asahi/lib/agx_nir_prolog_epilog.c

/*
 * Copyright 2024 Alyssa Rosenzweig
 * Copyright 2024 Valve Corporation
 * SPDX-License-Identifier: MIT
 */

#include "gallium/include/pipe/p_defines.h"
#include "util/format/u_formats.h"
#include "agx_abi.h"
#include "agx_linker.h"
#include "agx_nir.h"
#include "agx_nir_lower_gs.h"
#include "agx_nir_lower_vbo.h"
#include "agx_pack.h"
#include "agx_tilebuffer.h"
#include "libagx.h"
#include "nir.h"
#include "nir_builder.h"
#include "nir_builder_opcodes.h"
#include "nir_lower_blend.h"
#include "shader_enums.h"

/*
 * Insert code into a fragment shader to lower polygon stipple. The stipple is
 * passed in a sideband, rather than requiring a texture binding. This is
 * simpler for drivers to integrate and might be more efficient.
 */
static bool
agx_nir_lower_poly_stipple(nir_shader *s)
{
   assert(s->info.stage == MESA_SHADER_FRAGMENT);

   /* Insert at the beginning for performance. */
   nir_builder b_ =
      nir_builder_at(nir_before_impl(nir_shader_get_entrypoint(s)));
   nir_builder *b = &b_;

   /* The stipple coordinate is defined at the window coordinate mod 32. It's
    * reversed along the X-axis to simplify the driver, hence the NOT.
    */
   nir_def *raw = nir_u2u32(b, nir_load_pixel_coord(b));
   nir_def *coord = nir_umod_imm(
      b,
      nir_vec2(b, nir_inot(b, nir_channel(b, raw, 0)), nir_channel(b, raw, 1)),
      32);

   /* Extract the column from the packed bitfield */
   nir_def *pattern = nir_load_polygon_stipple_agx(b, nir_channel(b, coord, 1));
   nir_def *bit = nir_ubitfield_extract(b, pattern, nir_channel(b, coord, 0),
                                        nir_imm_int(b, 1));

   /* Discard fragments where the pattern is 0 */
   nir_demote_if(b, nir_ieq_imm(b, bit, 0));
   s->info.fs.uses_discard = true;

   nir_metadata_preserve(b->impl, nir_metadata_control_flow);
   return true;
}

static bool
lower_vbo(nir_shader *s, const struct agx_velem_key *key,
          const struct agx_robustness rs)
{
   struct agx_attribute out[AGX_MAX_VBUFS];

   for (unsigned i = 0; i < AGX_MAX_VBUFS; ++i) {
      out[i] = (struct agx_attribute){
         .divisor = key[i].divisor,
         .stride = key[i].stride,
         .format = key[i].format,
         .instanced = key[i].instanced,
      };
   }

   return agx_nir_lower_vbo(s, out, rs);
}

static int
map_vs_part_uniform(nir_intrinsic_instr *intr, unsigned nr_attribs)
{
   switch (intr->intrinsic) {
   case nir_intrinsic_load_vbo_base_agx:
      return 4 * nir_src_as_uint(intr->src[0]);
   case nir_intrinsic_load_attrib_clamp_agx:
      return (4 * nr_attribs) + (2 * nir_src_as_uint(intr->src[0]));
   case nir_intrinsic_load_first_vertex:
      return (6 * nr_attribs);
   case nir_intrinsic_load_base_instance:
      return (6 * nr_attribs) + 2;
   case nir_intrinsic_load_input_assembly_buffer_agx:
      return (6 * nr_attribs) + 8;
   default:
      return -1;
   }
}

static int
map_fs_part_uniform(nir_intrinsic_instr *intr)
{
   switch (intr->intrinsic) {
   case nir_intrinsic_load_blend_const_color_r_float:
      return 4;
   case nir_intrinsic_load_blend_const_color_g_float:
      return 6;
   case nir_intrinsic_load_blend_const_color_b_float:
      return 8;
   case nir_intrinsic_load_blend_const_color_a_float:
      return 10;
   default:
      return -1;
   }
}

