Mesa (master): nir: Add a loop analysis pass
Timothy Arceri
tarceri at kemper.freedesktop.org
Thu Dec 22 23:16:01 UTC 2016
Module: Mesa
Branch: master
Commit: 6772a17acc8ee90f9398348251a4455f988208fd
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=6772a17acc8ee90f9398348251a4455f988208fd
Author: Thomas Helland <thomashelland90 at gmail.com>
Date: Tue Dec 13 14:39:51 2016 +1100
nir: Add a loop analysis pass
This pass detects induction variables and calculates the
trip count of loops to be used for loop unrolling.
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: (Timothy Arceri)
- 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
V5: (Timothy Arceri)
- fix metadata mask value 0x10 vs 0x16
V6: (Timothy Arceri)
- merge loop_variable and nir_loop_variable structs and lists suggested by Jason
- remove induction var hash table and store pointer to induction information in
the loop_variable suggested by Jason.
- use lowercase list_addtail() suggested by Jason.
- tidy up init_loop_block() as per Jasons suggestions.
- replace switch with nir_op_infos[alu->op].num_inputs == 2 in
is_var_basic_induction_var() as suggested by Jason.
- use nir_block_last_instr() in and rename foreach_cf_node_ex_loop() as suggested
by Jason.
- fix else check for is_trivial_loop_terminator() as per Connors suggetions.
- simplify offset for induction valiables incremented before the exit conditions is
checked.
- replace nir_op_isub check with assert() as it should have been lowered away.
V7: (Timothy Arceri)
- use rzalloc() on nir_loop struct creation. Worked previously because ralloc()
was broken and always zeroed the struct.
- fix cf_node_find_loop_jumps() to find jumps when loops contain
nested if statements. Code is tidier as a result.
V8: (Timothy Arceri)
- move is_trivial_loop_terminator() to nir.h so we can use it to assert is
the loop unroll pass
- fix analysis to not bail when looking for terminator when the break is in the else
rather then the if
- added new loop terminator fields: break_block, continue_from_block and
continue_from_then so we don't have to gather these when doing unrolling.
- get correct array length when forcing unrolling of variables
indexed arrays that are the same size as the iteration count
- add support for induction variables of type float
- update trival loop terminator check to allow an if containing
instructions as long as both branches contain only a single
block.
V9: (Timothy)
- bunch of tidy ups and simplifications suggested by Jason.
- rewrote trivial terminator detection, now the only restriction is there
must be no nested jumps, anything else goes.
- rewrote the iteration test to use nir_eval_const_opcode().
- count instruction properly even when forcing an unroll.
- bunch of other tidy ups and simplifications.
V10: (Timothy)
- some trivial tidy ups suggested by Jason.
- conditional fix for break inside continue branch by Jason.
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
---
src/compiler/Makefile.sources | 2 +
src/compiler/nir/nir.c | 2 +-
src/compiler/nir/nir.h | 41 +-
src/compiler/nir/nir_loop_analyze.c | 844 ++++++++++++++++++++++++++++++++++++
src/compiler/nir/nir_loop_analyze.h | 92 ++++
src/compiler/nir/nir_metadata.c | 8 +-
6 files changed, 986 insertions(+), 3 deletions(-)
diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
index 15f410f..edc70f7 100644
--- a/src/compiler/Makefile.sources
+++ b/src/compiler/Makefile.sources
@@ -195,6 +195,8 @@ 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.c b/src/compiler/nir/nir.c
index 2d882f7..2c3531c 100644
--- a/src/compiler/nir/nir.c
+++ b/src/compiler/nir/nir.c
@@ -393,7 +393,7 @@ nir_if_create(nir_shader *shader)
nir_loop *
nir_loop_create(nir_shader *shader)
{
- nir_loop *loop = ralloc(shader, nir_loop);
+ nir_loop *loop = rzalloc(shader, nir_loop);
cf_init(&loop->cf_node, nir_cf_node_loop);
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 2c7237b..c7da1e7 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1506,9 +1506,41 @@ typedef struct nir_if {
} nir_if;
typedef struct {
+ nir_if *nif;
+
+ nir_instr *conditional_instr;
+
+ nir_block *break_block;
+ nir_block *continue_from_block;
+
+ bool continue_from_then;
+
+ 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;
+
