2012-03-27 23:13:14 +00:00
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/* Dead store elimination
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2019-06-02 15:48:37 +00:00
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Copyright (C) 2004-2019 Free Software Foundation, Inc.
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2012-03-27 23:13:14 +00:00
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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GCC is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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2017-04-10 11:32:00 +00:00
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#include "backend.h"
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#include "rtl.h"
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2012-03-27 23:13:14 +00:00
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#include "tree.h"
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2014-09-21 17:33:12 +00:00
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#include "gimple.h"
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2017-04-10 11:32:00 +00:00
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#include "tree-pass.h"
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#include "ssa.h"
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#include "gimple-pretty-print.h"
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#include "fold-const.h"
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2014-09-21 17:33:12 +00:00
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#include "gimple-iterator.h"
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#include "tree-cfg.h"
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#include "tree-dfa.h"
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2012-03-27 23:13:14 +00:00
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#include "domwalk.h"
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2014-09-21 17:33:12 +00:00
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#include "tree-cfgcleanup.h"
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2017-10-07 00:16:47 +00:00
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#include "params.h"
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#include "alias.h"
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2019-06-02 15:48:37 +00:00
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#include "tree-ssa-loop.h"
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2012-03-27 23:13:14 +00:00
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/* This file implements dead store elimination.
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A dead store is a store into a memory location which will later be
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overwritten by another store without any intervening loads. In this
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case the earlier store can be deleted.
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In our SSA + virtual operand world we use immediate uses of virtual
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operands to detect dead stores. If a store's virtual definition
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is used precisely once by a later store to the same location which
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post dominates the first store, then the first store is dead.
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The single use of the store's virtual definition ensures that
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there are no intervening aliased loads and the requirement that
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the second load post dominate the first ensures that if the earlier
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store executes, then the later stores will execute before the function
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exits.
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It may help to think of this as first moving the earlier store to
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the point immediately before the later store. Again, the single
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use of the virtual definition and the post-dominance relationship
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ensure that such movement would be safe. Clearly if there are
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back to back stores, then the second is redundant.
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Reviewing section 10.7.2 in Morgan's "Building an Optimizing Compiler"
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may also help in understanding this code since it discusses the
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relationship between dead store and redundant load elimination. In
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fact, they are the same transformation applied to different views of
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the CFG. */
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/* Bitmap of blocks that have had EH statements cleaned. We should
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remove their dead edges eventually. */
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static bitmap need_eh_cleanup;
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2017-10-07 00:16:47 +00:00
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/* Return value from dse_classify_store */
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enum dse_store_status
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{
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DSE_STORE_LIVE,
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DSE_STORE_MAYBE_PARTIAL_DEAD,
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DSE_STORE_DEAD
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};
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/* STMT is a statement that may write into memory. Analyze it and
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initialize WRITE to describe how STMT affects memory.
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Return TRUE if the the statement was analyzed, FALSE otherwise.
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It is always safe to return FALSE. But typically better optimziation
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can be achieved by analyzing more statements. */
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static bool
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initialize_ao_ref_for_dse (gimple *stmt, ao_ref *write)
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{
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/* It's advantageous to handle certain mem* functions. */
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if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
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{
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switch (DECL_FUNCTION_CODE (gimple_call_fndecl (stmt)))
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{
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case BUILT_IN_MEMCPY:
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case BUILT_IN_MEMMOVE:
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case BUILT_IN_MEMSET:
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{
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tree size = NULL_TREE;
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if (gimple_call_num_args (stmt) == 3)
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size = gimple_call_arg (stmt, 2);
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tree ptr = gimple_call_arg (stmt, 0);
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ao_ref_init_from_ptr_and_size (write, ptr, size);
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return true;
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}
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default:
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break;
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}
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}
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else if (is_gimple_assign (stmt))
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{
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ao_ref_init (write, gimple_assign_lhs (stmt));
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return true;
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}
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return false;
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}
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/* Given REF from the the alias oracle, return TRUE if it is a valid
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memory reference for dead store elimination, false otherwise.
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In particular, the reference must have a known base, known maximum
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size, start at a byte offset and have a size that is one or more
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bytes. */
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static bool
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valid_ao_ref_for_dse (ao_ref *ref)
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{
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return (ao_ref_base (ref)
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2018-12-28 15:30:48 +00:00
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&& known_size_p (ref->max_size)
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&& maybe_ne (ref->size, 0)
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&& known_eq (ref->max_size, ref->size)
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&& known_ge (ref->offset, 0)
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&& multiple_p (ref->offset, BITS_PER_UNIT)
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&& multiple_p (ref->size, BITS_PER_UNIT));
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2017-10-07 00:16:47 +00:00
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}
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2018-12-28 15:30:48 +00:00
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/* Try to normalize COPY (an ao_ref) relative to REF. Essentially when we are
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done COPY will only refer bytes found within REF. Return true if COPY
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is known to intersect at least one byte of REF. */
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2017-10-07 00:16:47 +00:00
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2018-12-28 15:30:48 +00:00
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static bool
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2017-10-07 00:16:47 +00:00
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normalize_ref (ao_ref *copy, ao_ref *ref)
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{
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2018-12-28 15:30:48 +00:00
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if (!ordered_p (copy->offset, ref->offset))
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return false;
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2017-10-07 00:16:47 +00:00
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/* If COPY starts before REF, then reset the beginning of
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COPY to match REF and decrease the size of COPY by the
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number of bytes removed from COPY. */
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2018-12-28 15:30:48 +00:00
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if (maybe_lt (copy->offset, ref->offset))
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2017-10-07 00:16:47 +00:00
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{
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2018-12-28 15:30:48 +00:00
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poly_int64 diff = ref->offset - copy->offset;
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if (maybe_le (copy->size, diff))
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return false;
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copy->size -= diff;
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2017-10-07 00:16:47 +00:00
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copy->offset = ref->offset;
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}
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2018-12-28 15:30:48 +00:00
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poly_int64 diff = copy->offset - ref->offset;
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if (maybe_le (ref->size, diff))
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return false;
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2017-10-07 00:16:47 +00:00
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/* If COPY extends beyond REF, chop off its size appropriately. */
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2018-12-28 15:30:48 +00:00
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poly_int64 limit = ref->size - diff;
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if (!ordered_p (limit, copy->size))
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return false;
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if (maybe_gt (copy->size, limit))
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copy->size = limit;
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return true;
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2017-10-07 00:16:47 +00:00
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}
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/* Clear any bytes written by STMT from the bitmap LIVE_BYTES. The base
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address written by STMT must match the one found in REF, which must
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have its base address previously initialized.