static bool
lower_non_monolithic_uniforms(nir_builder *b, nir_intrinsic_instr *intr,
                              void *data)
{
   int unif;
   if (b->shader->info.stage == MESA_SHADER_VERTEX) {
      unsigned *nr_attribs = data;
      unif = map_vs_part_uniform(intr, *nr_attribs);
   } else {
      unif = map_fs_part_uniform(intr);
   }

   if (unif >= 0) {
      b->cursor = nir_instr_remove(&intr->instr);
      nir_def *load = nir_load_preamble(b, 1, intr->def.bit_size, .base = unif);
      nir_def_rewrite_uses(&intr->def, load);
      return true;
   } else if (intr->intrinsic == nir_intrinsic_load_texture_handle_agx) {
      b->cursor = nir_instr_remove(&intr->instr);
      nir_def *offs =
         nir_imul_imm(b, nir_u2u32(b, intr->src[0].ssa), AGX_TEXTURE_LENGTH);
      nir_def_rewrite_uses(&intr->def, nir_vec2(b, nir_imm_int(b, 0), offs));
      return true;
   } else {
      return false;
   }
}

static bool
lower_adjacency(nir_builder *b, nir_intrinsic_instr *intr, void *data)
{
   const struct agx_vs_prolog_key *key = data;
   b->cursor = nir_before_instr(&intr->instr);

   if (intr->intrinsic != nir_intrinsic_load_vertex_id)
      return false;

   nir_def *id = nir_load_vertex_id(b);

   if (key->adjacency == MESA_PRIM_LINES_ADJACENCY) {
      id = libagx_map_to_line_adj(b, id);
   } else if (key->adjacency == MESA_PRIM_TRIANGLE_STRIP_ADJACENCY) {
      id = libagx_map_to_tri_strip_adj(b, id);
   } else if (key->adjacency == MESA_PRIM_LINE_STRIP_ADJACENCY) {
      id = libagx_map_to_line_strip_adj(b, id);
   } else if (key->adjacency == MESA_PRIM_TRIANGLES_ADJACENCY) {
      /* Sequence (0, 2, 4), (6, 8, 10), ... */
      id = nir_imul_imm(b, id, 2);
   } else {
      unreachable("unknown");
   }

   id = agx_nir_load_vertex_id(b, id, key->sw_index_size_B);

   nir_def_replace(&intr->def, id);
   return true;
}

void
agx_nir_vs_prolog(nir_builder *b, const void *key_)
{
   const struct agx_vs_prolog_key *key = key_;
   b->shader->info.stage = MESA_SHADER_VERTEX;
   b->shader->info.name = "VS prolog";

   /* First, construct a passthrough shader reading each attribute and exporting
    * the value. We also need to export vertex/instance ID in their usual regs.
    */
   unsigned i = 0;
   nir_def *vec = NULL;
   unsigned vec_idx = ~0;
   BITSET_FOREACH_SET(i, key->component_mask, AGX_MAX_ATTRIBS * 4) {
      unsigned a = i / 4;
      unsigned c = i % 4;

      if (vec_idx != a) {
         vec = nir_load_input(b, 4, 32, nir_imm_int(b, 0), .base = a);
         vec_idx = a;
      }

      nir_export_agx(b, nir_channel(b, vec, c), .base = AGX_ABI_VIN_ATTRIB(i));
   }

   nir_export_agx(b, nir_load_vertex_id(b), .base = AGX_ABI_VIN_VERTEX_ID);
   nir_export_agx(b, nir_load_instance_id(b), .base = AGX_ABI_VIN_INSTANCE_ID);

   /* Now lower the resulting program using the key */
   lower_vbo(b->shader, key->attribs, key->robustness);

   /* Clean up redundant vertex ID loads */
   if (!key->hw || key->adjacency) {
      NIR_PASS(_, b->shader, nir_opt_cse);
      NIR_PASS(_, b->shader, nir_opt_dce);
   }

   if (!key->hw) {
      agx_nir_lower_sw_vs(b->shader, key->sw_index_size_B);
   } else if (key->adjacency) {
      nir_shader_intrinsics_pass(b->shader, lower_adjacency,
                                 nir_metadata_control_flow, (void *)key);
   }