+ /* Unroll the loop regardless of its size */
+ bool force_unroll;
+
+ 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;
/**
@@ -1521,6 +1553,7 @@ typedef enum {
nir_metadata_dominance = 0x2,
nir_metadata_live_ssa_defs = 0x4,
nir_metadata_not_properly_reset = 0x8,
+ nir_metadata_loop_analysis = 0x10,
} nir_metadata;
typedef struct {
@@ -1749,6 +1782,8 @@ 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 {
@@ -1859,7 +1894,7 @@ 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);
@@ -2479,6 +2514,10 @@ 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..71cbe3c
--- /dev/null
+++ b/src/compiler/nir/nir_loop_analyze.c
@@ -0,0 +1,844 @@
+/*
+ * 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;
+
+struct 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 or a nested loop */
+ bool in_control_flow;
+
+} nir_loop_variable;
+
+typedef struct nir_basic_induction_var {
+ 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 *def_outside_loop; /* The phi-src outside the loop */
+} nir_basic_induction_var;
+
+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_control_flow;
+} 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_control_flow) {
+ var->in_control_flow = 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;
+}
+
+static bool
+init_loop_block(nir_block *block, loop_info_state *state,
+ bool in_control_flow)
+{
+ init_loop_state init_state = {.in_control_flow = in_control_flow,
+ .state = state };
+
+ nir_foreach_instr(instr, block) {
+ if (instr->type == nir_instr_type_intrinsic ||
+ instr->type == nir_instr_type_alu ||
+ instr->type == nir_instr_type_tex) {
+ state->loop->info->num_instructions++;
+ }
+
+ 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_constant(nir_loop_variable *var)
+{
+ return var->def->parent_instr->type == nir_instr_type_load_const;
+}
+
+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_control_flow);
+
+ if (mark_invariant(var->def, state))
+ list_del(&var->process_link);
+ }
+}
+
+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_control_flow && var->type != invariant);
+
+ /* 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))
+ 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_foreach_phi_src(src, phi) {
+ nir_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->in_control_flow)
+ break;
+
+ if (!src_var->in_loop) {
+ biv->def_outside_loop = src_var;
+ } else if (is_var_alu(src_var)) {
+ nir_alu_instr *alu = nir_instr_as_alu(src_var->def->parent_instr);
+
+ if (nir_op_infos[alu->op].num_inputs == 2) {
+ biv->alu_def = src_var;
+ biv->alu_op = alu->op;
+
+ for (unsigned i = 0; i < 2; i++) {
+ /* Is one of the operands const, and the other the phi */
+ if (alu->src[i].src.ssa->parent_instr->type == nir_instr_type_load_const &&
+ alu->src[1-i].src.ssa == &phi->dest.ssa)
+ biv->invariant = get_loop_var(alu->src[i].src.ssa, state);
+ }
+ }
+ }
+ }
+
+ if (biv->alu_def && biv->def_outside_loop && biv->invariant &&
+ is_var_constant(biv->def_outside_loop)) {
+ assert(is_var_constant(biv->invariant));
+ biv->alu_def->type = basic_induction;
+ biv->alu_def->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 inline bool
+ends_in_break(nir_block *block)
+{
+ if (exec_list_is_empty(&block->instr_list))
+ return false;
+
+ nir_instr *instr = nir_block_last_instr(block);
+ return instr->type == nir_instr_type_jump &&
+ nir_instr_as_jump(instr)->type == nir_jump_break;
+}
+
+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 (ends_in_break(last_then)) {
+ break_blk = last_then;
+ continue_from_blk = last_else;
+ continue_from_then = false;
+ } else if (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))
+ 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)
+ return false;
+
+ nir_loop_terminator *terminator =
+ rzalloc(state->loop->info, nir_loop_terminator);
+
+ list_add(&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;
+}
+
+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 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];
+ int32_t span = limit->i32[0] - initial_val;
+ iter = span / step->i32[0];
+ break;
+ }
+ case nir_op_uge:
+ case nir_op_ult: {
+ uint32_t initial_val = initial->u32[0];
+ uint32_t span = limit->u32[0] - initial_val;
+ iter = span / step->u32[0];
+ break;
+ }
+ case nir_op_fge:
