amd: lower load_sample_pos in NIR

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32782>

src/amd/common/ac_nir.c

@@ -250,6 +250,10 @@ lower_intrinsic_to_arg(nir_builder *b, nir_instr *instr, void *state)
    case nir_intrinsic_load_sample_id:
       replacement = ac_nir_unpack_arg(b, s->args, s->args->ancillary, 8, 4);
       break;
+   case nir_intrinsic_load_sample_pos:
+      replacement = nir_vec2(b, nir_ffract(b, ac_nir_load_arg(b, s->args, s->args->frag_pos[0])),
+                             nir_ffract(b, ac_nir_load_arg(b, s->args, s->args->frag_pos[1])));
+      break;
    default:
       return false;
    }

src/amd/compiler/aco_instruction_selection.cpp

@@ -8125,15 +8125,6 @@ visit_intrinsic(isel_context* ctx, nir_intrinsic_instr* instr)
    case nir_intrinsic_load_frag_shading_rate:
       emit_load_frag_shading_rate(ctx, get_ssa_temp(ctx, &instr->def));
       break;
-   case nir_intrinsic_load_sample_pos: {
-      Temp posx = get_arg(ctx, ctx->args->frag_pos[0]);
-      Temp posy = get_arg(ctx, ctx->args->frag_pos[1]);
-      bld.pseudo(
-         aco_opcode::p_create_vector, Definition(get_ssa_temp(ctx, &instr->def)),
-         posx.id() ? bld.vop1(aco_opcode::v_fract_f32, bld.def(v1), posx) : Operand::zero(),
-         posy.id() ? bld.vop1(aco_opcode::v_fract_f32, bld.def(v1), posy) : Operand::zero());
-      break;
-   }
    case nir_intrinsic_load_tess_coord: visit_load_tess_coord(ctx, instr); break;
    case nir_intrinsic_load_interpolated_input: visit_load_interpolated_input(ctx, instr); break;
    case nir_intrinsic_store_output: visit_store_output(ctx, instr); break;

src/amd/compiler/aco_instruction_selection_setup.cpp

@@ -558,7 +558,6 @@ init_context(isel_context* ctx, nir_shader* shader)
                case nir_intrinsic_load_interpolated_input:
                case nir_intrinsic_load_front_face_fsign:
                case nir_intrinsic_load_frag_shading_rate:
-               case nir_intrinsic_load_sample_pos:
                case nir_intrinsic_load_local_invocation_index:
                case nir_intrinsic_load_subgroup_invocation:
                case nir_intrinsic_load_tess_coord:

src/amd/llvm/ac_nir_to_llvm.c

@@ -2657,19 +2657,6 @@ static LLVMValueRef visit_var_atomic(struct ac_nir_context *ctx, const nir_intri
    return result;
 }
 
-static LLVMValueRef load_sample_pos(struct ac_nir_context *ctx)
-{
-   LLVMValueRef values[2];
-   LLVMValueRef pos[2];
-
-   pos[0] = ac_to_float(&ctx->ac, ac_get_arg(&ctx->ac, ctx->args->frag_pos[0]));
-   pos[1] = ac_to_float(&ctx->ac, ac_get_arg(&ctx->ac, ctx->args->frag_pos[1]));
-
-   values[0] = ac_build_fract(&ctx->ac, pos[0], 32);
-   values[1] = ac_build_fract(&ctx->ac, pos[1], 32);
-   return ac_build_gather_values(&ctx->ac, values, 2);
-}
-
 static LLVMValueRef lookup_interp_param(struct ac_nir_context *ctx, enum glsl_interp_mode interp,
                                         unsigned location)
 {
@@ -2969,9 +2956,6 @@ static bool visit_intrinsic(struct ac_nir_context *ctx, nir_intrinsic_instr *ins
       } else
          fprintf(stderr, "Unknown primitive id intrinsic: %d", ctx->stage);
       break;
-   case nir_intrinsic_load_sample_pos:
-      result = load_sample_pos(ctx);
-      break;
    case nir_intrinsic_load_frag_shading_rate:
       result = emit_load_frag_shading_rate(ctx);
       break;