--- /dev/null
+/*
+ * Copyright (c) 2019 Connor Abbott
+ *
+ * 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, sub license,
+ * 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 NON-INFRINGEMENT. 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 "gpir.h"
+
+/* Here we perform a few optimizations that can't currently be done in NIR:
+ *
+ * - Optimize the result of a conditional break/continue. In NIR something
+ * like:
+ *
+ * loop {
+ * ...
+ * if (cond)
+ * continue;
+ *
+ * would get lowered to:
+ *
+ * block_0:
+ * ...
+ * block_1:
+ * branch_cond !cond block_3
+ * block_2:
+ * branch_uncond block_0
+ * block_3:
+ * ...
+ *
+ * We recognize the conditional branch skipping over the unconditional
+ * branch, and turn it into:
+ *
+ * block_0:
+ * ...
+ * block_1:
+ * branch_cond cond block_0
+ * block_2:
+ * block_3:
+ * ...
+ */
+
+static void
+optimize_branches(gpir_compiler *comp)
+{
+ list_for_each_entry(gpir_block, block, &comp->block_list, list) {
+ /* Look for a block with a single unconditional branch. */
+ if (!list_is_singular(&block->node_list))
+ continue;
+
+ gpir_node *node = list_first_entry(&block->node_list, gpir_node, list);
+ if (node->op != gpir_op_branch_uncond)
+ continue;
+
+ gpir_block *target = gpir_node_to_branch(node)->dest;
+
+ /* Find the previous block */
+ if (block->list.prev == &comp->block_list)
+ continue;
+
+ gpir_block *prev_block = LIST_ENTRY(gpir_block, block->list.prev, list);
+ if (list_is_empty(&prev_block->node_list))
+ continue;
+
+ /* Previous block must end with a conditional branch */
+ gpir_node *prev_block_last =
+ list_last_entry(&prev_block->node_list, gpir_node, list);
+ if (prev_block_last->op != gpir_op_branch_cond)
+ continue;
+
+ /* That branch must branch to the block after this */
+ gpir_branch_node *prev_branch = gpir_node_to_branch(prev_block_last);
+ gpir_block *prev_target = prev_branch->dest;
+
+ if (&prev_target->list != block->list.next)
+ continue;
+
+ /* Hooray! Invert the conditional branch and change the target */
+ gpir_alu_node *cond = gpir_node_create(prev_block, gpir_op_not);
+ cond->children[0] = prev_branch->cond;
+ cond->num_child = 1;
+ gpir_node_add_dep(&cond->node, cond->children[0], GPIR_DEP_INPUT);
+ list_addtail(&cond->node.list, &prev_block_last->list);
+ gpir_node_insert_child(prev_block_last, prev_branch->cond, &cond->node);
+ prev_branch->dest = target;
+ prev_block->successors[1] = target;
+
+ /* Delete the branch */
+ list_del(&node->list);
+ block->successors[0] = LIST_ENTRY(gpir_block, block->list.next, list);
+ }
+}
+
+bool
+gpir_optimize(gpir_compiler *comp)
+{
+ optimize_branches(comp);
+
+ gpir_debug("after optimization\n");
+ gpir_node_print_prog_seq(comp);
+
+ return true;
+}
+
projects / mesa.git / commitdiff