+ case nir_op_flt:
+ case nir_op_feq:
+ case nir_op_fne: {
+ int32_t initial_val = initial->f32[0];
+ int32_t span = limit->f32[0] - initial_val;
+ iter = span / step->f32[0];
+ break;
+ }
+ default:
+ return -1;
+ }
+
+ return iter;
+}
+
+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)
+{
+ assert(nir_op_infos[cond_op].num_inputs == 2);
+
+ nir_const_value iter_src = { {0, } };
+ nir_op mul_op;
+ nir_op add_op;
+ switch (induction_base_type) {
+ case nir_type_float:
+ iter_src.f32[0] = (float) iter_int;
+ mul_op = nir_op_fmul;
+ add_op = nir_op_fadd;
+ break;
+ case nir_type_int:
+ case nir_type_uint:
+ iter_src.i32[0] = iter_int;
+ 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_src[2] = { iter_src, *step };
+ nir_const_value mul_result =
+ nir_eval_const_opcode(mul_op, 1, bit_size, mul_src);
+
+ /* Add the initial value to the accumulated induction variable total */
+ nir_const_value add_src[2] = { mul_result, *initial };
+ nir_const_value add_result =
+ nir_eval_const_opcode(add_op, 1, bit_size, add_src);
+
+ nir_const_value src[2] = { { {0, } }, { {0, } } };
+ 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, 1, bit_size, src);
+
+ return invert_cond ? (result.u32[0] == 0) : (result.u32[0] != 0);
+}
+
+static int
+calculate_iterations(nir_const_value *initial, nir_const_value *step,
+ nir_const_value *limit, nir_loop_variable *alu_def,
+ nir_alu_instr *cond_alu, bool limit_rhs, bool invert_cond)
+{
+ assert(initial != NULL && step != NULL && limit != NULL);
+
+ nir_alu_instr *alu = nir_instr_as_alu(alu_def->def->parent_instr);
+
+ /* 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[cond_alu->op].input_types[1]) == nir_type_int ||
+ nir_alu_type_get_base_type(nir_op_infos[cond_alu->op].input_types[1]) == nir_type_uint);
+ } else {
+ assert(nir_alu_type_get_base_type(nir_op_infos[cond_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;
+ if (cond_alu->src[0].src.ssa == alu_def->def ||
+ cond_alu->src[1].src.ssa == alu_def->def) {
+ trip_offset = 1;
+ }
+
+ int iter_int = get_iteration(cond_alu->op, initial, step, limit, alu);
+
+ /* 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);
+ */
+ 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);
+ for (int bias = -1; bias <= 1; bias++) {
+ const int iter_bias = iter_int + bias;
+
+ if (test_iterations(iter_bias, step, limit, cond_alu->op, bit_size,
+ induction_base_type, initial,
+ limit_rhs, invert_cond)) {
+ return iter_bias > 0 ? iter_bias - trip_offset : iter_bias;
+ }
+ }
+
+ 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 = -1;
+
+ list_for_each_entry(nir_loop_terminator, terminator,
+ &state->loop->info->loop_terminator_list,
+ loop_terminator_link) {
+
+ if (terminator->conditional_instr->type != nir_instr_type_alu) {
+ /* 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_alu_instr *alu = nir_instr_as_alu(terminator->conditional_instr);
+ nir_loop_variable *basic_ind = NULL;
+ nir_loop_variable *limit = NULL;
+ bool limit_rhs = true;
+
+ 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);
+
+ if (basic_ind->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->type != basic_induction || !is_var_constant(limit)) {
+ 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_const_value initial_val =
+ nir_instr_as_load_const(basic_ind->ind->def_outside_loop->
+ def->parent_instr)->value;
+
+ nir_const_value step_val =
+ nir_instr_as_load_const(basic_ind->ind->invariant->def->
+ parent_instr)->value;
+
+ nir_const_value limit_val =
+ nir_instr_as_load_const(limit->def->parent_instr)->value;
+
+ int iterations = calculate_iterations(&initial_val, &step_val,
+ &limit_val,
+ basic_ind->ind->alu_def, alu,
+ limit_rhs,
+ terminator->continue_from_then);
+
+ /* 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 == -1 || iterations < min_trip_count) {
+ min_trip_count = iterations;
+ limiting_terminator = terminator;
+ }
+ break;
+
+ default:
+ trip_count_known = false;
+ }
+ }
+
+ state->loop->info->is_trip_count_known = trip_count_known;
+ if (min_trip_count > -1)
+ state->loop->info->trip_count = min_trip_count;
+ state->loop->info->limiting_terminator = limiting_terminator;
+}
+
+/* Checks if we should force the loop to be unrolled regardless of size
+ * due to array access heuristics.
