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Prior to this commit rename_variables_block() is recursively called, performing a depth-first traversal of the control flow graph. The function uses a non-trivial amount of stack space for local variables, which puts us in danger of smashing the stack, given a sufficiently deep dominance tree. XCOM: Enemy Within contains a shader with such a dominance tree (1574 nir_blocks in total, depth of at least 143). Jason tells me that he believes that any walk over the nir_blocks that respects dominance is sufficient (a DFS might have been necessary prior to the introduction of nir_phi_builder). In fact, the introduction of nir_phi_builder made the problem worse: rename_variables_block(), walks to the bottom of the dominance tree before calling nir_phi_builder_value_get_block_def() which walks back to the top of the dominance tree... In any case, this patch ensures we avoid that problem as well. Cc: mesa-stable@lists.freedesktop.org Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97225 Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
116 lines
4.6 KiB
C
116 lines
4.6 KiB
C
/*
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* Copyright © 2016 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#pragma once
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#include "nir.h"
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/** A helper for placing phi nodes in a NIR shader
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*
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* Basic usage goes something like this:
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*
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* each variable, var, has:
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* a bitset var.defs of blocks where the variable is defined
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* a struct nir_phi_builder_value *pb_val
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*
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* // initialize bitsets
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* foreach block:
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* foreach def of variable var:
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* var.defs[def.block] = true;
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*
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* // initialize phi builder
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* pb = nir_phi_builder_create()
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* foreach var:
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* var.pb_val = nir_phi_builder_add_value(pb, var.defs)
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*
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* // Visit each block. This needs to visit dominators first;
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* // nir_foreach_block() will be ok.
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*
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* foreach block:
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* foreach instruction:
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* foreach use of variable var:
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* replace use with nir_phi_builder_get_block_def(var.pb_val)
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* foreach def of variable var:
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* create ssa def, register with
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* nir_phi_builder_set_block_def(var.pb_val)
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*
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* nir_phi_builder_finish(pb)
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*/
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struct nir_phi_builder;
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struct nir_phi_builder_value;
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/* Create a new phi builder.
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*
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* While this is fairly cheap, it does allocate some memory and walk the list
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* of blocks so it's recommended that you only call it once and use it to
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* build phis for several values.
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*/
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struct nir_phi_builder *nir_phi_builder_create(nir_function_impl *impl);
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/* Register a value with the builder.
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*
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* The 'defs' parameter specifies a bitset of blocks in which the given value
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* is defined. This is used to determine where to place the phi nodes.
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*/
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struct nir_phi_builder_value *
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nir_phi_builder_add_value(struct nir_phi_builder *pb, unsigned num_components,
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unsigned bit_size, const BITSET_WORD *defs);
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/* Register a definition for the given value and block.
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*
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* It is safe to call this function as many times as you wish for any given
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* block/value pair. However, it always replaces whatever was there
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* previously even if that definition is from a phi node. The phi builder
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* always uses the latest information it has, so you must be careful about the
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* order in which you register definitions. The final value at the end of the
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* block must be the last value registered.
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*/
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void
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nir_phi_builder_value_set_block_def(struct nir_phi_builder_value *val,
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nir_block *block, nir_ssa_def *def);
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/* Get the definition for the given value in the given block.
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*
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* This definition will always be the latest definition known for the given
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* block. If no definition is immediately available, it will crawl up the
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* dominance tree and insert phi nodes as needed until it finds one. In the
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* case that no suitable definition is found, it will return the result of a
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* nir_ssa_undef_instr with the correct number of components.
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*
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* Because this function only uses the latest available information for any
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* given block, you must have already finished registering definitions for any
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* blocks that dominate the current block in order to get the correct result.
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*/
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nir_ssa_def *
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nir_phi_builder_value_get_block_def(struct nir_phi_builder_value *val,
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nir_block *block);
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/* Finish building phi nodes and free the builder.
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*
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* This function does far more than just free memory. Prior to calling
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* nir_phi_builder_finish, no phi nodes have actually been inserted in the
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* program. This function is what finishes setting up phi node sources and
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* adds the phi nodes to the program.
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*/
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void nir_phi_builder_finish(struct nir_phi_builder *pb);
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