<div dir="ltr"> <div class="gmail_extra"> <div class="gmail_quote">On Fri, Sep 16, 2016 at 5:36 PM, Connor Abbott <<a href="mailto:cwabbott0@gmail.com" target="_blank">cwabbott0@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5">On Fri, Sep 16, 2016 at 6:25 PM, Jason Ekstrand <<a href="mailto:jason@jlekstrand.net">jason@jlekstrand.net</a>> wrote: > On Thu, Sep 15, 2016 at 12:03 AM, Timothy Arceri > <<a href="mailto:timothy.arceri@collabora.com">timothy.arceri@collabora.com</a>> wrote: >> >> From: Thomas Helland <<a href="mailto:thomashelland90@gmail.com">thomashelland90@gmail.com</a>> >> >> This pass detects induction variables and calculates the >> trip count of loops to be used for loop unrolling. >> >> I've removed support for float induction values for now, for the >> simple reason that they don't appear in my shader-db collection, >> and so I don't see it as common enough that we want to pollute the >> pass with this in the initial version. >> >> V2: Rebase, adapt to removal of function overloads >> >> V3: (Timothy Arceri) >> - don't try to find trip count if loop terminator conditional is a phi >> - fix trip count for do-while loops >> - replace conditional type != alu assert with return >> - disable unrolling of loops with continues >> - multiple fixes to memory allocation, stop leaking and don't destroy >> structs we want to use for unrolling. >> - fix iteration count bugs when induction var not on RHS of condition >> - add FIXME for && conditions >> - calculate trip count for unsigned induction/limit vars >> >> V4: >> - count instructions in a loop >> - set the limiting_terminator even if we can't find the trip count for >> all terminators. This is needed for complex unrolling where we handle >> 2 terminators and the trip count is unknown for one of them. >> - restruct structs so we don't keep information not required after >> analysis and remove dead fields. >> - force unrolling in some cases as per the rules in the GLSL IR pass >> --- >> src/compiler/Makefile.sources | 2 + >> src/compiler/nir/nir.h | 36 +- >> src/compiler/nir/nir_loop_analyze.c | 1012 >> +++++++++++++++++++++++++++++++++++ >> src/compiler/nir/nir_metadata.c | 8 +- >> 4 files changed, 1056 insertions(+), 2 deletions(-) >> create mode 100644 src/compiler/nir/nir_loop_analyze.c >> >> diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources >> index f5b4f9c..7ed26a9 100644 >> --- a/src/compiler/Makefile.sources >> +++ b/src/compiler/Makefile.sources >> @@ -190,6 +190,8 @@ NIR_FILES = \ >> nir/nir_intrinsics.c \ >> nir/nir_intrinsics.h \ >> nir/nir_liveness.c \ >> + nir/nir_loop_analyze.c \ >> + nir/nir_loop_analyze.h \ >> nir/nir_lower_alu_to_scalar.c \ >> nir/nir_lower_atomics.c \ >> nir/nir_lower_bitmap.c \ >> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h >> index ff7c422..49e8cd8 100644 >> --- a/src/compiler/nir/nir.h >> +++ b/src/compiler/nir/nir.h >> @@ -1549,9 +1549,36 @@ nir_if_last_else_node(nir_if *if_stmt) >> } >> >> typedef struct { >> + nir_if *nif; >> + >> + nir_instr *conditional_instr; >> + >> + struct list_head loop_terminator_link; >> +} nir_loop_terminator; >> + >> +typedef struct { >> + /* Number of instructions in the loop */ >> + unsigned num_instructions; >> + >> + /* How many times the loop is run (if known) */ >> + unsigned trip_count; >> + bool is_trip_count_known; > > > We could use 0 or -1 to indicate "I don't know trip count" instead of an > extra boolean. Not sure that it matters much. > >> >> + >> + /* Unroll the loop regardless of its size */ >> + bool force_unroll; > > > It seems a bit odd to have this decide to force-unroll. This is an analysis > pass, not a "make decisions" pass. > >> >> + >> + nir_loop_terminator *limiting_terminator; >> + >> + /* A list of loop_terminators terminating this loop. */ >> + struct list_head loop_terminator_list; >> +} nir_loop_info; >> + >> +typedef struct { >> nir_cf_node cf_node; >> >> struct exec_list body; /** < list of nir_cf_node */ >> + >> + nir_loop_info *info; >> } nir_loop; >> >> static inline nir_cf_node * >> @@ -1576,6 +1603,7 @@ typedef enum { >> nir_metadata_dominance = 0x2, >> nir_metadata_live_ssa_defs = 0x4, >> nir_metadata_not_properly_reset = 0x8, >> + nir_metadata_loop_analysis = 0x16, >> } nir_metadata; >> >> typedef struct { >> @@ -1758,6 +1786,8 @@ typedef struct nir_shader_compiler_options { >> * information must be inferred from the list of input nir_variables. >> */ >> bool