/* Array prefetching.
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/* Array prefetching.
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Copyright (C) 2005, 2007 Free Software Foundation, Inc.
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Copyright (C) 2005, 2007 Free Software Foundation, Inc.
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This file is part of GCC.
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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 it
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GCC is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 3, or (at your option) any
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Free Software Foundation; either version 3, or (at your option) any
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later version.
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later version.
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GCC is distributed in the hope that it will be useful, but WITHOUT
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GCC is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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for more details.
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You should have received a copy of the GNU General Public License
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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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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include "config.h"
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#include "system.h"
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#include "system.h"
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#include "coretypes.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "tm.h"
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#include "tree.h"
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#include "tree.h"
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#include "rtl.h"
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#include "rtl.h"
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#include "tm_p.h"
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#include "tm_p.h"
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#include "hard-reg-set.h"
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#include "hard-reg-set.h"
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#include "basic-block.h"
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#include "basic-block.h"
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#include "output.h"
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#include "output.h"
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#include "diagnostic.h"
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#include "diagnostic.h"
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#include "tree-flow.h"
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#include "tree-flow.h"
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#include "tree-dump.h"
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#include "tree-dump.h"
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#include "timevar.h"
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#include "timevar.h"
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#include "cfgloop.h"
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#include "cfgloop.h"
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#include "varray.h"
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#include "varray.h"
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#include "expr.h"
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#include "expr.h"
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#include "tree-pass.h"
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#include "tree-pass.h"
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#include "ggc.h"
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#include "ggc.h"
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#include "insn-config.h"
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#include "insn-config.h"
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#include "recog.h"
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#include "recog.h"
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#include "hashtab.h"
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#include "hashtab.h"
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#include "tree-chrec.h"
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#include "tree-chrec.h"
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#include "tree-scalar-evolution.h"
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#include "tree-scalar-evolution.h"
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#include "toplev.h"
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#include "toplev.h"
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#include "params.h"
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#include "params.h"
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#include "langhooks.h"
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#include "langhooks.h"
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/* This pass inserts prefetch instructions to optimize cache usage during
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/* This pass inserts prefetch instructions to optimize cache usage during
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accesses to arrays in loops. It processes loops sequentially and:
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accesses to arrays in loops. It processes loops sequentially and:
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1) Gathers all memory references in the single loop.
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1) Gathers all memory references in the single loop.
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2) For each of the references it decides when it is profitable to prefetch
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2) For each of the references it decides when it is profitable to prefetch
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it. To do it, we evaluate the reuse among the accesses, and determines
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it. To do it, we evaluate the reuse among the accesses, and determines
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two values: PREFETCH_BEFORE (meaning that it only makes sense to do
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two values: PREFETCH_BEFORE (meaning that it only makes sense to do
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prefetching in the first PREFETCH_BEFORE iterations of the loop) and
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prefetching in the first PREFETCH_BEFORE iterations of the loop) and
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PREFETCH_MOD (meaning that it only makes sense to prefetch in the
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PREFETCH_MOD (meaning that it only makes sense to prefetch in the
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iterations of the loop that are zero modulo PREFETCH_MOD). For example
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iterations of the loop that are zero modulo PREFETCH_MOD). For example
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(assuming cache line size is 64 bytes, char has size 1 byte and there
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(assuming cache line size is 64 bytes, char has size 1 byte and there
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is no hardware sequential prefetch):
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is no hardware sequential prefetch):
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char *a;
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char *a;
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for (i = 0; i < max; i++)
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for (i = 0; i < max; i++)
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{
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{
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a[255] = ...; (0)
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a[255] = ...; (0)
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a[i] = ...; (1)
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a[i] = ...; (1)
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a[i + 64] = ...; (2)
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a[i + 64] = ...; (2)
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a[16*i] = ...; (3)
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a[16*i] = ...; (3)
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a[187*i] = ...; (4)
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a[187*i] = ...; (4)
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a[187*i + 50] = ...; (5)
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a[187*i + 50] = ...; (5)
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}
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}
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(0) obviously has PREFETCH_BEFORE 1
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(0) obviously has PREFETCH_BEFORE 1
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(1) has PREFETCH_BEFORE 64, since (2) accesses the same memory
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(1) has PREFETCH_BEFORE 64, since (2) accesses the same memory
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location 64 iterations before it, and PREFETCH_MOD 64 (since
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location 64 iterations before it, and PREFETCH_MOD 64 (since
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it hits the same cache line otherwise).
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it hits the same cache line otherwise).
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(2) has PREFETCH_MOD 64
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(2) has PREFETCH_MOD 64
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(3) has PREFETCH_MOD 4
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(3) has PREFETCH_MOD 4
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(4) has PREFETCH_MOD 1. We do not set PREFETCH_BEFORE here, since
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(4) has PREFETCH_MOD 1. We do not set PREFETCH_BEFORE here, since
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the cache line accessed by (4) is the same with probability only
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the cache line accessed by (4) is the same with probability only
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7/32.
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7/32.
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(5) has PREFETCH_MOD 1 as well.
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(5) has PREFETCH_MOD 1 as well.
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3) We determine how much ahead we need to prefetch. The number of
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3) We determine how much ahead we need to prefetch. The number of
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iterations needed is time to fetch / time spent in one iteration of
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iterations needed is time to fetch / time spent in one iteration of
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the loop. The problem is that we do not know either of these values,
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the loop. The problem is that we do not know either of these values,
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so we just make a heuristic guess based on a magic (possibly)
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so we just make a heuristic guess based on a magic (possibly)
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target-specific constant and size of the loop.
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target-specific constant and size of the loop.
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4) Determine which of the references we prefetch. We take into account
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4) Determine which of the references we prefetch. We take into account
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that there is a maximum number of simultaneous prefetches (provided
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that there is a maximum number of simultaneous prefetches (provided
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by machine description). We prefetch as many prefetches as possible
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by machine description). We prefetch as many prefetches as possible
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while still within this bound (starting with those with lowest
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while still within this bound (starting with those with lowest
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prefetch_mod, since they are responsible for most of the cache
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prefetch_mod, since they are responsible for most of the cache
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misses).
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misses).
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5) We unroll and peel loops so that we are able to satisfy PREFETCH_MOD
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5) We unroll and peel loops so that we are able to satisfy PREFETCH_MOD
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and PREFETCH_BEFORE requirements (within some bounds), and to avoid
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and PREFETCH_BEFORE requirements (within some bounds), and to avoid
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prefetching nonaccessed memory.
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prefetching nonaccessed memory.
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TODO -- actually implement peeling.
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TODO -- actually implement peeling.
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6) We actually emit the prefetch instructions. ??? Perhaps emit the
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6) We actually emit the prefetch instructions. ??? Perhaps emit the
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prefetch instructions with guards in cases where 5) was not sufficient
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prefetch instructions with guards in cases where 5) was not sufficient
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to satisfy the constraints?
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to satisfy the constraints?
