| /* |
| * Copyright © 2015 Intel Corporation |
| * |
| * 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 |
| * the rights to use, copy, modify, merge, publish, distribute, sublicense, |
| * 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 NONINFRINGEMENT. IN NO EVENT SHALL |
| * THE AUTHORS OR COPYRIGHT HOLDERS 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 "nir.h" |
| #include "nir_builder.h" |
| #include "nir_xfb_info.h" |
| |
| /** |
| * \file nir_lower_gs_intrinsics.c |
| * |
| * Geometry Shaders can call EmitVertex()/EmitStreamVertex() to output an |
| * arbitrary number of vertices. However, the shader must declare the maximum |
| * number of vertices that it will ever output - further attempts to emit |
| * vertices result in undefined behavior according to the GLSL specification. |
| * |
| * Drivers might use this maximum number of vertices to allocate enough space |
| * to hold the geometry shader's output. Some drivers (such as i965) need to |
| * implement "safety checks" which ensure that the shader hasn't emitted too |
| * many vertices, to avoid overflowing that space and trashing other memory. |
| * |
| * The count of emitted vertices can also be useful in buffer offset |
| * calculations, so drivers know where to write the GS output. |
| * |
| * However, for simple geometry shaders that emit a statically determinable |
| * number of vertices, this extra bookkeeping is unnecessary and inefficient. |
| * By tracking the vertex count in NIR, we allow constant folding/propagation |
| * and dead control flow optimizations to eliminate most of it where possible. |
| * |
| * This pass introduces a new global variable which stores the current vertex |
| * count (initialized to 0), and converts emit_vertex/end_primitive intrinsics |
| * to their *_with_counter variants. emit_vertex is also wrapped in a safety |
| * check to avoid buffer overflows. Finally, it adds a set_vertex_count |
| * intrinsic at the end of the program, informing the driver of the final |
| * vertex count. |
| */ |
| |
| struct state { |
| nir_builder *builder; |
| nir_variable *vertex_count_vars[NIR_MAX_XFB_STREAMS]; |
| bool progress; |
| }; |
| |
| /** |
| * Replace emit_vertex intrinsics with: |
| * |
| * if (vertex_count < max_vertices) { |
| * emit_vertex_with_counter vertex_count ... |
| * vertex_count += 1 |
| * } |
| */ |
| static void |
| rewrite_emit_vertex(nir_intrinsic_instr *intrin, struct state *state) |
| { |
| nir_builder *b = state->builder; |
| unsigned stream = nir_intrinsic_stream_id(intrin); |
| |
| /* Load the vertex count */ |
| b->cursor = nir_before_instr(&intrin->instr); |
| assert(state->vertex_count_vars[stream] != NULL); |
| nir_ssa_def *count = nir_load_var(b, state->vertex_count_vars[stream]); |
| |
| nir_ssa_def *max_vertices = |
| nir_imm_int(b, b->shader->info.gs.vertices_out); |
| |
| /* Create: if (vertex_count < max_vertices) and insert it. |
| * |
| * The new if statement needs to be hooked up to the control flow graph |
| * before we start inserting instructions into it. |
| */ |
| nir_push_if(b, nir_ilt(b, count, max_vertices)); |
| |
| nir_intrinsic_instr *lowered = |
| nir_intrinsic_instr_create(b->shader, |
| nir_intrinsic_emit_vertex_with_counter); |
| nir_intrinsic_set_stream_id(lowered, stream); |
| lowered->src[0] = nir_src_for_ssa(count); |
| nir_builder_instr_insert(b, &lowered->instr); |
| |
| /* Increment the vertex count by 1 */ |
| nir_store_var(b, state->vertex_count_vars[stream], |
| nir_iadd(b, count, nir_imm_int(b, 1)), |
| 0x1); /* .x */ |
| |
| nir_pop_if(b, NULL); |
| |
| nir_instr_remove(&intrin->instr); |
| |
| state->progress = true; |