   /* Finally, lower uniforms according to our ABI */
   unsigned nr = DIV_ROUND_UP(BITSET_LAST_BIT(key->component_mask), 4);
   nir_shader_intrinsics_pass(b->shader, lower_non_monolithic_uniforms,
                              nir_metadata_control_flow, &nr);
   b->shader->info.io_lowered = true;
}

static bool
lower_input_to_prolog(nir_builder *b, nir_intrinsic_instr *intr, void *data)
{
   if (intr->intrinsic != nir_intrinsic_load_input)
      return false;

   unsigned idx = nir_src_as_uint(intr->src[0]) + nir_intrinsic_base(intr);
   unsigned comp = nir_intrinsic_component(intr);

   assert(intr->def.bit_size == 32 && "todo: push conversions up?");
   unsigned base = 4 * idx + comp;

   b->cursor = nir_before_instr(&intr->instr);
   nir_def *val =
      nir_load_exported_agx(b, intr->def.num_components, intr->def.bit_size,
                            .base = AGX_ABI_VIN_ATTRIB(base));

   BITSET_WORD *comps_read = data;
   nir_component_mask_t mask = nir_def_components_read(&intr->def);

   u_foreach_bit(c, mask) {
      BITSET_SET(comps_read, base + c);
   }

   nir_def_replace(&intr->def, val);
   return true;
}

bool
agx_nir_lower_vs_input_to_prolog(nir_shader *s,
                                 BITSET_WORD *attrib_components_read)
{
   return nir_shader_intrinsics_pass(s, lower_input_to_prolog,
                                     nir_metadata_control_flow,
                                     attrib_components_read);
}

static bool
lower_active_samples_to_register(nir_builder *b, nir_intrinsic_instr *intr,
                                 void *data)
{
   if (intr->intrinsic != nir_intrinsic_load_active_samples_agx)
      return false;

   b->cursor = nir_before_instr(&intr->instr);
   nir_def *id =
      nir_load_exported_agx(b, 1, 16, .base = AGX_ABI_FIN_SAMPLE_MASK);

   nir_def_replace(&intr->def, id);
   return true;
}

static bool
lower_tests_zs_intr(nir_builder *b, nir_intrinsic_instr *intr, void *data)
{
   bool *value = data;
   if (intr->intrinsic != nir_intrinsic_load_shader_part_tests_zs_agx)
      return false;

   b->cursor = nir_instr_remove(&intr->instr);
   nir_def_rewrite_uses(&intr->def, nir_imm_intN_t(b, *value ? 0xFF : 0, 16));
   return true;
}

static bool
lower_tests_zs(nir_shader *s, bool value)
{
   if (!s->info.fs.uses_discard)
      return false;

   return nir_shader_intrinsics_pass(s, lower_tests_zs_intr,
                                     nir_metadata_control_flow, &value);
}

static inline bool
blend_uses_2src(struct agx_blend_rt_key rt)
{
   enum pipe_blendfactor factors[] = {
      rt.rgb_src_factor,
      rt.rgb_dst_factor,
      rt.alpha_src_factor,
      rt.alpha_dst_factor,
   };

   for (unsigned i = 0; i < ARRAY_SIZE(factors); ++i) {
      switch (factors[i]) {
      case PIPE_BLENDFACTOR_SRC1_COLOR:
      case PIPE_BLENDFACTOR_SRC1_ALPHA:
      case PIPE_BLENDFACTOR_INV_SRC1_COLOR:
      case PIPE_BLENDFACTOR_INV_SRC1_ALPHA:
         return true;
      default:
         break;
      }
   }

   return false;
}

static void
copy_colour(nir_builder *b, const struct agx_fs_epilog_key *key,
            unsigned out_rt, unsigned in_loc, bool dual_src)
{
   unsigned size = (key->link.size_32 & BITFIELD_BIT(in_loc)) ? 32 : 16;