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Some other TODO:
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Some other TODO:
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-- write and use more general reuse analysis (that could be also used
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-- write and use more general reuse analysis (that could be also used
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in other cache aimed loop optimizations)
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in other cache aimed loop optimizations)
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-- make it behave sanely together with the prefetches given by user
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-- make it behave sanely together with the prefetches given by user
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(now we just ignore them; at the very least we should avoid
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(now we just ignore them; at the very least we should avoid
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optimizing loops in that user put his own prefetches)
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optimizing loops in that user put his own prefetches)
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-- we assume cache line size alignment of arrays; this could be
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-- we assume cache line size alignment of arrays; this could be
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improved. */
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improved. */
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/* Magic constants follow. These should be replaced by machine specific
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/* Magic constants follow. These should be replaced by machine specific
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numbers. */
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numbers. */
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/* A number that should roughly correspond to the number of instructions
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/* A number that should roughly correspond to the number of instructions
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executed before the prefetch is completed. */
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executed before the prefetch is completed. */
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#ifndef PREFETCH_LATENCY
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#ifndef PREFETCH_LATENCY
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#define PREFETCH_LATENCY 200
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#define PREFETCH_LATENCY 200
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#endif
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#endif
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/* Number of prefetches that can run at the same time. */
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/* Number of prefetches that can run at the same time. */
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#ifndef SIMULTANEOUS_PREFETCHES
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#ifndef SIMULTANEOUS_PREFETCHES
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#define SIMULTANEOUS_PREFETCHES 3
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#define SIMULTANEOUS_PREFETCHES 3
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#endif
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#endif
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/* True if write can be prefetched by a read prefetch. */
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/* True if write can be prefetched by a read prefetch. */
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#ifndef WRITE_CAN_USE_READ_PREFETCH
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#ifndef WRITE_CAN_USE_READ_PREFETCH
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#define WRITE_CAN_USE_READ_PREFETCH 1
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#define WRITE_CAN_USE_READ_PREFETCH 1
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#endif
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#endif
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/* True if read can be prefetched by a write prefetch. */
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/* True if read can be prefetched by a write prefetch. */
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#ifndef READ_CAN_USE_WRITE_PREFETCH
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#ifndef READ_CAN_USE_WRITE_PREFETCH
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#define READ_CAN_USE_WRITE_PREFETCH 0
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#define READ_CAN_USE_WRITE_PREFETCH 0
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#endif
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#endif
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/* Cache line size. Assumed to be a power of two. */
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/* Cache line size. Assumed to be a power of two. */
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#ifndef PREFETCH_BLOCK
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#ifndef PREFETCH_BLOCK
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#define PREFETCH_BLOCK 32
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#define PREFETCH_BLOCK 32
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#endif
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#endif
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/* Do we have a forward hardware sequential prefetching? */
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/* Do we have a forward hardware sequential prefetching? */
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#ifndef HAVE_FORWARD_PREFETCH
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#ifndef HAVE_FORWARD_PREFETCH
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#define HAVE_FORWARD_PREFETCH 0
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#define HAVE_FORWARD_PREFETCH 0
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#endif
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#endif
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/* Do we have a backward hardware sequential prefetching? */
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/* Do we have a backward hardware sequential prefetching? */
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#ifndef HAVE_BACKWARD_PREFETCH
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#ifndef HAVE_BACKWARD_PREFETCH
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#define HAVE_BACKWARD_PREFETCH 0
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#define HAVE_BACKWARD_PREFETCH 0
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#endif
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#endif
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/* In some cases we are only able to determine that there is a certain
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/* In some cases we are only able to determine that there is a certain
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probability that the two accesses hit the same cache line. In this
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probability that the two accesses hit the same cache line. In this
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case, we issue the prefetches for both of them if this probability
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case, we issue the prefetches for both of them if this probability
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is less then (1000 - ACCEPTABLE_MISS_RATE) promile. */
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is less then (1000 - ACCEPTABLE_MISS_RATE) promile. */
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#ifndef ACCEPTABLE_MISS_RATE
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#ifndef ACCEPTABLE_MISS_RATE
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#define ACCEPTABLE_MISS_RATE 50
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#define ACCEPTABLE_MISS_RATE 50
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#endif
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#endif
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#ifndef HAVE_prefetch
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#ifndef HAVE_prefetch
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#define HAVE_prefetch 0
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#define HAVE_prefetch 0
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#endif
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#endif
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/* The group of references between that reuse may occur. */
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/* The group of references between that reuse may occur. */
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struct mem_ref_group
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struct mem_ref_group
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{
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{
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tree base; /* Base of the reference. */
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tree base; /* Base of the reference. */
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HOST_WIDE_INT step; /* Step of the reference. */
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HOST_WIDE_INT step; /* Step of the reference. */
