*/
#include "nir.h"
+#include "nir_builder.h"
+
+static nir_alu_instr *
+get_parent_mov(nir_ssa_def *ssa)
+{
+ if (ssa->parent_instr->type != nir_instr_type_alu)
+ return NULL;
+
+ nir_alu_instr *alu = nir_instr_as_alu(ssa->parent_instr);
+ return (alu->op == nir_op_mov) ? alu : NULL;
+}
+
+static bool
+matching_mov(nir_alu_instr *mov1, nir_ssa_def *ssa)
+{
+ if (!mov1)
+ return false;
+
+ nir_alu_instr *mov2 = get_parent_mov(ssa);
+ return mov2 && nir_alu_srcs_equal(mov1, mov2, 0, 0);
+}
/*
* This is a pass for removing phi nodes that look like:
* a = phi(b, b, b, ...)
*
- * Note that we can't ignore undef sources here, or else we may create a
+ * Note that we can't always ignore undef sources here, or else we may create a
* situation where the definition of b isn't dominated by its uses. We're
* allowed to do this since the definition of b must dominate all of the
* phi node's predecessors, which means it must dominate the phi node as well
*/
static bool
-remove_phis_block(nir_block *block, void *state)
+remove_phis_block(nir_block *block, nir_builder *b)
{
- bool *progress = state;
+ bool progress = false;
- 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_ssa_def *def = NULL;
+ nir_alu_instr *mov = NULL;
bool srcs_same = true;
- nir_foreach_phi_src(phi, src) {
+ nir_foreach_phi_src(src, phi) {
assert(src->src.is_ssa);
/* For phi nodes at the beginning of loops, we may encounter some
if (def == NULL) {
def = src->src.ssa;
+ mov = get_parent_mov(def);
+ } else if (src->src.ssa->parent_instr->type == nir_instr_type_ssa_undef &&
+ nir_block_dominates(def->parent_instr->block, src->pred)) {
+ /* Ignore this undef source. */
} else {
- if (src->src.ssa != def) {
+ if (src->src.ssa != def && !matching_mov(mov, src->src.ssa)) {
srcs_same = false;
break;
}
if (!srcs_same)
continue;
- /* We must have found at least one definition, since there must be at
- * least one forward edge.
- */
- assert(def != NULL);
+ if (!def) {
+ /* In this case, the phi had no sources. So turn it into an undef. */
+
+ b->cursor = nir_after_phis(block);
+ def = nir_ssa_undef(b, phi->dest.ssa.num_components,
+ phi->dest.ssa.bit_size);
+ } else if (mov) {
+ /* If the sources were all movs from the same source with the same
+ * swizzle, then we can't just pick a random move because it may not
+ * dominate the phi node. Instead, we need to emit our own move after
+ * the phi which uses the shared source, and rewrite uses of the phi
+ * to use the move instead. This is ok, because while the movs may
+ * not all dominate the phi node, their shared source does.
+ */
+
+ b->cursor = nir_after_phis(block);
+ def = nir_mov_alu(b, mov->src[0], def->num_components);
+ }
assert(phi->dest.is_ssa);
nir_ssa_def_rewrite_uses(&phi->dest.ssa, nir_src_for_ssa(def));
nir_instr_remove(instr);
- *progress = true;
+ progress = true;
}
- return true;
+ return progress;
+}
+
+bool
+nir_opt_remove_phis_block(nir_block *block)
+{
+ nir_builder b;
+ nir_builder_init(&b, nir_cf_node_get_function(&block->cf_node));
+ return remove_phis_block(block, &b);
}
static bool
-remove_phis_impl(nir_function_impl *impl)
+nir_opt_remove_phis_impl(nir_function_impl *impl)
{
bool progress = false;
+ nir_builder bld;
+ nir_builder_init(&bld, impl);
- nir_foreach_block(impl, remove_phis_block, &progress);
+ nir_metadata_require(impl, nir_metadata_dominance);
+
+ nir_foreach_block(block, impl) {
+ progress |= remove_phis_block(block, &bld);
+ }
if (progress) {
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
+ } else {
+ nir_metadata_preserve(impl, nir_metadata_all);
}
return progress;
{
bool progress = false;
- nir_foreach_function(shader, function)
+ nir_foreach_function(function, shader)
if (function->impl)
- progress = remove_phis_impl(function->impl) || progress;
+ progress = nir_opt_remove_phis_impl(function->impl) || progress;
return progress;
}