| /* |
| * Copyright © 2015 Thomas Helland |
| * |
| * 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_constant_expressions.h" |
| #include "nir_loop_analyze.h" |
| |
| typedef enum { |
| undefined, |
| invariant, |
| not_invariant, |
| basic_induction |
| } nir_loop_variable_type; |
| |
| typedef struct nir_basic_induction_var { |
| nir_alu_instr *alu; /* The def of the alu-operation */ |
| nir_ssa_def *def_outside_loop; /* The phi-src outside the loop */ |
| } nir_basic_induction_var; |
| |
| typedef struct { |
| /* A link for the work list */ |
| struct list_head process_link; |
| |
| bool in_loop; |
| |
| /* The ssa_def associated with this info */ |
| nir_ssa_def *def; |
| |
| /* The type of this ssa_def */ |
| nir_loop_variable_type type; |
| |
| /* If this is of type basic_induction */ |
| struct nir_basic_induction_var *ind; |
| |
| /* True if variable is in an if branch */ |
| bool in_if_branch; |
| |
| /* True if variable is in a nested loop */ |
| bool in_nested_loop; |
| |
| } nir_loop_variable; |
| |
| typedef struct { |
| /* The loop we store information for */ |
| nir_loop *loop; |
| |
| /* Loop_variable for all ssa_defs in function */ |
| nir_loop_variable *loop_vars; |
| |
| /* A list of the loop_vars to analyze */ |
| struct list_head process_list; |
| |
| nir_variable_mode indirect_mask; |
| |
| } loop_info_state; |
| |
| static nir_loop_variable * |
| get_loop_var(nir_ssa_def *value, loop_info_state *state) |
| { |
| return &(state->loop_vars[value->index]); |
| } |
| |
| typedef struct { |
| loop_info_state *state; |
| bool in_if_branch; |
| bool in_nested_loop; |
| } init_loop_state; |
| |
| static bool |
| init_loop_def(nir_ssa_def *def, void *void_init_loop_state) |
| { |
| init_loop_state *loop_init_state = void_init_loop_state; |
| nir_loop_variable *var = get_loop_var(def, loop_init_state->state); |
| |
| if (loop_init_state->in_nested_loop) { |
| var->in_nested_loop = true; |
| } else if (loop_init_state->in_if_branch) { |
| var->in_if_branch = true; |
| } else { |
| /* Add to the tail of the list. That way we start at the beginning of |
| * the defs in the loop instead of the end when walking the list. This |
| * means less recursive calls. Only add defs that are not in nested |
| * loops or conditional blocks. |
| */ |
| list_addtail(&var->process_link, &loop_init_state->state->process_list); |
| } |
| |
| var->in_loop = true; |
| |
| return true; |
| } |
| |
| /** Calculate an estimated cost in number of instructions |
| * |
| * We do this so that we don't unroll loops which will later get massively |
| * inflated due to int64 or fp64 lowering. The estimates provided here don't |
| * have to be massively accurate; they just have to be good enough that loop |
| * unrolling doesn't cause things to blow up too much. |
| */ |
| static unsigned |
| instr_cost(nir_instr *instr, const nir_shader_compiler_options *options) |
| { |
| if (instr->type == nir_instr_type_intrinsic || |
| instr->type == nir_instr_type_tex) |
| return 1; |
| |
| if (instr->type != nir_instr_type_alu) |
| return 0; |
| |
| nir_alu_instr *alu = nir_instr_as_alu(instr); |
| const nir_op_info *info = &nir_op_infos[alu->op]; |
| |
| /* Assume everything 16 or 32-bit is cheap. |
| * |
| * There are no 64-bit ops that don't have a 64-bit thing as their |
| * destination or first source. |
| */ |
| if (nir_dest_bit_size(alu->dest.dest) < 64 && |
| nir_src_bit_size(alu->src[0].src) < 64) |
| return 1; |
| |
| bool is_fp64 = nir_dest_bit_size(alu->dest.dest) == 64 && |
| nir_alu_type_get_base_type(info->output_type) == nir_type_float; |
| for (unsigned i = 0; i < info->num_inputs; i++) { |
| if (nir_src_bit_size(alu->src[i].src) == 64 && |
| nir_alu_type_get_base_type(info->input_types[i]) == nir_type_float) |
| is_fp64 = true; |
| } |
| |
| if (is_fp64) { |
| /* If it's something lowered normally, it's expensive. */ |
| unsigned cost = 1; |
| if (options->lower_doubles_options & |
| nir_lower_doubles_op_to_options_mask(alu->op)) |
| cost *= 20; |
| |
| /* If it's full software, it's even more expensive */ |
| if (options->lower_doubles_options & nir_lower_fp64_full_software) |
| cost *= 100; |
| |
| return cost; |
| } else { |
| if (options->lower_int64_options & |
| nir_lower_int64_op_to_options_mask(alu->op)) { |
| /* These require a doing the division algorithm. */ |
| if (alu->op == nir_op_idiv || alu->op == nir_op_udiv || |
| alu->op == nir_op_imod || alu->op == nir_op_umod || |
| alu->op == nir_op_irem) |
| return 100; |
| |
| /* Other int64 lowering isn't usually all that expensive */ |
| return 5; |
| } |
| |
| return 1; |
| } |
| } |
| |
| static bool |
| init_loop_block(nir_block *block, loop_info_state *state, |
| bool in_if_branch, bool in_nested_loop, |
| const nir_shader_compiler_options *options) |