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struct mem_ref *refs; /* References in the group. */
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struct mem_ref *refs; /* References in the group. */
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struct mem_ref_group *next; /* Next group of references. */
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struct mem_ref_group *next; /* Next group of references. */
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};
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};
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/* Assigned to PREFETCH_BEFORE when all iterations are to be prefetched. */
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/* Assigned to PREFETCH_BEFORE when all iterations are to be prefetched. */
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#define PREFETCH_ALL (~(unsigned HOST_WIDE_INT) 0)
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#define PREFETCH_ALL (~(unsigned HOST_WIDE_INT) 0)
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/* The memory reference. */
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/* The memory reference. */
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struct mem_ref
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struct mem_ref
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{
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{
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tree stmt; /* Statement in that the reference appears. */
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tree stmt; /* Statement in that the reference appears. */
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tree mem; /* The reference. */
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tree mem; /* The reference. */
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HOST_WIDE_INT delta; /* Constant offset of the reference. */
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HOST_WIDE_INT delta; /* Constant offset of the reference. */
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bool write_p; /* Is it a write? */
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bool write_p; /* Is it a write? */
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struct mem_ref_group *group; /* The group of references it belongs to. */
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struct mem_ref_group *group; /* The group of references it belongs to. */
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unsigned HOST_WIDE_INT prefetch_mod;
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unsigned HOST_WIDE_INT prefetch_mod;
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/* Prefetch only each PREFETCH_MOD-th
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/* Prefetch only each PREFETCH_MOD-th
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iteration. */
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iteration. */
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unsigned HOST_WIDE_INT prefetch_before;
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unsigned HOST_WIDE_INT prefetch_before;
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/* Prefetch only first PREFETCH_BEFORE
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/* Prefetch only first PREFETCH_BEFORE
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iterations. */
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iterations. */
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bool issue_prefetch_p; /* Should we really issue the prefetch? */
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bool issue_prefetch_p; /* Should we really issue the prefetch? */
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struct mem_ref *next; /* The next reference in the group. */
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struct mem_ref *next; /* The next reference in the group. */
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};
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};
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/* Dumps information about reference REF to FILE. */
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/* Dumps information about reference REF to FILE. */
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static void
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static void
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dump_mem_ref (FILE *file, struct mem_ref *ref)
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dump_mem_ref (FILE *file, struct mem_ref *ref)
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{
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{
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fprintf (file, "Reference %p:\n", (void *) ref);
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fprintf (file, "Reference %p:\n", (void *) ref);
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fprintf (file, " group %p (base ", (void *) ref->group);
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fprintf (file, " group %p (base ", (void *) ref->group);
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print_generic_expr (file, ref->group->base, TDF_SLIM);
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print_generic_expr (file, ref->group->base, TDF_SLIM);
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fprintf (file, ", step ");
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fprintf (file, ", step ");
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fprintf (file, HOST_WIDE_INT_PRINT_DEC, ref->group->step);
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fprintf (file, HOST_WIDE_INT_PRINT_DEC, ref->group->step);
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fprintf (file, ")\n");
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fprintf (file, ")\n");
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|
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fprintf (dump_file, " delta ");
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fprintf (dump_file, " delta ");
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fprintf (file, HOST_WIDE_INT_PRINT_DEC, ref->delta);
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fprintf (file, HOST_WIDE_INT_PRINT_DEC, ref->delta);
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fprintf (file, "\n");
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fprintf (file, "\n");
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|
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fprintf (file, " %s\n", ref->write_p ? "write" : "read");
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fprintf (file, " %s\n", ref->write_p ? "write" : "read");
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|
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fprintf (file, "\n");
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fprintf (file, "\n");
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}
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}
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/* Finds a group with BASE and STEP in GROUPS, or creates one if it does not
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/* Finds a group with BASE and STEP in GROUPS, or creates one if it does not
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exist. */
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exist. */
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static struct mem_ref_group *
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static struct mem_ref_group *
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find_or_create_group (struct mem_ref_group **groups, tree base,
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find_or_create_group (struct mem_ref_group **groups, tree base,
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HOST_WIDE_INT step)
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HOST_WIDE_INT step)
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{
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{
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struct mem_ref_group *group;
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struct mem_ref_group *group;
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|
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for (; *groups; groups = &(*groups)->next)
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for (; *groups; groups = &(*groups)->next)
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{
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{
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if ((*groups)->step == step
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if ((*groups)->step == step
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&& operand_equal_p ((*groups)->base, base, 0))
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&& operand_equal_p ((*groups)->base, base, 0))
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return *groups;
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return *groups;
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|
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/* Keep the list of groups sorted by decreasing step. */
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/* Keep the list of groups sorted by decreasing step. */
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if ((*groups)->step < step)
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if ((*groups)->step < step)
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break;
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break;