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This routine must be conservative. If we don't know the offset or
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actual size written, assume nothing was written. */
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static void
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clear_bytes_written_by (sbitmap live_bytes, gimple *stmt, ao_ref *ref)
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{
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ao_ref write;
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if (!initialize_ao_ref_for_dse (stmt, &write))
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return;
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/* Verify we have the same base memory address, the write
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has a known size and overlaps with REF. */
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2018-12-28 15:30:48 +00:00
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HOST_WIDE_INT start, size;
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2017-10-07 00:16:47 +00:00
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if (valid_ao_ref_for_dse (&write)
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&& operand_equal_p (write.base, ref->base, OEP_ADDRESS_OF)
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2018-12-28 15:30:48 +00:00
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&& known_eq (write.size, write.max_size)
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&& normalize_ref (&write, ref)
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&& (write.offset - ref->offset).is_constant (&start)
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&& write.size.is_constant (&size))
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bitmap_clear_range (live_bytes, start / BITS_PER_UNIT,
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size / BITS_PER_UNIT);
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2017-10-07 00:16:47 +00:00
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}
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/* REF is a memory write. Extract relevant information from it and
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initialize the LIVE_BYTES bitmap. If successful, return TRUE.
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Otherwise return FALSE. */
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static bool
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setup_live_bytes_from_ref (ao_ref *ref, sbitmap live_bytes)
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{
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2018-12-28 15:30:48 +00:00
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HOST_WIDE_INT const_size;
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2017-10-07 00:16:47 +00:00
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if (valid_ao_ref_for_dse (ref)
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2018-12-28 15:30:48 +00:00
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&& ref->size.is_constant (&const_size)
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&& (const_size / BITS_PER_UNIT
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2017-10-07 00:16:47 +00:00
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<= PARAM_VALUE (PARAM_DSE_MAX_OBJECT_SIZE)))
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{
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bitmap_clear (live_bytes);
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2018-12-28 15:30:48 +00:00
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bitmap_set_range (live_bytes, 0, const_size / BITS_PER_UNIT);
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2017-10-07 00:16:47 +00:00
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return true;
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}
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return false;
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}
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/* Compute the number of elements that we can trim from the head and
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tail of ORIG resulting in a bitmap that is a superset of LIVE.
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Store the number of elements trimmed from the head and tail in
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TRIM_HEAD and TRIM_TAIL.
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STMT is the statement being trimmed and is used for debugging dump
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output only. */
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static void
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compute_trims (ao_ref *ref, sbitmap live, int *trim_head, int *trim_tail,
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gimple *stmt)
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{
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/* We use sbitmaps biased such that ref->offset is bit zero and the bitmap
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extends through ref->size. So we know that in the original bitmap
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bits 0..ref->size were true. We don't actually need the bitmap, just
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the REF to compute the trims. */
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/* Now identify how much, if any of the tail we can chop off. */
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2018-12-28 15:30:48 +00:00
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HOST_WIDE_INT const_size;
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2019-06-02 15:48:37 +00:00
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int last_live = bitmap_last_set_bit (live);
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2018-12-28 15:30:48 +00:00
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if (ref->size.is_constant (&const_size))
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{
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int last_orig = (const_size / BITS_PER_UNIT) - 1;
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2019-06-02 15:48:37 +00:00
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/* We can leave inconvenient amounts on the tail as
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residual handling in mem* and str* functions is usually
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reasonably efficient. */
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*trim_tail = last_orig - last_live;
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/* But don't trim away out of bounds accesses, as this defeats
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proper warnings.
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We could have a type with no TYPE_SIZE_UNIT or we could have a VLA
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where TYPE_SIZE_UNIT is not a constant. */
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if (*trim_tail
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&& TYPE_SIZE_UNIT (TREE_TYPE (ref->base))
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&& TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (ref->base))) == INTEGER_CST
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&& compare_tree_int (TYPE_SIZE_UNIT (TREE_TYPE (ref->base)),
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last_orig) <= 0)
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*trim_tail = 0;
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2018-12-28 15:30:48 +00:00
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}
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else
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*trim_tail = 0;
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2017-10-07 00:16:47 +00:00
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/* Identify how much, if any of the head we can chop off. */
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int first_orig = 0;
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int first_live = bitmap_first_set_bit (live);
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2019-06-02 15:48:37 +00:00
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*trim_head = first_live - first_orig;
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/* If more than a word remains, then make sure to keep the
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starting point at least word aligned. */
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if (last_live - first_live > UNITS_PER_WORD)
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*trim_head &= ~(UNITS_PER_WORD - 1);
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2017-10-07 00:16:47 +00:00
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if ((*trim_head || *trim_tail)
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&& dump_file && (dump_flags & TDF_DETAILS))
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{
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fprintf (dump_file, " Trimming statement (head = %d, tail = %d): ",
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*trim_head, *trim_tail);
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2018-12-28 15:30:48 +00:00
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print_gimple_stmt (dump_file, stmt, 0, dump_flags);
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2017-10-07 00:16:47 +00:00
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fprintf (dump_file, "\n");
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}
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}
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/* STMT initializes an object from COMPLEX_CST where one or more of the
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bytes written may be dead stores. REF is a representation of the
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memory written. LIVE is the bitmap of stores that are actually live.