| { |
| init_loop_state init_state = {.in_if_branch = in_if_branch, |
| .in_nested_loop = in_nested_loop, |
| .state = state }; |
| |
| nir_foreach_instr(instr, block) { |
| state->loop->info->instr_cost += instr_cost(instr, options); |
| nir_foreach_ssa_def(instr, init_loop_def, &init_state); |
| } |
| |
| return true; |
| } |
| |
| static inline bool |
| is_var_alu(nir_loop_variable *var) |
| { |
| return var->def->parent_instr->type == nir_instr_type_alu; |
| } |
| |
| static inline bool |
| is_var_phi(nir_loop_variable *var) |
| { |
| return var->def->parent_instr->type == nir_instr_type_phi; |
| } |
| |
| static inline bool |
| mark_invariant(nir_ssa_def *def, loop_info_state *state) |
| { |
| nir_loop_variable *var = get_loop_var(def, state); |
| |
| if (var->type == invariant) |
| return true; |
| |
| if (!var->in_loop) { |
| var->type = invariant; |
| return true; |
| } |
| |
| if (var->type == not_invariant) |
| return false; |
| |
| if (is_var_alu(var)) { |
| nir_alu_instr *alu = nir_instr_as_alu(def->parent_instr); |
| |
| for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) { |
| if (!mark_invariant(alu->src[i].src.ssa, state)) { |
| var->type = not_invariant; |
| return false; |
| } |
| } |
| var->type = invariant; |
| return true; |
| } |
| |
| /* Phis shouldn't be invariant except if one operand is invariant, and the |
| * other is the phi itself. These should be removed by opt_remove_phis. |
| * load_consts are already set to invariant and constant during init, |
| * and so should return earlier. Remaining op_codes are set undefined. |
| */ |
| var->type = not_invariant; |
| return false; |
| } |
| |
| static void |
| compute_invariance_information(loop_info_state *state) |
| { |
| /* An expression is invariant in a loop L if: |
| * (base cases) |
| * – it’s a constant |
| * – it’s a variable use, all of whose single defs are outside of L |
| * (inductive cases) |
| * – it’s a pure computation all of whose args are loop invariant |
| * – it’s a variable use whose single reaching def, and the |
| * rhs of that def is loop-invariant |
| */ |
| list_for_each_entry_safe(nir_loop_variable, var, &state->process_list, |
| process_link) { |
| assert(!var->in_if_branch && !var->in_nested_loop); |
| |
| if (mark_invariant(var->def, state)) |
| list_del(&var->process_link); |
| } |
| } |
| |
| /* If all of the instruction sources point to identical ALU instructions (as |
| * per nir_instrs_equal), return one of the ALU instructions. Otherwise, |
| * return NULL. |
| */ |
| static nir_alu_instr * |
| phi_instr_as_alu(nir_phi_instr *phi) |
| { |
| nir_alu_instr *first = NULL; |
| nir_foreach_phi_src(src, phi) { |
| assert(src->src.is_ssa); |
| if (src->src.ssa->parent_instr->type != nir_instr_type_alu) |
| return NULL; |
| |
| nir_alu_instr *alu = nir_instr_as_alu(src->src.ssa->parent_instr); |
| if (first == NULL) { |
| first = alu; |
| } else { |
| if (!nir_instrs_equal(&first->instr, &alu->instr)) |
| return NULL; |
| } |
| } |
| |
| return first; |
| } |
| |
| static bool |
| alu_src_has_identity_swizzle(nir_alu_instr *alu, unsigned src_idx) |
| { |
| assert(nir_op_infos[alu->op].input_sizes[src_idx] == 0); |
| assert(alu->dest.dest.is_ssa); |
| for (unsigned i = 0; i < alu->dest.dest.ssa.num_components; i++) { |
| if (alu->src[src_idx].swizzle[i] != i) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| static bool |
| compute_induction_information(loop_info_state *state) |
| { |
| bool found_induction_var = false; |
| list_for_each_entry_safe(nir_loop_variable, var, &state->process_list, |
| process_link) { |
| |
| /* It can't be an induction variable if it is invariant. Invariants and |
| * things in nested loops or conditionals should have been removed from |
| * the list by compute_invariance_information(). |
| */ |
| assert(!var->in_if_branch && !var->in_nested_loop && |
| var->type != invariant); |
| |
| /* We are only interested in checking phis for the basic induction |
| * variable case as its simple to detect. All basic induction variables |
| * have a phi node |
| */ |
| if (!is_var_phi(var)) |
| continue; |
| |
| nir_phi_instr *phi = nir_instr_as_phi(var->def->parent_instr); |
| nir_basic_induction_var *biv = rzalloc(state, nir_basic_induction_var); |
| |
| nir_loop_variable *alu_src_var = NULL; |
| nir_foreach_phi_src(src, phi) { |
| nir_loop_variable *src_var = get_loop_var(src->src.ssa, state); |
| |
| /* If one of the sources is in an if branch or nested loop then don't |
| * attempt to go any further. |
| */ |
| if (src_var->in_if_branch || src_var->in_nested_loop) |
| break; |
| |
| /* Detect inductions variables that are incremented in both branches |
| * of an unnested if rather than in a loop block. |
| */ |
| if (is_var_phi(src_var)) { |
| nir_phi_instr *src_phi = |