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}
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}
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|
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group = xcalloc (1, sizeof (struct mem_ref_group));
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group = xcalloc (1, sizeof (struct mem_ref_group));
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group->base = base;
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group->base = base;
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group->step = step;
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group->step = step;
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group->refs = NULL;
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group->refs = NULL;
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group->next = *groups;
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group->next = *groups;
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*groups = group;
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*groups = group;
|
|
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return group;
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return group;
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}
|
}
|
|
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/* Records a memory reference MEM in GROUP with offset DELTA and write status
|
/* Records a memory reference MEM in GROUP with offset DELTA and write status
|
WRITE_P. The reference occurs in statement STMT. */
|
WRITE_P. The reference occurs in statement STMT. */
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|
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static void
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static void
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record_ref (struct mem_ref_group *group, tree stmt, tree mem,
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record_ref (struct mem_ref_group *group, tree stmt, tree mem,
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HOST_WIDE_INT delta, bool write_p)
|
HOST_WIDE_INT delta, bool write_p)
|
{
|
{
|
struct mem_ref **aref;
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struct mem_ref **aref;
|
|
|
/* Do not record the same address twice. */
|
/* Do not record the same address twice. */
|
for (aref = &group->refs; *aref; aref = &(*aref)->next)
|
for (aref = &group->refs; *aref; aref = &(*aref)->next)
|
{
|
{
|
/* It does not have to be possible for write reference to reuse the read
|
/* It does not have to be possible for write reference to reuse the read
|
prefetch, or vice versa. */
|
prefetch, or vice versa. */
|
if (!WRITE_CAN_USE_READ_PREFETCH
|
if (!WRITE_CAN_USE_READ_PREFETCH
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&& write_p
|
&& write_p
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&& !(*aref)->write_p)
|
&& !(*aref)->write_p)
|
continue;
|
continue;
|
if (!READ_CAN_USE_WRITE_PREFETCH
|
if (!READ_CAN_USE_WRITE_PREFETCH
|
&& !write_p
|
&& !write_p
|
&& (*aref)->write_p)
|
&& (*aref)->write_p)
|
continue;
|
continue;
|
|
|
if ((*aref)->delta == delta)
|
if ((*aref)->delta == delta)
|
return;
|
return;
|
}
|
}
|
|
|
(*aref) = xcalloc (1, sizeof (struct mem_ref));
|
(*aref) = xcalloc (1, sizeof (struct mem_ref));
|
(*aref)->stmt = stmt;
|
(*aref)->stmt = stmt;
|
(*aref)->mem = mem;
|
(*aref)->mem = mem;
|
(*aref)->delta = delta;
|
(*aref)->delta = delta;
|
(*aref)->write_p = write_p;
|
(*aref)->write_p = write_p;
|
(*aref)->prefetch_before = PREFETCH_ALL;
|
(*aref)->prefetch_before = PREFETCH_ALL;
|
(*aref)->prefetch_mod = 1;
|
(*aref)->prefetch_mod = 1;
|
(*aref)->issue_prefetch_p = false;
|
(*aref)->issue_prefetch_p = false;
|
(*aref)->group = group;
|
(*aref)->group = group;
|
(*aref)->next = NULL;
|
(*aref)->next = NULL;
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
dump_mem_ref (dump_file, *aref);
|
dump_mem_ref (dump_file, *aref);
|
}
|
}
|
|
|
/* Release memory references in GROUPS. */
|
/* Release memory references in GROUPS. */
|
|
|
static void
|
static void
|
release_mem_refs (struct mem_ref_group *groups)
|
release_mem_refs (struct mem_ref_group *groups)
|
{
|
{
|
struct mem_ref_group *next_g;
|
struct mem_ref_group *next_g;
|
struct mem_ref *ref, *next_r;
|
struct mem_ref *ref, *next_r;
|
|
|
for (; groups; groups = next_g)
|
for (; groups; groups = next_g)
|
{
|
{
|
next_g = groups->next;
|
next_g = groups->next;
|
for (ref = groups->refs; ref; ref = next_r)
|
for (ref = groups->refs; ref; ref = next_r)
|
{
|
{
|
next_r = ref->next;
|
next_r = ref->next;
|
free (ref);
|
free (ref);
|
}
|
}
|
free (groups);
|
free (groups);
|
}
|
}
|
}
|
}
|
|
|
/* A structure used to pass arguments to idx_analyze_ref. */
|
/* A structure used to pass arguments to idx_analyze_ref. */
|
|
|
struct ar_data
|
struct ar_data
|
{
|
{
|
struct loop *loop; /* Loop of the reference. */
|
struct loop *loop; /* Loop of the reference. */
|
tree stmt; /* Statement of the reference. */
|
tree stmt; /* Statement of the reference. */
|
HOST_WIDE_INT *step; /* Step of the memory reference. */
|
HOST_WIDE_INT *step; /* Step of the memory reference. */
|
HOST_WIDE_INT *delta; /* Offset of the memory reference. */
|
HOST_WIDE_INT *delta; /* Offset of the memory reference. */
|
};
|
};
|
|
|
/* Analyzes a single INDEX of a memory reference to obtain information
|
/* Analyzes a single INDEX of a memory reference to obtain information
|
described at analyze_ref. Callback for for_each_index. */
|
described at analyze_ref. Callback for for_each_index. */
|
|
|
static bool
|
static bool
|
idx_analyze_ref (tree base, tree *index, void *data)
|
idx_analyze_ref (tree base, tree *index, void *data)
|
{
|
{
|
struct ar_data *ar_data = data;
|
struct ar_data *ar_data = data;
|
tree ibase, step, stepsize;
|
tree ibase, step, stepsize;
|
HOST_WIDE_INT istep, idelta = 0, imult = 1;
|
HOST_WIDE_INT istep, idelta = 0, imult = 1;
|
affine_iv iv;
|
affine_iv iv;
|
|
|
if (TREE_CODE (base) == MISALIGNED_INDIRECT_REF
|
if (TREE_CODE (base) == MISALIGNED_INDIRECT_REF
|
|| TREE_CODE (base) == ALIGN_INDIRECT_REF)
|
|| TREE_CODE (base) == ALIGN_INDIRECT_REF)
|
return false;
|
return false;
|
|
|
if (!simple_iv (ar_data->loop, ar_data->stmt, *index, &iv, false))
|
if (!simple_iv (ar_data->loop, ar_data->stmt, *index, &iv, false))
|
return false;
|
return false;
|
ibase = iv.base;
|
ibase = iv.base;
|
step = iv.step;
|
step = iv.step;
|
|
|
if (zero_p (step))
|
if (zero_p (step))
|
istep = 0;
|
istep = 0;
|
else
|
else
|
{
|
{
|
if (!cst_and_fits_in_hwi (step))
|
if (!cst_and_fits_in_hwi (step))
|
return false;
|
return false;
|
istep = int_cst_value (step);
|
istep = int_cst_value (step);
|
}
|
}
|
|
|
if (TREE_CODE (ibase) == PLUS_EXPR
|
if (TREE_CODE (ibase) == PLUS_EXPR
|
&& cst_and_fits_in_hwi (TREE_OPERAND (ibase, 1)))
|
&& cst_and_fits_in_hwi (TREE_OPERAND (ibase, 1)))
|
{
|
{
|
idelta = int_cst_value (TREE_OPERAND (ibase, 1));
|
idelta = int_cst_value (TREE_OPERAND (ibase, 1));
|
ibase = TREE_OPERAND (ibase, 0);
|
ibase = TREE_OPERAND (ibase, 0);
|
}
|
}
|
if (cst_and_fits_in_hwi (ibase))
|
if (cst_and_fits_in_hwi (ibase))
|
{
|
{
|
idelta += int_cst_value (ibase);
|
idelta += int_cst_value (ibase);
|
ibase = build_int_cst (TREE_TYPE (ibase), 0);
|
ibase = build_int_cst (TREE_TYPE (ibase), 0);
|
}
|
}
|
|
|
if (TREE_CODE (base) == ARRAY_REF)
|
if (TREE_CODE (base) == ARRAY_REF)
|
{
|
{
|
stepsize = array_ref_element_size (base);
|
stepsize = array_ref_element_size (base);
|
if (!cst_and_fits_in_hwi (stepsize))
|
if (!cst_and_fits_in_hwi (stepsize))
|
return false;
|
return false;
|
imult = int_cst_value (stepsize);
|
imult = int_cst_value (stepsize);
|
|
|
istep *= imult;
|
istep *= imult;
|
idelta *= imult;
|
idelta *= imult;
|
}
|
}
|
|
|
*ar_data->step += istep;
|
*ar_data->step += istep;
|
*ar_data->delta += idelta;
|
*ar_data->delta += idelta;
|
*index = ibase;
|
*index = ibase;
|
|
|
return true;
|
return true;
|
}
|
}
|
|
|
/* Tries to express REF_P in shape &BASE + STEP * iter + DELTA, where DELTA and
|
/* Tries to express REF_P in shape &BASE + STEP * iter + DELTA, where DELTA and
|
STEP are integer constants and iter is number of iterations of LOOP. The
|
STEP are integer constants and iter is number of iterations of LOOP. The
|
reference occurs in statement STMT. Strips nonaddressable component
|
reference occurs in statement STMT. Strips nonaddressable component
|
references from REF_P. */
|
references from REF_P. */
|
|
|
static bool
|
static bool
|
analyze_ref (struct loop *loop, tree *ref_p, tree *base,
|
analyze_ref (struct loop *loop, tree *ref_p, tree *base,
|
HOST_WIDE_INT *step, HOST_WIDE_INT *delta,
|
HOST_WIDE_INT *step, HOST_WIDE_INT *delta,
|
tree stmt)
|
tree stmt)
|
{
|
{
|
struct ar_data ar_data;
|
struct ar_data ar_data;
|
tree off;
|
tree off;
|
HOST_WIDE_INT bit_offset;
|
HOST_WIDE_INT bit_offset;
|
tree ref = *ref_p;
|
tree ref = *ref_p;
|
|
|
*step = 0;
|
*step = 0;
|
*delta = 0;
|
*delta = 0;
|
|
|
/* First strip off the component references. Ignore bitfields. */
|
/* First strip off the component references. Ignore bitfields. */
|
if (TREE_CODE (ref) == COMPONENT_REF
|
if (TREE_CODE (ref) == COMPONENT_REF
|
&& DECL_NONADDRESSABLE_P (TREE_OPERAND (ref, 1)))
|
&& DECL_NONADDRESSABLE_P (TREE_OPERAND (ref, 1)))
|
ref = TREE_OPERAND (ref, 0);
|
ref = TREE_OPERAND (ref, 0);
|
|
|
*ref_p = ref;
|
*ref_p = ref;
|
|
|
for (; TREE_CODE (ref) == COMPONENT_REF; ref = TREE_OPERAND (ref, 0))
|
for (; TREE_CODE (ref) == COMPONENT_REF; ref = TREE_OPERAND (ref, 0))
|
{
|
{
|
off = DECL_FIELD_BIT_OFFSET (TREE_OPERAND (ref, 1));
|
off = DECL_FIELD_BIT_OFFSET (TREE_OPERAND (ref, 1));
|
