tree-wide: replace MAYBE_UNUSED with ASSERTED

[mesa.git] / src / gallium / drivers / radeonsi / si_compute_prim_discard.c

/*
 * Copyright 2019 Advanced Micro Devices, Inc.
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * on the rights to use, copy, modify, merge, publish, distribute, sub
 * license, and/or sell copies of the Software, and to permit persons to whom
 * the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */

#include "si_pipe.h"
#include "si_shader_internal.h"
#include "sid.h"
#include "si_build_pm4.h"
#include "ac_llvm_cull.h"

#include "util/u_prim.h"
#include "util/u_suballoc.h"
#include "util/u_upload_mgr.h"
#include "util/fast_idiv_by_const.h"

/* Based on:
 * https://frostbite-wp-prd.s3.amazonaws.com/wp-content/uploads/2016/03/29204330/GDC_2016_Compute.pdf
 */

/* This file implements primitive culling using asynchronous compute.
 * It's written to be GL conformant.
 *
 * It takes a monolithic VS in LLVM IR returning gl_Position and invokes it
 * in a compute shader. The shader processes 1 primitive/thread by invoking
 * the VS for each vertex to get the positions, decomposes strips and fans
 * into triangles (if needed), eliminates primitive restart (if needed),
 * does (W<0) culling, face culling, view XY culling, zero-area and
 * small-primitive culling, and generates a new index buffer that doesn't
 * contain culled primitives.
 *
 * The index buffer is generated using the Ordered Count feature of GDS,
 * which is an atomic counter that is incremented in the wavefront launch
 * order, so that the original primitive order is preserved.
 *
 * Another GDS ordered counter is used to eliminate primitive restart indices.
 * If a restart index lands on an even thread ID, the compute shader has to flip
 * the primitive orientation of the whole following triangle strip. The primitive
 * orientation has to be correct after strip and fan decomposition for two-sided
 * shading to behave correctly. The decomposition also needs to be aware of
 * which vertex is the provoking vertex for flat shading to behave correctly.
 *
 * IB = a GPU command buffer
 *
 * Both the compute and gfx IBs run in parallel sort of like CE and DE.
 * The gfx IB has a CP barrier (REWIND packet) before a draw packet. REWIND
 * doesn't continue if its word isn't 0x80000000. Once compute shaders are
 * finished culling, the last wave will write the final primitive count from
 * GDS directly into the count word of the draw packet in the gfx IB, and
 * a CS_DONE event will signal the REWIND packet to continue. It's really
 * a direct draw with command buffer patching from the compute queue.
 *
 * The compute IB doesn't have to start when its corresponding gfx IB starts,
 * but can start sooner. The compute IB is signaled to start after the last
 * execution barrier in the *previous* gfx IB. This is handled as follows.
 * The kernel GPU scheduler starts the compute IB after the previous gfx IB has
 * started. The compute IB then waits (WAIT_REG_MEM) for a mid-IB fence that
 * represents the barrier in the previous gfx IB.
 *
 * Features:
 * - Triangle strips and fans are decomposed into an indexed triangle list.
 *   The decomposition differs based on the provoking vertex state.
 * - Instanced draws are converted into non-instanced draws for 16-bit indices.
 *   (InstanceID is stored in the high bits of VertexID and unpacked by VS)
 * - Primitive restart is fully supported with triangle strips, including
 *   correct primitive orientation across multiple waves. (restart indices
 *   reset primitive orientation)
 * - W<0 culling (W<0 is behind the viewer, sort of like near Z culling).
 * - Back face culling, incl. culling zero-area / degenerate primitives.
 * - View XY culling.
 * - View Z culling (disabled due to limited impact with perspective projection).
 * - Small primitive culling for all MSAA modes and all quant modes.
 *
 * The following are not implemented:
 * - ClipVertex/ClipDistance/CullDistance-based culling.
 * - Scissor culling.
 * - HiZ culling.
 *
 * Limitations (and unimplemented features that may be possible to implement):
 * - Only triangles, triangle strips, and triangle fans are supported.
 * - Primitive restart is only supported with triangle strips.
 * - Instancing and primitive restart can't be used together.
 * - Instancing is only supported with 16-bit indices and instance count <= 2^16.
 * - The instance divisor buffer is unavailable, so all divisors must be
 *   either 0 or 1.
 * - Multidraws where the vertex shader reads gl_DrawID are unsupported.
 * - No support for tessellation and geometry shaders.
 *   (patch elimination where tess factors are 0 would be possible to implement)
 * - The vertex shader must not contain memory stores.
 * - All VS resources must not have a write usage in the command buffer.
 *   (TODO: all shader buffers currently set the write usage)
 * - Bindless textures and images must not occur in the vertex shader.
 *
 * User data SGPR layout:
 *   INDEX_BUFFERS: pointer to constants
 *     0..3: input index buffer - typed buffer view
 *     4..7: output index buffer - typed buffer view
 *     8..11: viewport state - scale.xy, translate.xy
 *   VERTEX_COUNTER: counter address or first primitive ID
 *     - If unordered memory counter: address of "count" in the draw packet
 *       and is incremented atomically by the shader.
 *     - If unordered GDS counter: address of "count" in GDS starting from 0,
 *       must be initialized to 0 before the dispatch.
 *     - If ordered GDS counter: the primitive ID that should reset the vertex
 *       counter to 0 in GDS
 *   LAST_WAVE_PRIM_ID: the primitive ID that should write the final vertex
 *       count to memory if using GDS ordered append
 *   VERTEX_COUNT_ADDR: where the last wave should write the vertex count if
 *       using GDS ordered append
 *   VS.VERTEX_BUFFERS:           same value as VS
 *   VS.CONST_AND_SHADER_BUFFERS: same value as VS
 *   VS.SAMPLERS_AND_IMAGES:      same value as VS
 *   VS.BASE_VERTEX:              same value as VS
 *   VS.START_INSTANCE:           same value as VS
 *   NUM_PRIMS_UDIV_MULTIPLIER: For fast 31-bit division by the number of primitives
 *       per instance for instancing.
 *   NUM_PRIMS_UDIV_TERMS:
 *     - Bits [0:4]: "post_shift" for fast 31-bit division for instancing.
 *     - Bits [5:31]: The number of primitives per instance for computing the remainder.
 *   PRIMITIVE_RESTART_INDEX
 *   SMALL_PRIM_CULLING_PRECISION: Scale the primitive bounding box by this number.
 *
 *
 * The code contains 3 codepaths:
 * - Unordered memory counter (for debugging, random primitive order, no primitive restart)
 * - Unordered GDS counter (for debugging, random primitive order, no primitive restart)
 * - Ordered GDS counter (it preserves the primitive order)
 *
 * How to test primitive restart (the most complicated part because it needs
 * to get the primitive orientation right):
 *   Set THREADGROUP_SIZE to 2 to exercise both intra-wave and inter-wave
 *   primitive orientation flips with small draw calls, which is what most tests use.
 *   You can also enable draw call splitting into draw calls with just 2 primitives.
 */

/* At least 256 is needed for the fastest wave launch rate from compute queues
 * due to hw constraints. Nothing in the code needs more than 1 wave/threadgroup. */
#define THREADGROUP_SIZE                256 /* high numbers limit available VGPRs */
#define THREADGROUPS_PER_CU             1 /* TGs to launch on 1 CU before going onto the next, max 8 */
#define MAX_WAVES_PER_SH                0 /* no limit */
#define INDEX_STORES_USE_SLC            1 /* don't cache indices if L2 is full */
/* Don't cull Z. We already do (W < 0) culling for primitives behind the viewer. */
#define CULL_Z                          0
/* 0 = unordered memory counter, 1 = unordered GDS counter, 2 = ordered GDS counter */
#define VERTEX_COUNTER_GDS_MODE         2
#define GDS_SIZE_UNORDERED              (4 * 1024) /* only for the unordered GDS counter */

/* Grouping compute dispatches for small draw calls: How many primitives from multiple
 * draw calls to process by compute before signaling the gfx IB. This reduces the number
 * of EOP events + REWIND packets, because they decrease performance. */
#define PRIMS_PER_BATCH                 (512 * 1024)
/* Draw call splitting at the packet level. This allows signaling the gfx IB
 * for big draw calls sooner, but doesn't allow context flushes between packets.
 * Primitive restart is supported. Only implemented for ordered append. */
#define SPLIT_PRIMS_PACKET_LEVEL_VALUE  PRIMS_PER_BATCH
/* If there is not enough ring buffer space for the current IB, split draw calls into
 * this number of primitives, so that we can flush the context and get free ring space. */
#define SPLIT_PRIMS_DRAW_LEVEL          PRIMS_PER_BATCH

/* Derived values. */
#define WAVES_PER_TG                    DIV_ROUND_UP(THREADGROUP_SIZE, 64)
#define SPLIT_PRIMS_PACKET_LEVEL        (VERTEX_COUNTER_GDS_MODE == 2 ? \
                                         SPLIT_PRIMS_PACKET_LEVEL_VALUE : \
                                         UINT_MAX & ~(THREADGROUP_SIZE - 1))

#define REWIND_SIGNAL_BIT               0x80000000
/* For emulating the rewind packet on CI. */
#define FORCE_REWIND_EMULATION          0

void si_initialize_prim_discard_tunables(struct si_context *sctx)
{
        sctx->prim_discard_vertex_count_threshold = UINT_MAX; /* disable */

        if (sctx->chip_class == GFX6 || /* SI support is not implemented */
            !sctx->screen->info.has_gds_ordered_append ||
            sctx->screen->debug_flags & DBG(NO_PD) ||
            /* If aux_context == NULL, we are initializing aux_context right now. */
            !sctx->screen->aux_context)
                return;