| } |
| |
| /** |
| * Replace end_primitive with end_primitive_with_counter. |
| */ |
| static void |
| rewrite_end_primitive(nir_intrinsic_instr *intrin, struct state *state) |
| { |
| nir_builder *b = state->builder; |
| unsigned stream = nir_intrinsic_stream_id(intrin); |
| |
| b->cursor = nir_before_instr(&intrin->instr); |
| assert(state->vertex_count_vars[stream] != NULL); |
| nir_ssa_def *count = nir_load_var(b, state->vertex_count_vars[stream]); |
| |
| nir_intrinsic_instr *lowered = |
| nir_intrinsic_instr_create(b->shader, |
| nir_intrinsic_end_primitive_with_counter); |
| nir_intrinsic_set_stream_id(lowered, stream); |
| lowered->src[0] = nir_src_for_ssa(count); |
| nir_builder_instr_insert(b, &lowered->instr); |
| |
| nir_instr_remove(&intrin->instr); |
| |
| state->progress = true; |
| } |
| |
| static bool |
| rewrite_intrinsics(nir_block *block, struct state *state) |
| { |
| nir_foreach_instr_safe(instr, block) { |
| if (instr->type != nir_instr_type_intrinsic) |
| continue; |
| |
| nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); |
| switch (intrin->intrinsic) { |
| case nir_intrinsic_emit_vertex: |
| rewrite_emit_vertex(intrin, state); |
| break; |
| case nir_intrinsic_end_primitive: |
| rewrite_end_primitive(intrin, state); |
| break; |
| default: |
| /* not interesting; skip this */ |
| break; |
| } |
| } |
| |
| return true; |
| } |
| |
| /** |
| * Add a set_vertex_count intrinsic at the end of the program |
| * (representing the final vertex count). |
| */ |
| static void |
| append_set_vertex_count(nir_block *end_block, struct state *state) |
| { |
| nir_builder *b = state->builder; |
| nir_shader *shader = state->builder->shader; |
| |
| /* Insert the new intrinsic in all of the predecessors of the end block, |
| * but before any jump instructions (return). |
| */ |
| set_foreach(end_block->predecessors, entry) { |
| nir_block *pred = (nir_block *) entry->key; |
| b->cursor = nir_after_block_before_jump(pred); |
| |
| nir_ssa_def *count = nir_load_var(b, state->vertex_count_vars[0]); |
| |
| nir_intrinsic_instr *set_vertex_count = |
| nir_intrinsic_instr_create(shader, nir_intrinsic_set_vertex_count); |
| set_vertex_count->src[0] = nir_src_for_ssa(count); |
| |
| nir_builder_instr_insert(b, &set_vertex_count->instr); |
| } |
| } |
| |
| bool |
| nir_lower_gs_intrinsics(nir_shader *shader, bool per_stream) |
| { |
| struct state state; |
| state.progress = false; |
| |
| nir_function_impl *impl = nir_shader_get_entrypoint(shader); |
| assert(impl); |
| |
| nir_builder b; |
| nir_builder_init(&b, impl); |
| state.builder = &b; |
| |
| /* Create the counter variables */ |
| b.cursor = nir_before_cf_list(&impl->body); |
| for (unsigned i = 0; i < NIR_MAX_XFB_STREAMS; i++) { |
| if (per_stream && !(shader->info.gs.active_stream_mask & (1 << i))) |
| continue; |
| |
| if (i == 0 || per_stream) { |
| state.vertex_count_vars[i] = |
| nir_local_variable_create(impl, glsl_uint_type(), "vertex_count"); |
| /* initialize to 0 */ |
| nir_store_var(&b, state.vertex_count_vars[i], nir_imm_int(&b, 0), 0x1); |
| } else { |
| /* If per_stream is false, we only have one counter which we want to use |
| * for all streams. Duplicate the counter pointer so all streams use the |
| * same counter. |
| */ |
| state.vertex_count_vars[i] = state.vertex_count_vars[0]; |
| } |
| } |
| |
| nir_foreach_block_safe(block, impl) |
| rewrite_intrinsics(block, &state); |
| |
| /* This only works because we have a single main() function. */ |
| if (!per_stream) |
| append_set_vertex_count(impl->end_block, &state); |
| |
| nir_metadata_preserve(impl, 0); |
| |
| return state.progress; |
| } |