use_interpolated_input_intrinsics; >> + >> + unsigned max_unroll_iterations; >> } nir_shader_compiler_options; >> >> typedef struct nir_shader_info { >> @@ -1962,7 +1992,7 @@ nir_loop *nir_loop_create(nir_shader *shader); >> nir_function_impl *nir_cf_node_get_function(nir_cf_node *node); >> >> /** requests that the given pieces of metadata be generated */ >> -void nir_metadata_require(nir_function_impl *impl, nir_metadata >> required); >> +void nir_metadata_require(nir_function_impl *impl, nir_metadata required, >> ...); >> /** dirties all but the preserved metadata */ >> void nir_metadata_preserve(nir_function_impl *impl, nir_metadata >> preserved); >> >> @@ -2559,6 +2589,10 @@ void nir_lower_double_pack(nir_shader *shader); >> bool nir_normalize_cubemap_coords(nir_shader *shader); >> >> void nir_live_ssa_defs_impl(nir_function_impl *impl); >> + >> +void nir_loop_analyze_impl(nir_function_impl *impl, >> + nir_variable_mode indirect_mask); >> + >> bool nir_ssa_defs_interfere(nir_ssa_def *a, nir_ssa_def *b); >> >> void nir_convert_to_ssa_impl(nir_function_impl *impl); >> diff --git a/src/compiler/nir/nir_loop_analyze.c >> b/src/compiler/nir/nir_loop_analyze.c >> new file mode 100644 >> index 0000000..6bea9e5 >> --- /dev/null >> +++ b/src/compiler/nir/nir_loop_analyze.c >> @@ -0,0 +1,1012 @@ >> +/* >> + * 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" >> + >> +typedef enum { >> + undefined, >> + invariant, >> + basic_induction >> +} nir_loop_variable_type; >> + >> +typedef struct { >> + /* The ssa_def associated with this info */ >> + nir_ssa_def *def; >> + >> + /* The type of this ssa_def */ >> + nir_loop_variable_type type; >> + >> + /* If the ssa-def is constant */ >> + bool is_constant; >> + >> + bool in_conditional_block; >> + >> + bool in_nested_loop; >> +} nir_loop_variable; >> + >> +typedef struct { >> + nir_op alu_op; /* The type of alu-operation >> */ >> + nir_loop_variable *alu_def; /* The def of the >> alu-operation */ >> + nir_loop_variable *invariant; /* The invariant alu-operand >> */ >> + nir_loop_variable *phi; /* The other alu-operand >> */ >> + nir_loop_variable *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; >> + >> + nir_loop_variable *nir_loop_var; >> +} loop_variable; >> + >> +typedef struct { >> + bool contains_break; >> + bool contains_continue; >> +} loop_jumps; >> + >> +typedef struct { >> + /* The loop we store information for */ >> + nir_loop *loop; >> + >> + /* Loop_variable for all ssa_defs in function */ >> + loop_variable *loop_vars; >> + >> + /* Loop_variable for all ssa_defs in function */ >> + nir_loop_variable *nir_loop_vars; > > > Why are these two separate things? You have two arrays both indexed by > nir_ssa_def::index and both called loop_vars and one has a pointer to the > other. Can we just make 1 array? > >> >> + >> + /* A list of the loop_vars to analyze */ >> + struct list_head process_list; >> + >> + nir_loop_info *info; >> + >> + nir_variable_mode indirect_mask; >> + >> + struct hash_table *var_to_basic_ind; > > > Also, this seems like an unneeded level of indirection. Just put a pointer > in loop_variable that points to the induction var struct. > >> >> +} loop_info_state; >> + >> +static loop_variable * >> +get_loop_var(nir_ssa_def *value, loop_info_state *state) >> +{ >> + return &(state->loop_vars[value->index]); >> +} >> + >> +static nir_loop_variable * >> +get_nir_loop_var(nir_ssa_def *value, loop_info_state *state) >> +{ >> + return &(state->nir_loop_vars[value->index]); >> +} >> + >> +typedef struct { >> + loop_info_state *state; >> + bool mark_nested; >> + bool mark_in_conditional; >> +} 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; >> + loop_variable *var = get_loop_var(def, loop_init_state->state); >> + >> + /* 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. >> + */ >> + if (!