        /* TODO: enable this after the GDS kernel memory management is fixed */
        bool enable_on_pro_graphics_by_default = false;

        if (sctx->screen->debug_flags & DBG(ALWAYS_PD) ||
            sctx->screen->debug_flags & DBG(PD) ||
            (enable_on_pro_graphics_by_default &&
             sctx->screen->info.is_pro_graphics &&
             (sctx->family == CHIP_BONAIRE ||
              sctx->family == CHIP_HAWAII ||
              sctx->family == CHIP_TONGA ||
              sctx->family == CHIP_FIJI ||
              sctx->family == CHIP_POLARIS10 ||
              sctx->family == CHIP_POLARIS11 ||
              sctx->family == CHIP_VEGA10 ||
              sctx->family == CHIP_VEGA20))) {
                sctx->prim_discard_vertex_count_threshold = 6000 * 3; /* 6K triangles */

                if (sctx->screen->debug_flags & DBG(ALWAYS_PD))
                        sctx->prim_discard_vertex_count_threshold = 0; /* always enable */

                const uint32_t MB = 1024 * 1024;
                const uint64_t GB = 1024 * 1024 * 1024;

                /* The total size is double this per context.
                 * Greater numbers allow bigger gfx IBs.
                 */
                if (sctx->screen->info.vram_size <= 2 * GB)
                        sctx->index_ring_size_per_ib = 64 * MB;
                else if (sctx->screen->info.vram_size <= 4 * GB)
                        sctx->index_ring_size_per_ib = 128 * MB;
                else
                        sctx->index_ring_size_per_ib = 256 * MB;
        }
}

/* Opcode can be "add" or "swap". */
static LLVMValueRef
si_build_ds_ordered_op(struct si_shader_context *ctx, const char *opcode,
                       LLVMValueRef m0, LLVMValueRef value, unsigned ordered_count_index,
                       bool release, bool done)
{
        LLVMValueRef args[] = {
                LLVMBuildIntToPtr(ctx->ac.builder, m0,
                                  LLVMPointerType(ctx->i32, AC_ADDR_SPACE_GDS), ""),
                value,
                LLVMConstInt(ctx->i32, LLVMAtomicOrderingMonotonic, 0), /* ordering */
                ctx->i32_0, /* scope */
                ctx->i1false, /* volatile */
                LLVMConstInt(ctx->i32, ordered_count_index, 0),
                LLVMConstInt(ctx->i1, release, 0),
                LLVMConstInt(ctx->i1, done, 0),
        };

        char intrinsic[64];
        snprintf(intrinsic, sizeof(intrinsic), "llvm.amdgcn.ds.ordered.%s", opcode);
        return ac_build_intrinsic(&ctx->ac, intrinsic, ctx->i32, args, ARRAY_SIZE(args), 0);
}

static LLVMValueRef si_expand_32bit_pointer(struct si_shader_context *ctx, LLVMValueRef ptr)
{
        uint64_t hi = (uint64_t)ctx->screen->info.address32_hi << 32;
        ptr = LLVMBuildZExt(ctx->ac.builder, ptr, ctx->i64, "");
        ptr = LLVMBuildOr(ctx->ac.builder, ptr, LLVMConstInt(ctx->i64, hi, 0), "");
        return LLVMBuildIntToPtr(ctx->ac.builder, ptr,
                                 LLVMPointerType(ctx->i32, AC_ADDR_SPACE_GLOBAL), "");
}

struct si_thread0_section {
        struct si_shader_context *ctx;
        LLVMValueRef vgpr_result; /* a VGPR for the value on thread 0. */
        LLVMValueRef saved_exec;
};

/* Enter a section that only executes on thread 0. */
static void si_enter_thread0_section(struct si_shader_context *ctx,
                                     struct si_thread0_section *section,
                                     LLVMValueRef thread_id)
{
        section->ctx = ctx;
        section->vgpr_result = ac_build_alloca_undef(&ctx->ac, ctx->i32, "result0");

        /* This IF has 4 instructions:
         *   v_and_b32_e32 v, 63, v         ; get the thread ID
         *   v_cmp_eq_u32_e32 vcc, 0, v     ; thread ID == 0
         *   s_and_saveexec_b64 s, vcc
         *   s_cbranch_execz BB0_4
         *
         * It could just be s_and_saveexec_b64 s, 1.
         */
        ac_build_ifcc(&ctx->ac,
                      LLVMBuildICmp(ctx->ac.builder, LLVMIntEQ, thread_id,
                                    ctx->i32_0, ""), 12601);
}

/* Exit a section that only executes on thread 0 and broadcast the result
 * to all threads. */
static void si_exit_thread0_section(struct si_thread0_section *section,
                                    LLVMValueRef *result)
{
        struct si_shader_context *ctx = section->ctx;

        LLVMBuildStore(ctx->ac.builder, *result, section->vgpr_result);

        ac_build_endif(&ctx->ac, 12601);

        /* Broadcast the result from thread 0 to all threads. */
        *result = ac_build_readlane(&ctx->ac,
                        LLVMBuildLoad(ctx->ac.builder, section->vgpr_result, ""), NULL);
}

void si_build_prim_discard_compute_shader(struct si_shader_context *ctx)
{
        struct si_shader_key *key = &ctx->shader->key;
        LLVMBuilderRef builder = ctx->ac.builder;
        LLVMValueRef vs = ctx->main_fn;

        /* Always inline the VS function. */
        ac_add_function_attr(ctx->ac.context, vs, -1, AC_FUNC_ATTR_ALWAYSINLINE);
        LLVMSetLinkage(vs, LLVMPrivateLinkage);

        LLVMTypeRef const_desc_type;
        if (ctx->shader->selector->info.const_buffers_declared == 1 &&
            ctx->shader->selector->info.shader_buffers_declared == 0)
                const_desc_type = ctx->f32;
        else
                const_desc_type = ctx->v4i32;

        struct si_function_info fninfo;
        si_init_function_info(&fninfo);

        LLVMValueRef index_buffers_and_constants, vertex_counter, vb_desc, const_desc;
        LLVMValueRef base_vertex, start_instance, block_id, local_id, ordered_wave_id;
        LLVMValueRef restart_index, vp_scale[2], vp_translate[2], smallprim_precision;
        LLVMValueRef num_prims_udiv_multiplier, num_prims_udiv_terms, sampler_desc;
        LLVMValueRef last_wave_prim_id, vertex_count_addr;

        add_arg_assign(&fninfo, ARG_SGPR, ac_array_in_const32_addr_space(ctx->v4i32),
                       &index_buffers_and_constants);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &vertex_counter);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &last_wave_prim_id);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &vertex_count_addr);
        add_arg_assign(&fninfo, ARG_SGPR, ac_array_in_const32_addr_space(ctx->v4i32),
                       &vb_desc);
        add_arg_assign(&fninfo, ARG_SGPR, ac_array_in_const32_addr_space(const_desc_type),
                       &const_desc);
        add_arg_assign(&fninfo, ARG_SGPR, ac_array_in_const32_addr_space(ctx->v8i32),
                       &sampler_desc);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &base_vertex);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &start_instance);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &num_prims_udiv_multiplier);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &num_prims_udiv_terms);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &restart_index);
        add_arg_assign(&fninfo, ARG_SGPR, ctx->f32, &smallprim_precision);

        /* Block ID and thread ID inputs. */
        add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &block_id);
        if (VERTEX_COUNTER_GDS_MODE == 2)
                add_arg_assign(&fninfo, ARG_SGPR, ctx->i32, &ordered_wave_id);
        add_arg_assign(&fninfo, ARG_VGPR, ctx->i32, &local_id);

        /* Create the compute shader function. */
        unsigned old_type = ctx->type;
        ctx->type = PIPE_SHADER_COMPUTE;
        si_create_function(ctx, "prim_discard_cs", NULL, 0, &fninfo, THREADGROUP_SIZE);
        ctx->type = old_type;

        if (VERTEX_COUNTER_GDS_MODE == 1) {
                ac_llvm_add_target_dep_function_attr(ctx->main_fn, "amdgpu-gds-size",
                                                     GDS_SIZE_UNORDERED);
        }

        /* Assemble parameters for VS. */
        LLVMValueRef vs_params[16];
        unsigned num_vs_params = 0;
        unsigned param_vertex_id, param_instance_id;

        vs_params[num_vs_params++] = LLVMGetUndef(LLVMTypeOf(LLVMGetParam(vs, 0))); /* RW_BUFFERS */
        vs_params[num_vs_params++] = LLVMGetUndef(LLVMTypeOf(LLVMGetParam(vs, 1))); /* BINDLESS */
        vs_params[num_vs_params++] = const_desc;
        vs_params[num_vs_params++] = sampler_desc;
        vs_params[num_vs_params++] = LLVMConstInt(ctx->i32,
                                        S_VS_STATE_INDEXED(key->opt.cs_indexed), 0);
        vs_params[num_vs_params++] = base_vertex;
        vs_params[num_vs_params++] = start_instance;
        vs_params[num_vs_params++] = ctx->i32_0; /* DrawID */
        vs_params[num_vs_params++] = vb_desc;

        vs_params[(param_vertex_id = num_vs_params++)] = NULL; /* VertexID */
        vs_params[(param_instance_id = num_vs_params++)] = NULL; /* InstanceID */
        vs_params[num_vs_params++] = ctx->i32_0; /* unused (PrimID) */
        vs_params[num_vs_params++] = ctx->i32_0; /* unused */

        assert(num_vs_params <= ARRAY_SIZE(vs_params));
        assert(num_vs_params == LLVMCountParamTypes(LLVMGetElementType(LLVMTypeOf(vs))));

