drivers/radeonsi/si_state_msaa.c

/*
 * Copyright 2014 Advanced Micro Devices, Inc.
 *
 * SPDX-License-Identifier: MIT
 */

#include "si_build_pm4.h"

/* For MSAA sample positions. */
#define FILL_SREG(s0x, s0y, s1x, s1y, s2x, s2y, s3x, s3y)                                          \
   ((((unsigned)(s0x)&0xf) << 0) | (((unsigned)(s0y)&0xf) << 4) | (((unsigned)(s1x)&0xf) << 8) |   \
    (((unsigned)(s1y)&0xf) << 12) | (((unsigned)(s2x)&0xf) << 16) |                                \
    (((unsigned)(s2y)&0xf) << 20) | (((unsigned)(s3x)&0xf) << 24) | (((unsigned)(s3y)&0xf) << 28))

/* For obtaining location coordinates from registers */
#define SEXT4(x)               ((int)((x) | ((x)&0x8 ? 0xfffffff0 : 0)))
#define GET_SFIELD(reg, index) SEXT4(((reg) >> ((index)*4)) & 0xf)
#define GET_SX(reg, index)     GET_SFIELD((reg)[(index) / 4], ((index) % 4) * 2)
#define GET_SY(reg, index)     GET_SFIELD((reg)[(index) / 4], ((index) % 4) * 2 + 1)

/* The following sample ordering is required by EQAA.
 *
 * Sample 0 is approx. in the top-left quadrant.
 * Sample 1 is approx. in the bottom-right quadrant.
 *
 * Sample 2 is approx. in the bottom-left quadrant.
 * Sample 3 is approx. in the top-right quadrant.
 * (sample I={2,3} adds more detail to the vicinity of sample I-2)
 *
 * Sample 4 is approx. in the same quadrant as sample 0. (top-left)
 * Sample 5 is approx. in the same quadrant as sample 1. (bottom-right)
 * Sample 6 is approx. in the same quadrant as sample 2. (bottom-left)
 * Sample 7 is approx. in the same quadrant as sample 3. (top-right)
 * (sample I={4,5,6,7} adds more detail to the vicinity of sample I-4)
 *
 * The next 8 samples add more detail to the vicinity of the previous samples.
 * (sample I (I >= 8) adds more detail to the vicinity of sample I-8)
 *
 * The ordering is specified such that:
 *   If we take the first 2 samples, we should get good 2x MSAA.
 *   If we add 2 more samples, we should get good 4x MSAA with the same sample locations.
 *   If we add 4 more samples, we should get good 8x MSAA with the same sample locations.
 *   If we add 8 more samples, we should get perfect 16x MSAA with the same sample locations.
 *
 * The ordering also allows finding samples in the same vicinity.
 *
 * Group N of 2 samples in the same vicinity in 16x MSAA: {N,N+8}
 * Group N of 2 samples in the same vicinity in 8x MSAA: {N,N+4}
 * Group N of 2 samples in the same vicinity in 4x MSAA: {N,N+2}
 *
 * Groups of 4 samples in the same vicinity in 16x MSAA:
 *   Top left:     {0,4,8,12}
 *   Bottom right: {1,5,9,13}
 *   Bottom left:  {2,6,10,14}
 *   Top right:    {3,7,11,15}
 *
 * Groups of 4 samples in the same vicinity in 8x MSAA:
 *   Left half:  {0,2,4,6}
 *   Right half: {1,3,5,7}
 *
 * Groups of 8 samples in the same vicinity in 16x MSAA:
 *   Left half:  {0,2,4,6,8,10,12,14}
 *   Right half: {1,3,5,7,9,11,13,15}
 */

/* Important note: We have to use the standard DX positions because shader-based culling
 * relies on them.
 */

/* 1x MSAA */
static const uint32_t sample_locs_1x =
   FILL_SREG(0, 0, 0, 0, 0, 0, 0, 0); /* S1, S2, S3 fields are not used by 1x */
static const uint64_t centroid_priority_1x = 0x0000000000000000ull;

/* 2x MSAA (the positions are sorted for EQAA) */
static const uint32_t sample_locs_2x =
   FILL_SREG(-4, -4, 4, 4, 0, 0, 0, 0); /* S2 & S3 fields are not used by 2x MSAA */
static const uint64_t centroid_priority_2x = 0x1010101010101010ull;

/* 4x MSAA (the positions are sorted for EQAA) */
static const uint32_t sample_locs_4x = FILL_SREG(-2, -6, 2, 6, -6, 2, 6, -2);
static const uint64_t centroid_priority_4x = 0x3210321032103210ull;

