23 20:27:55 2022 +0800

ac/nir: add pass_tessfactors_by_reg param to hs output lower

radeonsi won't emit tess factor in the lower pass, need to keep
the output for llvm backend to pass it as parameter. This is used
by radeonsi for an optimization to save LDS write.

Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Reviewed-by: Timur Kristóf <timur.kristof at gmail.com>
Signed-off-by: Qiang Yu <yuq825 at gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16705>

---

 src/amd/common/ac_nir.h                      |  1 +
 src/amd/common/ac_nir_lower_tess_io_to_mem.c | 22 ++++++++++++++++++----
 src/amd/vulkan/radv_shader.c                 |  2 +-
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/amd/common/ac_nir.h b/src/amd/common/ac_nir.h
index 905529f0c55..e0364620548 100644
--- a/src/amd/common/ac_nir.h
+++ b/src/amd/common/ac_nir.h
@@ -89,6 +89,7 @@ ac_nir_lower_hs_outputs_to_mem(nir_shader *shader,
                                uint64_t tes_patch_inputs_read,
                                unsigned num_reserved_tcs_outputs,
                                unsigned num_reserved_tcs_patch_outputs,
+                               bool pass_tessfactors_by_reg,
                                bool emit_tess_factor_write);
 
 void
diff --git a/src/amd/common/ac_nir_lower_tess_io_to_mem.c b/src/amd/common/ac_nir_lower_tess_io_to_mem.c
index f3c3fc2ec1f..0da9cdefb9c 100644
--- a/src/amd/common/ac_nir_lower_tess_io_to_mem.c
+++ b/src/amd/common/ac_nir_lower_tess_io_to_mem.c
@@ -154,6 +154,11 @@ typedef struct {
     * subgroup that reads them.
     */
    bool tcs_out_patch_fits_subgroup;
+
+   /* Set if all invocations will write to all tess factors, so tess factors
+    * can be passed by register.
+    */
+   bool tcs_pass_tessfactors_by_reg;
 } lower_tess_io_state;
 
 static bool
@@ -402,7 +407,7 @@ lower_hs_per_vertex_input_load(nir_builder *b,
                           .align_mul = 16u, .align_offset = (nir_intrinsic_component(intrin) * 4u) % 16u);
 }
 
-static void
+static nir_ssa_def *
 lower_hs_output_store(nir_builder *b,
                       nir_intrinsic_instr *intrin,
                       lower_tess_io_state *st)
@@ -416,7 +421,8 @@ lower_hs_output_store(nir_builder *b,
    bool is_tess_factor = semantics.location == VARYING_SLOT_TESS_LEVEL_INNER ||
                          semantics.location == VARYING_SLOT_TESS_LEVEL_OUTER;
    bool write_to_vmem = !is_tess_factor && tcs_output_needs_vmem(intrin, st);
-   bool write_to_lds = is_tess_factor || tcs_output_needs_lds(intrin, b->shader);
+   bool write_to_lds = (is_tess_factor && !st->tcs_pass_tessfactors_by_reg) ||
+      tcs_output_needs_lds(intrin, b->shader);
 
    if (write_to_vmem) {
       nir_ssa_def *vmem_off = intrin->intrinsic == nir_intrinsic_store_per_vertex_output
@@ -439,6 +445,13 @@ lower_hs_output_store(nir_builder *b,
       nir_store_shared(b, store_val, lds_off, .write_mask = write_mask,
                        .align_mul = 16u, .align_offset = (nir_intrinsic_component(intrin) * 4u) % 16u);
    }
+
+   /* Keep tess factor nir_store_output instruction if it's going to be passed
+    * by reg instead of LDS, because it's used by radeonsi llvm backend to generate
+    * llvm variable which is read by the final llvm tess factor write epilog.
+    */
+   return is_tess_factor && st->tcs_pass_tessfactors_by_reg ?
+      NIR_LOWER_INSTR_PROGRESS : NIR_LOWER_INSTR_PROGRESS_REPLACE;
 }
 
 static nir_ssa_def *
@@ -481,8 +494,7 @@ lower_hs_output_access(nir_builder *b,
 
    if (intrin->intrinsic == nir_intrinsic_store_output ||
        intrin->intrinsic == nir_intrinsic_store_per_vertex_output) {
-      lower_hs_output_store(b, intrin, st);
-      return NIR_LOWER_INSTR_PROGRESS_REPLACE;
+      return lower_hs_output_store(b, intrin, st);
    } else if (intrin->intrinsic == nir_intrinsic_load_output ||
               intrin->intrinsic == nir_intrinsic_load_per_vertex_output) {
       return lower_hs_output_load(b, intrin, st);
@@ -693,6 +705,7 @@ ac_nir_lower_hs_outputs_to_mem(nir_shader *shader,
                                uint64_t tes_patch_inputs_read,
                                unsigned num_reserved_tcs_outputs,
                                unsigned num_reserved_tcs_patch_outputs,
+                               bool pass_tessfactors_by_reg,
                                bool emit_tess_factor_write)
 {
    assert(shader->info.stage == MESA_SHADER_TESS_CTRL);
@@ -705,6 +718,7 @@ ac_nir_lower_hs_outputs_to_mem(nir_shader *shader,
       .tcs_num_reserved_outputs = num_reserved_tcs_outputs,
       .tcs_num_reserved_patch_outputs = num_reserved_tcs_patch_outputs,
       .tcs_out_patch_fits_subgroup = 32 % shader->info.tess.tcs_vertices_out == 0,
+      .tcs_pass_tessfactors_by_reg = pass_tessfactors_by_reg,
       .map_io = map,
    };
 
diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
index 09d6381aa44..7f07b982bac 100644
--- a/src/amd/vulkan/radv_shader.c
+++ b/src/amd/vulkan/radv_shader.c
@@ -1124,7 +1124,7 @@ radv_lower_io_to_mem(struct radv_device *device, struct radv_pipeline_stage *sta
                  device->physical_device->rad_info.gfx_level,
                  info->tcs.tes_reads_tess_factors, info->tcs.tes_inputs_read,
                  info->tcs.tes_patch_inputs_read, info->tcs.num_linked_outputs,
-                 info->tcs.num_linked_patch_outputs, true);
+                 info->tcs.num_linked_patch_outputs, false, true);
 
       return true;
    } else if (nir->info.stage == MESA_SHADER_TESS_EVAL) {