        /* Load descriptors. (load 8 dwords at once) */
        LLVMValueRef input_indexbuf, output_indexbuf, tmp, desc[8];

        tmp = LLVMBuildPointerCast(builder, index_buffers_and_constants,
                                   ac_array_in_const32_addr_space(ctx->v8i32), "");
        tmp = ac_build_load_to_sgpr(&ctx->ac, tmp, ctx->i32_0);

        for (unsigned i = 0; i < 8; i++)
                desc[i] = ac_llvm_extract_elem(&ctx->ac, tmp, i);

        input_indexbuf = ac_build_gather_values(&ctx->ac, desc, 4);
        output_indexbuf = ac_build_gather_values(&ctx->ac, desc + 4, 4);

        /* Compute PrimID and InstanceID. */
        LLVMValueRef global_thread_id =
                ac_build_imad(&ctx->ac, block_id,
                              LLVMConstInt(ctx->i32, THREADGROUP_SIZE, 0), local_id);
        LLVMValueRef prim_id = global_thread_id; /* PrimID within an instance */
        LLVMValueRef instance_id = ctx->i32_0;

        if (key->opt.cs_instancing) {
                /* Unpack num_prims_udiv_terms. */
                LLVMValueRef post_shift = LLVMBuildAnd(builder, num_prims_udiv_terms,
                                                       LLVMConstInt(ctx->i32, 0x1f, 0), "");
                LLVMValueRef prims_per_instance = LLVMBuildLShr(builder, num_prims_udiv_terms,
                                                                LLVMConstInt(ctx->i32, 5, 0), "");
                /* Divide the total prim_id by the number of prims per instance. */
                instance_id = ac_build_fast_udiv_u31_d_not_one(&ctx->ac, prim_id,
                                                               num_prims_udiv_multiplier,
                                                               post_shift);
                /* Compute the remainder. */
                prim_id = LLVMBuildSub(builder, prim_id,
                                       LLVMBuildMul(builder, instance_id,
                                                    prims_per_instance, ""), "");
        }

        /* Generate indices (like a non-indexed draw call). */
        LLVMValueRef index[4] = {NULL, NULL, NULL, LLVMGetUndef(ctx->i32)};
        unsigned vertices_per_prim = 3;

        switch (key->opt.cs_prim_type) {
        case PIPE_PRIM_TRIANGLES:
                for (unsigned i = 0; i < 3; i++) {
                        index[i] = ac_build_imad(&ctx->ac, prim_id,
                                                 LLVMConstInt(ctx->i32, 3, 0),
                                                 LLVMConstInt(ctx->i32, i, 0));
                }
                break;
        case PIPE_PRIM_TRIANGLE_STRIP:
                for (unsigned i = 0; i < 3; i++) {
                        index[i] = LLVMBuildAdd(builder, prim_id,
                                                LLVMConstInt(ctx->i32, i, 0), "");
                }
                break;
        case PIPE_PRIM_TRIANGLE_FAN:
                /* Vertex 1 is first and vertex 2 is last. This will go to the hw clipper
                 * and rasterizer as a normal triangle, so we need to put the provoking
                 * vertex into the correct index variable and preserve orientation at the same time.
                 * gl_VertexID is preserved, because it's equal to the index.
                 */
                if (key->opt.cs_provoking_vertex_first) {
                        index[0] = LLVMBuildAdd(builder, prim_id, LLVMConstInt(ctx->i32, 1, 0), "");
                        index[1] = LLVMBuildAdd(builder, prim_id, LLVMConstInt(ctx->i32, 2, 0), "");
                        index[2] = ctx->i32_0;
                } else {
                        index[0] = ctx->i32_0;
                        index[1] = LLVMBuildAdd(builder, prim_id, LLVMConstInt(ctx->i32, 1, 0), "");
                        index[2] = LLVMBuildAdd(builder, prim_id, LLVMConstInt(ctx->i32, 2, 0), "");
                }
                break;
        default:
                unreachable("unexpected primitive type");
        }

        /* Fetch indices. */
        if (key->opt.cs_indexed) {
                for (unsigned i = 0; i < 3; i++) {
                        index[i] = ac_build_buffer_load_format(&ctx->ac, input_indexbuf,
                                                               index[i], ctx->i32_0, 1,
                                                               0, true);
                        index[i] = ac_to_integer(&ctx->ac, index[i]);
                }
        }

        /* Extract the ordered wave ID. */
        if (VERTEX_COUNTER_GDS_MODE == 2) {
                ordered_wave_id = LLVMBuildLShr(builder, ordered_wave_id,
                                                LLVMConstInt(ctx->i32, 6, 0), "");
                ordered_wave_id = LLVMBuildAnd(builder, ordered_wave_id,
                                               LLVMConstInt(ctx->i32, 0xfff, 0), "");
        }
        LLVMValueRef thread_id =
                LLVMBuildAnd(builder, local_id, LLVMConstInt(ctx->i32, 63, 0), "");

        /* Every other triangle in a strip has a reversed vertex order, so we
         * need to swap vertices of odd primitives to get the correct primitive
         * orientation when converting triangle strips to triangles. Primitive
         * restart complicates it, because a strip can start anywhere.
         */
        LLVMValueRef prim_restart_accepted = ctx->i1true;

        if (key->opt.cs_prim_type == PIPE_PRIM_TRIANGLE_STRIP) {
                /* Without primitive restart, odd primitives have reversed orientation.
                 * Only primitive restart can flip it with respect to the first vertex
                 * of the draw call.
                 */
                LLVMValueRef first_is_odd = ctx->i1false;

                /* Handle primitive restart. */
                if (key->opt.cs_primitive_restart) {
                        /* Get the GDS primitive restart continue flag and clear
                         * the flag in vertex_counter. This flag is used when the draw
                         * call was split and we need to load the primitive orientation
                         * flag from GDS for the first wave too.
                         */
                        LLVMValueRef gds_prim_restart_continue =
                                LLVMBuildLShr(builder, vertex_counter,
                                              LLVMConstInt(ctx->i32, 31, 0), "");
                        gds_prim_restart_continue =
                                LLVMBuildTrunc(builder, gds_prim_restart_continue, ctx->i1, "");
                        vertex_counter = LLVMBuildAnd(builder, vertex_counter,
                                                      LLVMConstInt(ctx->i32, 0x7fffffff, 0), "");

                        LLVMValueRef index0_is_reset;

                        for (unsigned i = 0; i < 3; i++) {
                                LLVMValueRef not_reset = LLVMBuildICmp(builder, LLVMIntNE, index[i],
                                                                       restart_index, "");
                                if (i == 0)
                                        index0_is_reset = LLVMBuildNot(builder, not_reset, "");
                                prim_restart_accepted = LLVMBuildAnd(builder, prim_restart_accepted,
                                                                     not_reset, "");
                        }

                        /* If the previous waves flip the primitive orientation
                         * of the current triangle strip, it will be stored in GDS.
                         *
                         * Sometimes the correct orientation is not needed, in which case
                         * we don't need to execute this.
                         */
                        if (key->opt.cs_need_correct_orientation && VERTEX_COUNTER_GDS_MODE == 2) {
                                /* If there are reset indices in this wave, get the thread index
                                 * where the most recent strip starts relative to each thread.
                                 */
                                LLVMValueRef preceding_threads_mask =
                                        LLVMBuildSub(builder,
                                                     LLVMBuildShl(builder, ctx->ac.i64_1,
                                                                  LLVMBuildZExt(builder, thread_id, ctx->i64, ""), ""),
                                                     ctx->ac.i64_1, "");

                                LLVMValueRef reset_threadmask = ac_get_i1_sgpr_mask(&ctx->ac, index0_is_reset);
                                LLVMValueRef preceding_reset_threadmask =
                                        LLVMBuildAnd(builder, reset_threadmask, preceding_threads_mask, "");
                                LLVMValueRef strip_start =
                                        ac_build_umsb(&ctx->ac, preceding_reset_threadmask, NULL);
                                strip_start = LLVMBuildAdd(builder, strip_start, ctx->i32_1, "");

                                /* This flips the orientatino based on reset indices within this wave only. */
                                first_is_odd = LLVMBuildTrunc(builder, strip_start, ctx->i1, "");

                                LLVMValueRef last_strip_start, prev_wave_state, ret, tmp;
                                LLVMValueRef is_first_wave, current_wave_resets_index;

                                /* Get the thread index where the last strip starts in this wave.
                                 *
                                 * If the last strip doesn't start in this wave, the thread index
                                 * will be 0.
                                 *
                                 * If the last strip starts in the next wave, the thread index will
                                 * be 64.
                                 */
                                last_strip_start = ac_build_umsb(&ctx->ac, reset_threadmask, NULL);
                                last_strip_start = LLVMBuildAdd(builder, last_strip_start, ctx->i32_1, "");

                                struct si_thread0_section section;
                                si_enter_thread0_section(ctx, &section, thread_id);

                                /* This must be done in the thread 0 section, because
                                 * we expect PrimID to be 0 for the whole first wave
                                 * in this expression.
                                 *
                                 * NOTE: This will need to be different if we wanna support
                                 * instancing with primitive restart.
                                 */
                                is_first_wave = LLVMBuildICmp(builder, LLVMIntEQ, prim_id, ctx->i32_0, "");
                                is_first_wave = LLVMBuildAnd(builder, is_first_wave,
                                                             LLVMBuildNot(builder,
                                                                          gds_prim_restart_continue, ""), "");
                                current_wave_resets_index = LLVMBuildICmp(builder, LLVMIntNE,
                                                                          last_strip_start, ctx->i32_0, "");

                                ret = ac_build_alloca_undef(&ctx->ac, ctx->i32, "prev_state");

