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diff --git a/src/compiler/nir/nir_phi_builder.h b/src/compiler/nir/nir_phi_builder.h
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+++ b/src/compiler/nir/nir_phi_builder.h
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+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include "nir.h"
+
+struct nir_phi_builder;
+struct nir_phi_builder_value;
+
+/* Create a new phi builder.
+ *
+ * While this is fairly cheap, it does allocate some memory and walk the list
+ * of blocks so it's recommended that you only call it once and use it to
+ * build phis for several values.
+ */
+struct nir_phi_builder *nir_phi_builder_create(nir_function_impl *impl);
+
+/* Register a value with the builder.
+ *
+ * The 'defs' parameter specifies a bitset of blocks in which the given value
+ * is defined.  This is used to determine where to place the phi nodes.
+ */
+struct nir_phi_builder_value *
+nir_phi_builder_add_value(struct nir_phi_builder *pb, unsigned num_components,
+                          const BITSET_WORD *defs);
+
+/* Register a definition for the given value and block.
+ *
+ * It is safe to call this function as many times as you wish for any given
+ * block/value pair.  However, it always replaces whatever was there
+ * previously even if that definition is from a phi node.  The phi builder
+ * always uses the latest information it has, so you must be careful about the
+ * order in which you register definitions.  The final value at the end of the
+ * block must be the last value registered.
+ */
+void
+nir_phi_builder_value_set_block_def(struct nir_phi_builder_value *val,
+                                    nir_block *block, nir_ssa_def *def);
+
+/* Get the definition for the given value in the given block.
+ *
+ * This definition will always be the latest definition known for the given
+ * block.  If no definition is immediately available, it will crawl up the
+ * dominance tree and insert phi nodes as needed until it finds one.  In the
+ * case that no suitable definition is found, it will return the result of a
+ * nir_ssa_undef_instr with the correct number of components.
+ *
+ * Because this function only uses the latest available information for any
+ * given block, you must have already finished registering definitions for any
+ * blocks that dominate the current block in order to get the correct result.
+ */
+nir_ssa_def *
+nir_phi_builder_value_get_block_def(struct nir_phi_builder_value *val,
+                                    nir_block *block);
+
+/* Finish building phi nodes and free the builder.
+ *
+ * This function does far more than just free memory.  Prior to calling
+ * nir_phi_builder_finish, no phi nodes have actually been inserted in the
+ * program.  This function is what finishes setting up phi node sources and
+ * adds the phi nodes to the program.
+ */
+void nir_phi_builder_finish(struct nir_phi_builder *pb);