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Attempt to rewrite STMT so that only the real or imaginary part of
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the object is actually stored. */
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static void
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maybe_trim_complex_store (ao_ref *ref, sbitmap live, gimple *stmt)
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{
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int trim_head, trim_tail;
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compute_trims (ref, live, &trim_head, &trim_tail, stmt);
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/* The amount of data trimmed from the head or tail must be at
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least half the size of the object to ensure we're trimming
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the entire real or imaginary half. By writing things this
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way we avoid more O(n) bitmap operations. */
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2018-12-28 15:30:48 +00:00
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if (known_ge (trim_tail * 2 * BITS_PER_UNIT, ref->size))
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2017-10-07 00:16:47 +00:00
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{
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/* TREE_REALPART is live */
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tree x = TREE_REALPART (gimple_assign_rhs1 (stmt));
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tree y = gimple_assign_lhs (stmt);
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y = build1 (REALPART_EXPR, TREE_TYPE (x), y);
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gimple_assign_set_lhs (stmt, y);
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gimple_assign_set_rhs1 (stmt, x);
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}
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2018-12-28 15:30:48 +00:00
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else if (known_ge (trim_head * 2 * BITS_PER_UNIT, ref->size))
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2017-10-07 00:16:47 +00:00
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{
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/* TREE_IMAGPART is live */
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tree x = TREE_IMAGPART (gimple_assign_rhs1 (stmt));
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tree y = gimple_assign_lhs (stmt);
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y = build1 (IMAGPART_EXPR, TREE_TYPE (x), y);
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gimple_assign_set_lhs (stmt, y);
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gimple_assign_set_rhs1 (stmt, x);
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}
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|
/* Other cases indicate parts of both the real and imag subobjects
|
|
|
|
are live. We do not try to optimize those cases. */
|
|
|
|
}
|
|
|
|
|
|
|
|
/* STMT initializes an object using a CONSTRUCTOR where one or more of the
|
|
|
|
bytes written are dead stores. ORIG is the bitmap of bytes stored by
|
|
|
|
STMT. LIVE is the bitmap of stores that are actually live.
|
|
|
|
|
|
|
|
Attempt to rewrite STMT so that only the real or imaginary part of
|
|
|
|
the object is actually stored.
|
|
|
|
|
|
|
|
The most common case for getting here is a CONSTRUCTOR with no elements
|
|
|
|
being used to zero initialize an object. We do not try to handle other
|
|
|
|
cases as those would force us to fully cover the object with the
|
|
|
|
CONSTRUCTOR node except for the components that are dead. */
|
|
|
|
|
|
|
|
static void
|
|
|
|
maybe_trim_constructor_store (ao_ref *ref, sbitmap live, gimple *stmt)
|
|
|
|
{
|
|
|
|
tree ctor = gimple_assign_rhs1 (stmt);
|
|
|
|
|
|
|
|
/* This is the only case we currently handle. It actually seems to
|
|
|
|
catch most cases of actual interest. */
|
|
|
|
gcc_assert (CONSTRUCTOR_NELTS (ctor) == 0);
|
|
|
|
|
|
|
|
int head_trim = 0;
|
|
|
|
int tail_trim = 0;
|
|
|
|
compute_trims (ref, live, &head_trim, &tail_trim, stmt);
|
|
|
|
|
|
|
|
/* Now we want to replace the constructor initializer
|
|
|
|
with memset (object + head_trim, 0, size - head_trim - tail_trim). */
|
|
|
|
if (head_trim || tail_trim)
|
|
|
|
{
|
|
|
|
/* We want &lhs for the MEM_REF expression. */
|
|
|
|
tree lhs_addr = build_fold_addr_expr (gimple_assign_lhs (stmt));
|
|
|
|
|
|
|
|
if (! is_gimple_min_invariant (lhs_addr))
|
|
|
|
return;
|
|
|
|
|
|
|
|
/* The number of bytes for the new constructor. */
|
2018-12-28 15:30:48 +00:00
|
|
|
poly_int64 ref_bytes = exact_div (ref->size, BITS_PER_UNIT);
|
|
|
|
poly_int64 count = ref_bytes - head_trim - tail_trim;
|
2017-10-07 00:16:47 +00:00
|
|
|
|
|
|
|
/* And the new type for the CONSTRUCTOR. Essentially it's just
|
|
|
|
a char array large enough to cover the non-trimmed parts of
|
|
|
|
the original CONSTRUCTOR. Note we want explicit bounds here
|
|
|
|
so that we know how many bytes to clear when expanding the
|
|
|
|
CONSTRUCTOR. */
|
|
|
|
tree type = build_array_type_nelts (char_type_node, count);
|
|
|
|
|
|
|
|
/* Build a suitable alias type rather than using alias set zero
|
|
|
|
to avoid pessimizing. */
|
|
|
|
tree alias_type = reference_alias_ptr_type (gimple_assign_lhs (stmt));
|
|
|
|
|
|
|
|
/* Build a MEM_REF representing the whole accessed area, starting
|
|
|
|
at the first byte not trimmed. */
|
|
|
|
tree exp = fold_build2 (MEM_REF, type, lhs_addr,
|
|
|
|
build_int_cst (alias_type, head_trim));
|
|
|
|
|
|
|
|
/* Now update STMT with a new RHS and LHS. */
|
|
|
|
gimple_assign_set_lhs (stmt, exp);
|
|
|
|
gimple_assign_set_rhs1 (stmt, build_constructor (type, NULL));
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* STMT is a memcpy, memmove or memset. Decrement the number of bytes
|
|
|
|
copied/set by DECREMENT. */
|
|
|
|
static void
|
|
|
|
decrement_count (gimple *stmt, int decrement)
|
|
|
|
{
|
|
|
|
tree *countp = gimple_call_arg_ptr (stmt, 2);
|
|
|
|
gcc_assert (TREE_CODE (*countp) == INTEGER_CST);
|
|
|
|
*countp = wide_int_to_tree (TREE_TYPE (*countp), (TREE_INT_CST_LOW (*countp)
|
|
|
|
- decrement));
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
static void
|
|
|
|
increment_start_addr (gimple *stmt, tree *where, int increment)
|
|
|
|
{
|
|
|
|
if (TREE_CODE (*where) == SSA_NAME)
|
|
|
|
{
|
|
|
|
tree tem = make_ssa_name (TREE_TYPE (*where));
|
|
|
|
gassign *newop
|
|
|
|
= gimple_build_assign (tem, POINTER_PLUS_EXPR, *where,
|
|
|
|
build_int_cst (sizetype, increment));
|
|
|
|
gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
|
|
|
|
gsi_insert_before (&gsi, newop, GSI_SAME_STMT);
|
|
|
|
*where = tem;
|
|
|
|
update_stmt (gsi_stmt (gsi));
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
*where = build_fold_addr_expr (fold_build2 (MEM_REF, char_type_node,
|
|
|
|
*where,
|
|
|
|
build_int_cst (ptr_type_node,
|
|
|
|
increment)));
|
|
|
|
}
|
|
|
|
|
|
|
|
/* STMT is builtin call that writes bytes in bitmap ORIG, some bytes are dead
|
|
|
|
(ORIG & ~NEW) and need not be stored. Try to rewrite STMT to reduce
|
|
|
|
the amount of data it actually writes.