                                /* Save the last strip start primitive index in GDS and read
                                 * the value that previous waves stored.
                                 *
                                 * if (is_first_wave || current_wave_resets_strip)
                                 *    // Read the value that previous waves stored and store a new one.
                                 *    first_is_odd = ds.ordered.swap(last_strip_start);
                                 * else
                                 *    // Just read the value that previous waves stored.
                                 *    first_is_odd = ds.ordered.add(0);
                                 */
                                ac_build_ifcc(&ctx->ac,
                                              LLVMBuildOr(builder, is_first_wave,
                                                          current_wave_resets_index, ""), 12602);
                                {
                                        /* The GDS address is always 0 with ordered append. */
                                        tmp = si_build_ds_ordered_op(ctx, "swap",
                                                                     ordered_wave_id, last_strip_start,
                                                                     1, true, false);
                                        LLVMBuildStore(builder, tmp, ret);
                                }
                                ac_build_else(&ctx->ac, 12603);
                                {
                                        /* Just read the value from GDS. */
                                        tmp = si_build_ds_ordered_op(ctx, "add",
                                                                     ordered_wave_id, ctx->i32_0,
                                                                     1, true, false);
                                        LLVMBuildStore(builder, tmp, ret);
                                }
                                ac_build_endif(&ctx->ac, 12602);

                                prev_wave_state = LLVMBuildLoad(builder, ret, "");
                                /* Ignore the return value if this is the first wave. */
                                prev_wave_state = LLVMBuildSelect(builder, is_first_wave,
                                                                  ctx->i32_0, prev_wave_state, "");
                                si_exit_thread0_section(&section, &prev_wave_state);
                                prev_wave_state = LLVMBuildTrunc(builder, prev_wave_state, ctx->i1, "");

                                /* If the strip start appears to be on thread 0 for the current primitive
                                 * (meaning the reset index is not present in this wave and might have
                                 * appeared in previous waves), use the value from GDS to determine
                                 * primitive orientation.
                                 *
                                 * If the strip start is in this wave for the current primitive, use
                                 * the value from the current wave to determine primitive orientation.
                                 */
                                LLVMValueRef strip_start_is0 = LLVMBuildICmp(builder, LLVMIntEQ,
                                                                             strip_start, ctx->i32_0, "");
                                first_is_odd = LLVMBuildSelect(builder, strip_start_is0, prev_wave_state,
                                                               first_is_odd, "");
                        }
                }
                /* prim_is_odd = (first_is_odd + current_is_odd) % 2. */
                LLVMValueRef prim_is_odd =
                        LLVMBuildXor(builder, first_is_odd,
                                     LLVMBuildTrunc(builder, thread_id, ctx->i1, ""), "");

                /* Determine the primitive orientation.
                 * Only swap the vertices that are not the provoking vertex. We need to keep
                 * the provoking vertex in place.
                 */
                if (key->opt.cs_provoking_vertex_first) {
                        LLVMValueRef index1 = index[1];
                        LLVMValueRef index2 = index[2];
                        index[1] = LLVMBuildSelect(builder, prim_is_odd, index2, index1, "");
                        index[2] = LLVMBuildSelect(builder, prim_is_odd, index1, index2, "");
                } else {
                        LLVMValueRef index0 = index[0];
                        LLVMValueRef index1 = index[1];
                        index[0] = LLVMBuildSelect(builder, prim_is_odd, index1, index0, "");
                        index[1] = LLVMBuildSelect(builder, prim_is_odd, index0, index1, "");
                }
        }

        /* Execute the vertex shader for each vertex to get vertex positions. */
        LLVMValueRef pos[3][4];
        for (unsigned i = 0; i < vertices_per_prim; i++) {
                vs_params[param_vertex_id] = index[i];
                vs_params[param_instance_id] = instance_id;

                LLVMValueRef ret = ac_build_call(&ctx->ac, vs, vs_params, num_vs_params);
                for (unsigned chan = 0; chan < 4; chan++)
                        pos[i][chan] = LLVMBuildExtractValue(builder, ret, chan, "");
        }

        /* Divide XYZ by W. */
        for (unsigned i = 0; i < vertices_per_prim; i++) {
                for (unsigned chan = 0; chan < 3; chan++)
                        pos[i][chan] = ac_build_fdiv(&ctx->ac, pos[i][chan], pos[i][3]);
        }

        /* Load the viewport state. */
        LLVMValueRef vp = ac_build_load_invariant(&ctx->ac, index_buffers_and_constants,
                                                  LLVMConstInt(ctx->i32, 2, 0));
        vp = LLVMBuildBitCast(builder, vp, ctx->v4f32, "");
        vp_scale[0] = ac_llvm_extract_elem(&ctx->ac, vp, 0);
        vp_scale[1] = ac_llvm_extract_elem(&ctx->ac, vp, 1);
        vp_translate[0] = ac_llvm_extract_elem(&ctx->ac, vp, 2);
        vp_translate[1] = ac_llvm_extract_elem(&ctx->ac, vp, 3);

        /* Do culling. */
        struct ac_cull_options options = {};
        options.cull_front = key->opt.cs_cull_front;
        options.cull_back = key->opt.cs_cull_back;
        options.cull_view_xy = true;
        options.cull_view_near_z = CULL_Z && key->opt.cs_cull_z;
        options.cull_view_far_z = CULL_Z && key->opt.cs_cull_z;
        options.cull_small_prims = true;
        options.cull_zero_area = true;
        options.cull_w = true;
        options.use_halfz_clip_space = key->opt.cs_halfz_clip_space;

        LLVMValueRef accepted =
                ac_cull_triangle(&ctx->ac, pos, prim_restart_accepted,
                                 vp_scale, vp_translate, smallprim_precision,
                                 &options);

        LLVMValueRef accepted_threadmask = ac_get_i1_sgpr_mask(&ctx->ac, accepted);

        /* Count the number of active threads by doing bitcount(accepted). */
        LLVMValueRef num_prims_accepted =
                ac_build_intrinsic(&ctx->ac, "llvm.ctpop.i64", ctx->i64,
                                   &accepted_threadmask, 1, AC_FUNC_ATTR_READNONE);
        num_prims_accepted = LLVMBuildTrunc(builder, num_prims_accepted, ctx->i32, "");

        LLVMValueRef start;

        /* Execute atomic_add on the vertex count. */
        struct si_thread0_section section;
        si_enter_thread0_section(ctx, &section, thread_id);
        {
                if (VERTEX_COUNTER_GDS_MODE == 0) {
                        LLVMValueRef num_indices = LLVMBuildMul(builder, num_prims_accepted,
                                                LLVMConstInt(ctx->i32, vertices_per_prim, 0), "");
                        vertex_counter = si_expand_32bit_pointer(ctx, vertex_counter);
                        start = LLVMBuildAtomicRMW(builder, LLVMAtomicRMWBinOpAdd,
                                                   vertex_counter, num_indices,
                                                   LLVMAtomicOrderingMonotonic, false);
                } else if (VERTEX_COUNTER_GDS_MODE == 1) {
                        LLVMValueRef num_indices = LLVMBuildMul(builder, num_prims_accepted,
                                                LLVMConstInt(ctx->i32, vertices_per_prim, 0), "");
                        vertex_counter = LLVMBuildIntToPtr(builder, vertex_counter,
                                                           LLVMPointerType(ctx->i32, AC_ADDR_SPACE_GDS), "");
                        start = LLVMBuildAtomicRMW(builder, LLVMAtomicRMWBinOpAdd,
                                                   vertex_counter, num_indices,
                                                   LLVMAtomicOrderingMonotonic, false);
                } else if (VERTEX_COUNTER_GDS_MODE == 2) {
                        LLVMValueRef tmp_store = ac_build_alloca_undef(&ctx->ac, ctx->i32, "");

                        /* If the draw call was split into multiple subdraws, each using
                         * a separate draw packet, we need to start counting from 0 for
                         * the first compute wave of the subdraw.
                         *
                         * vertex_counter contains the primitive ID of the first thread
                         * in the first wave.
                         *
                         * This is only correct with VERTEX_COUNTER_GDS_MODE == 2:
                         */
                        LLVMValueRef is_first_wave =
                                LLVMBuildICmp(builder, LLVMIntEQ, global_thread_id,
                                              vertex_counter, "");

                        /* Store the primitive count for ordered append, not vertex count.
                         * The idea is to avoid GDS initialization via CP DMA. The shader
                         * effectively stores the first count using "swap".
                         *
                         * if (first_wave) {
                         *    ds.ordered.swap(num_prims_accepted); // store the first primitive count
                         *    previous = 0;
                         * } else {
                         *    previous = ds.ordered.add(num_prims_accepted) // add the primitive count
                         * }
                         */
                        ac_build_ifcc(&ctx->ac, is_first_wave, 12604);
                        {
                                /* The GDS address is always 0 with ordered append. */
                                si_build_ds_ordered_op(ctx, "swap", ordered_wave_id,
                                                       num_prims_accepted, 0, true, true);
                                LLVMBuildStore(builder, ctx->i32_0, tmp_store);
                        }
                        ac_build_else(&ctx->ac, 12605);
                        {
                                LLVMBuildStore(builder,
                                               si_build_ds_ordered_op(ctx, "add", ordered_wave_id,
                                                                      num_prims_accepted, 0,
                                                                      true, true),
                                               tmp_store);
                        }
                        ac_build_endif(&ctx->ac, 12604);

                        start = LLVMBuildLoad(builder, tmp_store, "");
                }
        }
        si_exit_thread0_section(&section, &start);

        /* Write the final vertex count to memory. An EOS/EOP event could do this,
         * but those events are super slow and should be avoided if performance
         * is a concern. Thanks to GDS ordered append, we can emulate a CS_DONE
         * event like this.
         */
        if (VERTEX_COUNTER_GDS_MODE == 2) {
                ac_build_ifcc(&ctx->ac,
                              LLVMBuildICmp(builder, LLVMIntEQ, global_thread_id,
                                            last_wave_prim_id, ""), 12606);
                LLVMValueRef count = LLVMBuildAdd(builder, start, num_prims_accepted, "");
                count = LLVMBuildMul(builder, count,
                                     LLVMConstInt(ctx->i32, vertices_per_prim, 0), "");