(loop_init_state->mark_in_conditional || >> + loop_init_state->mark_nested)) >> + LIST_ADDTAIL(&(var->process_link), >> + &(loop_init_state->state->process_list)); > > > I have a mild preference for the lower-case variants. As I recall, they are > more for legacy. > >> >> + >> + if (loop_init_state->mark_in_conditional) >> + var->nir_loop_var->in_conditional_block = true; >> + >> + if (loop_init_state->mark_nested) >> + var->nir_loop_var->in_nested_loop = true; >> + >> + var->in_loop = true; >> + >> + return true; >> +} >> + >> +static bool >> +init_loop_block(nir_block *block, void *void_init_loop_state) > > > Can we make this function take the actual parameters and limit > init_loop_state to being the thing we use for init_loop_def. Passing piles > of pointers through made sense when Thomas originally wrote it but now that > we have better loop iteration macros, we can just pass arguments. > >> >> +{ >> + init_loop_state *loop_init_state = void_init_loop_state; >> + >> + nir_foreach_instr(instr, block) >> + nir_foreach_ssa_def(instr, init_loop_def, loop_init_state); >> + >> + return true; >> +} >> + >> +static inline bool >> +is_var_alu(loop_variable *var) >> +{ >> + return (var->nir_loop_var->def->parent_instr->type == >> nir_instr_type_alu); >> +} >> + >> +static inline bool >> +is_var_phi(loop_variable *var) >> +{ >> + return (var->nir_loop_var->def->parent_instr->type == >> nir_instr_type_phi); >> +} >> + >> +static inline bool >> +is_ssa_def_invariant(nir_ssa_def *def, loop_info_state *state) >> +{ >> + loop_variable *var = get_loop_var(def, state); >> + >> + if (var->nir_loop_var->type == invariant) >> + return true; >> + >> + if (!var->in_loop) { >> + var->nir_loop_var->type = invariant; >> + return true; >> + } >> + >> + if (var->nir_loop_var->type == basic_induction) >> + 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 (!is_ssa_def_invariant(alu->src[i].src.ssa, state)) >> + return false; >> + } >> + var->nir_loop_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->nir_loop_var->type = undefined; >> + 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 >> + */ >> + bool changes; >> + >> + do { >> + changes = false; >> + list_for_each_entry_safe(loop_variable, var, >> + &state->process_list, process_link) { >> + >> + if (var->nir_loop_var->in_conditional_block || >> + var->nir_loop_var->in_nested_loop) { >> + LIST_DEL(&var->process_link); >> + continue; >> + } >> + >> + if (is_ssa_def_invariant(var->nir_loop_var->def, state)) { >> + LIST_DEL(&var->process_link); >> + changes = true; >> + } >> + } >> + } while (changes); >> +} >> + >> +static inline bool >> +is_var_basic_induction_var(loop_variable *var, loop_info_state *state) >> +{ >> + if (var->nir_loop_var->type == basic_induction) >> + return true; >> + >> + /* We are only interested in checking phi's for the basic induction >> + * variable case as its simple to detect. All basic induction >> variables >> + * have a phi node >> + */ >> + if (!is_var_phi(var)) >> + return false; >> + >> + nir_phi_instr *phi = >> nir_instr_as_phi(var->nir_loop_var->def->parent_instr); >> + >> + nir_basic_induction_var *biv = rzalloc(state, >> nir_basic_induction_var); >> + biv->phi = var->nir_loop_var; >> + >> + nir_foreach_phi_src(src, phi) { >> + loop_variable *src_var = get_loop_var(src->src.ssa, state); >> + >> + /* If one of the sources is in a conditional or nested block then >> panic. >> + */ >> + if (src_var->nir_loop_var->in_conditional_block || >> + src_var->nir_loop_var->in_nested_loop) >> + break; >> + >> + if (!src_var->in_loop) >> + biv->def_outside_loop = src_var->nir_loop_var; > > > Could we assert biv->def_outside_loop == NULL > >> >> + >> + if (src_var->in_loop && is_var_alu(src_var)) { >> + nir_alu_instr *alu = >> + nir_instr_as_alu(src_var->nir_loop_var->def->parent_instr); >> + >> + switch (alu->op) { >> + case nir_op_fadd: case nir_op_iadd: case >> nir_op_uadd_carry: >> + case nir_op_fsub: case nir_op_isub: case >> nir_op_usub_borrow: >> + case nir_op_fmul: case nir_op_imul: case nir_op_umul_high: >> + case nir_op_fdiv: case nir_op_idiv: case nir_op_udiv: > > > Is there a reason why this is an explicit list and not simply > "nir_op_infos[alu->op].num_inputs == 2"? > >> >> + >> + biv->alu_def = src_var->nir_loop_var; >> + >> + for (unsigned i = 0; i < 2; i++) { >> + /* Is one of the operands invariant, and the other the phi >> */ >> + if (is_ssa_def_invariant(alu->src[i].src.ssa, state) && >> + alu->src[1-i].src.ssa->index == phi->dest.ssa.index) >> + biv->invariant = get_nir_loop_var(alu->src[i].src.ssa, >> + state); >> + } >> + >> + biv->alu_op = alu->op; >> + break; >> + default: >> + break; >> + } >> + } >> + } >> + >> + if (biv->alu_def && biv->def_outside_loop && biv->invariant && >> biv->phi) { >> + biv->alu_def->type = basic_induction; >> + biv->phi->type = basic_induction; >> + _mesa_hash_table_insert(state->var_to_basic_ind, biv->alu_def, >> biv); >> + _mesa_hash_table_insert(state->var_to_basic_ind, biv->phi, biv); >> + return true; >> + } >> + >> + /* The requirements