bit_offset = TREE_INT_CST_LOW (off);
|
bit_offset = TREE_INT_CST_LOW (off);
|
gcc_assert (bit_offset % BITS_PER_UNIT == 0);
|
gcc_assert (bit_offset % BITS_PER_UNIT == 0);
|
|
|
*delta += bit_offset / BITS_PER_UNIT;
|
*delta += bit_offset / BITS_PER_UNIT;
|
}
|
}
|
|
|
*base = unshare_expr (ref);
|
*base = unshare_expr (ref);
|
ar_data.loop = loop;
|
ar_data.loop = loop;
|
ar_data.stmt = stmt;
|
ar_data.stmt = stmt;
|
ar_data.step = step;
|
ar_data.step = step;
|
ar_data.delta = delta;
|
ar_data.delta = delta;
|
return for_each_index (base, idx_analyze_ref, &ar_data);
|
return for_each_index (base, idx_analyze_ref, &ar_data);
|
}
|
}
|
|
|
/* Record a memory reference REF to the list REFS. The reference occurs in
|
/* Record a memory reference REF to the list REFS. The reference occurs in
|
LOOP in statement STMT and it is write if WRITE_P. */
|
LOOP in statement STMT and it is write if WRITE_P. */
|
|
|
static void
|
static void
|
gather_memory_references_ref (struct loop *loop, struct mem_ref_group **refs,
|
gather_memory_references_ref (struct loop *loop, struct mem_ref_group **refs,
|
tree ref, bool write_p, tree stmt)
|
tree ref, bool write_p, tree stmt)
|
{
|
{
|
tree base;
|
tree base;
|
HOST_WIDE_INT step, delta;
|
HOST_WIDE_INT step, delta;
|
struct mem_ref_group *agrp;
|
struct mem_ref_group *agrp;
|
|
|
if (!analyze_ref (loop, &ref, &base, &step, &delta, stmt))
|
if (!analyze_ref (loop, &ref, &base, &step, &delta, stmt))
|
return;
|
return;
|
|
|
/* Now we know that REF = &BASE + STEP * iter + DELTA, where DELTA and STEP
|
/* Now we know that REF = &BASE + STEP * iter + DELTA, where DELTA and STEP
|
are integer constants. */
|
are integer constants. */
|
agrp = find_or_create_group (refs, base, step);
|
agrp = find_or_create_group (refs, base, step);
|
record_ref (agrp, stmt, ref, delta, write_p);
|
record_ref (agrp, stmt, ref, delta, write_p);
|
}
|
}
|
|
|
/* Record the suitable memory references in LOOP. */
|
/* Record the suitable memory references in LOOP. */
|
|
|
static struct mem_ref_group *
|
static struct mem_ref_group *
|
gather_memory_references (struct loop *loop)
|
gather_memory_references (struct loop *loop)
|
{
|
{
|
basic_block *body = get_loop_body_in_dom_order (loop);
|
basic_block *body = get_loop_body_in_dom_order (loop);
|
basic_block bb;
|
basic_block bb;
|
unsigned i;
|
unsigned i;
|
block_stmt_iterator bsi;
|
block_stmt_iterator bsi;
|
tree stmt, lhs, rhs;
|
tree stmt, lhs, rhs;
|
struct mem_ref_group *refs = NULL;
|
struct mem_ref_group *refs = NULL;
|
|
|
/* Scan the loop body in order, so that the former references precede the
|
/* Scan the loop body in order, so that the former references precede the
|
later ones. */
|
later ones. */
|
for (i = 0; i < loop->num_nodes; i++)
|
for (i = 0; i < loop->num_nodes; i++)
|
{
|
{
|
bb = body[i];
|
bb = body[i];
|
if (bb->loop_father != loop)
|
if (bb->loop_father != loop)
|
continue;
|
continue;
|
|
|
for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
|
for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
|
{
|
{
|
stmt = bsi_stmt (bsi);
|
stmt = bsi_stmt (bsi);
|
if (TREE_CODE (stmt) != MODIFY_EXPR)
|
if (TREE_CODE (stmt) != MODIFY_EXPR)
|
continue;
|
continue;
|
|
|
lhs = TREE_OPERAND (stmt, 0);
|
lhs = TREE_OPERAND (stmt, 0);
|
rhs = TREE_OPERAND (stmt, 1);
|
rhs = TREE_OPERAND (stmt, 1);
|
|
|
if (REFERENCE_CLASS_P (rhs))
|
if (REFERENCE_CLASS_P (rhs))
|
gather_memory_references_ref (loop, &refs, rhs, false, stmt);
|
gather_memory_references_ref (loop, &refs, rhs, false, stmt);
|
if (REFERENCE_CLASS_P (lhs))
|
if (REFERENCE_CLASS_P (lhs))
|
gather_memory_references_ref (loop, &refs, lhs, true, stmt);
|
gather_memory_references_ref (loop, &refs, lhs, true, stmt);
|
}
|
}
|
}
|
}
|
free (body);
|
free (body);
|
|
|
return refs;
|
return refs;
|
}
|
}
|
|
|
/* Prune the prefetch candidate REF using the self-reuse. */
|
/* Prune the prefetch candidate REF using the self-reuse. */
|
|
|
static void
|
static void
|
prune_ref_by_self_reuse (struct mem_ref *ref)
|
prune_ref_by_self_reuse (struct mem_ref *ref)
|
{
|
{
|
HOST_WIDE_INT step = ref->group->step;
|
HOST_WIDE_INT step = ref->group->step;
|
bool backward = step < 0;
|
bool backward = step < 0;
|
|
|
if (step == 0)
|
if (step == 0)
|
{
|
{
|
/* Prefetch references to invariant address just once. */
|
/* Prefetch references to invariant address just once. */
|
ref->prefetch_before = 1;
|
ref->prefetch_before = 1;
|
return;
|
return;
|
}
|
}
|
|
|
if (backward)
|
if (backward)
|
step = -step;
|
step = -step;
|
|
|
if (step > PREFETCH_BLOCK)
|
if (step > PREFETCH_BLOCK)
|
return;
|
return;
|
|
|
if ((backward && HAVE_BACKWARD_PREFETCH)
|
if ((backward && HAVE_BACKWARD_PREFETCH)
|
|| (!backward && HAVE_FORWARD_PREFETCH))
|
|| (!backward && HAVE_FORWARD_PREFETCH))
|
{
|
{
|
ref->prefetch_before = 1;
|
ref->prefetch_before = 1;
|
return;
|
return;
|
}
|
}
|
|
|
ref->prefetch_mod = PREFETCH_BLOCK / step;
|
ref->prefetch_mod = PREFETCH_BLOCK / step;
|
}
|
}
|
|
|
/* Divides X by BY, rounding down. */
|
/* Divides X by BY, rounding down. */
|
|
|
static HOST_WIDE_INT
|
static HOST_WIDE_INT
|
ddown (HOST_WIDE_INT x, unsigned HOST_WIDE_INT by)
|
ddown (HOST_WIDE_INT x, unsigned HOST_WIDE_INT by)
|
{
|
{
|
gcc_assert (by > 0);
|
gcc_assert (by > 0);
|
|
|
if (x >= 0)
|
if (x >= 0)
|
return x / by;
|
return x / by;
|
else
|
else
|
return (x + by - 1) / by;
|
return (x + by - 1) / by;
|
}
|
}
|
|
|
/* Prune the prefetch candidate REF using the reuse with BY.
|
/* Prune the prefetch candidate REF using the reuse with BY.
|
If BY_IS_BEFORE is true, BY is before REF in the loop. */
|
If BY_IS_BEFORE is true, BY is before REF in the loop. */
|
|
|
static void
|
static void
|
prune_ref_by_group_reuse (struct mem_ref *ref, struct mem_ref *by,
|
prune_ref_by_group_reuse (struct mem_ref *ref, struct mem_ref *by,
|
bool by_is_before)
|
bool by_is_before)
|
{
|
{
|
HOST_WIDE_INT step = ref->group->step;
|
HOST_WIDE_INT step = ref->group->step;
|
bool backward = step < 0;
|
bool backward = step < 0;
|
HOST_WIDE_INT delta_r = ref->delta, delta_b = by->delta;
|
HOST_WIDE_INT delta_r = ref->delta, delta_b = by->delta;
|
HOST_WIDE_INT delta = delta_b - delta_r;
|
HOST_WIDE_INT delta = delta_b - delta_r;
|
HOST_WIDE_INT hit_from;
|
HOST_WIDE_INT hit_from;
|
unsigned HOST_WIDE_INT prefetch_before, prefetch_block;
|
unsigned HOST_WIDE_INT prefetch_before, prefetch_block;
|
|
|
if (delta == 0)
|
if (delta == 0)
|
{
|
{
|
/* If the references has the same address, only prefetch the
|
/* If the references has the same address, only prefetch the
|
former. */
|
former. */
|
if (by_is_before)
|
if (by_is_before)
|
ref->prefetch_before = 0;
|
ref->prefetch_before = 0;
|
|
|
return;
|
return;
|
}
|
}
|
|
|
if (!step)
|
if (!step)
|
{
|
{
|
/* If the reference addresses are invariant and fall into the
|
/* If the reference addresses are invariant and fall into the
|
same cache line, prefetch just the first one. */
|
same cache line, prefetch just the first one. */
|
if (!by_is_before)
|
if (!by_is_before)
|
return;
|
return;
|
|
|
if (ddown (ref->delta, PREFETCH_BLOCK)
|
if (ddown (ref->delta, PREFETCH_BLOCK)
|
!= ddown (by->delta, PREFETCH_BLOCK))
|
!= ddown (by->delta, PREFETCH_BLOCK))
|
return;
|
return;
|
|
|
ref->prefetch_before = 0;
|
ref->prefetch_before = 0;
|
return;
|
return;
|
}
|
}
|
|
|
/* Only prune the reference that is behind in the array. */
|
/* Only prune the reference that is behind in the array. */
|
if (backward)
|
if (backward)
|
{
|
{
|
if (delta > 0)
|
if (delta > 0)
|
return;
|
return;
|
|
|
/* Transform the data so that we may assume that the accesses
|
/* Transform the data so that we may assume that the accesses
|
are forward. */
|
are forward. */
|
delta = - delta;
|
delta = - delta;
|
step = -step;
|
step = -step;
|
delta_r = PREFETCH_BLOCK - 1 - delta_r;
|
delta_r = PREFETCH_BLOCK - 1 - delta_r;
|
delta_b = PREFETCH_BLOCK - 1 - delta_b;
|
delta_b = PREFETCH_BLOCK - 1 - delta_b;
|
}
|
}
|
else
|
else
|
{
|
{
|
if (delta < 0)
|
if (delta < 0)
|
return;
|
return;
|
}
|
}
|
|
|
/* Check whether the two references are likely to hit the same cache
|
/* Check whether the two references are likely to hit the same cache
|
line, and how distant the iterations in that it occurs are from
|
line, and how distant the iterations in that it occurs are from
|
each other. */
|
each other. */
|
|
|
if (step <= PREFETCH_BLOCK)
|
if (step <= PREFETCH_BLOCK)
|
{
|
{
|
/* The accesses are sure to meet. Let us check when. */
|
/* The accesses are sure to meet. Let us check when. */
|
hit_from = ddown (delta_b, PREFETCH_BLOCK) * PREFETCH_BLOCK;
|
hit_from = ddown (delta_b, PREFETCH_BLOCK) * PREFETCH_BLOCK;
|
prefetch_before = (hit_from - delta_r + step - 1) / step;
|
prefetch_before = (hit_from - delta_r + step - 1) / step;
|
|
|
if (prefetch_before < ref->prefetch_before)
|
if (prefetch_before < ref->prefetch_before)
|
ref->prefetch_before = prefetch_before;
|
ref->prefetch_before = prefetch_before;
|
|
|
return;
|
return;
|
}
|
}
|
|
|
/* A more complicated case. First let us ensure that size of cache line
|
/* A more complicated case. First let us ensure that size of cache line
|
and step are coprime (here we assume that PREFETCH_BLOCK is a power
|
and step are coprime (here we assume that PREFETCH_BLOCK is a power
|
of two. */
|
of two. */
|
prefetch_block = PREFETCH_BLOCK;
|
prefetch_block = PREFETCH_BLOCK;
|
while ((step & 1) == 0
|
while ((step & 1) == 0
|
&& prefetch_block > 1)
|
&& prefetch_block > 1)
|
{
|
{
|
step >>= 1;
|
step >>= 1;
|
prefetch_block >>= 1;
|
prefetch_block >>= 1;
|
delta >>= 1;
|
delta >>= 1;
|
}
|
}
|
|
|
/* Now step > prefetch_block, and step and prefetch_block are coprime.