|
|
|
|
|
|
|
|
Right now we only support trimming from the head or the tail of the
|
|
|
|
memory region. In theory we could split the mem* call, but it's
|
|
|
|
likely of marginal value. */
|
|
|
|
|
|
|
|
static void
|
|
|
|
maybe_trim_memstar_call (ao_ref *ref, sbitmap live, gimple *stmt)
|
|
|
|
{
|
|
|
|
switch (DECL_FUNCTION_CODE (gimple_call_fndecl (stmt)))
|
|
|
|
{
|
|
|
|
case BUILT_IN_MEMCPY:
|
|
|
|
case BUILT_IN_MEMMOVE:
|
|
|
|
{
|
|
|
|
int head_trim, tail_trim;
|
|
|
|
compute_trims (ref, live, &head_trim, &tail_trim, stmt);
|
|
|
|
|
|
|
|
/* Tail trimming is easy, we can just reduce the count. */
|
|
|
|
if (tail_trim)
|
|
|
|
decrement_count (stmt, tail_trim);
|
|
|
|
|
|
|
|
/* Head trimming requires adjusting all the arguments. */
|
|
|
|
if (head_trim)
|
|
|
|
{
|
|
|
|
tree *dst = gimple_call_arg_ptr (stmt, 0);
|
|
|
|
increment_start_addr (stmt, dst, head_trim);
|
|
|
|
tree *src = gimple_call_arg_ptr (stmt, 1);
|
|
|
|
increment_start_addr (stmt, src, head_trim);
|
|
|
|
decrement_count (stmt, head_trim);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
case BUILT_IN_MEMSET:
|
|
|
|
{
|
|
|
|
int head_trim, tail_trim;
|
|
|
|
compute_trims (ref, live, &head_trim, &tail_trim, stmt);
|
|
|
|
|
|
|
|
/* Tail trimming is easy, we can just reduce the count. */
|
|
|
|
if (tail_trim)
|
|
|
|
decrement_count (stmt, tail_trim);
|
|
|
|
|
|
|
|
/* Head trimming requires adjusting all the arguments. */
|
|
|
|
if (head_trim)
|
|
|
|
{
|
|
|
|
tree *dst = gimple_call_arg_ptr (stmt, 0);
|
|
|
|
increment_start_addr (stmt, dst, head_trim);
|
|
|
|
decrement_count (stmt, head_trim);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
default:
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* STMT is a memory write where one or more bytes written are dead
|
|
|
|
stores. ORIG is the bitmap of bytes stored by STMT. LIVE is the
|
|
|
|
bitmap of stores that are actually live.
|
|
|
|
|
|
|
|
Attempt to rewrite STMT so that it writes fewer memory locations. Right
|
|
|
|
now we only support trimming at the start or end of the memory region.
|
|
|
|
It's not clear how much there is to be gained by trimming from the middle
|
|
|
|
of the region. */
|
|
|
|
|
|
|
|
static void
|
|
|
|
maybe_trim_partially_dead_store (ao_ref *ref, sbitmap live, gimple *stmt)
|
|
|
|
{
|
|
|
|
if (is_gimple_assign (stmt)
|
|
|
|
&& TREE_CODE (gimple_assign_lhs (stmt)) != TARGET_MEM_REF)
|
|
|
|
{
|
|
|
|
switch (gimple_assign_rhs_code (stmt))
|
|
|
|
{
|
|
|
|
case CONSTRUCTOR:
|
|
|
|
maybe_trim_constructor_store (ref, live, stmt);
|
|
|
|
break;
|
|
|
|
case COMPLEX_CST:
|
|
|
|
maybe_trim_complex_store (ref, live, stmt);
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2018-12-28 15:30:48 +00:00
|
|
|
/* Return TRUE if USE_REF reads bytes from LIVE where live is
|
|
|
|
derived from REF, a write reference.
|
|
|
|
|
|
|
|
While this routine may modify USE_REF, it's passed by value, not
|
|
|
|
location. So callers do not see those modifications. */
|
|
|
|
|
|
|
|
static bool
|
|
|
|
live_bytes_read (ao_ref use_ref, ao_ref *ref, sbitmap live)
|
|
|
|
{
|
|
|
|
/* We have already verified that USE_REF and REF hit the same object.
|
|
|
|
Now verify that there's actually an overlap between USE_REF and REF. */
|
|
|
|
HOST_WIDE_INT start, size;
|
|
|
|
if (normalize_ref (&use_ref, ref)
|
|
|
|
&& (use_ref.offset - ref->offset).is_constant (&start)
|
|
|
|
&& use_ref.size.is_constant (&size))
|
|
|
|
{
|
|
|
|
/* If USE_REF covers all of REF, then it will hit one or more
|
|
|
|
live bytes. This avoids useless iteration over the bitmap
|
|
|
|
below. */
|
|
|
|
if (start == 0 && known_eq (size, ref->size))
|
|
|
|
return true;
|
|
|
|
|
|
|
|
/* Now check if any of the remaining bits in use_ref are set in LIVE. */
|
|
|
|
return bitmap_bit_in_range_p (live, start / BITS_PER_UNIT,
|
|
|
|
(start + size - 1) / BITS_PER_UNIT);
|
|
|
|
}
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
2019-06-02 15:48:37 +00:00
|
|
|
/* Callback for dse_classify_store calling for_each_index. Verify that
|
|
|
|
indices are invariant in the loop with backedge PHI in basic-block DATA. */
|
|
|
|
|
|
|
|
static bool
|
|
|
|
check_name (tree, tree *idx, void *data)
|
|
|
|
{
|
|
|
|
basic_block phi_bb = (basic_block) data;
|
|
|
|
if (TREE_CODE (*idx) == SSA_NAME
|
|
|
|
&& !SSA_NAME_IS_DEFAULT_DEF (*idx)
|
|
|
|
&& dominated_by_p (CDI_DOMINATORS, gimple_bb (SSA_NAME_DEF_STMT (*idx)),
|
|
|
|
phi_bb))
|
|
|
|
return false;
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
2012-03-27 23:13:14 +00:00
|
|
|
/* A helper of dse_optimize_stmt.
|
2019-06-02 15:48:37 +00:00
|
|
|
Given a GIMPLE_ASSIGN in STMT that writes to REF, classify it
|
|
|
|
according to downstream uses and defs. Sets *BY_CLOBBER_P to true
|
|
|
|
if only clobber statements influenced the classification result.