   nir_def *value =
      nir_load_exported_agx(b, 4, size, .base = AGX_ABI_FOUT_COLOUR(in_loc));

   if (key->link.loc0_w_1 && in_loc == 0) {
      value =
         nir_vector_insert_imm(b, value, nir_imm_floatN_t(b, 1.0, size), 3);
   }

   nir_store_output(b, value, nir_imm_int(b, 0),
                    .io_semantics.location = FRAG_RESULT_DATA0 + out_rt,
                    .io_semantics.dual_source_blend_index = dual_src,
                    .src_type = nir_type_float | size);
}

void
agx_nir_fs_epilog(nir_builder *b, const void *key_)
{
   const struct agx_fs_epilog_key *key = key_;
   b->shader->info.stage = MESA_SHADER_FRAGMENT;
   b->shader->info.name = "FS epilog";

   /* First, construct a passthrough shader reading each colour and outputting
    * the value.
    */
   for (unsigned rt = 0; rt < ARRAY_SIZE(key->remap); ++rt) {
      int location = key->remap[rt];

      /* Negative remaps indicate the attachment isn't written. */
      if (location >= 0 && key->link.loc_written & BITFIELD_BIT(location)) {
         copy_colour(b, key, rt, location, false);

         /* If this render target uses dual source blending, also copy the dual
          * source colour. While the copy_colour above is needed even for
          * missing attachments to handle alpha-to-coverage, this copy is only
          * for blending so should be suppressed for missing attachments to keep
          * the assert from blowing up on OpenGL.
          */
         if (blend_uses_2src(key->blend.rt[rt]) &&
             key->rt_formats[rt] != PIPE_FORMAT_NONE) {

            assert(location == 0);
            copy_colour(b, key, rt, 1, true);
         }
      }
   }

   /* Grab registers early, this has to happen in the first block. */
   nir_def *sample_id = NULL, *write_samples = NULL;
   if (key->link.sample_shading) {
      sample_id =
         nir_load_exported_agx(b, 1, 16, .base = AGX_ABI_FOUT_SAMPLE_MASK);
   }

   if (key->link.sample_mask_after_force_early) {
      write_samples =
         nir_load_exported_agx(b, 1, 16, .base = AGX_ABI_FOUT_WRITE_SAMPLES);
   }

   /* Now lower the resulting program using the key */
   struct agx_tilebuffer_layout tib = agx_build_tilebuffer_layout(
      key->rt_formats, ARRAY_SIZE(key->rt_formats), key->nr_samples, true);

   if (key->force_small_tile)
      tib.tile_size = (struct agx_tile_size){16, 16};

   bool force_translucent = false;
   nir_lower_blend_options opts = {
      .scalar_blend_const = true,
      .logicop_enable = key->blend.logicop_func != PIPE_LOGICOP_COPY,
      .logicop_func = key->blend.logicop_func,
   };

   static_assert(ARRAY_SIZE(opts.format) == 8, "max RTs out of sync");

   for (unsigned i = 0; i < 8; ++i) {
      opts.format[i] = key->rt_formats[i];
      opts.rt[i] = (nir_lower_blend_rt){
         .rgb.src_factor = key->blend.rt[i].rgb_src_factor,
         .rgb.dst_factor = key->blend.rt[i].rgb_dst_factor,
         .rgb.func = key->blend.rt[i].rgb_func,

         .alpha.src_factor = key->blend.rt[i].alpha_src_factor,
         .alpha.dst_factor = key->blend.rt[i].alpha_dst_factor,
         .alpha.func = key->blend.rt[i].alpha_func,

         .colormask = key->blend.rt[i].colormask,
      };
   }

   /* It's more efficient to use masked stores (with
    * agx_nir_lower_tilebuffer) than to emulate colour masking with
    * nir_lower_blend.
    */
   uint8_t colormasks[8] = {0};

   for (unsigned i = 0; i < 8; ++i) {
      if (key->rt_formats[i] == PIPE_FORMAT_NONE)
         continue;