| nir_instr_as_phi(src_var->def->parent_instr); |
| nir_alu_instr *src_phi_alu = phi_instr_as_alu(src_phi); |
| if (src_phi_alu) { |
| src_var = get_loop_var(&src_phi_alu->dest.dest.ssa, state); |
| if (!src_var->in_if_branch) |
| break; |
| } |
| } |
| |
| if (!src_var->in_loop && !biv->def_outside_loop) { |
| biv->def_outside_loop = src_var->def; |
| } else if (is_var_alu(src_var) && !biv->alu) { |
| alu_src_var = src_var; |
| nir_alu_instr *alu = nir_instr_as_alu(src_var->def->parent_instr); |
| |
| if (nir_op_infos[alu->op].num_inputs == 2) { |
| for (unsigned i = 0; i < 2; i++) { |
| /* Is one of the operands const, and the other the phi. The |
| * phi source can't be swizzled in any way. |
| */ |
| if (nir_src_is_const(alu->src[i].src) && |
| alu->src[1-i].src.ssa == &phi->dest.ssa && |
| alu_src_has_identity_swizzle(alu, 1 - i)) |
| biv->alu = alu; |
| } |
| } |
| |
| if (!biv->alu) |
| break; |
| } else { |
| biv->alu = NULL; |
| break; |
| } |
| } |
| |
| if (biv->alu && biv->def_outside_loop && |
| biv->def_outside_loop->parent_instr->type == nir_instr_type_load_const) { |
| alu_src_var->type = basic_induction; |
| alu_src_var->ind = biv; |
| var->type = basic_induction; |
| var->ind = biv; |
| |
| found_induction_var = true; |
| } else { |
| ralloc_free(biv); |
| } |
| } |
| return found_induction_var; |
| } |
| |
| static bool |
| initialize_ssa_def(nir_ssa_def *def, void *void_state) |
| { |
| loop_info_state *state = void_state; |
| nir_loop_variable *var = get_loop_var(def, state); |
| |
| var->in_loop = false; |
| var->def = def; |
| |
| if (def->parent_instr->type == nir_instr_type_load_const) { |
| var->type = invariant; |
| } else { |
| var->type = undefined; |
| } |
| |
| return true; |
| } |
| |
| static bool |
| find_loop_terminators(loop_info_state *state) |
| { |
| bool success = false; |
| foreach_list_typed_safe(nir_cf_node, node, node, &state->loop->body) { |
| if (node->type == nir_cf_node_if) { |
| nir_if *nif = nir_cf_node_as_if(node); |
| |
| nir_block *break_blk = NULL; |
| nir_block *continue_from_blk = NULL; |
| bool continue_from_then = true; |
| |
| nir_block *last_then = nir_if_last_then_block(nif); |
| nir_block *last_else = nir_if_last_else_block(nif); |
| if (nir_block_ends_in_break(last_then)) { |
| break_blk = last_then; |
| continue_from_blk = last_else; |
| continue_from_then = false; |
| } else if (nir_block_ends_in_break(last_else)) { |
| break_blk = last_else; |
| continue_from_blk = last_then; |
| } |
| |
| /* If there is a break then we should find a terminator. If we can |
| * not find a loop terminator, but there is a break-statement then |
| * we should return false so that we do not try to find trip-count |
| */ |
| if (!nir_is_trivial_loop_if(nif, break_blk)) { |
| state->loop->info->complex_loop = true; |
| return false; |
| } |
| |
| /* Continue if the if contained no jumps at all */ |
| if (!break_blk) |
| continue; |
| |
| if (nif->condition.ssa->parent_instr->type == nir_instr_type_phi) { |
| state->loop->info->complex_loop = true; |
| return false; |
| } |
| |
| nir_loop_terminator *terminator = |
| rzalloc(state->loop->info, nir_loop_terminator); |
| |
| list_addtail(&terminator->loop_terminator_link, |
| &state->loop->info->loop_terminator_list); |
| |
| terminator->nif = nif; |
| terminator->break_block = break_blk; |
| terminator->continue_from_block = continue_from_blk; |
| terminator->continue_from_then = continue_from_then; |
| terminator->conditional_instr = nif->condition.ssa->parent_instr; |
| |
| success = true; |
| } |
| } |
| |
| return success; |
| } |
| |
| /* This function looks for an array access within a loop that uses an |
| * induction variable for the array index. If found it returns the size of the |
| * array, otherwise 0 is returned. If we find an induction var we pass it back |
| * to the caller via array_index_out. |
| */ |
| static unsigned |
| find_array_access_via_induction(loop_info_state *state, |
| nir_deref_instr *deref, |
| nir_loop_variable **array_index_out) |
| { |
| for (nir_deref_instr *d = deref; d; d = nir_deref_instr_parent(d)) { |
| if (d->deref_type != nir_deref_type_array) |
| continue; |
| |
| assert(d->arr.index.is_ssa); |
| nir_loop_variable *array_index = get_loop_var(d->arr.index.ssa, state); |
| |
| if (array_index->type != basic_induction) |
| continue; |
| |
| if (array_index_out) |
| *array_index_out = array_index; |
| |
| nir_deref_instr *parent = nir_deref_instr_parent(d); |
| if (glsl_type_is_array_or_matrix(parent->type)) { |
| return glsl_get_length(parent->type); |
| } else { |
| assert(glsl_type_is_vector(parent->type)); |
| return glsl_get_vector_elements(parent->type); |
| } |
| } |
| |
| return 0; |
| } |
| |
| static bool |
| guess_loop_limit(loop_info_state *state, nir_const_value *limit_val, |
