* Implements a small peephole optimization that looks for
*
* if (cond) {
- * <empty>
+ * <then SSA defs>
* } else {
- * <empty>
+ * <else SSA defs>
* }
* phi
* ...
* phi
*
- * and replaces it with a series of selects. It can also handle the case
- * where, instead of being empty, the if may contain some move operations
- * whose only use is one of the following phi nodes. This happens all the
- * time when the SSA form comes from a conditional assignment with a
- * swizzle.
+ * and replaces it with:
+ *
+ * <then SSA defs>
+ * <else SSA defs>
+ * bcsel
+ * ...
+ * bcsel
+ *
+ * where the SSA defs are ALU operations or other cheap instructions (not
+ * texturing, for example).
+ *
+ * If the number of ALU operations in the branches is greater than the limit
+ * parameter, then the optimization is skipped. In limit=0 mode, the SSA defs
+ * must only be MOVs which we expect to get copy-propagated away once they're
+ * out of the inner blocks.
*/
-struct peephole_select_state {
- void *mem_ctx;
- bool progress;
-};
-
static bool
-block_check_for_allowed_instrs(nir_block *block)
+block_check_for_allowed_instrs(nir_block *block, unsigned *count, bool alu_ok)
{
- nir_foreach_instr(block, instr) {
+ nir_foreach_instr(instr, block) {
switch (instr->type) {
case nir_instr_type_intrinsic: {
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
switch (intrin->intrinsic) {
- case nir_intrinsic_load_var:
- switch (intrin->variables[0]->var->data.mode) {
+ case nir_intrinsic_load_deref:
+ switch (nir_src_as_deref(intrin->src[0])->mode) {
case nir_var_shader_in:
case nir_var_uniform:
break;
}
break;
+ case nir_intrinsic_load_uniform:
+ if (!alu_ok)
+ return false;
+ break;
+
default:
return false;
}
break;
}
+ case nir_instr_type_deref:
case nir_instr_type_load_const:
break;
case nir_op_vec2:
case nir_op_vec3:
case nir_op_vec4:
- /* It must be a move-like operation. */
break;
default:
- return false;
+ if (!alu_ok) {
+ /* It must be a move-like operation. */
+ return false;
+ }
+ break;
}
- /* Can't handle saturate */
- if (mov->dest.saturate)
- return false;
-
/* It must be SSA */
if (!mov->dest.dest.is_ssa)
return false;
- /* It cannot have any if-uses */
- if (!list_empty(&mov->dest.dest.ssa.if_uses))
- return false;
+ if (alu_ok) {
+ (*count)++;
+ } else {
+ /* Can't handle saturate */
+ if (mov->dest.saturate)
+ return false;
- /* The only uses of this definition must be phi's in the successor */
- nir_foreach_use(&mov->dest.dest.ssa, use) {
- if (use->parent_instr->type != nir_instr_type_phi ||
- use->parent_instr->block != block->successors[0])
+ /* It cannot have any if-uses */
+ if (!list_empty(&mov->dest.dest.ssa.if_uses))
return false;
+
+ /* The only uses of this definition must be phis in the successor */
+ nir_foreach_use(use, &mov->dest.dest.ssa) {
+ if (use->parent_instr->type != nir_instr_type_phi ||
+ use->parent_instr->block != block->successors[0])
+ return false;
+ }
}
break;
}
}
static bool
-nir_opt_peephole_select_block(nir_block *block, void *void_state)
+nir_opt_peephole_select_block(nir_block *block, nir_shader *shader,
+ unsigned limit)
{
- struct peephole_select_state *state = void_state;
-
- /* If the block is empty, then it certainly doesn't have any phi nodes,
- * so we can skip it. This also ensures that we do an early skip on the
- * end block of the function which isn't actually attached to the CFG.