      /* TODO: Flakes some dEQPs, seems to invoke UB. Revisit later.
       * dEQP-GLES2.functional.fragment_ops.interaction.basic_shader.77
       * dEQP-GLES2.functional.fragment_ops.interaction.basic_shader.98
       */
      if (0 /* agx_tilebuffer_supports_mask(&tib, i) */) {
         colormasks[i] = key->blend.rt[i].colormask;
         opts.rt[i].colormask = (uint8_t)BITFIELD_MASK(4);
      } else {
         colormasks[i] = (uint8_t)BITFIELD_MASK(4);
      }

      /* If not all bound RTs are fully written to, we need to force
       * translucent pass type. agx_nir_lower_tilebuffer will take
       * care of this for its own colormasks input.
       */
      unsigned comps = util_format_get_nr_components(key->rt_formats[i]);
      if ((opts.rt[i].colormask & BITFIELD_MASK(comps)) !=
          BITFIELD_MASK(comps)) {
         force_translucent = true;
      }
   }

   /* Alpha-to-coverage must be lowered before alpha-to-one */
   if (key->blend.alpha_to_coverage)
      NIR_PASS(_, b->shader, agx_nir_lower_alpha_to_coverage, tib.nr_samples);

   /* Depth/stencil writes must be deferred until after all discards,
    * particularly alpha-to-coverage.
    */
   if (key->link.write_z || key->link.write_s) {
      nir_store_zs_agx(
         b, nir_imm_intN_t(b, 0xFF, 16),
         nir_load_exported_agx(b, 1, 32, .base = AGX_ABI_FOUT_Z),
         nir_load_exported_agx(b, 1, 16, .base = AGX_ABI_FOUT_S),
         .base = (key->link.write_z ? 1 : 0) | (key->link.write_s ? 2 : 0));

      if (key->link.write_z)
         b->shader->info.outputs_written |= BITFIELD64_BIT(FRAG_RESULT_DEPTH);

      if (key->link.write_s)
         b->shader->info.outputs_written |= BITFIELD64_BIT(FRAG_RESULT_STENCIL);
   }

   /* Alpha-to-one must be lowered before blending */
   if (key->blend.alpha_to_one)
      NIR_PASS(_, b->shader, agx_nir_lower_alpha_to_one);

   NIR_PASS(_, b->shader, nir_lower_blend, &opts);

   unsigned rt_spill = key->link.rt_spill_base;
   NIR_PASS(_, b->shader, agx_nir_lower_tilebuffer, &tib, colormasks, &rt_spill,
            write_samples, &force_translucent);
   NIR_PASS(_, b->shader, agx_nir_lower_texture);
   NIR_PASS(_, b->shader, agx_nir_lower_multisampled_image_store);

   /* If the API shader runs once per sample, then the epilog runs once per
    * sample as well, so we need to lower our code to run for a single sample.
    *
    * If the API shader runs once per pixel, then the epilog runs once per
    * pixel. So we run through the monolithic MSAA lowering, which wraps the
    * epilog in the sample loop if needed. This localizes sample shading
    * to the epilog, when sample shading is not used but blending is.
    */
   if (key->link.sample_shading) {
      /* Lower the resulting discards. Done in agx_nir_lower_monolithic_msaa for
       * the pixel shaded path. Must be done before agx_nir_lower_to_per_sample
       * to avoid duplicating tests.
       */
      if (key->blend.alpha_to_coverage) {
         NIR_PASS(_, b->shader, agx_nir_lower_sample_mask);
      }

      NIR_PASS(_, b->shader, agx_nir_lower_to_per_sample);
      NIR_PASS(_, b->shader, agx_nir_lower_fs_active_samples_to_register);

      /* Ensure the sample ID is preserved in register. We do this late since it
       * has to go in the last block, and the above passes might add control
       * flow when lowering.
       */
      b->cursor = nir_after_impl(b->impl);
      nir_export_agx(b, sample_id, .base = AGX_ABI_FIN_SAMPLE_MASK);
   } else {
      NIR_PASS(_, b->shader, agx_nir_lower_monolithic_msaa, key->nr_samples);
   }