|
/* Now step > prefetch_block, and step and prefetch_block are coprime.
|
Determine the probability that the accesses hit the same cache line. */
|
Determine the probability that the accesses hit the same cache line. */
|
|
|
prefetch_before = delta / step;
|
prefetch_before = delta / step;
|
delta %= step;
|
delta %= step;
|
if ((unsigned HOST_WIDE_INT) delta
|
if ((unsigned HOST_WIDE_INT) delta
|
<= (prefetch_block * ACCEPTABLE_MISS_RATE / 1000))
|
<= (prefetch_block * ACCEPTABLE_MISS_RATE / 1000))
|
{
|
{
|
if (prefetch_before < ref->prefetch_before)
|
if (prefetch_before < ref->prefetch_before)
|
ref->prefetch_before = prefetch_before;
|
ref->prefetch_before = prefetch_before;
|
|
|
return;
|
return;
|
}
|
}
|
|
|
/* Try also the following iteration. */
|
/* Try also the following iteration. */
|
prefetch_before++;
|
prefetch_before++;
|
delta = step - delta;
|
delta = step - delta;
|
if ((unsigned HOST_WIDE_INT) delta
|
if ((unsigned HOST_WIDE_INT) delta
|
<= (prefetch_block * ACCEPTABLE_MISS_RATE / 1000))
|
<= (prefetch_block * ACCEPTABLE_MISS_RATE / 1000))
|
{
|
{
|
if (prefetch_before < ref->prefetch_before)
|
if (prefetch_before < ref->prefetch_before)
|
ref->prefetch_before = prefetch_before;
|
ref->prefetch_before = prefetch_before;
|
|
|
return;
|
return;
|
}
|
}
|
|
|
/* The ref probably does not reuse by. */
|
/* The ref probably does not reuse by. */
|
return;
|
return;
|
}
|
}
|
|
|
/* Prune the prefetch candidate REF using the reuses with other references
|
/* Prune the prefetch candidate REF using the reuses with other references
|
in REFS. */
|
in REFS. */
|
|
|
static void
|
static void
|
prune_ref_by_reuse (struct mem_ref *ref, struct mem_ref *refs)
|
prune_ref_by_reuse (struct mem_ref *ref, struct mem_ref *refs)
|
{
|
{
|
struct mem_ref *prune_by;
|
struct mem_ref *prune_by;
|
bool before = true;
|
bool before = true;
|
|
|
prune_ref_by_self_reuse (ref);
|
prune_ref_by_self_reuse (ref);
|
|
|
for (prune_by = refs; prune_by; prune_by = prune_by->next)
|
for (prune_by = refs; prune_by; prune_by = prune_by->next)
|
{
|
{
|
if (prune_by == ref)
|
if (prune_by == ref)
|
{
|
{
|
before = false;
|
before = false;
|
continue;
|
continue;
|
}
|
}
|
|
|
if (!WRITE_CAN_USE_READ_PREFETCH
|
if (!WRITE_CAN_USE_READ_PREFETCH
|
&& ref->write_p
|
&& ref->write_p
|
&& !prune_by->write_p)
|
&& !prune_by->write_p)
|
continue;
|
continue;
|
if (!READ_CAN_USE_WRITE_PREFETCH
|
if (!READ_CAN_USE_WRITE_PREFETCH
|
&& !ref->write_p
|
&& !ref->write_p
|
&& prune_by->write_p)
|
&& prune_by->write_p)
|
continue;
|
continue;
|
|
|
prune_ref_by_group_reuse (ref, prune_by, before);
|
prune_ref_by_group_reuse (ref, prune_by, before);
|
}
|
}
|
}
|
}
|
|
|
/* Prune the prefetch candidates in GROUP using the reuse analysis. */
|
/* Prune the prefetch candidates in GROUP using the reuse analysis. */
|
|
|
static void
|
static void
|
prune_group_by_reuse (struct mem_ref_group *group)
|
prune_group_by_reuse (struct mem_ref_group *group)
|
{
|
{
|
struct mem_ref *ref_pruned;
|
struct mem_ref *ref_pruned;
|
|
|
for (ref_pruned = group->refs; ref_pruned; ref_pruned = ref_pruned->next)
|
for (ref_pruned = group->refs; ref_pruned; ref_pruned = ref_pruned->next)
|
{
|
{
|
prune_ref_by_reuse (ref_pruned, group->refs);
|
prune_ref_by_reuse (ref_pruned, group->refs);
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
{
|
{
|
fprintf (dump_file, "Reference %p:", (void *) ref_pruned);
|
fprintf (dump_file, "Reference %p:", (void *) ref_pruned);
|
|
|
if (ref_pruned->prefetch_before == PREFETCH_ALL
|
if (ref_pruned->prefetch_before == PREFETCH_ALL
|
&& ref_pruned->prefetch_mod == 1)
|
&& ref_pruned->prefetch_mod == 1)
|
fprintf (dump_file, " no restrictions");
|
fprintf (dump_file, " no restrictions");
|
else if (ref_pruned->prefetch_before == 0)
|
else if (ref_pruned->prefetch_before == 0)
|
fprintf (dump_file, " do not prefetch");
|
fprintf (dump_file, " do not prefetch");
|
else if (ref_pruned->prefetch_before <= ref_pruned->prefetch_mod)
|
else if (ref_pruned->prefetch_before <= ref_pruned->prefetch_mod)
|
fprintf (dump_file, " prefetch once");
|
fprintf (dump_file, " prefetch once");
|
else
|
else
|
{
|
{
|
if (ref_pruned->prefetch_before != PREFETCH_ALL)
|
if (ref_pruned->prefetch_before != PREFETCH_ALL)
|
{
|
{
|
fprintf (dump_file, " prefetch before ");
|
fprintf (dump_file, " prefetch before ");
|
fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
|
fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
|
ref_pruned->prefetch_before);
|
ref_pruned->prefetch_before);
|
}
|
}
|
if (ref_pruned->prefetch_mod != 1)
|
if (ref_pruned->prefetch_mod != 1)
|
{
|
{
|
fprintf (dump_file, " prefetch mod ");
|
fprintf (dump_file, " prefetch mod ");
|
fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
|
fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
|
ref_pruned->prefetch_mod);
|
ref_pruned->prefetch_mod);
|
}
|
}
|
}
|
}
|
fprintf (dump_file, "\n");
|
fprintf (dump_file, "\n");
|
}
|
}
|
}
|
}
|
}
|
}
|
|
|
/* Prune the list of prefetch candidates GROUPS using the reuse analysis. */
|
/* Prune the list of prefetch candidates GROUPS using the reuse analysis. */
|
|
|
static void
|
static void
|
prune_by_reuse (struct mem_ref_group *groups)
|
prune_by_reuse (struct mem_ref_group *groups)
|
{
|
{
|
for (; groups; groups = groups->next)
|
for (; groups; groups = groups->next)
|
prune_group_by_reuse (groups);
|
prune_group_by_reuse (groups);
|
}
|
}
|
|
|
/* Returns true if we should issue prefetch for REF. */
|
/* Returns true if we should issue prefetch for REF. */
|
|
|
static bool
|
static bool
|
should_issue_prefetch_p (struct mem_ref *ref)
|
should_issue_prefetch_p (struct mem_ref *ref)
|
{
|
{
|
/* For now do not issue prefetches for only first few of the
|
/* For now do not issue prefetches for only first few of the
|
iterations. */
|
iterations. */
|
if (ref->prefetch_before != PREFETCH_ALL)
|
if (ref->prefetch_before != PREFETCH_ALL)
|
return false;
|
return false;
|
|
|
return true;
|
return true;
|
}
|
}
|
|
|
/* Decide which of the prefetch candidates in GROUPS to prefetch.
