[Mesa-dev] [PATCH] ac/nir: only load used VGPRs thread dimensions

[Samuel Pitoiset]

Just noticed that we can reduce the number of input VGPRs
when dimensions y (and/or z) are unused. Similar to work groups.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
---
 src/amd/common/ac_nir_to_llvm.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index 391a4c2a60..5ba0d937c8 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -95,7 +95,7 @@ struct nir_to_llvm_context {
 	LLVMValueRef view_index;
 	LLVMValueRef num_work_groups;
 	LLVMValueRef workgroup_ids[3];
-	LLVMValueRef local_invocation_ids;
+	LLVMValueRef local_invocation_ids[3];
 	LLVMValueRef tg_size;
 
 	LLVMValueRef vertex_buffers;
@@ -829,8 +829,14 @@ static void create_function(struct nir_to_llvm_context *ctx,
 
 		if (ctx->shader_info->info.cs.uses_local_invocation_idx)
 			add_arg(&args, ARG_SGPR, ctx->ac.i32, &ctx->tg_size);
-		add_arg(&args, ARG_VGPR, ctx->ac.v3i32,
-			&ctx->local_invocation_ids);
+
+		for (int i = 0; i < 3; i++) {
+			ctx->local_invocation_ids[i] = NULL;
+			if (ctx->shader_info->info.cs.uses_thread_id[i]) {
+				add_arg(&args, ARG_VGPR, ctx->ac.i32,
+					&ctx->local_invocation_ids[i]);
+			}
+		}
 		break;
 	case MESA_SHADER_VERTEX:
 		declare_global_input_sgprs(ctx, stage, has_previous_stage,
@@ -4370,7 +4376,14 @@ static void visit_intrinsic(struct ac_nir_context *ctx,
 		break;
 	}
 	case nir_intrinsic_load_local_invocation_id: {
-		result = ctx->nctx->local_invocation_ids;
+		LLVMValueRef values[3];
+
+		for (int i = 0; i < 3; i++) {
+			values[i] = ctx->nctx->local_invocation_ids[i] ?
+				    ctx->nctx->local_invocation_ids[i] : ctx->ac.i32_0;
+		}
+
+		result = ac_build_gather_values(&ctx->ac, values, 3);
 		break;
 	}
 	case nir_intrinsic_load_base_instance:
-- 
2.16.1