| nir_ssa_scalar basic_ind) |
| { |
| unsigned min_array_size = 0; |
| |
| nir_foreach_block_in_cf_node(block, &state->loop->cf_node) { |
| nir_foreach_instr(instr, block) { |
| if (instr->type != nir_instr_type_intrinsic) |
| continue; |
| |
| nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); |
| |
| /* Check for arrays variably-indexed by a loop induction variable. */ |
| if (intrin->intrinsic == nir_intrinsic_load_deref || |
| intrin->intrinsic == nir_intrinsic_store_deref || |
| intrin->intrinsic == nir_intrinsic_copy_deref) { |
| |
| nir_loop_variable *array_idx = NULL; |
| unsigned array_size = |
| find_array_access_via_induction(state, |
| nir_src_as_deref(intrin->src[0]), |
| &array_idx); |
| if (array_idx && basic_ind.def == array_idx->def && |
| (min_array_size == 0 || min_array_size > array_size)) { |
| /* Array indices are scalars */ |
| assert(basic_ind.def->num_components == 1); |
| min_array_size = array_size; |
| } |
| |
| if (intrin->intrinsic != nir_intrinsic_copy_deref) |
| continue; |
| |
| array_size = |
| find_array_access_via_induction(state, |
| nir_src_as_deref(intrin->src[1]), |
| &array_idx); |
| if (array_idx && basic_ind.def == array_idx->def && |
| (min_array_size == 0 || min_array_size > array_size)) { |
| /* Array indices are scalars */ |
| assert(basic_ind.def->num_components == 1); |
| min_array_size = array_size; |
| } |
| } |
| } |
| } |
| |
| if (min_array_size) { |
| *limit_val = nir_const_value_for_uint(min_array_size, |
| basic_ind.def->bit_size); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| static bool |
| try_find_limit_of_alu(nir_ssa_scalar limit, nir_const_value *limit_val, |
| nir_loop_terminator *terminator, loop_info_state *state) |
| { |
| if (!nir_ssa_scalar_is_alu(limit)) |
| return false; |
| |
| nir_op limit_op = nir_ssa_scalar_alu_op(limit); |
| if (limit_op == nir_op_imin || limit_op == nir_op_fmin) { |
| for (unsigned i = 0; i < 2; i++) { |
| nir_ssa_scalar src = nir_ssa_scalar_chase_alu_src(limit, i); |
| if (nir_ssa_scalar_is_const(src)) { |
| *limit_val = nir_ssa_scalar_as_const_value(src); |
| terminator->exact_trip_count_unknown = true; |
| return true; |
| } |
| } |
| } |
| |
| return false; |
| } |
| |
| static nir_const_value |
| eval_const_unop(nir_op op, unsigned bit_size, nir_const_value src0, |
| unsigned execution_mode) |
| { |
| assert(nir_op_infos[op].num_inputs == 1); |
| nir_const_value dest; |
| nir_const_value *src[1] = { &src0 }; |
| nir_eval_const_opcode(op, &dest, 1, bit_size, src, execution_mode); |
| return dest; |
| } |
| |
| static nir_const_value |
| eval_const_binop(nir_op op, unsigned bit_size, |
| nir_const_value src0, nir_const_value src1, |
| unsigned execution_mode) |
| { |
| assert(nir_op_infos[op].num_inputs == 2); |
| nir_const_value dest; |
| nir_const_value *src[2] = { &src0, &src1 }; |
| nir_eval_const_opcode(op, &dest, 1, bit_size, src, execution_mode); |
| return dest; |
| } |
| |
| static int32_t |
| get_iteration(nir_op cond_op, nir_const_value initial, nir_const_value step, |
| nir_const_value limit, unsigned bit_size, |
| unsigned execution_mode) |
| { |
| nir_const_value span, iter; |
| |
| switch (cond_op) { |
| case nir_op_ige: |
| case nir_op_ilt: |
| case nir_op_ieq: |
| case nir_op_ine: |
| span = eval_const_binop(nir_op_isub, bit_size, limit, initial, |
| execution_mode); |
| iter = eval_const_binop(nir_op_idiv, bit_size, span, step, |
| execution_mode); |
| break; |
| |
| case nir_op_uge: |
| case nir_op_ult: |
| span = eval_const_binop(nir_op_isub, bit_size, limit, initial, |
| execution_mode); |
| iter = eval_const_binop(nir_op_udiv, bit_size, span, step, |
| execution_mode); |
| break; |
| |
| case nir_op_fge: |
| case nir_op_flt: |
| case nir_op_feq: |
| case nir_op_fne: |
| span = eval_const_binop(nir_op_fsub, bit_size, limit, initial, |
| execution_mode); |
| iter = eval_const_binop(nir_op_fdiv, bit_size, span, |
| step, execution_mode); |
| iter = eval_const_unop(nir_op_f2i64, bit_size, iter, execution_mode); |
| break; |
| |
| default: |
| return -1; |
| } |
| |
| uint64_t iter_u64 = nir_const_value_as_uint(iter, bit_size); |
| return iter_u64 > INT_MAX ? -1 : (int)iter_u64; |
| } |
| |
| static bool |
| will_break_on_first_iteration(nir_const_value step, |
| nir_alu_type induction_base_type, |
| unsigned trip_offset, |
| nir_op cond_op, unsigned bit_size, |
| nir_const_value initial, |
| nir_const_value limit, |
| bool limit_rhs, bool invert_cond, |
| unsigned execution_mode) |
| { |
| if (trip_offset == 1) { |
| nir_op add_op; |
| switch (induction_base_type) { |
| case nir_type_float: |
| add_op = nir_op_fadd; |
| break; |
| case nir_type_int: |
| case nir_type_uint: |
| add_op = nir_op_iadd; |
| break; |
| default: |
| unreachable("Unhandled induction variable base type!"); |