|
/* Decide which of the prefetch candidates in GROUPS to prefetch.
|
AHEAD is the number of iterations to prefetch ahead (which corresponds
|
AHEAD is the number of iterations to prefetch ahead (which corresponds
|
to the number of simultaneous instances of one prefetch running at a
|
to the number of simultaneous instances of one prefetch running at a
|
time). UNROLL_FACTOR is the factor by that the loop is going to be
|
time). UNROLL_FACTOR is the factor by that the loop is going to be
|
unrolled. Returns true if there is anything to prefetch. */
|
unrolled. Returns true if there is anything to prefetch. */
|
|
|
static bool
|
static bool
|
schedule_prefetches (struct mem_ref_group *groups, unsigned unroll_factor,
|
schedule_prefetches (struct mem_ref_group *groups, unsigned unroll_factor,
|
unsigned ahead)
|
unsigned ahead)
|
{
|
{
|
unsigned max_prefetches, n_prefetches;
|
unsigned max_prefetches, n_prefetches;
|
struct mem_ref *ref;
|
struct mem_ref *ref;
|
bool any = false;
|
bool any = false;
|
|
|
max_prefetches = (SIMULTANEOUS_PREFETCHES * unroll_factor) / ahead;
|
max_prefetches = (SIMULTANEOUS_PREFETCHES * unroll_factor) / ahead;
|
if (max_prefetches > (unsigned) SIMULTANEOUS_PREFETCHES)
|
if (max_prefetches > (unsigned) SIMULTANEOUS_PREFETCHES)
|
max_prefetches = SIMULTANEOUS_PREFETCHES;
|
max_prefetches = SIMULTANEOUS_PREFETCHES;
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, "Max prefetches to issue: %d.\n", max_prefetches);
|
fprintf (dump_file, "Max prefetches to issue: %d.\n", max_prefetches);
|
|
|
if (!max_prefetches)
|
if (!max_prefetches)
|
return false;
|
return false;
|
|
|
/* For now we just take memory references one by one and issue
|
/* For now we just take memory references one by one and issue
|
prefetches for as many as possible. The groups are sorted
|
prefetches for as many as possible. The groups are sorted
|
starting with the largest step, since the references with
|
starting with the largest step, since the references with
|
large step are more likely to cause many cache misses. */
|
large step are more likely to cause many cache misses. */
|
|
|
for (; groups; groups = groups->next)
|
for (; groups; groups = groups->next)
|
for (ref = groups->refs; ref; ref = ref->next)
|
for (ref = groups->refs; ref; ref = ref->next)
|
{
|
{
|
if (!should_issue_prefetch_p (ref))
|
if (!should_issue_prefetch_p (ref))
|
continue;
|
continue;
|
|
|
ref->issue_prefetch_p = true;
|
ref->issue_prefetch_p = true;
|
|
|
/* If prefetch_mod is less then unroll_factor, we need to insert
|
/* If prefetch_mod is less then unroll_factor, we need to insert
|
several prefetches for the reference. */
|
several prefetches for the reference. */
|
n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
|
n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
|
/ ref->prefetch_mod);
|
/ ref->prefetch_mod);
|
if (max_prefetches <= n_prefetches)
|
if (max_prefetches <= n_prefetches)
|
return true;
|
return true;
|
|
|
max_prefetches -= n_prefetches;
|
max_prefetches -= n_prefetches;
|
any = true;
|
any = true;
|
}
|
}
|
|
|
return any;
|
return any;
|
}
|
}
|
|
|
/* Determine whether there is any reference suitable for prefetching
|
/* Determine whether there is any reference suitable for prefetching
|
in GROUPS. */
|
in GROUPS. */
|
|
|
static bool
|
static bool
|
anything_to_prefetch_p (struct mem_ref_group *groups)
|
anything_to_prefetch_p (struct mem_ref_group *groups)
|
{
|
{
|
struct mem_ref *ref;
|
struct mem_ref *ref;
|
|
|
for (; groups; groups = groups->next)
|
for (; groups; groups = groups->next)
|
for (ref = groups->refs; ref; ref = ref->next)
|
for (ref = groups->refs; ref; ref = ref->next)
|
if (should_issue_prefetch_p (ref))
|
if (should_issue_prefetch_p (ref))
|
return true;
|
return true;
|
|
|
return false;
|
return false;
|
}
|
}
|
|
|
/* Issue prefetches for the reference REF into loop as decided before.
|
/* Issue prefetches for the reference REF into loop as decided before.
|
HEAD is the number of iterations to prefetch ahead. UNROLL_FACTOR
|
HEAD is the number of iterations to prefetch ahead. UNROLL_FACTOR
|
is the factor by which LOOP was unrolled. */
|
is the factor by which LOOP was unrolled. */
|
|
|
static void
|
static void
|
issue_prefetch_ref (struct mem_ref *ref, unsigned unroll_factor, unsigned ahead)
|
issue_prefetch_ref (struct mem_ref *ref, unsigned unroll_factor, unsigned ahead)
|
{
|
{
|
HOST_WIDE_INT delta;
|
HOST_WIDE_INT delta;
|
tree addr, addr_base, prefetch, params, write_p;
|
tree addr, addr_base, prefetch, params, write_p;
|
block_stmt_iterator bsi;
|
block_stmt_iterator bsi;
|
unsigned n_prefetches, ap;
|
unsigned n_prefetches, ap;
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, "Issued prefetch for %p.\n", (void *) ref);
|
fprintf (dump_file, "Issued prefetch for %p.\n", (void *) ref);
|
|
|
bsi = bsi_for_stmt (ref->stmt);
|
bsi = bsi_for_stmt (ref->stmt);
|
|
|
n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
|
n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
|
/ ref->prefetch_mod);
|
/ ref->prefetch_mod);
|
addr_base = build_fold_addr_expr_with_type (ref->mem, ptr_type_node);
|
addr_base = build_fold_addr_expr_with_type (ref->mem, ptr_type_node);
|
addr_base = force_gimple_operand_bsi (&bsi, unshare_expr (addr_base), true, NULL);
|
addr_base = force_gimple_operand_bsi (&bsi, unshare_expr (addr_base), true, NULL);
|
|
|
for (ap = 0; ap < n_prefetches; ap++)
|
for (ap = 0; ap < n_prefetches; ap++)
|
{
|
{
|
/* Determine the address to prefetch. */
|
/* Determine the address to prefetch. */
|
delta = (ahead + ap * ref->prefetch_mod) * ref->group->step;
|
delta = (ahead + ap * ref->prefetch_mod) * ref->group->step;
|
addr = fold_build2 (PLUS_EXPR, ptr_type_node,
|
addr = fold_build2 (PLUS_EXPR, ptr_type_node,
|
addr_base, build_int_cst (ptr_type_node, delta));
|
addr_base, build_int_cst (ptr_type_node, delta));
|
addr = force_gimple_operand_bsi (&bsi, unshare_expr (addr), true, NULL);
|
addr = force_gimple_operand_bsi (&bsi, unshare_expr (addr), true, NULL);
|
|
|
/* Create the prefetch instruction. */
|
/* Create the prefetch instruction. */
|
write_p = ref->write_p ? integer_one_node : integer_zero_node;
|
write_p = ref->write_p ? integer_one_node : integer_zero_node;
|
params = tree_cons (NULL_TREE, addr,
|
params = tree_cons (NULL_TREE, addr,
|
tree_cons (NULL_TREE, write_p, NULL_TREE));
|
tree_cons (NULL_TREE, write_p, NULL_TREE));
|
|
|
prefetch = build_function_call_expr (built_in_decls[BUILT_IN_PREFETCH],
|
prefetch = build_function_call_expr (built_in_decls[BUILT_IN_PREFETCH],
|
params);
|
params);
|
bsi_insert_before (&bsi, prefetch, BSI_SAME_STMT);
|
bsi_insert_before (&bsi, prefetch, BSI_SAME_STMT);
|
}
|
}
|
}
|
}
|
|
|
/* Issue prefetches for the references in GROUPS into loop as decided before.