for a basic induction variable are not fulfilled >> */ >> + ralloc_free(biv); >> + return false; >> +} >> + >> +static bool >> +compute_induction_information(loop_info_state *state) >> +{ >> + bool changes; >> + bool found_induction_var = false; >> + >> + do { >> + changes = false; >> + list_for_each_entry_safe(loop_variable, var, >> + &state->process_list, process_link) { >> + >> + /* It can't be an induction variable if it is invariant. We >> don't >> + * want to deal with things in nested loops or conditionals. >> + */ >> + if (var->nir_loop_var->type == invariant || >> + var->nir_loop_var->in_conditional_block || >> + var->nir_loop_var->in_nested_loop) { >> + LIST_DEL(&(var->process_link)); >> + continue; >> + } >> + >> + if (is_var_basic_induction_var(var, state)) { >> + /* If a phi is marked basic_ind we also mark the alu_def >> basic_ind >> + * at the same time. It will then be detected as basic_ind >> here, >> + * on the second passing, and be removed from the list. >> + */ >> + LIST_DEL(&(var->process_link)); >> + changes = true; >> + found_induction_var = true; >> + } >> + } >> + } while (changes); >> + >> + return found_induction_var; >> +} >> + >> +static bool >> +initialize_ssa_def(nir_ssa_def *def, void *void_state) >> +{ >> + loop_info_state *state = void_state; >> + loop_variable *var = get_loop_var(def, state); >> + >> + var->nir_loop_var = get_nir_loop_var(def, state); >> + >> + var->in_loop = false; >> + var->nir_loop_var->def = def; >> + >> + if (def->parent_instr->type == nir_instr_type_load_const) { >> + var->nir_loop_var->type = invariant; >> + var->nir_loop_var->is_constant = true; >> + } else { >> + var->nir_loop_var->type = undefined; >> + } >> + >> + return true; >> +} >> + >> +static bool >> +foreach_cf_node_ex_loop(nir_cf_node *node, void *state) > > > There's no good reason for this to be a void *; it just leads to extra > casting. Also, this function could use a better name. Maybe > cf_node_find_loop_jumps? > >> >> +{ >> + nir_block *block; >> + >> + switch (node->type) { >> + case nir_cf_node_block: >> + block = nir_cf_node_as_block(node); >> + nir_foreach_instr(instr, block) { > > > Jumps are always the last instruction in a block. There's no sense in > walking all of them just to find the jump. Use nir_block_last_instr() > instead. > >> >> + if (instr->type == nir_instr_type_jump) { >> + if (nir_instr_as_jump(instr)->type == nir_jump_break) { >> + ((loop_jumps *) state)->contains_break = true; >> + } else if (nir_instr_as_jump(instr)->type == >> nir_jump_continue) { >> + ((loop_jumps *) state)->contains_continue = true; >> + } >> + } >> + } >> + return true; >> + >> + case nir_cf_node_if: { >> + nir_if *if_stmt = nir_cf_node_as_if(node); >> + >> + foreach_list_typed_safe(nir_cf_node, node, node, >> &if_stmt->then_list) >> + if (!foreach_cf_node_ex_loop(node, state)) >> + return false; >> + >> + foreach_list_typed_safe(nir_cf_node, node, node, >> &if_stmt->else_list) >> + if (!foreach_cf_node_ex_loop(node, state)) >> + return false; >> + >> + break; >> + } > > > Maybe add an explicit case for nir_cf_node_loop with a comment that we don't > care about inner loops. > >> >> + >> + default: >> + break; >> + } >> + >> + return false; >> +} >> + >> +static bool >> +is_trivial_loop_terminator(nir_if *nif) >> +{ >> + /* If there is stuff in the else-block that means that this is not a >> + * simple break on true if-statement and so we bail >> + */ >> + foreach_list_typed_safe(nir_cf_node, node, node, &nif->else_list) >> + if (node->type == nir_cf_node_block) >> + nir_foreach_instr(instr, nir_cf_node_as_block(node)) >> + return false; > > > How about "if (!exec_list_empty(&nif->else_list)) return false;"? That > seems far simpler. </div></div>That won't work, since cf lists are never empty. I think the intent was to check that the else branch consists of one empty basic block, in which case it's broken -- it could have just a loop, for example, and we wouldn't return false. I think what you want to do is get the first node, cast it to a basic block, bail if it has any instructions, and then bail if it doesn't equal the last node. </blockquote><div> </div><div>You are correct, sir. That is what I meant. </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5"> > >> >> + >> + nir_cf_node *first_then = nir_if_first_then_node(nif); >> + nir_block *first_then_block = nir_cf_node_as_block(first_then); >> + nir_instr *first_instr = nir_block_first_instr(first_then_block); >> + >> + if (first_instr && first_instr->type == nir_instr_type_jump && >> + nir_instr_as_jump(first_instr)->type == nir_jump_break) { >> + return true; >> + } >> + >> + return false; >> +} >> + >> +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); >> + >> + /* Don't check the nested loops if there are breaks */ >> + loop_jumps lj; >> + lj.contains_break = false; >> + lj.contains_continue = false; >> + >> + foreach_cf_node_ex_loop(&nif->cf_node, &lj); >> + >> + if (lj.contains_continue) >> + return false; >> + >> + if (!lj.contains_break) >> + continue; >> + >> + /* 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 (!is_trivial_loop_terminator(nif)) >> + return false; >> + >> + if (nif->condition.ssa->parent_instr->type == >> nir_instr_type_phi) >> + return false; >> + >> + nir_loop_terminator *terminator = >> + rzalloc(state->info, nir_loop_terminator); >> + >> + list_add(&terminator->loop_terminator_link, >> + &state->info->loop_terminator_list); >> + >> + terminator->nif = nif; >> + terminator->conditional_instr = >> nif->condition.ssa->parent_instr; >> + >> + success = true; >> + } >> + } >> + >> + return success; >> +} >> + >> +static nir_basic_induction_var * >> +get_basic_ind_var_for_loop_var(loop_variable *var, loop_info_state >> *state) >> +{ >> + assert(var->nir_loop_var->type == basic_induction); >> + >> + struct hash_entry *entry = >> + _mesa_hash_table_search(state->var_to_basic_ind, >> var->nir_loop_var); >> + >> + return entry->data; >> +} >> + >> +static int32_t >> +get_iteration(nir_op cond_op, nir_const_value *initial, nir_const_value >> *step, >> + nir_const_value *limit, nir_alu_instr *alu, int32_t >> *init_val, >> + bool increment_before) >> +{ >> + int32_t iter; >> + >> + switch (cond_op) { >> + case nir_op_ige: >> + case nir_op_ilt: >> + case nir_op_ieq: >> + case nir_op_ine: { >> + int32_t initial_val = initial->i32[0]; >> + if (increment_before) { >> + initial_val = alu->op == nir_op_iadd ? >> + initial_val + step->i32[0] : initial_val - step->i32[0]; >> + } >> + >> + int32_t span = limit->i32[0] - initial_val; >> + iter = span / step->i32[0]; >> + *init_val = initial_val; >> + break; >> + } >> + case nir_op_uge: >> + case nir_op_ult: { >> + uint32_t initial_val = initial->u32[0]; >> + if (increment_before) { >> + initial_val = alu->op == nir_op_iadd ? >> + initial_val + step->u32[0] : initial_val - step->u32[0]; >> + } >> + >> + uint32_t span = limit->u32[0] - initial_val; >> + iter = span / step->u32[0]; >> + *init_val = initial_val; >> + break; >> + } >> + default: >> + return -1; >> + } >> + >> + return iter; >> +} >> + >> +static uint32_t >> +utest_interations(int32_t iter_int, nir_const_value *step, >> + nir_const_value *limit, nir_op cond_op, >> + uint32_t initial_val, bool limit_rhs) >> +{ >> + bool valid_loop = false; >> + uint32_t mul = iter_int * step->u32[0]; >> + uint32_t uadd = mul + initial_val; >> + >> + switch (cond_op) { >> + case nir_op_uge: >> + valid_loop = limit_rhs ? uadd >= limit->u32[0] : uadd <= >> limit->u32[0]; >> + break; >> + case nir_op_ult: >> + valid_loop = limit_rhs ? uadd < limit->u32[0] : uadd > >> limit->u32[0]; >> + break; >> + default: >> + unreachable("Unhandled loop condition!"); >> + } >> + >> + return valid_loop; >> +} >> + >> +static int32_t >> +itest_interations(int32_t iter_int, nir_const_value *step, >> + nir_const_value *limit, nir_op cond_op, >> + int32_t initial_val, bool limit_rhs) >> +{ >> + bool valid_loop = false; >> + int32_t mul = iter_int * step->i32[0]; >> + int32_t iadd = mul + initial_val; >> + >> + switch (cond_op) { >> + case nir_op_ige: >> + valid_loop = limit_rhs ? iadd >= limit->i32[0] : iadd <= >> limit->i32[0]; >> + break; >> + case nir_op_ilt: >> + valid_loop = limit_rhs ? iadd < limit->i32[0] : iadd > >> limit->i32[0]; >> + break; >> + case nir_op_ieq: >> + valid_loop = iadd == limit->i32[0]; >> + break; >> + case nir_op_ine: >> + valid_loop = iadd != limit->i32[0]; >> + break; >> + default: >> + unreachable("Unhandled loop condition!"); >> + } >> + >> + return valid_loop; >> +} >> + >> +static int >> +calculate_iterations(nir_const_value *initial, nir_const_value *step, >> + nir_const_value *limit, nir_op cond_op, >> + nir_loop_variable *alu_def, nir_alu_instr *cond_alu, >> + bool limit_rhs) >> +{ >> + assert(initial != NULL && step != NULL && limit != NULL); >> + >> + nir_alu_instr *alu = nir_instr_as_alu(alu_def->def->parent_instr); >> + >> + /* Unsupported alu operation */ >> + if (!