- */
- if (exec_list_is_empty(&block->instr_list))
- return true;
-
if (nir_cf_node_is_first(&block->cf_node))
- return true;
+ return false;
nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node);
if (prev_node->type != nir_cf_node_if)
- return true;
+ return false;
nir_if *if_stmt = nir_cf_node_as_if(prev_node);
- nir_cf_node *then_node = nir_if_first_then_node(if_stmt);
- nir_cf_node *else_node = nir_if_first_else_node(if_stmt);
+ nir_block *then_block = nir_if_first_then_block(if_stmt);
+ nir_block *else_block = nir_if_first_else_block(if_stmt);
/* We can only have one block in each side ... */
- if (nir_if_last_then_node(if_stmt) != then_node ||
- nir_if_last_else_node(if_stmt) != else_node)
- return true;
-
- nir_block *then_block = nir_cf_node_as_block(then_node);
- nir_block *else_block = nir_cf_node_as_block(else_node);
+ if (nir_if_last_then_block(if_stmt) != then_block ||
+ nir_if_last_else_block(if_stmt) != else_block)
+ return false;
/* ... and those blocks must only contain "allowed" instructions. */
- if (!block_check_for_allowed_instrs(then_block) ||
- !block_check_for_allowed_instrs(else_block))
- return true;
+ unsigned count = 0;
+ if (!block_check_for_allowed_instrs(then_block, &count, limit != 0) ||
+ !block_check_for_allowed_instrs(else_block, &count, limit != 0))
+ return false;
+
+ if (count > limit)
+ return false;
/* At this point, we know that the previous CFG node is an if-then
* statement containing only moves to phi nodes in this block. We can
*/
nir_block *prev_block = nir_cf_node_as_block(nir_cf_node_prev(prev_node));
- assert(prev_block->cf_node.type == nir_cf_node_block);
/* First, we move the remaining instructions from the blocks to the
* block before. We have already guaranteed that this is safe by
* calling block_check_for_allowed_instrs()
*/
- nir_foreach_instr_safe(then_block, instr) {
+ nir_foreach_instr_safe(instr, then_block) {
exec_node_remove(&instr->node);
instr->block = prev_block;
exec_list_push_tail(&prev_block->instr_list, &instr->node);
}
- nir_foreach_instr_safe(else_block, instr) {
+ nir_foreach_instr_safe(instr, else_block) {
exec_node_remove(&instr->node);
instr->block = prev_block;
exec_list_push_tail(&prev_block->instr_list, &instr->node);
}
- nir_foreach_instr_safe(block, instr) {
+ nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_phi)
break;
nir_phi_instr *phi = nir_instr_as_phi(instr);
- nir_alu_instr *sel = nir_alu_instr_create(state->mem_ctx, nir_op_bcsel);
+ nir_alu_instr *sel = nir_alu_instr_create(shader, nir_op_bcsel);
nir_src_copy(&sel->src[0].src, &if_stmt->condition, sel);
/* Splat the condition to all channels */
memset(sel->src[0].swizzle, 0, sizeof sel->src[0].swizzle);
assert(exec_list_length(&phi->srcs) == 2);
- nir_foreach_phi_src(phi, src) {
+ nir_foreach_phi_src(src, phi) {
assert(src->pred == then_block || src->pred == else_block);
assert(src->src.is_ssa);
}
nir_ssa_dest_init(&sel->instr, &sel->dest.dest,
- phi->dest.ssa.num_components, phi->dest.ssa.name);
+ phi->dest.ssa.num_components,
+ phi->dest.ssa.bit_size, phi->dest.ssa.name);
sel->dest.write_mask = (1 << phi->dest.ssa.num_components) - 1;
nir_ssa_def_rewrite_uses(&phi->dest.ssa,
}
nir_cf_node_remove(&if_stmt->cf_node);
- state->progress = true;
-
return true;
}
static bool
-nir_opt_peephole_select_impl(nir_function_impl *impl)
+nir_opt_peephole_select_impl(nir_function_impl *impl, unsigned limit)
{
- struct peephole_select_state state;
-
- state.mem_ctx = ralloc_parent(impl);
- state.progress = false;
+ nir_shader *shader = impl->function->shader;
+ bool progress = false;
- nir_foreach_block(impl, nir_opt_peephole_select_block, &state);
+ nir_foreach_block_safe(block, impl) {
+ progress |= nir_opt_peephole_select_block(block, shader, limit);
+ }
- if (state.progress)
+ if (progress)
nir_metadata_preserve(impl, nir_metadata_none);
- return state.progress;
+ return progress;
}
bool
-nir_opt_peephole_select(nir_shader *shader)
+nir_opt_peephole_select(nir_shader *shader, unsigned limit)
{
bool progress = false;
- nir_foreach_function(shader, function) {
+ nir_foreach_function(function, shader) {
if (function->impl)
- progress |= nir_opt_peephole_select_impl(function->impl);
+ progress |= nir_opt_peephole_select_impl(function->impl, limit);
}
return progress;