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nir/opt_if: Rework condition propagation

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Instead of doing our own constant folding, we just emit instructions and
let constant folding happen.  This is substantially simpler and lets us
use the nir_imm_bool helper instead of dealing with the const_value's
ourselves.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
This commit is contained in:
Jason Ekstrand
2018-10-19 21:42:22 -05:00
parent 4cd8a58595
commit a3b4cb3458
1 changed files with 31 additions and 62 deletions
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93
src/compiler/nir/nir_opt_if.c
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@@ -376,31 +376,15 @@ opt_if_loop_terminator(nir_if *nif)
return true;
}
static void
replace_if_condition_use_with_const(nir_builder *b, nir_src *use,
nir_const_value nir_boolean,
bool if_condition)
{
/* Create const */
nir_ssa_def *const_def = nir_build_imm(b, 1, 32, nir_boolean);
/* Rewrite use to use const */
nir_src new_src = nir_src_for_ssa(const_def);
if (if_condition)
nir_if_rewrite_condition(use->parent_if, new_src);
else
nir_instr_rewrite_src(use->parent_instr, use, new_src);
}
static bool
evaluate_if_condition(nir_if *nif, nir_cursor cursor, uint32_t *value)
evaluate_if_condition(nir_if *nif, nir_cursor cursor, bool *value)
{
nir_block *use_block = nir_cursor_current_block(cursor);
if (nir_block_dominates(nir_if_first_then_block(nif), use_block)) {
*value = NIR_TRUE;
*value = true;
return true;
} else if (nir_block_dominates(nir_if_first_else_block(nif), use_block)) {
*value = NIR_FALSE;
*value = false;
return true;
} else {
return false;
@@ -459,52 +443,31 @@ propagate_condition_eval(nir_builder *b, nir_if *nif, nir_src *use_src,
nir_src *alu_use, nir_alu_instr *alu,
bool is_if_condition)
{
bool progress = false;
bool bool_value;
if (!evaluate_if_condition(nif, b->cursor, &bool_value))
return false;
nir_const_value bool_value;
b->cursor = nir_before_src(alu_use, is_if_condition);
if (nir_op_infos[alu->op].num_inputs == 1) {
assert(alu->op == nir_op_inot || alu->op == nir_op_b2i);
if (evaluate_if_condition(nif, b->cursor, &bool_value.u32[0])) {
assert(nir_src_bit_size(alu->src[0].src) == 32);
nir_const_value result =
nir_eval_const_opcode(alu->op, 1, 32, &bool_value);
replace_if_condition_use_with_const(b, alu_use, result,
is_if_condition);
progress = true;
}
} else {
assert(alu->op == nir_op_ior || alu->op == nir_op_iand);
if (evaluate_if_condition(nif, b->cursor, &bool_value.u32[0])) {
nir_ssa_def *def[2];
for (unsigned i = 0; i < 2; i++) {
if (alu->src[i].src.ssa == use_src->ssa) {
def[i] = nir_build_imm(b, 1, 32, bool_value);
} else {
def[i] = alu->src[i].src.ssa;
}
}
nir_ssa_def *nalu =
nir_build_alu(b, alu->op, def[0], def[1], NULL, NULL);
/* Rewrite use to use new alu instruction */
nir_src new_src = nir_src_for_ssa(nalu);
if (is_if_condition)
nir_if_rewrite_condition(alu_use->parent_if, new_src);
else
nir_instr_rewrite_src(alu_use->parent_instr, alu_use, new_src);
progress = true;
nir_ssa_def *def[2] = { };
for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
if (alu->src[i].src.ssa == use_src->ssa) {
def[i] = nir_imm_bool(b, bool_value);
} else {
def[i] = alu->src[i].src.ssa;
}
}
nir_ssa_def *nalu = nir_build_alu(b, alu->op, def[0], def[1], NULL, NULL);
return progress;
/* Rewrite use to use new alu instruction */
nir_src new_src = nir_src_for_ssa(nalu);
if (is_if_condition)
nir_if_rewrite_condition(alu_use->parent_if, new_src);
else
nir_instr_rewrite_src(alu_use->parent_instr, alu_use, new_src);
return true;
}
static bool
@@ -526,11 +489,17 @@ evaluate_condition_use(nir_builder *b, nir_if *nif, nir_src *use_src,
{
bool progress = false;
nir_const_value value;
b->cursor = nir_before_src(use_src, is_if_condition);
if (evaluate_if_condition(nif, b->cursor, &value.u32[0])) {
replace_if_condition_use_with_const(b, use_src, value, is_if_condition);
bool bool_value;
if (evaluate_if_condition(nif, b->cursor, &bool_value)) {
/* Rewrite use to use const */
nir_src imm_src = nir_src_for_ssa(nir_imm_bool(b, bool_value));
if (is_if_condition)
nir_if_rewrite_condition(use_src->parent_if, imm_src);
else
nir_instr_rewrite_src(use_src->parent_instr, use_src, imm_src);
progress = true;
}