                /* GFX8 needs to disable caching, so that the CP can see the stored value.
                 * MTYPE=3 bypasses TC L2.
                 */
                if (ctx->screen->info.chip_class <= GFX8) {
                        LLVMValueRef desc[] = {
                                vertex_count_addr,
                                LLVMConstInt(ctx->i32,
                                        S_008F04_BASE_ADDRESS_HI(ctx->screen->info.address32_hi), 0),
                                LLVMConstInt(ctx->i32, 4, 0),
                                LLVMConstInt(ctx->i32, S_008F0C_DATA_FORMAT(V_008F0C_BUF_DATA_FORMAT_32) |
                                                       S_008F0C_MTYPE(3 /* uncached */), 0),
                        };
                        LLVMValueRef rsrc = ac_build_gather_values(&ctx->ac, desc, 4);
                        ac_build_buffer_store_dword(&ctx->ac, rsrc, count, 1, ctx->i32_0,
                                                    ctx->i32_0, 0, ac_glc | ac_slc, false);
                } else {
                        LLVMBuildStore(builder, count,
                                       si_expand_32bit_pointer(ctx, vertex_count_addr));
                }
                ac_build_endif(&ctx->ac, 12606);
        } else {
                /* For unordered modes that increment a vertex count instead of
                 * primitive count, convert it into the primitive index.
                 */
                start = LLVMBuildUDiv(builder, start,
                                      LLVMConstInt(ctx->i32, vertices_per_prim, 0), "");
        }

        /* Now we need to store the indices of accepted primitives into
         * the output index buffer.
         */
        ac_build_ifcc(&ctx->ac, accepted, 16607);
        {
                /* Get the number of bits set before the index of this thread. */
                LLVMValueRef prim_index = ac_build_mbcnt(&ctx->ac, accepted_threadmask);

                /* We have lowered instancing. Pack the instance ID into vertex ID. */
                if (key->opt.cs_instancing) {
                        instance_id = LLVMBuildShl(builder, instance_id,
                                                   LLVMConstInt(ctx->i32, 16, 0), "");

                        for (unsigned i = 0; i < vertices_per_prim; i++)
                                index[i] = LLVMBuildOr(builder, index[i], instance_id, "");
                }

                if (VERTEX_COUNTER_GDS_MODE == 2) {
                        /* vertex_counter contains the first primitive ID
                         * for this dispatch. If the draw call was split into
                         * multiple subdraws, the first primitive ID is > 0
                         * for subsequent subdraws. Each subdraw uses a different
                         * portion of the output index buffer. Offset the store
                         * vindex by the first primitive ID to get the correct
                         * store address for the subdraw.
                         */
                        start = LLVMBuildAdd(builder, start, vertex_counter, "");
                }

                /* Write indices for accepted primitives. */
                LLVMValueRef vindex = LLVMBuildAdd(builder, start, prim_index, "");
                LLVMValueRef vdata = ac_build_gather_values(&ctx->ac, index, 3);

                if (!ac_has_vec3_support(ctx->ac.chip_class, true))
                        vdata = ac_build_expand_to_vec4(&ctx->ac, vdata, 3);

                ac_build_buffer_store_format(&ctx->ac, output_indexbuf, vdata,
                                             vindex, ctx->i32_0, 3,
                                             ac_glc | (INDEX_STORES_USE_SLC ? ac_slc : 0));
        }
        ac_build_endif(&ctx->ac, 16607);

        LLVMBuildRetVoid(builder);
}

/* Return false if the shader isn't ready. */
static bool si_shader_select_prim_discard_cs(struct si_context *sctx,
                                             const struct pipe_draw_info *info,
                                             bool primitive_restart)
{
        struct si_state_rasterizer *rs = sctx->queued.named.rasterizer;
        struct si_shader_key key;

        /* Primitive restart needs ordered counters. */
        assert(!primitive_restart || VERTEX_COUNTER_GDS_MODE == 2);
        assert(!primitive_restart || info->instance_count == 1);

        memset(&key, 0, sizeof(key));
        si_shader_selector_key_vs(sctx, sctx->vs_shader.cso, &key, &key.part.vs.prolog);
        assert(!key.part.vs.prolog.instance_divisor_is_fetched);

        key.part.vs.prolog.unpack_instance_id_from_vertex_id = 0;
        key.opt.vs_as_prim_discard_cs = 1;
        key.opt.cs_prim_type = info->mode;
        key.opt.cs_indexed = info->index_size != 0;
        key.opt.cs_instancing = info->instance_count > 1;
        key.opt.cs_primitive_restart = primitive_restart;
        key.opt.cs_provoking_vertex_first = rs->provoking_vertex_first;

        /* Primitive restart with triangle strips needs to preserve primitive
         * orientation for cases where front and back primitive orientation matters.
         */
        if (primitive_restart) {
                struct si_shader_selector *ps = sctx->ps_shader.cso;

                key.opt.cs_need_correct_orientation =
                        rs->cull_front != rs->cull_back ||
                        ps->info.uses_frontface ||
                        (rs->two_side && ps->info.colors_read);
        }

        if (rs->rasterizer_discard) {
                /* Just for performance testing and analysis of trivial bottlenecks.
                 * This should result in a very short compute shader. */
                key.opt.cs_cull_front = 1;
                key.opt.cs_cull_back = 1;
        } else {
                key.opt.cs_cull_front =
                        sctx->viewports.y_inverted ? rs->cull_back : rs->cull_front;
                key.opt.cs_cull_back =
                        sctx->viewports.y_inverted ? rs->cull_front : rs->cull_back;
        }

        if (!rs->depth_clamp_any && CULL_Z) {
                key.opt.cs_cull_z = 1;
                key.opt.cs_halfz_clip_space = rs->clip_halfz;
        }

        sctx->cs_prim_discard_state.cso = sctx->vs_shader.cso;
        sctx->cs_prim_discard_state.current = NULL;

        struct si_compiler_ctx_state compiler_state;
        compiler_state.compiler = &sctx->compiler;
        compiler_state.debug = sctx->debug;
        compiler_state.is_debug_context = sctx->is_debug;

        return si_shader_select_with_key(sctx->screen, &sctx->cs_prim_discard_state,
                                         &compiler_state, &key, -1, true) == 0 &&
               /* Disallow compute shaders using the scratch buffer. */
               sctx->cs_prim_discard_state.current->config.scratch_bytes_per_wave == 0;
}

static bool si_initialize_prim_discard_cmdbuf(struct si_context *sctx)
{
        if (sctx->index_ring)
                return true;

        if (!sctx->prim_discard_compute_cs) {
                struct radeon_winsys *ws = sctx->ws;
                unsigned gds_size = VERTEX_COUNTER_GDS_MODE == 1 ? GDS_SIZE_UNORDERED :
                                    VERTEX_COUNTER_GDS_MODE == 2 ? 8 : 0;
                unsigned num_oa_counters = VERTEX_COUNTER_GDS_MODE == 2 ? 2 : 0;

                if (gds_size) {
                        sctx->gds = ws->buffer_create(ws, gds_size, 4,
                                                      RADEON_DOMAIN_GDS, 0);
                        if (!sctx->gds)
                                return false;

                        ws->cs_add_buffer(sctx->gfx_cs, sctx->gds,
                                          RADEON_USAGE_READWRITE, 0, 0);
                }
                if (num_oa_counters) {
                        assert(gds_size);
                        sctx->gds_oa = ws->buffer_create(ws, num_oa_counters,
                                                         1, RADEON_DOMAIN_OA, 0);
                        if (!sctx->gds_oa)
                                return false;

                        ws->cs_add_buffer(sctx->gfx_cs, sctx->gds_oa,
                                          RADEON_USAGE_READWRITE, 0, 0);
                }

                sctx->prim_discard_compute_cs =
                        ws->cs_add_parallel_compute_ib(sctx->gfx_cs,
                                                       num_oa_counters > 0);
                if (!sctx->prim_discard_compute_cs)
                        return false;
        }

        if (!sctx->index_ring) {
                sctx->index_ring =
                        si_aligned_buffer_create(sctx->b.screen,
                                                 SI_RESOURCE_FLAG_UNMAPPABLE,
                                                 PIPE_USAGE_DEFAULT,
                                                 sctx->index_ring_size_per_ib * 2,
                                                 2 * 1024 * 1024);
                if (!sctx->index_ring)
                        return false;
        }
        return true;
}

static bool si_check_ring_space(struct si_context *sctx, unsigned out_indexbuf_size)
{
        return sctx->index_ring_offset +
               align(out_indexbuf_size, sctx->screen->info.tcc_cache_line_size) <=
               sctx->index_ring_size_per_ib;
}

enum si_prim_discard_outcome
si_prepare_prim_discard_or_split_draw(struct si_context *sctx,
                                      const struct pipe_draw_info *info,
                                      bool primitive_restart)
{
        /* If the compute shader compilation isn't finished, this returns false. */
        if (!si_shader_select_prim_discard_cs(sctx, info, primitive_restart))
                return SI_PRIM_DISCARD_DISABLED;

        if (!si_initialize_prim_discard_cmdbuf(sctx))
                return SI_PRIM_DISCARD_DISABLED;

        struct radeon_cmdbuf *gfx_cs = sctx->gfx_cs;
        unsigned prim = info->mode;
        unsigned count = info->count;
        unsigned instance_count = info->instance_count;
        unsigned num_prims_per_instance = u_decomposed_prims_for_vertices(prim, count);
        unsigned num_prims = num_prims_per_instance * instance_count;
        unsigned out_indexbuf_size = num_prims * 12;
        bool ring_full = !si_check_ring_space(sctx, out_indexbuf_size);
        const unsigned split_prims_draw_level = SPLIT_PRIMS_DRAW_LEVEL;