/* 8x MSAA (the positions are sorted for EQAA) */
static const uint32_t sample_locs_8x[] = {
   FILL_SREG(-3, -5, 5, 1, -1, 3, 7, -7),
   FILL_SREG(-7, -1, 3, 7, -5, 5, 1, -3),
   /* The following are unused by hardware, but we emit them to IBs
    * instead of multiple SET_CONTEXT_REG packets. */
   0,
   0,
};
static const uint64_t centroid_priority_8x = 0x3546012735460127ull;

/* 16x MSAA (the positions are sorted for EQAA) */
static const uint32_t sample_locs_16x[] = {
   FILL_SREG(-5, -2, 5, 3, -2, 6, 3, -5),
   FILL_SREG(-4, -6, 1, 1, -6, 4, 7, -4),
   FILL_SREG(-1, -3, 6, 7, -3, 2, 0, -7),
   /* We use -7 where DX sample locations want -8, which allows us to make
    * the PA_SU_PRIM_FILTER_CNTL register immutable. That's a quality compromise
    * for underused 16x EQAA.
    */
   FILL_SREG(-7, -7 /* DX uses -8 */, 2, 5, -7 /* DX uses -8 */, 0, 4, -1),
};
static const uint64_t centroid_priority_16x = 0xc97e64b231d0fa85ull;

/* distance from the pixel center, indexed by log2(nr_samples) */
unsigned si_msaa_max_distance[5] = {
   0, /* no AA */
   4, /* 2x MSAA */
   6, /* 4x MSAA */
   7, /* 8x MSAA */
   7, /* 16x MSAA */
};

static void si_get_sample_position(struct pipe_context *ctx, unsigned sample_count,
                                   unsigned sample_index, float *out_value)
{
   const uint32_t *sample_locs;

   switch (sample_count) {
   case 1:
   default:
      sample_locs = &sample_locs_1x;
      break;
   case 2:
      sample_locs = &sample_locs_2x;
      break;
   case 4:
      sample_locs = &sample_locs_4x;
      break;
   case 8:
      sample_locs = sample_locs_8x;
      break;
   case 16:
      sample_locs = sample_locs_16x;
      break;
   }

   out_value[0] = (GET_SX(sample_locs, sample_index) + 8) / 16.0f;
   out_value[1] = (GET_SY(sample_locs, sample_index) + 8) / 16.0f;
}

static void si_emit_max_4_sample_locs(struct si_context *sctx, uint64_t centroid_priority,
                                      uint32_t sample_locs)
{
   if (sctx->screen->info.has_set_context_pairs_packed) {
      radeon_begin(&sctx->gfx_cs);
      gfx11_begin_packed_context_regs();
      gfx11_set_context_reg(R_028BD4_PA_SC_CENTROID_PRIORITY_0, centroid_priority);
      gfx11_set_context_reg(R_028BD8_PA_SC_CENTROID_PRIORITY_1, centroid_priority >> 32);
      gfx11_set_context_reg(R_028BF8_PA_SC_AA_SAMPLE_LOCS_PIXEL_X0Y0_0, sample_locs);
      gfx11_set_context_reg(R_028C08_PA_SC_AA_SAMPLE_LOCS_PIXEL_X1Y0_0, sample_locs);
      gfx11_set_context_reg(R_028C18_PA_SC_AA_SAMPLE_LOCS_PIXEL_X0Y1_0, sample_locs);
      gfx11_set_context_reg(R_028C28_PA_SC_AA_SAMPLE_LOCS_PIXEL_X1Y1_0, sample_locs);
      gfx11_end_packed_context_regs();
      radeon_end();
   } else {
      radeon_begin(&sctx->gfx_cs);
      radeon_set_context_reg_seq(R_028BD4_PA_SC_CENTROID_PRIORITY_0, 2);
      radeon_emit(centroid_priority);
      radeon_emit(centroid_priority >> 32);
      radeon_set_context_reg(R_028BF8_PA_SC_AA_SAMPLE_LOCS_PIXEL_X0Y0_0, sample_locs);
      radeon_set_context_reg(R_028C08_PA_SC_AA_SAMPLE_LOCS_PIXEL_X1Y0_0, sample_locs);
      radeon_set_context_reg(R_028C18_PA_SC_AA_SAMPLE_LOCS_PIXEL_X0Y1_0, sample_locs);
      radeon_set_context_reg(R_028C28_PA_SC_AA_SAMPLE_LOCS_PIXEL_X1Y1_0, sample_locs);
      radeon_end();
   }
}

