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nir/loop_analyze: Refactor detection of limit vars

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This commit reworks both get_induction_and_limit_vars() and
try_find_trip_count_vars_in_iand to return true on success and not
modify their output parameters on failure.  This makes their callers
significantly simpler.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
This commit is contained in:
Jason Ekstrand
2019-06-24 17:33:02 -05:00
parent 8f7405ed9d
commit 0333649e63
1 changed files with 50 additions and 53 deletions
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103
src/compiler/nir/nir_loop_analyze.c
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@@ -810,27 +810,32 @@ is_supported_terminator_condition(nir_alu_instr *alu)
}
static bool
get_induction_and_limit_vars(nir_alu_instr *alu, nir_loop_variable **ind,
get_induction_and_limit_vars(nir_alu_instr *alu,
nir_loop_variable **ind,
nir_loop_variable **limit,
bool *limit_rhs,
loop_info_state *state)
{
bool limit_rhs = true;
nir_loop_variable *rhs, *lhs;
lhs = get_loop_var(alu->src[0].src.ssa, state);
rhs = get_loop_var(alu->src[1].src.ssa, state);
/* We assume that the limit is the "right" operand */
*ind = get_loop_var(alu->src[0].src.ssa, state);
*limit = get_loop_var(alu->src[1].src.ssa, state);
if ((*ind)->type != basic_induction) {
/* We had it the wrong way, flip things around */
*ind = get_loop_var(alu->src[1].src.ssa, state);
*limit = get_loop_var(alu->src[0].src.ssa, state);
limit_rhs = false;
if (lhs->type == basic_induction) {
*ind = lhs;
*limit = rhs;
*limit_rhs = true;
return true;
} else if (rhs->type == basic_induction) {
*ind = rhs;
*limit = lhs;
*limit_rhs = false;
return true;
} else {
return false;
}
return limit_rhs;
}
static void
static bool
try_find_trip_count_vars_in_iand(nir_alu_instr **alu,
nir_loop_variable **ind,
nir_loop_variable **limit,
@@ -848,7 +853,7 @@ try_find_trip_count_vars_in_iand(nir_alu_instr **alu,
/* We don't handle swizzles here */
if ((*alu)->src[0].swizzle[0] > 0 || (*alu)->src[1].swizzle[0] > 0)
return;
return false;
if (iand_def->parent_instr->type != nir_instr_type_alu ||
zero_def->parent_instr->type != nir_instr_type_load_const) {
@@ -859,49 +864,49 @@ try_find_trip_count_vars_in_iand(nir_alu_instr **alu,
/* If we still didn't find what we need then return */
if (zero_def->parent_instr->type != nir_instr_type_load_const)
return;
return false;
}
/* If the loop is not breaking on (x && y) == 0 then return */
nir_const_value *zero =
nir_instr_as_load_const(zero_def->parent_instr)->value;
if (zero[0].i32 != 0)
return;
return false;
}
if (iand_def->parent_instr->type != nir_instr_type_alu)
return;
return false;
nir_alu_instr *iand = nir_instr_as_alu(iand_def->parent_instr);
if (iand->op != nir_op_iand)
return;
return false;
/* We don't handle swizzles here */
if ((*alu)->src[0].swizzle[0] > 0 || (*alu)->src[1].swizzle[0] > 0)
return;
return false;
/* Check if iand src is a terminator condition and try get induction var
* and trip limit var.
*/
nir_ssa_def *src = iand->src[0].src.ssa;
if (src->parent_instr->type == nir_instr_type_alu) {
*alu = nir_instr_as_alu(src->parent_instr);
if (is_supported_terminator_condition(*alu))
*limit_rhs = get_induction_and_limit_vars(*alu, ind, limit, state);
}
/* Try the other iand src if needed */
if (*ind == NULL || (*ind && (*ind)->type != basic_induction) ||
!is_var_constant(*limit)) {
src = iand->src[1].src.ssa;
bool found_induction_var = false;
for (unsigned i = 0; i < 2; i++) {
nir_ssa_def *src = iand->src[i].src.ssa;
if (src->parent_instr->type == nir_instr_type_alu) {
nir_alu_instr *tmp_alu = nir_instr_as_alu(src->parent_instr);
if (is_supported_terminator_condition(tmp_alu)) {
*alu = tmp_alu;
*limit_rhs = get_induction_and_limit_vars(*alu, ind, limit, state);
nir_alu_instr *src_alu = nir_instr_as_alu(src->parent_instr);
if (is_supported_terminator_condition(src_alu) &&
get_induction_and_limit_vars(src_alu, ind, limit,
limit_rhs, state)) {
*alu = src_alu;
found_induction_var = true;
/* If we've found one with a constant limit, stop. */
if (is_var_constant(*limit))
return true;
}
}
}
return found_induction_var;
}
/* Run through each of the terminators of the loop and try to infer a possible
@@ -936,37 +941,29 @@ find_trip_count(loop_info_state *state)
bool limit_rhs;
nir_loop_variable *basic_ind = NULL;
nir_loop_variable *limit;
if (alu->op == nir_op_inot || alu->op == nir_op_ieq) {
nir_alu_instr *new_alu = alu;
try_find_trip_count_vars_in_iand(&new_alu, &basic_ind, &limit,
&limit_rhs, state);
if ((alu->op == nir_op_inot || alu->op == nir_op_ieq) &&
try_find_trip_count_vars_in_iand(&alu, &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.
*/
if (basic_ind && basic_ind->type == basic_induction) {
alu = new_alu;
alu_op = inverse_comparison(alu);
trip_count_known = false;
terminator->exact_trip_count_unknown = true;
}
alu_op = inverse_comparison(alu);
trip_count_known = false;
terminator->exact_trip_count_unknown = true;
}
if (!basic_ind) {
if (!is_supported_terminator_condition(alu)) {
trip_count_known = false;
continue;
if (is_supported_terminator_condition(alu)) {
get_induction_and_limit_vars(alu, &basic_ind,
&limit, &limit_rhs, state);
}
limit_rhs = get_induction_and_limit_vars(alu, &basic_ind, &limit,
state);
}
/* The comparison has to have a basic induction variable for us to be
* able to find trip counts.
*/
if (basic_ind->type != basic_induction) {
if (!basic_ind) {
trip_count_known = false;
continue;
}