| } |
| |
| initial = eval_const_binop(add_op, bit_size, initial, step, |
| execution_mode); |
| } |
| |
| nir_const_value *src[2]; |
| src[limit_rhs ? 0 : 1] = &initial; |
| src[limit_rhs ? 1 : 0] = &limit; |
| |
| /* Evaluate the loop exit condition */ |
| nir_const_value result; |
| nir_eval_const_opcode(cond_op, &result, 1, bit_size, src, execution_mode); |
| |
| return invert_cond ? !result.b : result.b; |
| } |
| |
| static bool |
| test_iterations(int32_t iter_int, nir_const_value step, |
| nir_const_value limit, nir_op cond_op, unsigned bit_size, |
| nir_alu_type induction_base_type, |
| nir_const_value initial, bool limit_rhs, bool invert_cond, |
| unsigned execution_mode) |
| { |
| assert(nir_op_infos[cond_op].num_inputs == 2); |
| |
| nir_const_value iter_src; |
| nir_op mul_op; |
| nir_op add_op; |
| switch (induction_base_type) { |
| case nir_type_float: |
| iter_src = nir_const_value_for_float(iter_int, bit_size); |
| mul_op = nir_op_fmul; |
| add_op = nir_op_fadd; |
| break; |
| case nir_type_int: |
| case nir_type_uint: |
| iter_src = nir_const_value_for_int(iter_int, bit_size); |
| mul_op = nir_op_imul; |
| add_op = nir_op_iadd; |
| break; |
| default: |
| unreachable("Unhandled induction variable base type!"); |
| } |
| |
| /* Multiple the iteration count we are testing by the number of times we |
| * step the induction variable each iteration. |
| */ |
| nir_const_value mul_result = |
| eval_const_binop(mul_op, bit_size, iter_src, step, execution_mode); |
| |
| /* Add the initial value to the accumulated induction variable total */ |
| nir_const_value add_result = |
| eval_const_binop(add_op, bit_size, mul_result, initial, execution_mode); |
| |
| nir_const_value *src[2]; |
| src[limit_rhs ? 0 : 1] = &add_result; |
| src[limit_rhs ? 1 : 0] = &limit; |
| |
| /* Evaluate the loop exit condition */ |
| nir_const_value result; |
| nir_eval_const_opcode(cond_op, &result, 1, bit_size, src, execution_mode); |
| |
| return invert_cond ? !result.b : result.b; |
| } |
| |
| static int |
| calculate_iterations(nir_const_value initial, nir_const_value step, |
| nir_const_value limit, nir_alu_instr *alu, |
| nir_ssa_scalar cond, nir_op alu_op, bool limit_rhs, |
| bool invert_cond, unsigned execution_mode) |
| { |
| /* nir_op_isub should have been lowered away by this point */ |
| assert(alu->op != nir_op_isub); |
| |
| /* Make sure the alu type for our induction variable is compatible with the |
| * conditional alus input type. If its not something has gone really wrong. |
| */ |
| nir_alu_type induction_base_type = |
| nir_alu_type_get_base_type(nir_op_infos[alu->op].output_type); |
| if (induction_base_type == nir_type_int || induction_base_type == nir_type_uint) { |
| assert(nir_alu_type_get_base_type(nir_op_infos[alu_op].input_types[1]) == nir_type_int || |
| nir_alu_type_get_base_type(nir_op_infos[alu_op].input_types[1]) == nir_type_uint); |
| } else { |
| assert(nir_alu_type_get_base_type(nir_op_infos[alu_op].input_types[0]) == |
| induction_base_type); |
| } |
| |
| /* Check for nsupported alu operations */ |
| if (alu->op != nir_op_iadd && alu->op != nir_op_fadd) |
| return -1; |
| |
| /* do-while loops can increment the starting value before the condition is |
| * checked. e.g. |
| * |
| * do { |
| * ndx++; |
| * } while (ndx < 3); |
| * |
| * Here we check if the induction variable is used directly by the loop |
| * condition and if so we assume we need to step the initial value. |
| */ |
| unsigned trip_offset = 0; |
| nir_alu_instr *cond_alu = nir_instr_as_alu(cond.def->parent_instr); |
| if (cond_alu->src[0].src.ssa == &alu->dest.dest.ssa || |
| cond_alu->src[1].src.ssa == &alu->dest.dest.ssa) { |
| trip_offset = 1; |
| } |
| |
| assert(nir_src_bit_size(alu->src[0].src) == |
| nir_src_bit_size(alu->src[1].src)); |
| unsigned bit_size = nir_src_bit_size(alu->src[0].src); |
| |
| /* get_iteration works under assumption that iterator will be |
| * incremented or decremented until it hits the limit, |
| * however if the loop condition is false on the first iteration |
| * get_iteration's assumption is broken. Handle such loops first. |
| */ |
| if (will_break_on_first_iteration(step, induction_base_type, trip_offset, |
| alu_op, bit_size, initial, |
| limit, limit_rhs, invert_cond, |
| execution_mode)) { |
| return 0; |
| } |
| |
| int iter_int = get_iteration(alu_op, initial, step, limit, bit_size, |
| execution_mode); |
| |
| /* If iter_int is negative the loop is ill-formed or is the conditional is |
| * unsigned with a huge iteration count so don't bother going any further. |
| */ |
| if (iter_int < 0) |
| return -1; |
| |
| /* An explanation from the GLSL unrolling pass: |
| * |
| * Make sure that the calculated number of iterations satisfies the exit |