        /* Split draws at the draw call level if the ring is full. This makes
         * better use of the ring space.
         */
        if (ring_full &&
            num_prims > split_prims_draw_level &&
            instance_count == 1 && /* TODO: support splitting instanced draws */
            (1 << prim) & ((1 << PIPE_PRIM_TRIANGLES) |
                           (1 << PIPE_PRIM_TRIANGLE_STRIP))) {
                /* Split draws. */
                struct pipe_draw_info split_draw = *info;
                split_draw.primitive_restart = primitive_restart;

                unsigned base_start = split_draw.start;

                if (prim == PIPE_PRIM_TRIANGLES) {
                        unsigned vert_count_per_subdraw = split_prims_draw_level * 3;
                        assert(vert_count_per_subdraw < count);

                        for (unsigned start = 0; start < count; start += vert_count_per_subdraw) {
                                split_draw.start = base_start + start;
                                split_draw.count = MIN2(count - start, vert_count_per_subdraw);

                                sctx->b.draw_vbo(&sctx->b, &split_draw);
                        }
                } else if (prim == PIPE_PRIM_TRIANGLE_STRIP) {
                        /* No primitive pair can be split, because strips reverse orientation
                         * for odd primitives. */
                        STATIC_ASSERT(split_prims_draw_level % 2 == 0);

                        unsigned vert_count_per_subdraw = split_prims_draw_level;

                        for (unsigned start = 0; start < count - 2; start += vert_count_per_subdraw) {
                                split_draw.start = base_start + start;
                                split_draw.count = MIN2(count - start, vert_count_per_subdraw + 2);

                                sctx->b.draw_vbo(&sctx->b, &split_draw);

                                if (start == 0 &&
                                    primitive_restart &&
                                    sctx->cs_prim_discard_state.current->key.opt.cs_need_correct_orientation)
                                        sctx->preserve_prim_restart_gds_at_flush = true;
                        }
                        sctx->preserve_prim_restart_gds_at_flush = false;
                } else {
                        assert(0);
                }

                return SI_PRIM_DISCARD_DRAW_SPLIT;
        }

        /* Just quit if the draw call doesn't fit into the ring and can't be split. */
        if (out_indexbuf_size > sctx->index_ring_size_per_ib) {
                if (SI_PRIM_DISCARD_DEBUG)
                        puts("PD failed: draw call too big, can't be split");
                return SI_PRIM_DISCARD_DISABLED;
        }

        unsigned num_subdraws = DIV_ROUND_UP(num_prims, SPLIT_PRIMS_PACKET_LEVEL);
        unsigned need_compute_dw = 11 /* shader */ + 34 /* first draw */ +
                                   24 * (num_subdraws - 1) + /* subdraws */
                                   20; /* leave some space at the end */
        unsigned need_gfx_dw = si_get_minimum_num_gfx_cs_dwords(sctx);

        if (sctx->chip_class <= GFX7 || FORCE_REWIND_EMULATION)
                need_gfx_dw += 9; /* NOP(2) + WAIT_REG_MEM(7), then chain */
        else
                need_gfx_dw += num_subdraws * 8; /* use REWIND(2) + DRAW(6) */

        if (ring_full ||
            (VERTEX_COUNTER_GDS_MODE == 1 && sctx->compute_gds_offset + 8 > GDS_SIZE_UNORDERED) ||
            !sctx->ws->cs_check_space(gfx_cs, need_gfx_dw, false)) {
                /* If the current IB is empty but the size is too small, add a NOP
                 * packet to force a flush and get a bigger IB.
                 */
                if (!radeon_emitted(gfx_cs, sctx->initial_gfx_cs_size) &&
                    gfx_cs->current.cdw + need_gfx_dw > gfx_cs->current.max_dw) {
                        radeon_emit(gfx_cs, PKT3(PKT3_NOP, 0, 0));
                        radeon_emit(gfx_cs, 0);
                }

                si_flush_gfx_cs(sctx, RADEON_FLUSH_ASYNC_START_NEXT_GFX_IB_NOW, NULL);
        }

        /* The compute IB is always chained, but we need to call cs_check_space to add more space. */
        struct radeon_cmdbuf *cs = sctx->prim_discard_compute_cs;
        ASSERTED bool compute_has_space = sctx->ws->cs_check_space(cs, need_compute_dw, false);
        assert(compute_has_space);
        assert(si_check_ring_space(sctx, out_indexbuf_size));
        return SI_PRIM_DISCARD_ENABLED;
}

void si_compute_signal_gfx(struct si_context *sctx)
{
        struct radeon_cmdbuf *cs = sctx->prim_discard_compute_cs;
        unsigned writeback_L2_flags = 0;

        /* The writeback L2 flags vary with each chip generation. */
        /* CI needs to flush vertex indices to memory. */
        if (sctx->chip_class <= GFX7)
                writeback_L2_flags = EVENT_TC_WB_ACTION_ENA;
        else if (sctx->chip_class == GFX8 && VERTEX_COUNTER_GDS_MODE == 0)
                writeback_L2_flags = EVENT_TC_WB_ACTION_ENA | EVENT_TC_NC_ACTION_ENA;

        if (!sctx->compute_num_prims_in_batch)
                return;

        assert(sctx->compute_rewind_va);

        /* After the queued dispatches are done and vertex counts are written to
         * the gfx IB, signal the gfx IB to continue. CP doesn't wait for
         * the dispatches to finish, it only adds the CS_DONE event into the event
         * queue.
         */
        si_cp_release_mem(sctx, cs, V_028A90_CS_DONE, writeback_L2_flags,
                          sctx->chip_class <= GFX8 ? EOP_DST_SEL_MEM : EOP_DST_SEL_TC_L2,
                          writeback_L2_flags ? EOP_INT_SEL_SEND_DATA_AFTER_WR_CONFIRM :
                                               EOP_INT_SEL_NONE,
                          EOP_DATA_SEL_VALUE_32BIT,
                          NULL,
                          sctx->compute_rewind_va |
                          ((uint64_t)sctx->screen->info.address32_hi << 32),
                          REWIND_SIGNAL_BIT, /* signaling value for the REWIND packet */
                          SI_NOT_QUERY);

        sctx->compute_rewind_va = 0;
        sctx->compute_num_prims_in_batch = 0;
}

/* Dispatch a primitive discard compute shader. */
void si_dispatch_prim_discard_cs_and_draw(struct si_context *sctx,
                                          const struct pipe_draw_info *info,
                                          unsigned index_size,
                                          unsigned base_vertex,
                                          uint64_t input_indexbuf_va,
                                          unsigned input_indexbuf_num_elements)
{
        struct radeon_cmdbuf *gfx_cs = sctx->gfx_cs;
        struct radeon_cmdbuf *cs = sctx->prim_discard_compute_cs;
        unsigned num_prims_per_instance = u_decomposed_prims_for_vertices(info->mode, info->count);
        if (!num_prims_per_instance)
                return;

        unsigned num_prims = num_prims_per_instance * info->instance_count;
        unsigned vertices_per_prim, output_indexbuf_format;

        switch (info->mode) {
        case PIPE_PRIM_TRIANGLES:
        case PIPE_PRIM_TRIANGLE_STRIP:
        case PIPE_PRIM_TRIANGLE_FAN:
                vertices_per_prim = 3;
                output_indexbuf_format = V_008F0C_BUF_DATA_FORMAT_32_32_32;
                break;
        default:
                unreachable("unsupported primitive type");
                return;
        }

        unsigned out_indexbuf_offset;
        uint64_t output_indexbuf_size = num_prims * vertices_per_prim * 4;
        bool first_dispatch = !sctx->prim_discard_compute_ib_initialized;

        /* Initialize the compute IB if it's empty. */
        if (!sctx->prim_discard_compute_ib_initialized) {
                /* 1) State initialization. */
                sctx->compute_gds_offset = 0;
                sctx->compute_ib_last_shader = NULL;

                if (sctx->last_ib_barrier_fence) {
                        assert(!sctx->last_ib_barrier_buf);
                        sctx->ws->cs_add_fence_dependency(gfx_cs,
                                                          sctx->last_ib_barrier_fence,
                                                          RADEON_DEPENDENCY_PARALLEL_COMPUTE_ONLY);
                }

                /* 2) IB initialization. */

                /* This needs to be done at the beginning of IBs due to possible
                 * TTM buffer moves in the kernel.
                 *
                 * TODO: update for GFX10
                 */
                si_emit_surface_sync(sctx, cs,
                                     S_0085F0_TC_ACTION_ENA(1) |
                                     S_0085F0_TCL1_ACTION_ENA(1) |
                                     S_0301F0_TC_WB_ACTION_ENA(sctx->chip_class >= GFX8) |
                                     S_0085F0_SH_ICACHE_ACTION_ENA(1) |
                                     S_0085F0_SH_KCACHE_ACTION_ENA(1));

                /* Restore the GDS prim restart counter if needed. */
                if (sctx->preserve_prim_restart_gds_at_flush) {
                        si_cp_copy_data(sctx, cs,
                                        COPY_DATA_GDS, NULL, 4,
                                        COPY_DATA_SRC_MEM, sctx->wait_mem_scratch, 4);
                }

                si_emit_initial_compute_regs(sctx, cs);

                radeon_set_sh_reg(cs, R_00B860_COMPUTE_TMPRING_SIZE,
                                  S_00B860_WAVES(sctx->scratch_waves) |
                                  S_00B860_WAVESIZE(0)); /* no scratch */