(alu->op == nir_op_iadd || alu->op == nir_op_isub)) > > > You only allow iadd and isub except that we lower away isub so you'll never > see it. Probably best to remove the dead code. Also... > > 1) You don't handle swizzles at all > 2) You don't handle things other than 64 or 16-bit. Those are coming soon; > they need to be supported. > >> >> + 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. >> + */ >> + bool increment_before = false; >> + if (cond_alu->src[0].src.ssa == alu_def->def || >> + cond_alu->src[1].src.ssa == alu_def->def) { >> + increment_before = true; > > > Is there a reason why this can't be handled as "trip_count + 1"? This seems > way overcomplicated. > >> >> + } >> + >> + int32_t initial_val; >> + int iter_int = get_iteration(cond_op, initial, step, limit, alu, >> + &initial_val, increment_before); >> + >> + /* 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); >> + */ >> + const int bias[] = { -1, 1, 1 }; >> + >> + for (unsigned i = 0; i < ARRAY_SIZE(bias); i++) { >> + iter_int = iter_int + bias[i]; >> + >> + switch (cond_op) { >> + case nir_op_ige: >> + case nir_op_ilt: >> + case nir_op_ieq: >> + case nir_op_ine: >> + if (itest_interations(iter_int, step, limit, cond_op, >> initial_val, >> + limit_rhs)) { >> + return iter_int; >> + } >> + break; >> + case nir_op_uge: >> + case nir_op_ult: >> + if (utest_interations(iter_int, step, limit, cond_op, >> + (uint32_t) initial_val, limit_rhs)) { >> + return iter_int; > > > I think it would be clearer if we combined these two functions. > >> >> + } >> + break; >> + default: >> + return -1; >> + } >> + } >> + >> + return -1; >> +} >> + >> +/* 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) >> +{ >> + bool trip_count_known = true; >> + nir_loop_terminator *limiting_terminator = NULL; >> + int min_trip_count = -2; >> + >> + list_for_each_entry(nir_loop_terminator, terminator, >> + &state->info->loop_terminator_list, >> + loop_terminator_link) { >> + >> + if (terminator->conditional_instr->type != nir_instr_type_alu) { >> + /* If we get here the loop is likely not really a loop and will >> get >> + * cleaned up elsewhere. >> + */ > > > The if statement (and its contents) seem fine but the comment here seems > sketchy. > >> >> + trip_count_known = false; >> + continue; >> + } >> + >> + nir_alu_instr *alu = >> nir_instr_as_alu(terminator->conditional_instr); >> + loop_variable *basic_ind = NULL; >> + loop_variable *limit = NULL; >> + bool limit_rhs = true; >> + nir_op cond_op; >> + >> + switch (alu->op) { >> + case nir_op_fge: case nir_op_ige: case nir_op_uge: >> + case nir_op_flt: case nir_op_ilt: case nir_op_ult: >> + case nir_op_feq: case nir_op_ieq: >> + case nir_op_fne: case nir_op_ine: >> + >> + /* We assume that the limit is the "right" operand */ >> + basic_ind = get_loop_var(alu->src[0].src.ssa, state); >> + limit = get_loop_var(alu->src[1].src.ssa, state); >> + cond_op = alu->op; >> + >> + if (basic_ind->nir_loop_var->type != basic_induction) { >> + /* We had it the wrong way, flip things around */ >> + basic_ind = get_loop_var(alu->src[1].src.ssa, state); >> + limit = get_loop_var(alu->src[0].src.ssa, state); >> + limit_rhs = false; >> + } >> + >> + /* The comparison has to have a basic induction variable >> + * and a constant for us to be able to find trip counts >> + */ >> + if (basic_ind->nir_loop_var->type != basic_induction || >> + !limit->nir_loop_var->is_constant) { >> + trip_count_known = false; >> + continue; >> + } >> + >> + nir_basic_induction_var *ind = >> + get_basic_ind_var_for_loop_var(basic_ind, state); >> + >> + if (!ind->def_outside_loop->is_constant || >> + !ind->invariant->is_constant) { >> + trip_count_known = false; >> + continue; >> + } >> + >> + /* 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_load_const_instr *initial_instr = >> + nir_instr_as_load_const( >> + ind->def_outside_loop->def->parent_instr); >> + >> + nir_const_value initial_val = initial_instr->value; >> + >> + nir_load_const_instr *step_instr = >> + nir_instr_as_load_const( >> + ind->invariant->def->parent_instr); >> + >> + nir_const_value step_val = step_instr->value; >> + >> + nir_load_const_instr *limit_instr = >> + nir_instr_as_load_const( >> + limit->nir_loop_var->def->parent_instr); >> + >> + nir_const_value limit_val = limit_instr->value; >> + >> + int iterations = calculate_iterations(&initial_val, &step_val, >> + &limit_val, cond_op, >> + ind->alu_def, alu, >> limit_rhs); >> + >> + /* Where we not able to calculate the iteration count */ >> + if (iterations == -1) { >> + trip_count_known = false; >> + 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 (min_trip_count == -2 || iterations < min_trip_count) { > > > Can we have a #define for -2 so that it has a name. > >> >> + min_trip_count = iterations; >> + limiting_terminator = terminator; >> + } >> + break; >> + >> + default: >> + trip_count_known = false; >> + } >> + } >> + >> + state->info->is_trip_count_known = trip_count_known; >> + if (min_trip_count > -2) >> + state->info->trip_count = min_trip_count; >> + state->info->limiting_terminator = limiting_terminator; >> +} >> + >> +/* Checks if we should force the loop to be unrolled regardless of size >> */ >> +static bool >> +force_unroll(loop_info_state *state, nir_shader *ns, nir_deref_var >> *variable) >> +{ >> + nir_deref *tail = &variable->deref; >> + >> + while (tail->child != NULL) { >> + tail = tail->child; >> + >> + if (tail->deref_type == nir_deref_type_array) { >> + >> + nir_deref_array *deref_array = nir_deref_as_array(tail); >> + if (deref_array->deref_array_type != >> nir_deref_array_type_indirect) >> + continue; >> + >> + nir_loop_variable *array_index = >> + get_nir_loop_var(deref_array->indirect.ssa, state); >> + >> + if (array_index->type != basic_induction) >> + continue; >> + >> + /* If an array is indexed by a loop induction variable, and the >> + * array size is exactly the number of loop iterations, this is >> + * probably a simple for-loop trying to access each element in >> + * turn; the application may expect it to be unrolled. >> + */ >> + if (glsl_get_length(tail->type) == state->info->trip_count) { >> + state->info->force_unroll = true; >> + return state->info->force_unroll; >> + } >> + >> + if (variable->var->data.mode & state->indirect_mask) { >> + state->info->force_unroll = true; >> + return state->info->force_unroll; >> + } > > > Thinking a bit about analysis vs. lowering... > > I wonder if it wouldn't be better to make the loop anlaysis pass be a bit > more informational and less decision making. For instance, it could record > what all variable modes it has seen be indexed by an induction variable and > let the pass using the analysis decide whether or not to force-unroll. For > that matter, it could just produce a hash map from induction variables to > the loop for which they are an induction variable. You could also just > record the trip count per-loop. That all seems a bit more like things an > analysis pass would do than just setting a force_unroll bit. > > Please don't feel like you need to make any changes in this direction yet. > I'm mostly trying to open the discussion up a bit and feel out exactly how > we want things to be structured. > > I think I've written you a long enough book for now. I'll try to look at > the others as I get time. > > --Jason > >> >> + } >> + } >> + >> + return false; >> +} >> + >> +static bool >> +count_instructions(loop_info_state *state, nir_shader *ns, nir_block >> *block) >> +{ >> + nir_foreach_instr(instr, block) { >> + if (instr->type == nir_instr_type_intrinsic || >> + instr->type == nir_instr_type_alu) { >> + state->info->num_instructions++; >> + } >> + >> + 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_var || >> + intrin->intrinsic == nir_intrinsic_store_var || >> + intrin->intrinsic == nir_intrinsic_copy_var) { >> + unsigned num_vars = >> + nir_intrinsic_infos[intrin->intrinsic].num_variables; >> + for (unsigned i = 0; i < num_vars; i++) { >> + if (force_unroll(state, ns, intrin->variables[i])) >> + return true; >> + } >> + } >> + } >> + >> + return false; >> +} >> + >> +static void >> +get_loop_info(loop_info_state *state, nir_function_impl *impl) >> +{ >> + /* Initialize all variables to "outside_loop". This also marks defs >> + * invariant and constant if they are nir_instr_type_load_const's >> + */ >> + nir_foreach_block(block, impl) { >> + nir_foreach_instr(instr, block) >> + nir_foreach_ssa_def(instr, initialize_ssa_def, state); >> + } >> + >> + init_loop_state init_state = {.mark_in_conditional = false, >> + .mark_nested = false, .state = 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_state.mark_in_conditional = false; >> + init_state.mark_nested = false; >> + init_loop_block(nir_cf_node_as_block(node), &init_state); >> + break; >> + >> + case