+ */
+static bool
+force_unroll_array_access(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_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(variable->deref.type) ==
+ state->loop->info->trip_count) {
+ state->loop->info->force_unroll = true;
+ return state->loop->info->force_unroll;
+ }
+
+ if (variable->var->data.mode & state->indirect_mask) {
+ state->loop->info->force_unroll = true;
+ return state->loop->info->force_unroll;
+ }
+ }
+ }
+
+ return false;
+}
+
+static bool
+force_unroll_heuristics(loop_info_state *state, nir_shader *ns,
+ 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_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_array_access(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);
+ }
+
+ /* 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);
+ break;
+
+ case nir_cf_node_if:
+ nir_foreach_block_in_cf_node(block, node)
+ init_loop_block(block, state, true);
+ break;
+
+ case nir_cf_node_loop:
+ nir_foreach_block_in_cf_node(block, node) {
+ init_loop_block(block, state, true);
+ }
+ break;
+
+ case nir_cf_node_function:
+ break;
+ }
+ }
+
+ /* 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;
+
+ /* 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;
+ }
+
+ /* 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 (force_unroll_heuristics(state, ns, nir_cf_node_as_block(node)))
+ break;
+ } else {
+ nir_foreach_block_in_cf_node(block, node) {
+ if (force_unroll_heuristics(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, 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);
+}
diff --git a/src/compiler/nir/nir_loop_analyze.h b/src/compiler/nir/nir_loop_analyze.h
new file mode 100644
index 0000000..b7f862e
--- /dev/null
+++ b/src/compiler/nir/nir_loop_analyze.h
@@ -0,0 +1,92 @@
+/*
+ * Copyright © 2016 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.
+ */
+
+#pragma once
+
+#include "nir.h"
+
+/* Returns true if nir_cf_node contains a jump other than the expected_jump
+ * parameter.
+ */
+static inline bool
+contains_other_jump(nir_cf_node *node, nir_instr *expected_jump)
+{
+ switch (node->type) {
+ case nir_cf_node_block: {
+ nir_instr *lst_instr = nir_block_last_instr(nir_cf_node_as_block(node));
+
+ /* dead_cf should have eliminated any instruction after the first break
+ */
+ nir_foreach_instr(instr, nir_cf_node_as_block(node))
+ assert(instr->type != nir_instr_type_jump || instr == lst_instr);
+
+ if (lst_instr && lst_instr->type == nir_instr_type_jump &&
+ lst_instr != expected_jump)
+ return true;
+ else
+ return false;
+ }
+ 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 (contains_other_jump(node, expected_jump))
+ return true;
+ }
+
+ foreach_list_typed_safe(nir_cf_node, node, node, &if_stmt->else_list) {
+ if (contains_other_jump(node, expected_jump))
+ return true;
+ }
+
+ return false;
+ }
+ case nir_cf_node_loop:
+ return true;
+
+ default:
+ unreachable("Unhandled cf node type");
+ }
+}
+
+/* Here we define a trivial if as containing only a single break that must be
+ * located at the end of either the then or else branch of the top level if,
+ * there must be no other breaks or any other type of jump. Or we pass NULL
+ * to break_block the if must contains no jumps at all.
+ */
+static inline bool
+nir_is_trivial_loop_if(nir_if *nif, nir_block *break_block)
+{
+ nir_instr *last_instr = NULL;
+
+ if (break_block) {
+ last_instr = nir_block_last_instr(break_block);
+ assert(last_instr && last_instr->type == nir_instr_type_jump &&
+ nir_instr_as_jump(last_instr)->type == nir_jump_break);
+ }
+
+ if (contains_other_jump(&nif->cf_node, last_instr))
+ return false;
+
+ return true;
+}
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
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