* we can do the comparison as part of the ADD instruction directly:
*
* add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F
+ *
+ * If there had been a use of the flag register and another CMP using g70
+ *
+ * add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F
+ * (+f0) sel(8) g71<F> g72<8,8,1>F g73<8,8,1>F
+ * cmp.ge.f0(8) null g70<8,8,1>F 0F
+ *
+ * we can recognize that the CMP is generating the flag value that already
+ * exists and therefore remove the instruction.
*/
static bool
-opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
+opt_cmod_propagation_local(bblock_t *block)
{
bool progress = false;
int ip = block->end_ip + 1;
foreach_inst_in_block_reverse_safe(fs_inst, inst, block) {
ip--;
- if (inst->opcode != BRW_OPCODE_CMP ||
+ if ((inst->opcode != BRW_OPCODE_AND &&
+ inst->opcode != BRW_OPCODE_CMP &&
+ inst->opcode != BRW_OPCODE_MOV) ||
inst->predicate != BRW_PREDICATE_NONE ||
!inst->dst.is_null() ||
inst->src[0].file != GRF ||
- inst->src[0].abs ||
- inst->src[0].negate ||
- !inst->src[1].is_zero())
+ inst->src[0].abs)
+ continue;
+
+ /* Only an AND.NZ can be propagated. Many AND.Z instructions are
+ * generated (for ir_unop_not in fs_visitor::emit_bool_to_cond_code).
+ * Propagating those would require inverting the condition on the CMP.
+ * This changes both the flag value and the register destination of the
+ * CMP. That result may be used elsewhere, so we can't change its value
+ * on a whim.
+ */
+ if (inst->opcode == BRW_OPCODE_AND &&
+ !(inst->src[1].is_one() &&
+ inst->conditional_mod == BRW_CONDITIONAL_NZ &&
+ !inst->src[0].negate))
continue;
+ if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero())
+ continue;
+
+ if (inst->opcode == BRW_OPCODE_MOV &&
+ inst->conditional_mod != BRW_CONDITIONAL_NZ)
+ continue;
+
+ bool read_flag = false;
foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst,
block) {
if (scan_inst->overwrites_reg(inst->src[0])) {
scan_inst->dst.reg_offset != inst->src[0].reg_offset)
break;
+ /* CMP's result is the same regardless of dest type. */
+ if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
+ scan_inst->opcode == BRW_OPCODE_CMP &&
+ (inst->dst.type == BRW_REGISTER_TYPE_D ||
+ inst->dst.type == BRW_REGISTER_TYPE_UD)) {
+ inst->remove(block);
+ progress = true;
+ break;
+ }
+
+ /* If the AND wasn't handled by the previous case, it isn't safe
+ * to remove it.
+ */
+ if (inst->opcode == BRW_OPCODE_AND)
+ break;
+
+ /* Comparisons operate differently for ints and floats */
+ if (scan_inst->dst.type != inst->dst.type &&
+ (scan_inst->dst.type == BRW_REGISTER_TYPE_F ||
+ inst->dst.type == BRW_REGISTER_TYPE_F))
+ break;
+
+ /* If the instruction generating inst's source also wrote the
+ * flag, and inst is doing a simple .nz comparison, then inst
+ * is redundant - the appropriate value is already in the flag
+ * register. Delete inst.
+ */
+ if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
+ !inst->src[0].negate &&
+ scan_inst->writes_flag()) {
+ inst->remove(block);
+ progress = true;
+ break;
+ }
+
+ /* Otherwise, try propagating the conditional. */
+ enum brw_conditional_mod cond =
+ inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod)
+ : inst->conditional_mod;
+
if (scan_inst->can_do_cmod() &&
- (scan_inst->conditional_mod == BRW_CONDITIONAL_NONE ||
- scan_inst->conditional_mod == inst->conditional_mod)) {
- scan_inst->conditional_mod = inst->conditional_mod;
+ ((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
+ scan_inst->conditional_mod == cond)) {
+ scan_inst->conditional_mod = cond;
inst->remove(block);
progress = true;
}
break;
}
- if (scan_inst->reads_flag() || scan_inst->writes_flag())
+ if (scan_inst->writes_flag())
break;
+
+ read_flag = read_flag || scan_inst->reads_flag();
}
}
bool progress = false;
foreach_block_reverse(block, cfg) {
- progress = opt_cmod_propagation_local(this, block) || progress;
+ progress = opt_cmod_propagation_local(block) || progress;
}
if (progress)