|
|
|
|
Returns the classification. */
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
static dse_store_status
|
2019-06-02 15:48:37 +00:00
|
|
|
dse_classify_store (ao_ref *ref, gimple *stmt,
|
|
|
|
bool byte_tracking_enabled, sbitmap live_bytes,
|
|
|
|
bool *by_clobber_p = NULL)
|
2012-03-27 23:13:14 +00:00
|
|
|
{
|
2017-04-10 11:32:00 +00:00
|
|
|
gimple *temp;
|
2019-06-02 15:48:37 +00:00
|
|
|
int cnt = 0;
|
|
|
|
auto_bitmap visited;
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2019-06-02 15:48:37 +00:00
|
|
|
if (by_clobber_p)
|
|
|
|
*by_clobber_p = true;
|
2012-03-27 23:13:14 +00:00
|
|
|
|
|
|
|
/* Find the first dominated statement that clobbers (part of) the
|
|
|
|
memory stmt stores to with no intermediate statement that may use
|
|
|
|
part of the memory stmt stores. That is, find a store that may
|
|
|
|
prove stmt to be a dead store. */
|
|
|
|
temp = stmt;
|
|
|
|
do
|
|
|
|
{
|
2019-06-02 15:48:37 +00:00
|
|
|
gimple *use_stmt;
|
2012-03-27 23:13:14 +00:00
|
|
|
imm_use_iterator ui;
|
|
|
|
bool fail = false;
|
|
|
|
tree defvar;
|
|
|
|
|
|
|
|
if (gimple_code (temp) == GIMPLE_PHI)
|
2019-06-02 15:48:37 +00:00
|
|
|
{
|
|
|
|
/* If we visit this PHI by following a backedge then we have to
|
|
|
|
make sure ref->ref only refers to SSA names that are invariant
|
|
|
|
with respect to the loop represented by this PHI node. */
|
|
|
|
if (dominated_by_p (CDI_DOMINATORS, gimple_bb (stmt),
|
|
|
|
gimple_bb (temp))
|
|
|
|
&& !for_each_index (ref->ref ? &ref->ref : &ref->base,
|
|
|
|
check_name, gimple_bb (temp)))
|
|
|
|
return DSE_STORE_LIVE;
|
|
|
|
defvar = PHI_RESULT (temp);
|
|
|
|
bitmap_set_bit (visited, SSA_NAME_VERSION (defvar));
|
|
|
|
}
|
2012-03-27 23:13:14 +00:00
|
|
|
else
|
|
|
|
defvar = gimple_vdef (temp);
|
2019-06-02 15:48:37 +00:00
|
|
|
auto_vec<gimple *, 10> defs;
|
|
|
|
gimple *phi_def = NULL;
|
2012-03-27 23:13:14 +00:00
|
|
|
FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar)
|
|
|
|
{
|
2019-06-02 15:48:37 +00:00
|
|
|
/* Limit stmt walking. */
|
|
|
|
if (++cnt > PARAM_VALUE (PARAM_DSE_MAX_ALIAS_QUERIES_PER_STORE))
|
2012-03-27 23:13:14 +00:00
|
|
|
{
|
|
|
|
fail = true;
|
|
|
|
BREAK_FROM_IMM_USE_STMT (ui);
|
|
|
|
}
|
2019-06-02 15:48:37 +00:00
|
|
|
|
|
|
|
/* We have visited ourselves already so ignore STMT for the
|
|
|
|
purpose of chaining. */
|
|
|
|
if (use_stmt == stmt)
|
|
|
|
;
|
2012-03-27 23:13:14 +00:00
|
|
|
/* In simple cases we can look through PHI nodes, but we
|
|
|
|
have to be careful with loops and with memory references
|
|
|
|
containing operands that are also operands of PHI nodes.
|
|
|
|
See gcc.c-torture/execute/20051110-*.c. */
|
|
|
|
else if (gimple_code (use_stmt) == GIMPLE_PHI)
|
|
|
|
{
|
2019-06-02 15:48:37 +00:00
|
|
|
/* If we already visited this PHI ignore it for further
|
|
|
|
processing. */
|
|
|
|
if (!bitmap_bit_p (visited,
|
|
|
|
SSA_NAME_VERSION (PHI_RESULT (use_stmt))))
|
2012-03-27 23:13:14 +00:00
|
|
|
{
|
2019-06-02 15:48:37 +00:00
|
|
|
defs.safe_push (use_stmt);
|
|
|
|
phi_def = use_stmt;
|
2012-03-27 23:13:14 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
/* If the statement is a use the store is not dead. */
|
2015-08-28 15:33:40 +00:00
|
|
|
else if (ref_maybe_used_by_stmt_p (use_stmt, ref))
|
2012-03-27 23:13:14 +00:00
|
|
|
{
|
2018-12-28 15:30:48 +00:00
|
|
|
/* Handle common cases where we can easily build an ao_ref
|
|
|
|
structure for USE_STMT and in doing so we find that the
|
|
|
|
references hit non-live bytes and thus can be ignored. */
|
2019-06-02 15:48:37 +00:00
|
|
|
if (byte_tracking_enabled
|
|
|
|
&& is_gimple_assign (use_stmt))
|
2018-12-28 15:30:48 +00:00
|
|
|
{
|
2019-06-02 15:48:37 +00:00
|
|
|
ao_ref use_ref;
|
|
|
|
ao_ref_init (&use_ref, gimple_assign_rhs1 (use_stmt));
|
|
|
|
if (valid_ao_ref_for_dse (&use_ref)
|
|
|
|
&& use_ref.base == ref->base
|
|
|
|
&& known_eq (use_ref.size, use_ref.max_size)
|
|
|
|
&& !live_bytes_read (use_ref, ref, live_bytes))
|
2018-12-28 15:30:48 +00:00
|
|
|
{
|
2019-06-02 15:48:37 +00:00
|
|
|
/* If this is a store, remember it as we possibly
|
|
|
|
need to walk the defs uses. */
|
|
|
|
if (gimple_vdef (use_stmt))
|
|
|
|
defs.safe_push (use_stmt);
|
|
|
|
continue;
|
2018-12-28 15:30:48 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2012-03-27 23:13:14 +00:00
|
|
|
fail = true;
|
|
|
|
BREAK_FROM_IMM_USE_STMT (ui);
|
|
|
|
}
|
2019-06-02 15:48:37 +00:00
|
|
|
/* If this is a store, remember it as we possibly need to walk the
|
|
|
|
defs uses. */
|
2012-03-27 23:13:14 +00:00
|
|
|
else if (gimple_vdef (use_stmt))
|
2019-06-02 15:48:37 +00:00
|
|
|
defs.safe_push (use_stmt);
|
2012-03-27 23:13:14 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
if (fail)
|
2017-10-07 00:16:47 +00:00
|
|
|
{
|
|
|
|
/* STMT might be partially dead and we may be able to reduce
|
|
|
|
how many memory locations it stores into. */
|
|
|
|
if (byte_tracking_enabled && !gimple_clobber_p (stmt))
|
|
|
|
return DSE_STORE_MAYBE_PARTIAL_DEAD;
|
|
|
|
return DSE_STORE_LIVE;
|
|
|
|
}
|
2012-03-27 23:13:14 +00:00
|
|
|
|
|
|
|
/* If we didn't find any definition this means the store is dead
|
|
|
|
if it isn't a store to global reachable memory. In this case
|
|
|
|
just pretend the stmt makes itself dead. Otherwise fail. */
