[Mesa-dev] [PATCH 2/2] ac/nir: don't write tcs outputs to LDS that aren't read back.

[Dave Airlie]

From: Dave Airlie <airl...@redhat.com>

If the TCS doesn't read back the outputs, no need to store them
to LDS in the first place. (except for tess factors).

This seems to give about 50fps (3290->3330) with tessellation demo.

I haven't tested if it impacts DoW3 at all.

Signed-off-by: Dave Airlie <airl...@redhat.com>
---
 src/amd/common/ac_nir_to_llvm.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index 1ecdeca..b58bae9 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -149,6 +149,9 @@ struct nir_to_llvm_context {
        unsigned tes_primitive_mode;
        uint64_t tess_outputs_written;
        uint64_t tess_patch_outputs_written;
+
+       uint32_t tcs_patch_outputs_read;
+       uint64_t tcs_outputs_read;
 };
 
 static inline struct nir_to_llvm_context *
@@ -2789,7 +2792,15 @@ store_tcs_output(struct nir_to_llvm_context *ctx,
        const unsigned comp = instr->variables[0]->var->data.location_frac;
        const bool per_vertex = nir_is_per_vertex_io(instr->variables[0]->var, 
ctx->stage);
        const bool is_compact = instr->variables[0]->var->data.compact;
+       bool store_lds = true;
 
+       if (instr->variables[0]->var->data.patch) {
+               if (!(ctx->tcs_patch_outputs_read & (1U << 
instr->variables[0]->var->data.location)))
+                       store_lds = false;
+       } else {
+               if (!(ctx->tcs_outputs_read & (1ULL << 
instr->variables[0]->var->data.location)))
+                       store_lds = false;
+       }
        get_deref_offset(ctx->nir, instr->variables[0],
                         false, NULL, per_vertex ? &vertex_index : NULL,
                         &const_index, &indir_index);
@@ -2826,7 +2837,8 @@ store_tcs_output(struct nir_to_llvm_context *ctx,
                        continue;
                LLVMValueRef value = llvm_extract_elem(&ctx->ac, src, chan - 
comp);
 
-               ac_lds_store(&ctx->ac, dw_addr, value);
+               if (store_lds || is_tess_factor)
+                       ac_lds_store(&ctx->ac, dw_addr, value);
 
                if (!is_tess_factor && writemask != 0xF)
                        ac_build_buffer_store_dword(&ctx->ac, 
ctx->hs_ring_tess_offchip, value, 1,
@@ -6550,6 +6562,9 @@ LLVMModuleRef 
ac_translate_nir_to_llvm(LLVMTargetMachineRef tm,
                        ctx.gs_next_vertex = ac_build_alloca(&ctx.ac, 
ctx.ac.i32, "gs_next_vertex");
 
                        ctx.gs_max_out_vertices = 
shaders[i]->info.gs.vertices_out;
+               } else if (shaders[i]->info.stage == MESA_SHADER_TESS_CTRL) {
+                       ctx.tcs_outputs_read = shaders[i]->info.outputs_read;
+                       ctx.tcs_patch_outputs_read = 
shaders[i]->info.patch_outputs_read;
                } else if (shaders[i]->info.stage == MESA_SHADER_TESS_EVAL) {
                        ctx.tes_primitive_mode = 
shaders[i]->info.tess.primitive_mode;
                } else if (shaders[i]->info.stage == MESA_SHADER_VERTEX) {
-- 
2.9.5

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