--- /dev/null
+/*
+ * Copyright © 2019 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "ir3_nir.h"
+#include "compiler/nir/nir_builder.h"
+
+/**
+ * This pass moves varying fetches (and the instructions they depend on
+ * into the start block.
+ *
+ * We need to set the (ei) "end input" flag on the last varying fetch.
+ * And we want to ensure that all threads execute the instruction that
+ * sets (ei). The easiest way to ensure this is to move all varying
+ * fetches into the start block. Which is something we used to get for
+ * free by using lower_all_io_to_temps=true.
+ *
+ * This may come at the cost of additional register usage. OTOH setting
+ * the (ei) flag earlier probably frees up more VS to run.
+ */
+
+
+typedef struct {
+ nir_shader *shader;
+ nir_block *start_block;
+ struct nir_instr *cursor;
+} state;
+
+static void move_instruction_to_start_block(state *state, nir_instr *instr);
+
+static bool
+move_src(nir_src *src, void *state)
+{
+ /* At this point we shouldn't have any non-ssa src: */
+ debug_assert(src->is_ssa);
+ move_instruction_to_start_block(state, src->ssa->parent_instr);
+ return true;
+}
+
+static void
+move_instruction_to_start_block(state *state, nir_instr *instr)
+{
+ /* first move (recursively) all src's to ensure they appear before
+ * load*_input that we are trying to move:
+ */
+ nir_foreach_src(instr, move_src, state);
+
+ /* and then move the instruction itself:
+ */
+ exec_node_remove(&instr->node);
+
+ if (state->cursor) {
+ exec_node_insert_after(&state->cursor->node, &instr->node);
+ } else {
+ exec_list_push_head(&state->start_block->instr_list, &instr->node);
+ }
+
+ state->cursor = instr;
+ instr->block = state->start_block;
+}
+
+static bool
+move_varying_inputs_block(state *state, nir_block *block)
+{
+ bool progress = false;
+
+ nir_foreach_instr_safe(instr, block) {
+ if (instr->type != nir_instr_type_intrinsic)
+ continue;
+
+ nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+
+ switch (intr->intrinsic) {
+ case nir_intrinsic_load_interpolated_input:
+ case nir_intrinsic_load_input:
+ /* TODO any others to handle? */
+ break;
+ default:
+ continue;
+ }
+
+ debug_assert(intr->dest.is_ssa);
+
+ state->cursor = NULL;
+ move_instruction_to_start_block(state, instr);
+
+ progress = true;
+ }
+
+ return progress;
+}
+
+bool
+ir3_nir_move_varying_inputs(nir_shader *shader)
+{
+ bool progress = false;
+
+ debug_assert(shader->info.stage == MESA_SHADER_FRAGMENT);
+
+ nir_foreach_function (function, shader) {
+ state state;
+
+ if (!function->impl)
+ continue;
+
+ state.shader = shader;
+ state.start_block = nir_start_block(function->impl);
+
+ bool progress = false;
+ nir_foreach_block (block, function->impl) {
+ /* don't need to move anything that is already in the first block */
+ if (block == state.start_block)
+ continue;
+ progress |= move_varying_inputs_block(&state, block);
+ }
+
+ if (progress) {
+ nir_metadata_preserve(function->impl,
+ nir_metadata_block_index | nir_metadata_dominance);
+ }
+ }
+
+ return progress;
+}