|
2019-06-02 15:48:37 +00:00
|
|
|
if (defs.is_empty ())
|
2012-03-27 23:13:14 +00:00
|
|
|
{
|
2015-08-28 15:33:40 +00:00
|
|
|
if (ref_may_alias_global_p (ref))
|
2017-10-07 00:16:47 +00:00
|
|
|
return DSE_STORE_LIVE;
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2019-06-02 15:48:37 +00:00
|
|
|
if (by_clobber_p)
|
|
|
|
*by_clobber_p = false;
|
|
|
|
return DSE_STORE_DEAD;
|
2012-03-27 23:13:14 +00:00
|
|
|
}
|
2017-10-07 00:16:47 +00:00
|
|
|
|
2019-06-02 15:48:37 +00:00
|
|
|
/* Process defs and remove those we need not process further. */
|
|
|
|
for (unsigned i = 0; i < defs.length ();)
|
|
|
|
{
|
|
|
|
gimple *def = defs[i];
|
|
|
|
gimple *use_stmt;
|
|
|
|
use_operand_p use_p;
|
|
|
|
/* If the path to check starts with a kill we do not need to
|
|
|
|
process it further.
|
|
|
|
??? With byte tracking we need only kill the bytes currently
|
|
|
|
live. */
|
|
|
|
if (stmt_kills_ref_p (def, ref))
|
|
|
|
{
|
|
|
|
if (by_clobber_p && !gimple_clobber_p (def))
|
|
|
|
*by_clobber_p = false;
|
|
|
|
defs.unordered_remove (i);
|
|
|
|
}
|
|
|
|
/* In addition to kills we can remove defs whose only use
|
|
|
|
is another def in defs. That can only ever be PHIs of which
|
|
|
|
we track a single for simplicity reasons (we fail for multiple
|
|
|
|
PHIs anyways). We can also ignore defs that feed only into
|
|
|
|
already visited PHIs. */
|
|
|
|
else if (gimple_code (def) != GIMPLE_PHI
|
|
|
|
&& single_imm_use (gimple_vdef (def), &use_p, &use_stmt)
|
|
|
|
&& (use_stmt == phi_def
|
|
|
|
|| (gimple_code (use_stmt) == GIMPLE_PHI
|
|
|
|
&& bitmap_bit_p (visited,
|
|
|
|
SSA_NAME_VERSION
|
|
|
|
(PHI_RESULT (use_stmt))))))
|
|
|
|
defs.unordered_remove (i);
|
|
|
|
else
|
|
|
|
++i;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* If all defs kill the ref we are done. */
|
|
|
|
if (defs.is_empty ())
|
|
|
|
return DSE_STORE_DEAD;
|
|
|
|
/* If more than one def survives fail. */
|
|
|
|
if (defs.length () > 1)
|
|
|
|
{
|
|
|
|
/* STMT might be partially dead and we may be able to reduce
|
|
|
|
how many memory locations it stores into. */
|
|
|
|
if (byte_tracking_enabled && !gimple_clobber_p (stmt))
|
|
|
|
return DSE_STORE_MAYBE_PARTIAL_DEAD;
|
|
|
|
return DSE_STORE_LIVE;
|
|
|
|
}
|
|
|
|
temp = defs[0];
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2019-06-02 15:48:37 +00:00
|
|
|
/* Track partial kills. */
|
|
|
|
if (byte_tracking_enabled)
|
|
|
|
{
|
|
|
|
clear_bytes_written_by (live_bytes, temp, ref);
|
|
|
|
if (bitmap_empty_p (live_bytes))
|
|
|
|
{
|
|
|
|
if (by_clobber_p && !gimple_clobber_p (temp))
|
|
|
|
*by_clobber_p = false;
|
|
|
|
return DSE_STORE_DEAD;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
/* Continue walking until there are no more live bytes. */
|
|
|
|
while (1);
|
2017-10-07 00:16:47 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
class dse_dom_walker : public dom_walker
|
|
|
|
{
|
|
|
|
public:
|
|
|
|
dse_dom_walker (cdi_direction direction)
|
2018-12-28 15:30:48 +00:00
|
|
|
: dom_walker (direction),
|
|
|
|
m_live_bytes (PARAM_VALUE (PARAM_DSE_MAX_OBJECT_SIZE)),
|
|
|
|
m_byte_tracking_enabled (false) {}
|
2017-10-07 00:16:47 +00:00
|
|
|
|
|
|
|
virtual edge before_dom_children (basic_block);
|
|
|
|
|
|
|
|
private:
|
2018-12-28 15:30:48 +00:00
|
|
|
auto_sbitmap m_live_bytes;
|
2017-10-07 00:16:47 +00:00
|
|
|
bool m_byte_tracking_enabled;
|
|
|
|
void dse_optimize_stmt (gimple_stmt_iterator *);
|
|
|
|
};
|
|
|
|
|
|
|
|
/* Delete a dead call at GSI, which is mem* call of some kind. */
|
|
|
|
static void
|
|
|
|
delete_dead_call (gimple_stmt_iterator *gsi)
|
|
|
|
{
|
|
|
|
gimple *stmt = gsi_stmt (*gsi);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
|
|
{
|
|
|
|
fprintf (dump_file, " Deleted dead call: ");
|
2018-12-28 15:30:48 +00:00
|
|
|
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
|
2017-10-07 00:16:47 +00:00
|
|
|
fprintf (dump_file, "\n");
|
|
|
|
}
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
tree lhs = gimple_call_lhs (stmt);
|
|
|
|
if (lhs)
|
|
|
|
{
|
|
|
|
tree ptr = gimple_call_arg (stmt, 0);
|
|
|
|
gimple *new_stmt = gimple_build_assign (lhs, ptr);
|
|
|
|
unlink_stmt_vdef (stmt);
|
|
|
|
if (gsi_replace (gsi, new_stmt, true))
|
|
|
|
bitmap_set_bit (need_eh_cleanup, gimple_bb (stmt)->index);
|
|
|
|
}
|
|
|
|
else
|
|
|
|
{
|
|
|
|
/* Then we need to fix the operand of the consuming stmt. */
|
|
|
|
unlink_stmt_vdef (stmt);
|
|
|
|
|
|
|
|
/* Remove the dead store. */
|
|
|
|
if (gsi_remove (gsi, true))
|
|
|
|
bitmap_set_bit (need_eh_cleanup, gimple_bb (stmt)->index);
|
|
|
|
release_defs (stmt);
|
|
|
|
}
|
2012-03-27 23:13:14 +00:00
|
|
|
}
|
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
/* Delete a dead store at GSI, which is a gimple assignment. */
|
|
|
|
|
|
|
|
static void
|
|
|
|
delete_dead_assignment (gimple_stmt_iterator *gsi)
|
|
|
|
{
|
|
|
|
gimple *stmt = gsi_stmt (*gsi);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
|
|
{
|
|
|
|
fprintf (dump_file, " Deleted dead store: ");
|
2018-12-28 15:30:48 +00:00
|
|
|
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
|
2017-10-07 00:16:47 +00:00
|
|
|
fprintf (dump_file, "\n");
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Then we need to fix the operand of the consuming stmt. */