static void si_emit_max_16_sample_locs(struct si_context *sctx, uint64_t centroid_priority,
                                       const uint32_t *sample_locs, unsigned num_samples)
{
   radeon_begin(&sctx->gfx_cs);
   radeon_set_context_reg_seq(R_028BD4_PA_SC_CENTROID_PRIORITY_0, 2);
   radeon_emit(centroid_priority);
   radeon_emit(centroid_priority >> 32);
   radeon_set_context_reg_seq(R_028BF8_PA_SC_AA_SAMPLE_LOCS_PIXEL_X0Y0_0,
                              num_samples == 8 ? 14 : 16);
   radeon_emit_array(sample_locs, 4);
   radeon_emit_array(sample_locs, 4);
   radeon_emit_array(sample_locs, 4);
   radeon_emit_array(sample_locs, num_samples == 8 ? 2 : 4);
   radeon_end();
}

static void si_emit_sample_locations(struct si_context *sctx, unsigned index)
{
   struct radeon_cmdbuf *cs = &sctx->gfx_cs;
   struct si_state_rasterizer *rs = sctx->queued.named.rasterizer;
   unsigned nr_samples = sctx->framebuffer.nr_samples;

   /* Smoothing (only possible with nr_samples == 1) uses the same
    * sample locations as the MSAA it simulates.
    */
   if (nr_samples <= 1 && sctx->smoothing_enabled)
      nr_samples = SI_NUM_SMOOTH_AA_SAMPLES;

   /* Always set MSAA sample locations even with 1x MSAA for simplicity.
    *
    * The only chips that don't need to set them for 1x MSAA are GFX6-8 except Polaris,
    * but there is no benefit in not resetting them to 0 when changing framebuffers from MSAA
    * to non-MSAA.
    */
   if (nr_samples != sctx->sample_locs_num_samples) {
      switch (nr_samples) {
      default:
      case 1:
         si_emit_max_4_sample_locs(sctx, centroid_priority_1x, sample_locs_1x);
         break;
      case 2:
         si_emit_max_4_sample_locs(sctx, centroid_priority_2x, sample_locs_2x);
         break;
      case 4:
         si_emit_max_4_sample_locs(sctx, centroid_priority_4x, sample_locs_4x);
         break;
      case 8:
         si_emit_max_16_sample_locs(sctx, centroid_priority_8x, sample_locs_8x, 8);
         break;
      case 16:
         si_emit_max_16_sample_locs(sctx, centroid_priority_16x, sample_locs_16x, 16);
         break;
      }
      sctx->sample_locs_num_samples = nr_samples;
   }

   if (sctx->screen->info.has_small_prim_filter_sample_loc_bug) {
      /* For hardware with the sample location bug, the problem is that in order to use the small
       * primitive filter, we need to explicitly set the sample locations to 0. But the DB doesn't
       * properly process the change of sample locations without a flush, and so we can end up
       * with incorrect Z values.
       *
       * Instead of doing a flush, just disable the small primitive filter when MSAA is
       * force-disabled.
       *
       * The alternative of setting sample locations to 0 would require a DB flush to avoid
       * Z errors, see https://bugs.freedesktop.org/show_bug.cgi?id=96908
       */
      bool small_prim_filter_enable = sctx->framebuffer.nr_samples <= 1 || rs->multisample_enable;
      assert(sctx->family >= CHIP_POLARIS10);

      radeon_begin(cs);
      radeon_opt_set_context_reg(sctx, R_028830_PA_SU_SMALL_PRIM_FILTER_CNTL,
                                 SI_TRACKED_PA_SU_SMALL_PRIM_FILTER_CNTL,
                                 S_028830_SMALL_PRIM_FILTER_ENABLE(small_prim_filter_enable) |
                                 /* Small line culling doesn't work on Polaris10-12. */
                                 S_028830_LINE_FILTER_DISABLE(sctx->family <= CHIP_POLARIS12));
      radeon_end();
   }
}

void si_init_msaa_functions(struct si_context *sctx)
{
   int i;

   sctx->atoms.s.sample_locations.emit = si_emit_sample_locations;
   sctx->b.get_sample_position = si_get_sample_position;

   si_get_sample_position(&sctx->b, 1, 0, sctx->sample_positions.x1[0]);

   for (i = 0; i < 2; i++)
      si_get_sample_position(&sctx->b, 2, i, sctx->sample_positions.x2[i]);
   for (i = 0; i < 4; i++)
      si_get_sample_position(&sctx->b, 4, i, sctx->sample_positions.x4[i]);
   for (i = 0; i < 8; i++)
      si_get_sample_position(&sctx->b, 8, i, sctx->sample_positions.x8[i]);
   for (i = 0; i < 16; i++)
      si_get_sample_position(&sctx->b, 16, i, sctx->sample_positions.x16[i]);
}