radv/gfx9: reduce the number of input VGPRs for the GS stage

This can still be improved, but let's start with this.

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

diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
index ab8ba42..3187980 100644 (file)
--- a/src/amd/vulkan/radv_shader.c
+++ b/src/amd/vulkan/radv_shader.c
@@ -411,8 +411,21 @@ radv_fill_shader_variant(struct radv_device *device,
 
        if (device->physical_device->rad_info.chip_class >= GFX9 &&
            stage == MESA_SHADER_GEOMETRY) {
+               struct ac_shader_info *info = &variant->info.info;
+               unsigned gs_vgpr_comp_cnt;
+
+               /* If offsets 4, 5 are used, GS_VGPR_COMP_CNT is ignored and
+                * VGPR[0:4] are always loaded.
+                */
+               if (info->uses_invocation_id)
+                       gs_vgpr_comp_cnt = 3; /* VGPR3 contains InvocationID. */
+               else if (info->uses_prim_id)
+                       gs_vgpr_comp_cnt = 2; /* VGPR2 contains PrimitiveID. */
+               else
+                       gs_vgpr_comp_cnt = 1; /* TODO: use input_prim */
+
                /* TODO: Figure out how many we actually need. */
-               variant->rsrc1 |= S_00B228_GS_VGPR_COMP_CNT(3);
+               variant->rsrc1 |= S_00B228_GS_VGPR_COMP_CNT(gs_vgpr_comp_cnt);
                variant->rsrc2 |= S_00B22C_ES_VGPR_COMP_CNT(3) |
                                  S_00B22C_OC_LDS_EN(1);
        } else if (device->physical_device->rad_info.chip_class >= GFX9 &&