| * condition. This is needed to catch off-by-one errors and some types of |
| * ill-formed loops. For example, we need to detect that the following |
| * loop does not have a maximum iteration count. |
| * |
| * for (float x = 0.0; x != 0.9; x += 0.2); |
| */ |
| for (int bias = -1; bias <= 1; bias++) { |
| const int iter_bias = iter_int + bias; |
| |
| if (test_iterations(iter_bias, step, limit, alu_op, bit_size, |
| induction_base_type, initial, |
| limit_rhs, invert_cond, execution_mode)) { |
| return iter_bias > 0 ? iter_bias - trip_offset : iter_bias; |
| } |
| } |
| |
| return -1; |
| } |
| |
| static nir_op |
| inverse_comparison(nir_op alu_op) |
| { |
| switch (alu_op) { |
| case nir_op_fge: |
| return nir_op_flt; |
| case nir_op_ige: |
| return nir_op_ilt; |
| case nir_op_uge: |
| return nir_op_ult; |
| case nir_op_flt: |
| return nir_op_fge; |
| case nir_op_ilt: |
| return nir_op_ige; |
| case nir_op_ult: |
| return nir_op_uge; |
| case nir_op_feq: |
| return nir_op_fne; |
| case nir_op_ieq: |
| return nir_op_ine; |
| case nir_op_fne: |
| return nir_op_feq; |
| case nir_op_ine: |
| return nir_op_ieq; |
| default: |
| unreachable("Unsuported comparison!"); |
| } |
| } |
| |
| static bool |
| is_supported_terminator_condition(nir_ssa_scalar cond) |
| { |
| if (!nir_ssa_scalar_is_alu(cond)) |
| return false; |
| |
| nir_alu_instr *alu = nir_instr_as_alu(cond.def->parent_instr); |
| return nir_alu_instr_is_comparison(alu) && |
| nir_op_infos[alu->op].num_inputs == 2; |
| } |
| |
| static bool |
| get_induction_and_limit_vars(nir_ssa_scalar cond, |
| nir_ssa_scalar *ind, |
| nir_ssa_scalar *limit, |
| bool *limit_rhs, |
| loop_info_state *state) |
| { |
| nir_ssa_scalar rhs, lhs; |
| lhs = nir_ssa_scalar_chase_alu_src(cond, 0); |
| rhs = nir_ssa_scalar_chase_alu_src(cond, 1); |
| |
| if (get_loop_var(lhs.def, state)->type == basic_induction) { |
| *ind = lhs; |
| *limit = rhs; |
| *limit_rhs = true; |
| return true; |
| } else if (get_loop_var(rhs.def, state)->type == basic_induction) { |
| *ind = rhs; |
| *limit = lhs; |
| *limit_rhs = false; |
| return true; |
| } else { |
| return false; |
| } |
| } |
| |
| static bool |
| try_find_trip_count_vars_in_iand(nir_ssa_scalar *cond, |
| nir_ssa_scalar *ind, |
| nir_ssa_scalar *limit, |
| bool *limit_rhs, |
| loop_info_state *state) |
| { |
| const nir_op alu_op = nir_ssa_scalar_alu_op(*cond); |
| assert(alu_op == nir_op_ieq || alu_op == nir_op_inot); |
| |
| nir_ssa_scalar iand = nir_ssa_scalar_chase_alu_src(*cond, 0); |
| |
| if (alu_op == nir_op_ieq) { |
| nir_ssa_scalar zero = nir_ssa_scalar_chase_alu_src(*cond, 1); |
| |
| if (!nir_ssa_scalar_is_alu(iand) || !nir_ssa_scalar_is_const(zero)) { |
| /* Maybe we had it the wrong way, flip things around */ |
| nir_ssa_scalar tmp = zero; |
| zero = iand; |
| iand = tmp; |
| |
| /* If we still didn't find what we need then return */ |
| if (!nir_ssa_scalar_is_const(zero)) |
| return false; |
| } |
| |
| /* If the loop is not breaking on (x && y) == 0 then return */ |
| if (nir_ssa_scalar_as_uint(zero) != 0) |
| return false; |
| } |
| |
| if (!nir_ssa_scalar_is_alu(iand)) |
| return false; |
| |
| if (nir_ssa_scalar_alu_op(iand) != nir_op_iand) |
| return false; |
| |
| /* Check if iand src is a terminator condition and try get induction var |
| * and trip limit var. |
| */ |
| bool found_induction_var = false; |
| for (unsigned i = 0; i < 2; i++) { |
| nir_ssa_scalar src = nir_ssa_scalar_chase_alu_src(iand, i); |
| if (is_supported_terminator_condition(src) && |
| get_induction_and_limit_vars(src, ind, limit, limit_rhs, state)) { |
| *cond = src; |
| found_induction_var = true; |
| |
| /* If we've found one with a constant limit, stop. */ |
| if (nir_ssa_scalar_is_const(*limit)) |
| return true; |
| } |
| } |
| |
| return found_induction_var; |
| } |
| |
| /* Run through each of the terminators of the loop and try to infer a possible |
| * trip-count. We need to check them all, and set the lowest trip-count as the |
| * trip-count of our loop. If one of the terminators has an undecidable |
| * trip-count we can not safely assume anything about the duration of the |
| * loop. |
| */ |
| static void |
| find_trip_count(loop_info_state *state, unsigned execution_mode) |
| { |
| bool trip_count_known = true; |
| bool guessed_trip_count = false; |
| nir_loop_terminator *limiting_terminator = NULL; |
| int max_trip_count = -1; |
| |
| list_for_each_entry(nir_loop_terminator, terminator, |
| &state->loop->info->loop_terminator_list, |
| loop_terminator_link) { |
| assert(terminator->nif->condition.is_ssa); |
| nir_ssa_scalar cond = { terminator->nif->condition.ssa, 0 }; |
| |
| if (!nir_ssa_scalar_is_alu(cond)) { |
| /* If we get here the loop is dead and will get cleaned up by the |
| * nir_opt_dead_cf pass. |
| */ |
| trip_count_known = false; |