|
|
|
|
unlink_stmt_vdef (stmt);
|
|
|
|
|
|
|
|
/* Remove the dead store. */
|
|
|
|
basic_block bb = gimple_bb (stmt);
|
|
|
|
if (gsi_remove (gsi, true))
|
|
|
|
bitmap_set_bit (need_eh_cleanup, bb->index);
|
|
|
|
|
|
|
|
/* And release any SSA_NAMEs set in this statement back to the
|
|
|
|
SSA_NAME manager. */
|
|
|
|
release_defs (stmt);
|
|
|
|
}
|
2012-03-27 23:13:14 +00:00
|
|
|
|
|
|
|
/* Attempt to eliminate dead stores in the statement referenced by BSI.
|
|
|
|
|
|
|
|
A dead store is a store into a memory location which will later be
|
|
|
|
overwritten by another store without any intervening loads. In this
|
|
|
|
case the earlier store can be deleted.
|
|
|
|
|
|
|
|
In our SSA + virtual operand world we use immediate uses of virtual
|
|
|
|
operands to detect dead stores. If a store's virtual definition
|
|
|
|
is used precisely once by a later store to the same location which
|
|
|
|
post dominates the first store, then the first store is dead. */
|
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
void
|
|
|
|
dse_dom_walker::dse_optimize_stmt (gimple_stmt_iterator *gsi)
|
2012-03-27 23:13:14 +00:00
|
|
|
{
|
2017-04-10 11:32:00 +00:00
|
|
|
gimple *stmt = gsi_stmt (*gsi);
|
2012-03-27 23:13:14 +00:00
|
|
|
|
|
|
|
/* If this statement has no virtual defs, then there is nothing
|
|
|
|
to do. */
|
|
|
|
if (!gimple_vdef (stmt))
|
|
|
|
return;
|
|
|
|
|
2014-09-21 17:33:12 +00:00
|
|
|
/* Don't return early on *this_2(D) ={v} {CLOBBER}. */
|
|
|
|
if (gimple_has_volatile_ops (stmt)
|
|
|
|
&& (!gimple_clobber_p (stmt)
|
|
|
|
|| TREE_CODE (gimple_assign_lhs (stmt)) != MEM_REF))
|
2012-03-27 23:13:14 +00:00
|
|
|
return;
|
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
ao_ref ref;
|
|
|
|
if (!initialize_ao_ref_for_dse (stmt, &ref))
|
|
|
|
return;
|
|
|
|
|
2015-08-28 15:33:40 +00:00
|
|
|
/* We know we have virtual definitions. We can handle assignments and
|
|
|
|
some builtin calls. */
|
|
|
|
if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
|
|
|
|
{
|
|
|
|
switch (DECL_FUNCTION_CODE (gimple_call_fndecl (stmt)))
|
|
|
|
{
|
|
|
|
case BUILT_IN_MEMCPY:
|
|
|
|
case BUILT_IN_MEMMOVE:
|
|
|
|
case BUILT_IN_MEMSET:
|
|
|
|
{
|
2017-10-07 00:16:47 +00:00
|
|
|
/* Occasionally calls with an explicit length of zero
|
|
|
|
show up in the IL. It's pointless to do analysis
|
|
|
|
on them, they're trivially dead. */
|
|
|
|
tree size = gimple_call_arg (stmt, 2);
|
|
|
|
if (integer_zerop (size))
|
2015-08-28 15:33:40 +00:00
|
|
|
{
|
2017-10-07 00:16:47 +00:00
|
|
|
delete_dead_call (gsi);
|
|
|
|
return;
|
2015-08-28 15:33:40 +00:00
|
|
|
}
|
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
enum dse_store_status store_status;
|
|
|
|
m_byte_tracking_enabled
|
|
|
|
= setup_live_bytes_from_ref (&ref, m_live_bytes);
|
2019-06-02 15:48:37 +00:00
|
|
|
store_status = dse_classify_store (&ref, stmt,
|
2017-10-07 00:16:47 +00:00
|
|
|
m_byte_tracking_enabled,
|
|
|
|
m_live_bytes);
|
|
|
|
if (store_status == DSE_STORE_LIVE)
|
|
|
|
return;
|
|
|
|
|
|
|
|
if (store_status == DSE_STORE_MAYBE_PARTIAL_DEAD)
|
2015-08-28 15:33:40 +00:00
|
|
|
{
|
2017-10-07 00:16:47 +00:00
|
|
|
maybe_trim_memstar_call (&ref, m_live_bytes, stmt);
|
|
|
|
return;
|
2015-08-28 15:33:40 +00:00
|
|
|
}
|
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
if (store_status == DSE_STORE_DEAD)
|
|
|
|
delete_dead_call (gsi);
|
|
|
|
return;
|
2015-08-28 15:33:40 +00:00
|
|
|
}
|
2017-10-07 00:16:47 +00:00
|
|
|
|
2015-08-28 15:33:40 +00:00
|
|
|
default:
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2012-03-27 23:13:14 +00:00
|
|
|
if (is_gimple_assign (stmt))
|
|
|
|
{
|
2019-06-02 15:48:37 +00:00
|
|
|
bool by_clobber_p = false;
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2015-08-28 15:33:40 +00:00
|
|
|
/* Self-assignments are zombies. */
|
|
|
|
if (operand_equal_p (gimple_assign_rhs1 (stmt),
|
|
|
|
gimple_assign_lhs (stmt), 0))
|
2019-06-02 15:48:37 +00:00
|
|
|
;
|
2015-08-28 15:33:40 +00:00
|
|
|
else
|
|
|
|
{
|
2017-10-07 00:16:47 +00:00
|
|
|
m_byte_tracking_enabled
|
|
|
|
= setup_live_bytes_from_ref (&ref, m_live_bytes);
|
|
|
|
enum dse_store_status store_status;
|
2019-06-02 15:48:37 +00:00
|
|
|
store_status = dse_classify_store (&ref, stmt,
|
2017-10-07 00:16:47 +00:00
|
|
|
m_byte_tracking_enabled,
|
2019-06-02 15:48:37 +00:00
|
|
|
m_live_bytes, &by_clobber_p);
|
2017-10-07 00:16:47 +00:00
|
|
|
if (store_status == DSE_STORE_LIVE)
|
2015-08-28 15:33:40 +00:00
|
|
|
return;
|
2017-10-07 00:16:47 +00:00
|
|
|
|
|
|
|
if (store_status == DSE_STORE_MAYBE_PARTIAL_DEAD)
|
|
|
|
{
|
|
|
|
maybe_trim_partially_dead_store (&ref, m_live_bytes, stmt);
|
|
|
|
return;
|
|
|
|
}
|
2015-08-28 15:33:40 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/* Now we know that use_stmt kills the LHS of stmt. */
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2014-09-21 17:33:12 +00:00
|
|
|
/* But only remove *this_2(D) ={v} {CLOBBER} if killed by
|
|
|
|
another clobber stmt. */
|
|
|
|
if (gimple_clobber_p (stmt)
|
2019-06-02 15:48:37 +00:00
|
|
|
&& !by_clobber_p)
|
2014-09-21 17:33:12 +00:00
|
|
|
return;
|
|
|
|
|
2017-10-07 00:16:47 +00:00
|
|
|
delete_dead_assignment (gsi);
|
2012-03-27 23:13:14 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2017-04-10 11:32:00 +00:00