                /* Only 1D grids are launched. */
                radeon_set_sh_reg_seq(cs, R_00B820_COMPUTE_NUM_THREAD_Y, 2);
                radeon_emit(cs, S_00B820_NUM_THREAD_FULL(1) |
                                S_00B820_NUM_THREAD_PARTIAL(1));
                radeon_emit(cs, S_00B824_NUM_THREAD_FULL(1) |
                                S_00B824_NUM_THREAD_PARTIAL(1));

                radeon_set_sh_reg_seq(cs, R_00B814_COMPUTE_START_Y, 2);
                radeon_emit(cs, 0);
                radeon_emit(cs, 0);

                /* Disable ordered alloc for OA resources. */
                for (unsigned i = 0; i < 2; i++) {
                        radeon_set_uconfig_reg_seq(cs, R_031074_GDS_OA_CNTL, 3);
                        radeon_emit(cs, S_031074_INDEX(i));
                        radeon_emit(cs, 0);
                        radeon_emit(cs, S_03107C_ENABLE(0));
                }

                if (sctx->last_ib_barrier_buf) {
                        assert(!sctx->last_ib_barrier_fence);
                        radeon_add_to_buffer_list(sctx, gfx_cs, sctx->last_ib_barrier_buf,
                                                  RADEON_USAGE_READ, RADEON_PRIO_FENCE);
                        si_cp_wait_mem(sctx, cs,
                                       sctx->last_ib_barrier_buf->gpu_address +
                                       sctx->last_ib_barrier_buf_offset, 1, 1,
                                       WAIT_REG_MEM_EQUAL);
                }

                sctx->prim_discard_compute_ib_initialized = true;
        }

        /* Allocate the output index buffer. */
        output_indexbuf_size = align(output_indexbuf_size,
                                     sctx->screen->info.tcc_cache_line_size);
        assert(sctx->index_ring_offset + output_indexbuf_size <= sctx->index_ring_size_per_ib);
        out_indexbuf_offset = sctx->index_ring_base + sctx->index_ring_offset;
        sctx->index_ring_offset += output_indexbuf_size;

        radeon_add_to_buffer_list(sctx, gfx_cs, sctx->index_ring, RADEON_USAGE_READWRITE,
                                  RADEON_PRIO_SHADER_RW_BUFFER);
        uint64_t out_indexbuf_va = sctx->index_ring->gpu_address + out_indexbuf_offset;

        /* Prepare index buffer descriptors. */
        struct si_resource *indexbuf_desc = NULL;
        unsigned indexbuf_desc_offset;
        unsigned desc_size = 12 * 4;
        uint32_t *desc;

        u_upload_alloc(sctx->b.const_uploader, 0, desc_size,
                       si_optimal_tcc_alignment(sctx, desc_size),
                       &indexbuf_desc_offset, (struct pipe_resource**)&indexbuf_desc,
                       (void**)&desc);
        radeon_add_to_buffer_list(sctx, gfx_cs, indexbuf_desc, RADEON_USAGE_READ,
                                  RADEON_PRIO_DESCRIPTORS);

        /* Input index buffer. */
        desc[0] = input_indexbuf_va;
        desc[1] = S_008F04_BASE_ADDRESS_HI(input_indexbuf_va >> 32) |
                  S_008F04_STRIDE(index_size);
        desc[2] = input_indexbuf_num_elements * (sctx->chip_class == GFX8 ? index_size : 1);
        desc[3] = S_008F0C_DST_SEL_X(V_008F0C_SQ_SEL_X) |
                  S_008F0C_NUM_FORMAT(V_008F0C_BUF_NUM_FORMAT_UINT) |
                  S_008F0C_DATA_FORMAT(index_size == 1 ? V_008F0C_BUF_DATA_FORMAT_8 :
                                       index_size == 2 ? V_008F0C_BUF_DATA_FORMAT_16 :
                                                         V_008F0C_BUF_DATA_FORMAT_32);

        /* Output index buffer. */
        desc[4] = out_indexbuf_va;
        desc[5] = S_008F04_BASE_ADDRESS_HI(out_indexbuf_va >> 32) |
                  S_008F04_STRIDE(vertices_per_prim * 4);
        desc[6] = num_prims * (sctx->chip_class == GFX8 ? vertices_per_prim * 4 : 1);
        desc[7] = S_008F0C_DST_SEL_X(V_008F0C_SQ_SEL_X) |
                  S_008F0C_DST_SEL_Y(V_008F0C_SQ_SEL_Y) |
                  S_008F0C_DST_SEL_Z(V_008F0C_SQ_SEL_Z) |
                  S_008F0C_DST_SEL_W(V_008F0C_SQ_SEL_0) |
                  S_008F0C_NUM_FORMAT(V_008F0C_BUF_NUM_FORMAT_UINT) |
                  S_008F0C_DATA_FORMAT(output_indexbuf_format);

        /* Viewport state.
         * This is needed by the small primitive culling, because it's done
         * in screen space.
         */
        float scale[2], translate[2];

        scale[0] = sctx->viewports.states[0].scale[0];
        scale[1] = sctx->viewports.states[0].scale[1];
        translate[0] = sctx->viewports.states[0].translate[0];
        translate[1] = sctx->viewports.states[0].translate[1];

        /* The viewport shouldn't flip the X axis for the small prim culling to work. */
        assert(-scale[0] + translate[0] <= scale[0] + translate[0]);

        /* If the Y axis is inverted (OpenGL default framebuffer), reverse it.
         * This is because the viewport transformation inverts the clip space
         * bounding box, so min becomes max, which breaks small primitive
         * culling.
         */
        if (sctx->viewports.y_inverted) {
                scale[1] = -scale[1];
                translate[1] = -translate[1];
        }

        /* Scale the framebuffer up, so that samples become pixels and small
         * primitive culling is the same for all sample counts.
         * This only works with the standard DX sample positions, because
         * the samples are evenly spaced on both X and Y axes.
         */
        unsigned num_samples = sctx->framebuffer.nr_samples;
        assert(num_samples >= 1);

        for (unsigned i = 0; i < 2; i++) {
                scale[i] *= num_samples;
                translate[i] *= num_samples;
        }

        desc[8] = fui(scale[0]);
        desc[9] = fui(scale[1]);
        desc[10] = fui(translate[0]);
        desc[11] = fui(translate[1]);

        /* Better subpixel precision increases the efficiency of small
         * primitive culling. */
        unsigned quant_mode = sctx->viewports.as_scissor[0].quant_mode;
        float small_prim_cull_precision;

        if (quant_mode == SI_QUANT_MODE_12_12_FIXED_POINT_1_4096TH)
                small_prim_cull_precision = num_samples / 4096.0;
        else if (quant_mode == SI_QUANT_MODE_14_10_FIXED_POINT_1_1024TH)
                small_prim_cull_precision = num_samples / 1024.0;
        else
                small_prim_cull_precision = num_samples / 256.0;

        /* Set user data SGPRs. */
        /* This can't be greater than 14 if we want the fastest launch rate. */
        unsigned user_sgprs = 13;

        uint64_t index_buffers_va = indexbuf_desc->gpu_address + indexbuf_desc_offset;
        unsigned vs_const_desc = si_const_and_shader_buffer_descriptors_idx(PIPE_SHADER_VERTEX);
        unsigned vs_sampler_desc = si_sampler_and_image_descriptors_idx(PIPE_SHADER_VERTEX);
        uint64_t vs_const_desc_va = sctx->descriptors[vs_const_desc].gpu_address;
        uint64_t vs_sampler_desc_va = sctx->descriptors[vs_sampler_desc].gpu_address;
        uint64_t vb_desc_va = sctx->vb_descriptors_buffer ?
                                      sctx->vb_descriptors_buffer->gpu_address +
                                      sctx->vb_descriptors_offset : 0;
        unsigned gds_offset, gds_size;
        struct si_fast_udiv_info32 num_prims_udiv = {};

        if (info->instance_count > 1)
                num_prims_udiv = si_compute_fast_udiv_info32(num_prims_per_instance, 31);

        /* Limitations on how these two are packed in the user SGPR. */
        assert(num_prims_udiv.post_shift < 32);
        assert(num_prims_per_instance < 1 << 27);

        si_resource_reference(&indexbuf_desc, NULL);

        bool primitive_restart = sctx->cs_prim_discard_state.current->key.opt.cs_primitive_restart;

        if (VERTEX_COUNTER_GDS_MODE == 1) {
                gds_offset = sctx->compute_gds_offset;
                gds_size = primitive_restart ? 8 : 4;
                sctx->compute_gds_offset += gds_size;

                /* Reset the counters in GDS for the first dispatch using WRITE_DATA.
                 * The remainder of the GDS will be cleared after the dispatch packet
                 * in parallel with compute shaders.
                 */
                if (first_dispatch) {
                        radeon_emit(cs, PKT3(PKT3_WRITE_DATA, 2 + gds_size/4, 0));
                        radeon_emit(cs, S_370_DST_SEL(V_370_GDS) | S_370_WR_CONFIRM(1));
                        radeon_emit(cs, gds_offset);
                        radeon_emit(cs, 0);
                        radeon_emit(cs, 0); /* value to write */
                        if (gds_size == 8)
                                radeon_emit(cs, 0);
                }
        }