   /* Finally, lower uniforms according to our ABI */
   nir_shader_intrinsics_pass(b->shader, lower_non_monolithic_uniforms,
                              nir_metadata_control_flow, NULL);

   /* There is no shader part after the epilog, so we're always responsible for
    * running our own tests, unless the fragment shader forced early tests.
    */
   NIR_PASS(_, b->shader, lower_tests_zs, !key->link.already_ran_zs);

   b->shader->info.io_lowered = true;
   b->shader->info.fs.uses_fbfetch_output |= force_translucent;
   b->shader->info.fs.uses_sample_shading = key->link.sample_shading;
}

struct lower_epilog_ctx {
   struct agx_fs_epilog_link_info *info;
   nir_variable *masked_samples;
};

static bool
lower_output_to_epilog(nir_builder *b, nir_intrinsic_instr *intr, void *data)
{
   struct lower_epilog_ctx *ctx = data;
   struct agx_fs_epilog_link_info *info = ctx->info;

   if (intr->intrinsic == nir_intrinsic_store_zs_agx) {
      assert(nir_src_as_uint(intr->src[0]) == 0xff && "msaa not yet lowered");
      b->cursor = nir_instr_remove(&intr->instr);

      unsigned base = nir_intrinsic_base(intr);
      info->write_z = !!(base & 1);
      info->write_s = !!(base & 2);

      if (info->write_z)
         nir_export_agx(b, intr->src[1].ssa, .base = AGX_ABI_FOUT_Z);

      if (info->write_s)
         nir_export_agx(b, intr->src[2].ssa, .base = AGX_ABI_FOUT_S);

      return true;
   }

   if (intr->intrinsic == nir_intrinsic_discard_agx &&
       b->shader->info.fs.early_fragment_tests) {

      if (!ctx->masked_samples) {
         b->cursor = nir_before_impl(nir_shader_get_entrypoint(b->shader));

         ctx->masked_samples =
            nir_local_variable_create(b->impl, glsl_uint16_t_type(), NULL);

         nir_store_var(b, ctx->masked_samples, nir_imm_intN_t(b, 0xFF, 16),
                       nir_component_mask(1));
      }

      b->cursor = nir_before_instr(&intr->instr);

      nir_def *mask = nir_load_var(b, ctx->masked_samples);
      nir_def *mask_2 =
         nir_ixor(b, intr->src[0].ssa, nir_imm_intN_t(b, 0xff, 16));

      mask = nir_iand(b, mask, mask_2);
      nir_store_var(b, ctx->masked_samples, mask, nir_component_mask(1));

      nir_instr_remove(&intr->instr);
      return true;
   }

   if (intr->intrinsic != nir_intrinsic_store_output)
      return false;

   nir_io_semantics sem = nir_intrinsic_io_semantics(intr);

   /* Fix up gl_FragColor */
   if (sem.location == FRAG_RESULT_COLOR) {
      sem.location = FRAG_RESULT_DATA0;
      info->broadcast_rt0 = true;
   }

   /* We don't use the epilog for sample mask writes */
   if (sem.location < FRAG_RESULT_DATA0)
      return false;

   /* Determine the ABI location. Dual source blending aliases a second
    * render target, so get that out of the way now.
    */
   unsigned loc = sem.location - FRAG_RESULT_DATA0;
   loc += nir_src_as_uint(intr->src[1]);

   if (sem.dual_source_blend_index) {
      assert(loc == 0);
      loc = 1;
   }

   b->cursor = nir_instr_remove(&intr->instr);
   nir_def *vec = intr->src[0].ssa;

   info->loc_written |= BITFIELD_BIT(loc);

   if (vec->bit_size == 32)
      info->size_32 |= BITFIELD_BIT(loc);
   else
      assert(vec->bit_size == 16);

   uint32_t one_f = (vec->bit_size == 32 ? fui(1.0) : _mesa_float_to_half(1.0));
   unsigned comp = nir_intrinsic_component(intr);