|
|
|
edge
|
2014-09-21 17:33:12 +00:00
|
|
|
dse_dom_walker::before_dom_children (basic_block bb)
|
2012-03-27 23:13:14 +00:00
|
|
|
{
|
|
|
|
gimple_stmt_iterator gsi;
|
|
|
|
|
2014-09-21 17:33:12 +00:00
|
|
|
for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
|
|
|
|
{
|
|
|
|
dse_optimize_stmt (&gsi);
|
|
|
|
if (gsi_end_p (gsi))
|
|
|
|
gsi = gsi_last_bb (bb);
|
|
|
|
else
|
|
|
|
gsi_prev (&gsi);
|
|
|
|
}
|
2017-04-10 11:32:00 +00:00
|
|
|
return NULL;
|
2012-03-27 23:13:14 +00:00
|
|
|
}
|
|
|
|
|
2015-08-28 15:33:40 +00:00
|
|
|
namespace {
|
2012-03-27 23:13:14 +00:00
|
|
|
|
2015-08-28 15:33:40 +00:00
|
|
|
const pass_data pass_data_dse =
|
|
|
|
{
|
|
|
|
GIMPLE_PASS, /* type */
|
|
|
|
"dse", /* name */
|
|
|
|
OPTGROUP_NONE, /* optinfo_flags */
|
|
|
|
TV_TREE_DSE, /* tv_id */
|
|
|
|
( PROP_cfg | PROP_ssa ), /* properties_required */
|
|
|
|
0, /* properties_provided */
|
|
|
|
0, /* properties_destroyed */
|
|
|
|
0, /* todo_flags_start */
|
|
|
|
0, /* todo_flags_finish */
|
|
|
|
};
|
|
|
|
|
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class pass_dse : public gimple_opt_pass
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{
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public:
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pass_dse (gcc::context *ctxt)
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: gimple_opt_pass (pass_data_dse, ctxt)
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{}
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/* opt_pass methods: */
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opt_pass * clone () { return new pass_dse (m_ctxt); }
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virtual bool gate (function *) { return flag_tree_dse != 0; }
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virtual unsigned int execute (function *);
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}; // class pass_dse
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unsigned int
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pass_dse::execute (function *fun)
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2012-03-27 23:13:14 +00:00
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{
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need_eh_cleanup = BITMAP_ALLOC (NULL);
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renumber_gimple_stmt_uids ();
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/* We might consider making this a property of each pass so that it
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can be [re]computed on an as-needed basis. Particularly since
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this pass could be seen as an extension of DCE which needs post
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dominators. */
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calculate_dominance_info (CDI_POST_DOMINATORS);
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calculate_dominance_info (CDI_DOMINATORS);
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/* Dead store elimination is fundamentally a walk of the post-dominator
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tree and a backwards walk of statements within each block. */
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2015-08-28 15:33:40 +00:00
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dse_dom_walker (CDI_POST_DOMINATORS).walk (fun->cfg->x_exit_block_ptr);
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2012-03-27 23:13:14 +00:00
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/* Removal of stores may make some EH edges dead. Purge such edges from
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the CFG as needed. */
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if (!bitmap_empty_p (need_eh_cleanup))
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{
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gimple_purge_all_dead_eh_edges (need_eh_cleanup);
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cleanup_tree_cfg ();
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}
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BITMAP_FREE (need_eh_cleanup);
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2017-10-07 00:16:47 +00:00
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2012-03-27 23:13:14 +00:00
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/* For now, just wipe the post-dominator information. */
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free_dominance_info (CDI_POST_DOMINATORS);
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return 0;
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}
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2014-09-21 17:33:12 +00:00
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} // anon namespace
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gimple_opt_pass *
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make_pass_dse (gcc::context *ctxt)
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{
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return new pass_dse (ctxt);
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}
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