        /* Set shader registers. */
        struct si_shader *shader = sctx->cs_prim_discard_state.current;

        if (shader != sctx->compute_ib_last_shader) {
                radeon_add_to_buffer_list(sctx, gfx_cs, shader->bo, RADEON_USAGE_READ,
                                          RADEON_PRIO_SHADER_BINARY);
                uint64_t shader_va = shader->bo->gpu_address;

                assert(shader->config.scratch_bytes_per_wave == 0);
                assert(shader->config.num_vgprs * WAVES_PER_TG <= 256 * 4);

                radeon_set_sh_reg_seq(cs, R_00B830_COMPUTE_PGM_LO, 2);
                radeon_emit(cs, shader_va >> 8);
                radeon_emit(cs, S_00B834_DATA(shader_va >> 40));

                radeon_set_sh_reg_seq(cs, R_00B848_COMPUTE_PGM_RSRC1, 2);
                radeon_emit(cs, S_00B848_VGPRS((shader->config.num_vgprs - 1) / 4) |
                                S_00B848_SGPRS((shader->config.num_sgprs - 1) / 8) |
                                S_00B848_FLOAT_MODE(shader->config.float_mode) |
                                S_00B848_DX10_CLAMP(1));
                radeon_emit(cs, S_00B84C_SCRATCH_EN(0 /* no scratch */) |
                                S_00B84C_USER_SGPR(user_sgprs) |
                                S_00B84C_TGID_X_EN(1 /* only blockID.x is used */) |
                                S_00B84C_TG_SIZE_EN(VERTEX_COUNTER_GDS_MODE == 2 /* need the wave ID */) |
                                S_00B84C_TIDIG_COMP_CNT(0 /* only threadID.x is used */) |
                                S_00B84C_LDS_SIZE(shader->config.lds_size));

                radeon_set_sh_reg(cs, R_00B854_COMPUTE_RESOURCE_LIMITS,
                        ac_get_compute_resource_limits(&sctx->screen->info,
                                                       WAVES_PER_TG,
                                                       MAX_WAVES_PER_SH,
                                                       THREADGROUPS_PER_CU));
                sctx->compute_ib_last_shader = shader;
        }

        STATIC_ASSERT(SPLIT_PRIMS_PACKET_LEVEL % THREADGROUP_SIZE == 0);

        /* Big draw calls are split into smaller dispatches and draw packets. */
        for (unsigned start_prim = 0; start_prim < num_prims; start_prim += SPLIT_PRIMS_PACKET_LEVEL) {
                unsigned num_subdraw_prims;

                if (start_prim + SPLIT_PRIMS_PACKET_LEVEL < num_prims)
                        num_subdraw_prims = SPLIT_PRIMS_PACKET_LEVEL;
                else
                        num_subdraw_prims = num_prims - start_prim;

                /* Small dispatches are executed back to back until a specific primitive
                 * count is reached. Then, a CS_DONE is inserted to signal the gfx IB
                 * to start drawing the batch. This batching adds latency to the gfx IB,
                 * but CS_DONE and REWIND are too slow.
                 */
                if (sctx->compute_num_prims_in_batch + num_subdraw_prims > PRIMS_PER_BATCH)
                        si_compute_signal_gfx(sctx);

                if (sctx->compute_num_prims_in_batch == 0) {
                        assert((gfx_cs->gpu_address >> 32) == sctx->screen->info.address32_hi);
                        sctx->compute_rewind_va = gfx_cs->gpu_address + (gfx_cs->current.cdw + 1) * 4;

                        if (sctx->chip_class <= GFX7 || FORCE_REWIND_EMULATION) {
                                radeon_emit(gfx_cs, PKT3(PKT3_NOP, 0, 0));
                                radeon_emit(gfx_cs, 0);

                                si_cp_wait_mem(sctx, gfx_cs,
                                               sctx->compute_rewind_va |
                                               (uint64_t)sctx->screen->info.address32_hi << 32,
                                               REWIND_SIGNAL_BIT, REWIND_SIGNAL_BIT,
                                               WAIT_REG_MEM_EQUAL | WAIT_REG_MEM_PFP);

                                /* Use INDIRECT_BUFFER to chain to a different buffer
                                 * to discard the CP prefetch cache.
                                 */
                                sctx->ws->cs_check_space(gfx_cs, 0, true);
                        } else {
                                radeon_emit(gfx_cs, PKT3(PKT3_REWIND, 0, 0));
                                radeon_emit(gfx_cs, 0);
                        }
                }

                sctx->compute_num_prims_in_batch += num_subdraw_prims;

                uint32_t count_va = gfx_cs->gpu_address + (gfx_cs->current.cdw + 4) * 4;
                uint64_t index_va = out_indexbuf_va + start_prim * 12;

                /* Emit the draw packet into the gfx IB. */
                radeon_emit(gfx_cs, PKT3(PKT3_DRAW_INDEX_2, 4, 0));
                radeon_emit(gfx_cs, num_prims * vertices_per_prim);
                radeon_emit(gfx_cs, index_va);
                radeon_emit(gfx_cs, index_va >> 32);
                radeon_emit(gfx_cs, 0);
                radeon_emit(gfx_cs, V_0287F0_DI_SRC_SEL_DMA);

                /* Continue with the compute IB. */
                if (start_prim == 0) {
                        uint32_t gds_prim_restart_continue_bit = 0;

                        if (sctx->preserve_prim_restart_gds_at_flush) {
                                assert(primitive_restart &&
                                       info->mode == PIPE_PRIM_TRIANGLE_STRIP);
                                assert(start_prim < 1 << 31);
                                gds_prim_restart_continue_bit = 1 << 31;
                        }

                        radeon_set_sh_reg_seq(cs, R_00B900_COMPUTE_USER_DATA_0, user_sgprs);
                        radeon_emit(cs, index_buffers_va);
                        radeon_emit(cs,
                                    VERTEX_COUNTER_GDS_MODE == 0 ? count_va :
                                    VERTEX_COUNTER_GDS_MODE == 1 ? gds_offset :
                                                                   start_prim |
                                                                   gds_prim_restart_continue_bit);
                        radeon_emit(cs, start_prim + num_subdraw_prims - 1);
                        radeon_emit(cs, count_va);
                        radeon_emit(cs, vb_desc_va);
                        radeon_emit(cs, vs_const_desc_va);
                        radeon_emit(cs, vs_sampler_desc_va);
                        radeon_emit(cs, base_vertex);
                        radeon_emit(cs, info->start_instance);
                        radeon_emit(cs, num_prims_udiv.multiplier);
                        radeon_emit(cs, num_prims_udiv.post_shift |
                                        (num_prims_per_instance << 5));
                        radeon_emit(cs, info->restart_index);
                        /* small-prim culling precision (same as rasterizer precision = QUANT_MODE) */
                        radeon_emit(cs, fui(small_prim_cull_precision));
                } else {
                        assert(VERTEX_COUNTER_GDS_MODE == 2);
                        /* Only update the SGPRs that changed. */
                        radeon_set_sh_reg_seq(cs, R_00B904_COMPUTE_USER_DATA_1, 3);
                        radeon_emit(cs, start_prim);
                        radeon_emit(cs, start_prim + num_subdraw_prims - 1);
                        radeon_emit(cs, count_va);
                }

                /* Set grid dimensions. */
                unsigned start_block = start_prim / THREADGROUP_SIZE;
                unsigned num_full_blocks = num_subdraw_prims / THREADGROUP_SIZE;
                unsigned partial_block_size = num_subdraw_prims % THREADGROUP_SIZE;

                radeon_set_sh_reg(cs, R_00B810_COMPUTE_START_X, start_block);
                radeon_set_sh_reg(cs, R_00B81C_COMPUTE_NUM_THREAD_X,
                                  S_00B81C_NUM_THREAD_FULL(THREADGROUP_SIZE) |
                                  S_00B81C_NUM_THREAD_PARTIAL(partial_block_size));

                radeon_emit(cs, PKT3(PKT3_DISPATCH_DIRECT, 3, 0) |
                                PKT3_SHADER_TYPE_S(1));
                radeon_emit(cs, start_block + num_full_blocks + !!partial_block_size);
                radeon_emit(cs, 1);
                radeon_emit(cs, 1);
                radeon_emit(cs, S_00B800_COMPUTE_SHADER_EN(1) |
                                S_00B800_PARTIAL_TG_EN(!!partial_block_size) |
                                S_00B800_ORDERED_APPEND_ENBL(VERTEX_COUNTER_GDS_MODE == 2) |
                                S_00B800_ORDER_MODE(0 /* launch in order */));

                /* This is only for unordered append. Ordered append writes this from
                 * the shader.
                 *
                 * Note that EOP and EOS events are super slow, so emulating the event
                 * in a shader is an important optimization.
                 */
                if (VERTEX_COUNTER_GDS_MODE == 1) {
                        si_cp_release_mem(sctx, cs, V_028A90_CS_DONE, 0,
                                          sctx->chip_class <= GFX8 ? EOP_DST_SEL_MEM : EOP_DST_SEL_TC_L2,
                                          EOP_INT_SEL_NONE,
                                          EOP_DATA_SEL_GDS,
                                          NULL,
                                          count_va | ((uint64_t)sctx->screen->info.address32_hi << 32),
                                          EOP_DATA_GDS(gds_offset / 4, 1),
                                          SI_NOT_QUERY);

                        /* Now that compute shaders are running, clear the remainder of GDS. */
                        if (first_dispatch) {
                                unsigned offset = gds_offset + gds_size;
                                si_cp_dma_clear_buffer(sctx, cs, NULL, offset,
                                                       GDS_SIZE_UNORDERED - offset,
                                                       0,
                                                       SI_CPDMA_SKIP_CHECK_CS_SPACE |
                                                       SI_CPDMA_SKIP_GFX_SYNC |
                                                       SI_CPDMA_SKIP_SYNC_BEFORE,
                                                       SI_COHERENCY_NONE, L2_BYPASS);
                        }
                }
                first_dispatch = false;

                assert(cs->current.cdw <= cs->current.max_dw);
                assert(gfx_cs->current.cdw <= gfx_cs->current.max_dw);
        }
}