   u_foreach_bit(c, nir_intrinsic_write_mask(intr)) {
      nir_scalar s = nir_scalar_resolved(vec, c);
      if (loc == 0 && c == 3 && nir_scalar_is_const(s) &&
          nir_scalar_as_uint(s) == one_f) {

         info->loc0_w_1 = true;
      } else {
         unsigned stride = vec->bit_size / 16;

         nir_export_agx(b, nir_channel(b, vec, c),
                        .base = AGX_ABI_FOUT_COLOUR(loc) + (comp + c) * stride);
      }
   }

   return true;
}

bool
agx_nir_lower_fs_output_to_epilog(nir_shader *s,
                                  struct agx_fs_epilog_link_info *out)
{
   struct lower_epilog_ctx ctx = {.info = out};

   nir_shader_intrinsics_pass(s, lower_output_to_epilog,
                              nir_metadata_control_flow, &ctx);

   if (ctx.masked_samples) {
      nir_builder b =
         nir_builder_at(nir_after_impl(nir_shader_get_entrypoint(s)));

      nir_export_agx(&b, nir_load_var(&b, ctx.masked_samples),
                     .base = AGX_ABI_FOUT_WRITE_SAMPLES);
      out->sample_mask_after_force_early = true;

      bool progress;
      do {
         progress = false;
         NIR_PASS(progress, s, nir_lower_vars_to_ssa);
         NIR_PASS(progress, s, nir_opt_dce);
      } while (progress);
   }

   out->sample_shading = s->info.fs.uses_sample_shading;
   return true;
}

bool
agx_nir_lower_fs_active_samples_to_register(nir_shader *s)
{
   return nir_shader_intrinsics_pass(s, lower_active_samples_to_register,
                                     nir_metadata_control_flow, NULL);
}

static bool
agx_nir_lower_stats_fs(nir_shader *s)
{
   assert(s->info.stage == MESA_SHADER_FRAGMENT);
   nir_builder b_ =
      nir_builder_at(nir_before_impl(nir_shader_get_entrypoint(s)));
   nir_builder *b = &b_;

   nir_push_if(b, nir_inot(b, nir_load_helper_invocation(b, 1)));
   nir_def *samples = nir_bit_count(b, nir_load_sample_mask_in(b));
   unsigned query = PIPE_STAT_QUERY_PS_INVOCATIONS;

   nir_def *addr = nir_load_stat_query_address_agx(b, .base = query);
   nir_global_atomic(b, 32, addr, samples, .atomic_op = nir_atomic_op_iadd);

   nir_pop_if(b, NULL);
   nir_metadata_preserve(b->impl, nir_metadata_control_flow);
   return true;
}

void
agx_nir_fs_prolog(nir_builder *b, const void *key_)
{
   const struct agx_fs_prolog_key *key = key_;
   b->shader->info.stage = MESA_SHADER_FRAGMENT;
   b->shader->info.name = "FS prolog";

   /* First, insert code for any emulated features */
   if (key->api_sample_mask != 0xff) {
      /* Kill samples that are NOT covered by the mask */
      nir_discard_agx(b, nir_imm_intN_t(b, key->api_sample_mask ^ 0xff, 16));
      b->shader->info.fs.uses_discard = true;
   }

   if (key->statistics) {
      NIR_PASS(_, b->shader, agx_nir_lower_stats_fs);
   }

   if (key->cull_distance_size) {
      NIR_PASS(_, b->shader, agx_nir_lower_cull_distance_fs,
               key->cull_distance_size);
   }

   if (key->polygon_stipple) {
      NIR_PASS_V(b->shader, agx_nir_lower_poly_stipple);
   }

   /* Then, lower the prolog */
   NIR_PASS(_, b->shader, agx_nir_lower_discard_zs_emit);
   NIR_PASS(_, b->shader, agx_nir_lower_sample_mask);
   NIR_PASS(_, b->shader, nir_shader_intrinsics_pass,
            lower_non_monolithic_uniforms, nir_metadata_control_flow, NULL);
   NIR_PASS(_, b->shader, lower_tests_zs, key->run_zs_tests);

   b->shader->info.io_lowered = true;
}