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Revert "radv/rt: use derefs for the traversal stack"

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This reverts commit 3750663c72.

Doing things with derefs adds extra instructions for multiplying the
index with the element size, e.g.

BBF0_13:
   s_waitcnt vmcnt(0)
   v_mov_b32_e32 v27, v55
   s_mov_b32 s23, exec_lo
   v_cmpx_ne_i32_e32 -1, v27
   s_cbranch_execz _L14
BBF0_14:
   v_lshlrev_b32_e32 v48, 2, v46  <--
   ds_write_b32 v48, v27
   v_add_nc_u32_e32 v46, 32, v46
_L14:
   s_mov_b32 exec_lo, s23
   v_mov_b32_e32 v27, v54
   s_mov_b32 s23, exec_lo
   v_cmpx_ne_i32_e32 -1, v27
   s_cbranch_execz _L15
BBF0_15:
   v_lshlrev_b32_e32 v48, 2, v46 <--
   ds_write_b32 v48, v27
   v_add_nc_u32_e32 v46, 32, v46

On Q2RTC indirect lighting this saves about 2.3 VALU instructions
per loop iteration, which is ~4% of VALU instructions (we're at
58 per iteration now according to RGP).

Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18538>
This commit is contained in:
Bas Nieuwenhuizen
2022-09-11 16:18:14 +02:00
parent 85ca0b12a2
commit 40a235c9a8
1 changed files with 22 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/amd/vulkan/radv_pipeline_rt.c
+22 -18
View File
@@ -1397,15 +1397,15 @@ build_traversal_shader(struct radv_device *device,
struct rt_variables vars = create_rt_variables(b.shader, pCreateInfo, dst_vars->stack_sizes);
map_rt_variables(var_remap, &vars, dst_vars);
unsigned stack_entry_size = 4;
unsigned lanes = device->physical_device->rt_wave_size;
unsigned elements = lanes * MAX_STACK_ENTRY_COUNT;
nir_variable *stack_var = nir_variable_create(b.shader, nir_var_mem_shared,
glsl_array_type(glsl_uint_type(), elements, 0),
"trav_stack");
nir_deref_instr *stack_deref = nir_build_deref_var(&b, stack_var);
nir_deref_instr *stack;
nir_ssa_def *stack_idx_stride = nir_imm_int(&b, lanes);
nir_ssa_def *stack_idx_base = nir_load_local_invocation_index(&b);
unsigned stack_entry_stride = stack_entry_size * lanes;
nir_ssa_def *stack_entry_stride_def = nir_imm_int(&b, stack_entry_stride);
nir_ssa_def *stack_base =
nir_iadd_imm(&b, nir_imul_imm(&b, nir_load_local_invocation_index(&b), stack_entry_size),
b.shader->info.shared_size);
b.shader->info.shared_size += stack_entry_stride * MAX_STACK_ENTRY_COUNT;
nir_ssa_def *accel_struct = nir_load_var(&b, vars.accel_struct);
@@ -1429,7 +1429,7 @@ build_traversal_shader(struct radv_device *device,
nir_store_var(&b, trav_vars.sbt_offset_and_flags, nir_imm_int(&b, 0), 1);
nir_store_var(&b, trav_vars.instance_addr, nir_imm_int64(&b, 0), 1);
nir_store_var(&b, trav_vars.stack, stack_idx_base, 1);
nir_store_var(&b, trav_vars.stack, stack_base, 1);
nir_store_var(&b, trav_vars.top_stack, nir_imm_int(&b, 0), 1);
nir_store_var(&b, trav_vars.current_node, bvh_root, 0x1);
@@ -1438,7 +1438,7 @@ build_traversal_shader(struct radv_device *device,
nir_push_if(&b, nir_ieq_imm(&b, nir_load_var(&b, trav_vars.current_node), -1));
{
nir_push_if(&b, nir_ieq(&b, nir_load_var(&b, trav_vars.stack), stack_idx_base));
nir_push_if(&b, nir_ieq(&b, nir_load_var(&b, trav_vars.stack), stack_base));
nir_jump(&b, nir_jump_break);
nir_pop_if(&b, NULL);
@@ -1458,10 +1458,12 @@ build_traversal_shader(struct radv_device *device,
nir_pop_if(&b, NULL);
nir_store_var(&b, trav_vars.stack,
nir_isub(&b, nir_load_var(&b, trav_vars.stack), stack_idx_stride), 1);
nir_isub(&b, nir_load_var(&b, trav_vars.stack), stack_entry_stride_def), 1);
stack = nir_build_deref_array(&b, stack_deref, nir_load_var(&b, trav_vars.stack));
nir_store_var(&b, trav_vars.current_node, nir_load_deref(&b, stack), 0x1);
nir_store_var(&b, trav_vars.current_node,
nir_load_shared(&b, 1, 32, nir_load_var(&b, trav_vars.stack), .base = 0,
.align_mul = stack_entry_size),
0x1);
}
nir_pop_if(&b, NULL);
@@ -1553,11 +1555,11 @@ build_traversal_shader(struct radv_device *device,
nir_ssa_def *new_node = nir_channel(&b, result, i);
nir_push_if(&b, nir_ine_imm(&b, new_node, 0xffffffff));
{
stack = nir_build_deref_array(&b, stack_deref, nir_load_var(&b, trav_vars.stack));
nir_store_deref(&b, stack, new_node, 0x1);
nir_store_var(&b, trav_vars.stack,
nir_iadd(&b, nir_load_var(&b, trav_vars.stack), stack_idx_stride),
1);
nir_store_shared(&b, new_node, nir_load_var(&b, trav_vars.stack), .base = 0,
.align_mul = stack_entry_size);
nir_store_var(
&b, trav_vars.stack,
nir_iadd(&b, nir_load_var(&b, trav_vars.stack), stack_entry_stride_def), 1);
}
nir_pop_if(&b, NULL);
}
@@ -1620,6 +1622,8 @@ insert_traversal(struct radv_device *device, const VkRayTracingPipelineCreateInf
{
struct hash_table *var_remap = _mesa_pointer_hash_table_create(NULL);
nir_shader *shader = build_traversal_shader(device, pCreateInfo, vars, var_remap);
b->shader->info.shared_size += shader->info.shared_size;
assert(b->shader->info.shared_size <= 32768);
/* For now, just inline the traversal shader */
nir_push_if(b, nir_ieq_imm(b, nir_load_var(b, vars->idx), 1));