nir_cf_node_if: >> + init_state.mark_in_conditional = true; >> + init_state.mark_nested = false; >> + nir_foreach_block_in_cf_node(block, node) >> + init_loop_block(block, &init_state); >> + break; >> + >> + case nir_cf_node_loop: >> + init_state.mark_in_conditional = false; >> + init_state.mark_nested = true; >> + nir_foreach_block_in_cf_node(block, node) { >> + init_loop_block(block, &init_state); >> + } >> + break; >> + >> + case nir_cf_node_function: >> + break; >> + } >> + } >> + >> + /* Induction analysis needs invariance information so get that first >> */ >> + compute_invariance_information(state); >> + >> + /* We may now have filled the process_list with instructions from >> inside >> + * the nested blocks in the loop. Remove all instructions from the >> list >> + * nir_foreach_block_in_cf_node before we start computing induction >> + * information. >> + */ >> + list_inithead(&state->process_list); >> + >> + /* Add all entries in the outermost part of the loop to the processing >> list. >> + * Don't include defs inn nested loops or in conditionals. >> + */ >> + init_state.mark_in_conditional = false; >> + init_state.mark_nested = false; >> + >> + foreach_list_typed_safe(nir_cf_node, node, node, &state->loop->body) >> + if (node->type == nir_cf_node_block) >> + init_loop_block(nir_cf_node_as_block(node), &init_state); >> + >> + /* We have invariance information so try to find induction variables >> */ >> + if (!compute_induction_information(state)) >> + return; >> + >> + /* 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)) >> + return; >> + >> + /* Run through each of the terminators and try to compute a trip-count >> */ >> + find_trip_count(state); >> + >> + nir_shader *ns = impl->function->shader; >> + foreach_list_typed_safe(nir_cf_node, node, node, &state->loop->body) { >> + if (node->type == nir_cf_node_block) { >> + if (count_instructions(state, ns, nir_cf_node_as_block(node))) >> + break; >> + } else { >> + nir_foreach_block_in_cf_node(block, node) { >> + if (count_instructions(state, ns, block)) >> + 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, loop_variable, >> impl->ssa_alloc); >> + state->loop = loop; >> + state->nir_loop_vars = rzalloc_array(mem_ctx, nir_loop_variable, >> + impl->ssa_alloc); >> + >> + LIST_INITHEAD(&state->process_list); >> + >> + if (loop->info) >> + ralloc_free(loop->info); >> + >> + state->info = rzalloc(loop, nir_loop_info); >> + >> + LIST_INITHEAD(&state->info->loop_terminator_list); >> + >> + state->var_to_basic_ind = >> + _mesa_hash_table_create(state->info, _mesa_hash_pointer, >> + _mesa_key_pointer_equal); >> + >> + 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); >> + >> + loop->info = state->info; >> + >> + ralloc_free(mem_ctx); >> +} >> + >> +void >> +nir_loop_analyze_impl(nir_function_impl *impl, >> + nir_variable_mode indirect_mask) >> +{ >> + if (impl->function->shader->options->max_unroll_iterations == 0) >> + return; >> + >> + nir_index_ssa_defs(impl); >> + foreach_list_typed(nir_cf_node, node, node, &impl->body) >> + process_loops(node, indirect_mask); >> +} >> diff --git a/src/compiler/nir/nir_metadata.c >> b/src/compiler/nir/nir_metadata.c >> index 9e1cff5..f71cf43 100644 >> --- a/src/compiler/nir/nir_metadata.c >> +++ b/src/compiler/nir/nir_metadata.c >> @@ -31,7 +31,7 @@ >> */ >> >> void >> -nir_metadata_require(nir_function_impl *impl, nir_metadata required) >> +nir_metadata_require(nir_function_impl *impl, nir_metadata required, ...) >> { >> #define NEEDS_UPDATE(X) ((required & ~impl->valid_metadata) & (X)) >> >> @@ -41,6 +41,12 @@ nir_metadata_require(nir_function_impl *impl, >> nir_metadata required) >> nir_calc_dominance_impl(impl); >> if (NEEDS_UPDATE(nir_metadata_live_ssa_defs)) >> nir_live_ssa_defs_impl(impl); >> + if (NEEDS_UPDATE(nir_metadata_loop_analysis)) { >> + va_list ap; >> + va_start(ap, required); >> + nir_loop_analyze_impl(impl, va_arg(ap, nir_variable_mode)); >> + va_end(ap); >> + } >> >> #undef NEEDS_UPDATE >> >> -- >> 2.7.4 >> >> _______________________________________________ >> mesa-dev mailing list >> <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> >> <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> > > > > _______________________________________________ > mesa-dev mailing list > <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> > <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> > </div></div></blockquote></div> </div></div>