| continue; |
| } |
| |
| nir_op alu_op = nir_ssa_scalar_alu_op(cond); |
| |
| bool limit_rhs; |
| nir_ssa_scalar basic_ind = { NULL, 0 }; |
| nir_ssa_scalar limit; |
| if ((alu_op == nir_op_inot || alu_op == nir_op_ieq) && |
| try_find_trip_count_vars_in_iand(&cond, &basic_ind, &limit, |
| &limit_rhs, state)) { |
| |
| /* The loop is exiting on (x && y) == 0 so we need to get the |
| * inverse of x or y (i.e. which ever contained the induction var) in |
| * order to compute the trip count. |
| */ |
| alu_op = inverse_comparison(nir_ssa_scalar_alu_op(cond)); |
| trip_count_known = false; |
| terminator->exact_trip_count_unknown = true; |
| } |
| |
| if (!basic_ind.def) { |
| if (is_supported_terminator_condition(cond)) { |
| get_induction_and_limit_vars(cond, &basic_ind, |
| &limit, &limit_rhs, state); |
| } |
| } |
| |
| /* The comparison has to have a basic induction variable for us to be |
| * able to find trip counts. |
| */ |
| if (!basic_ind.def) { |
| trip_count_known = false; |
| continue; |
| } |
| |
| terminator->induction_rhs = !limit_rhs; |
| |
| /* Attempt to find a constant limit for the loop */ |
| nir_const_value limit_val; |
| if (nir_ssa_scalar_is_const(limit)) { |
| limit_val = nir_ssa_scalar_as_const_value(limit); |
| } else { |
| trip_count_known = false; |
| |
| if (!try_find_limit_of_alu(limit, &limit_val, terminator, state)) { |
| /* Guess loop limit based on array access */ |
| if (!guess_loop_limit(state, &limit_val, basic_ind)) { |
| continue; |
| } |
| |
| guessed_trip_count = true; |
| } |
| } |
| |
| /* We have determined that we have the following constants: |
| * (With the typical int i = 0; i < x; i++; as an example) |
| * - Upper limit. |
| * - Starting value |
| * - Step / iteration size |
| * Thats all thats needed to calculate the trip-count |
| */ |
| |
| nir_basic_induction_var *ind_var = |
| get_loop_var(basic_ind.def, state)->ind; |
| |
| /* The basic induction var might be a vector but, because we guarantee |
| * earlier that the phi source has a scalar swizzle, we can take the |
| * component from basic_ind. |
| */ |
| nir_ssa_scalar initial_s = { ind_var->def_outside_loop, basic_ind.comp }; |
| nir_ssa_scalar alu_s = { &ind_var->alu->dest.dest.ssa, basic_ind.comp }; |
| |
| nir_const_value initial_val = nir_ssa_scalar_as_const_value(initial_s); |
| |
| /* We are guaranteed by earlier code that at least one of these sources |
| * is a constant but we don't know which. |
| */ |
| nir_const_value step_val; |
| memset(&step_val, 0, sizeof(step_val)); |
| UNUSED bool found_step_value = false; |
| assert(nir_op_infos[ind_var->alu->op].num_inputs == 2); |
| for (unsigned i = 0; i < 2; i++) { |
| nir_ssa_scalar alu_src = nir_ssa_scalar_chase_alu_src(alu_s, i); |
| if (nir_ssa_scalar_is_const(alu_src)) { |
| found_step_value = true; |
| step_val = nir_ssa_scalar_as_const_value(alu_src); |
| break; |
| } |
| } |
| assert(found_step_value); |
| |
| int iterations = calculate_iterations(initial_val, step_val, limit_val, |
| ind_var->alu, cond, |
| alu_op, limit_rhs, |
| terminator->continue_from_then, |
| execution_mode); |
| |
| /* Where we not able to calculate the iteration count */ |
| if (iterations == -1) { |
| trip_count_known = false; |
| guessed_trip_count = false; |
| continue; |
| } |
| |
| if (guessed_trip_count) { |
| guessed_trip_count = false; |
| if (state->loop->info->guessed_trip_count == 0 || |
| state->loop->info->guessed_trip_count > iterations) |
| state->loop->info->guessed_trip_count = iterations; |
| |
| continue; |
| } |
| |
| /* If this is the first run or we have found a smaller amount of |
| * iterations than previously (we have identified a more limiting |
| * terminator) set the trip count and limiting terminator. |
| */ |
| if (max_trip_count == -1 || iterations < max_trip_count) { |
| max_trip_count = iterations; |
| limiting_terminator = terminator; |
| } |
| } |
| |
| state->loop->info->exact_trip_count_known = trip_count_known; |
| if (max_trip_count > -1) |
| state->loop->info->max_trip_count = max_trip_count; |
| state->loop->info->limiting_terminator = limiting_terminator; |
| } |
| |
| static bool |
| force_unroll_array_access(loop_info_state *state, nir_deref_instr *deref) |
| { |
| unsigned array_size = find_array_access_via_induction(state, deref, NULL); |
| if (array_size) { |
| if (array_size == state->loop->info->max_trip_count) |
| return true; |
| |
| if (deref->mode & state->indirect_mask) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| static bool |
| force_unroll_heuristics(loop_info_state *state, nir_block *block) |
| { |
| nir_foreach_instr(instr, block) { |
| if (instr->type != nir_instr_type_intrinsic) |
| continue; |
| |
| nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); |
| |
