ac/nir: avoid loading unused VS input components

Polaris10:
Totals from affected shaders:
SGPRS: 122840 -> 120984 (-1.51 %)
VGPRS: 78812 -> 78440 (-0.47 %)
Spilled SGPRs: 177 -> 129 (-27.12 %)
Code Size: 2950028 -> 2941276 (-0.30 %) bytes
Max Waves: 17899 -> 17976 (0.43 %)

Vega10:
Totals from affected shaders:
SGPRS: 117144 -> 115776 (-1.17 %)
VGPRS: 77580 -> 77532 (-0.06 %)
Spilled SGPRs: 0 -> 152 (0.00 %)
Code Size: 3352656 -> 3347860 (-0.14 %) bytes
Max Waves: 19756 -> 19866 (0.56 %)

This increases SGPRs spilling a bit with Talos, but I have
some other ideas that might reduce it.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index e44afbb9b226a005ea60dc971f4f3800cef0cb25..15d6759ced16f3fe768f7bc9dd5207e8c28de345 100644 (file)
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -5317,6 +5317,9 @@ handle_vs_input_decl(struct nir_to_llvm_context *ctx,
        int index = variable->data.location - VERT_ATTRIB_GENERIC0;
        int idx = variable->data.location;
        unsigned attrib_count = glsl_count_attribute_slots(variable->type, true);
+       uint8_t input_usage_mask =
+               ctx->shader_info->info.vs.input_usage_mask[variable->data.location];
+       unsigned num_channels = util_last_bit(input_usage_mask);
 
        variable->data.driver_location = idx * 4;
 
@@ -5341,7 +5344,9 @@ handle_vs_input_decl(struct nir_to_llvm_context *ctx,
                input = ac_build_buffer_load_format(&ctx->ac, t_list,
                                                    buffer_index,
                                                    ctx->ac.i32_0,
-                                                   4, false, true);
+                                                   num_channels, false, true);
+
+               input = ac_build_expand_to_vec4(&ctx->ac, input, num_channels);
 
                for (unsigned chan = 0; chan < 4; chan++) {
                        LLVMValueRef llvm_chan = LLVMConstInt(ctx->ac.i32, chan, false);