| /* Check for arrays variably-indexed by a loop induction variable. |
| * Unrolling the loop may convert that access into constant-indexing. |
| */ |
| if (intrin->intrinsic == nir_intrinsic_load_deref || |
| intrin->intrinsic == nir_intrinsic_store_deref || |
| intrin->intrinsic == nir_intrinsic_copy_deref) { |
| if (force_unroll_array_access(state, |
| nir_src_as_deref(intrin->src[0]))) |
| return true; |
| |
| if (intrin->intrinsic == nir_intrinsic_copy_deref && |
| force_unroll_array_access(state, |
| nir_src_as_deref(intrin->src[1]))) |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| static void |
| get_loop_info(loop_info_state *state, nir_function_impl *impl) |
| { |
| nir_shader *shader = impl->function->shader; |
| const nir_shader_compiler_options *options = shader->options; |
| |
| /* Initialize all variables to "outside_loop". This also marks defs |
| * invariant and constant if they are nir_instr_type_load_consts |
| */ |
| nir_foreach_block(block, impl) { |
| nir_foreach_instr(instr, block) |
| nir_foreach_ssa_def(instr, initialize_ssa_def, state); |
| } |
| |
| /* Add all entries in the outermost part of the loop to the processing list |
| * Mark the entries in conditionals or in nested loops accordingly |
| */ |
| foreach_list_typed_safe(nir_cf_node, node, node, &state->loop->body) { |
| switch (node->type) { |
| |
| case nir_cf_node_block: |
| init_loop_block(nir_cf_node_as_block(node), state, |
| false, false, options); |
| break; |
| |
| case nir_cf_node_if: |
| nir_foreach_block_in_cf_node(block, node) |
| init_loop_block(block, state, true, false, options); |
| break; |
| |
| case nir_cf_node_loop: |
| nir_foreach_block_in_cf_node(block, node) { |
| init_loop_block(block, state, false, true, options); |
| } |
| break; |
| |
| case nir_cf_node_function: |
| break; |
| } |
| } |
| |
| /* Try to find all simple terminators of the loop. If we can't find any, |
| * or we find possible terminators that have side effects then bail. |
| */ |
| if (!find_loop_terminators(state)) { |
| list_for_each_entry_safe(nir_loop_terminator, terminator, |
| &state->loop->info->loop_terminator_list, |
| loop_terminator_link) { |
| list_del(&terminator->loop_terminator_link); |
| ralloc_free(terminator); |
| } |
| return; |
| } |
| |
| /* Induction analysis needs invariance information so get that first */ |
| compute_invariance_information(state); |
| |
| /* We have invariance information so try to find induction variables */ |
| if (!compute_induction_information(state)) |
| return; |
| |
| /* Run through each of the terminators and try to compute a trip-count */ |
| find_trip_count(state, impl->function->shader->info.float_controls_execution_mode); |
| |
| nir_foreach_block_in_cf_node(block, &state->loop->cf_node) { |
| if (force_unroll_heuristics(state, block)) { |
| state->loop->info->force_unroll = true; |
| break; |
| } |
| } |
| } |
| |
| static loop_info_state * |
| initialize_loop_info_state(nir_loop *loop, void *mem_ctx, |
| nir_function_impl *impl) |
| { |
| loop_info_state *state = rzalloc(mem_ctx, loop_info_state); |
| state->loop_vars = rzalloc_array(mem_ctx, nir_loop_variable, |
| impl->ssa_alloc); |
| state->loop = loop; |
| |
| list_inithead(&state->process_list); |
| |
| if (loop->info) |
| ralloc_free(loop->info); |
| |
| loop->info = rzalloc(loop, nir_loop_info); |
| |
| list_inithead(&loop->info->loop_terminator_list); |
| |
| return state; |
| } |
| |
| static void |
| process_loops(nir_cf_node *cf_node, nir_variable_mode indirect_mask) |
| { |
| switch (cf_node->type) { |
| case nir_cf_node_block: |
| return; |
| case nir_cf_node_if: { |
| nir_if *if_stmt = nir_cf_node_as_if(cf_node); |
| foreach_list_typed(nir_cf_node, nested_node, node, &if_stmt->then_list) |
| process_loops(nested_node, indirect_mask); |
| foreach_list_typed(nir_cf_node, nested_node, node, &if_stmt->else_list) |
| process_loops(nested_node, indirect_mask); |
| return; |
| } |
| case nir_cf_node_loop: { |
| nir_loop *loop = nir_cf_node_as_loop(cf_node); |
| foreach_list_typed(nir_cf_node, nested_node, node, &loop->body) |
| process_loops(nested_node, indirect_mask); |
| break; |
| } |
| default: |
| unreachable("unknown cf node type"); |
| } |
| |
| nir_loop *loop = nir_cf_node_as_loop(cf_node); |
| nir_function_impl *impl = nir_cf_node_get_function(cf_node); |
| void *mem_ctx = ralloc_context(NULL); |
| |
| loop_info_state *state = initialize_loop_info_state(loop, mem_ctx, impl); |
| state->indirect_mask = indirect_mask; |
| |
| get_loop_info(state, impl); |
| |
| ralloc_free(mem_ctx); |
| } |
| |
| void |
| nir_loop_analyze_impl(nir_function_impl *impl, |
| nir_variable_mode indirect_mask) |
| { |
| nir_index_ssa_defs(impl); |
| foreach_list_typed(nir_cf_node, node, node, &impl->body) |
| process_loops(node, indirect_mask); |
| } |