|
/* Issue prefetches for the references in GROUPS into loop as decided before.
|
HEAD is the number of iterations to prefetch ahead. UNROLL_FACTOR is the
|
HEAD is the number of iterations to prefetch ahead. UNROLL_FACTOR is the
|
factor by that LOOP was unrolled. */
|
factor by that LOOP was unrolled. */
|
|
|
static void
|
static void
|
issue_prefetches (struct mem_ref_group *groups,
|
issue_prefetches (struct mem_ref_group *groups,
|
unsigned unroll_factor, unsigned ahead)
|
unsigned unroll_factor, unsigned ahead)
|
{
|
{
|
struct mem_ref *ref;
|
struct mem_ref *ref;
|
|
|
for (; groups; groups = groups->next)
|
for (; groups; groups = groups->next)
|
for (ref = groups->refs; ref; ref = ref->next)
|
for (ref = groups->refs; ref; ref = ref->next)
|
if (ref->issue_prefetch_p)
|
if (ref->issue_prefetch_p)
|
issue_prefetch_ref (ref, unroll_factor, ahead);
|
issue_prefetch_ref (ref, unroll_factor, ahead);
|
}
|
}
|
|
|
/* Determines whether we can profitably unroll LOOP FACTOR times, and if
|
/* Determines whether we can profitably unroll LOOP FACTOR times, and if
|
this is the case, fill in DESC by the description of number of
|
this is the case, fill in DESC by the description of number of
|
iterations. */
|
iterations. */
|
|
|
static bool
|
static bool
|
should_unroll_loop_p (struct loop *loop, struct tree_niter_desc *desc,
|
should_unroll_loop_p (struct loop *loop, struct tree_niter_desc *desc,
|
unsigned factor)
|
unsigned factor)
|
{
|
{
|
if (!can_unroll_loop_p (loop, factor, desc))
|
if (!can_unroll_loop_p (loop, factor, desc))
|
return false;
|
return false;
|
|
|
/* We only consider loops without control flow for unrolling. This is not
|
/* We only consider loops without control flow for unrolling. This is not
|
a hard restriction -- tree_unroll_loop works with arbitrary loops
|
a hard restriction -- tree_unroll_loop works with arbitrary loops
|
as well; but the unrolling/prefetching is usually more profitable for
|
as well; but the unrolling/prefetching is usually more profitable for
|
loops consisting of a single basic block, and we want to limit the
|
loops consisting of a single basic block, and we want to limit the
|
code growth. */
|
code growth. */
|
if (loop->num_nodes > 2)
|
if (loop->num_nodes > 2)
|
return false;
|
return false;
|
|
|
return true;
|
return true;
|
}
|
}
|
|
|
/* Determine the coefficient by that unroll LOOP, from the information
|
/* Determine the coefficient by that unroll LOOP, from the information
|
contained in the list of memory references REFS. Description of
|
contained in the list of memory references REFS. Description of
|
umber of iterations of LOOP is stored to DESC. AHEAD is the number
|
umber of iterations of LOOP is stored to DESC. AHEAD is the number
|
of iterations ahead that we need to prefetch. NINSNS is number of
|
of iterations ahead that we need to prefetch. NINSNS is number of
|
insns of the LOOP. */
|
insns of the LOOP. */
|
|
|
static unsigned
|
static unsigned
|
determine_unroll_factor (struct loop *loop, struct mem_ref_group *refs,
|
determine_unroll_factor (struct loop *loop, struct mem_ref_group *refs,
|
unsigned ahead, unsigned ninsns,
|
unsigned ahead, unsigned ninsns,
|
struct tree_niter_desc *desc)
|
struct tree_niter_desc *desc)
|
{
|
{
|
unsigned upper_bound, size_factor, constraint_factor;
|
unsigned upper_bound, size_factor, constraint_factor;
|
unsigned factor, max_mod_constraint, ahead_factor;
|
unsigned factor, max_mod_constraint, ahead_factor;
|
struct mem_ref_group *agp;
|
struct mem_ref_group *agp;
|
struct mem_ref *ref;
|
struct mem_ref *ref;
|
|
|
upper_bound = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES);
|
upper_bound = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES);
|
|
|
/* First check whether the loop is not too large to unroll. */
|
/* First check whether the loop is not too large to unroll. */
|
size_factor = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / ninsns;
|
size_factor = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / ninsns;
|
if (size_factor <= 1)
|
if (size_factor <= 1)
|
return 1;
|
return 1;
|
|
|
if (size_factor < upper_bound)
|
if (size_factor < upper_bound)
|
upper_bound = size_factor;
|
upper_bound = size_factor;
|
|
|
max_mod_constraint = 1;
|
max_mod_constraint = 1;
|
for (agp = refs; agp; agp = agp->next)
|
for (agp = refs; agp; agp = agp->next)
|
for (ref = agp->refs; ref; ref = ref->next)
|
for (ref = agp->refs; ref; ref = ref->next)
|
if (should_issue_prefetch_p (ref)
|
if (should_issue_prefetch_p (ref)
|
&& ref->prefetch_mod > max_mod_constraint)
|
&& ref->prefetch_mod > max_mod_constraint)
|
max_mod_constraint = ref->prefetch_mod;
|
max_mod_constraint = ref->prefetch_mod;
|
|
|
/* Set constraint_factor as large as needed to be able to satisfy the
|
/* Set constraint_factor as large as needed to be able to satisfy the
|
largest modulo constraint. */
|
largest modulo constraint. */
|
constraint_factor = max_mod_constraint;
|
constraint_factor = max_mod_constraint;
|
|
|
/* If ahead is too large in comparison with the number of available
|
/* If ahead is too large in comparison with the number of available
|
prefetches, unroll the loop as much as needed to be able to prefetch
|
prefetches, unroll the loop as much as needed to be able to prefetch
|
at least partially some of the references in the loop. */
|
at least partially some of the references in the loop. */
|
ahead_factor = ((ahead + SIMULTANEOUS_PREFETCHES - 1)
|
ahead_factor = ((ahead + SIMULTANEOUS_PREFETCHES - 1)
|
/ SIMULTANEOUS_PREFETCHES);
|
/ SIMULTANEOUS_PREFETCHES);
|
|
|
/* Unroll as much as useful, but bound the code size growth. */
|
/* Unroll as much as useful, but bound the code size growth. */
|
if (constraint_factor < ahead_factor)
|
if (constraint_factor < ahead_factor)
|
factor = ahead_factor;
|
factor = ahead_factor;
|
else
|
else
|
factor = constraint_factor;
|
factor = constraint_factor;
|
if (factor > upper_bound)
|
if (factor > upper_bound)
|
factor = upper_bound;
|
factor = upper_bound;
|
|
|
if (!should_unroll_loop_p (loop, desc, factor))
|
if (!should_unroll_loop_p (loop, desc, factor))
|
return 1;
|
return 1;
|
|
|
return factor;
|
return factor;
|
}
|
}
|
|
|
/* Issue prefetch instructions for array references in LOOP. Returns
|
/* Issue prefetch instructions for array references in LOOP. Returns
|
true if the LOOP was unrolled. LOOPS is the array containing all
|
true if the LOOP was unrolled. LOOPS is the array containing all
|
loops. */
|
loops. */
|
|
|
static bool
|
static bool
|
loop_prefetch_arrays (struct loops *loops, struct loop *loop)
|
loop_prefetch_arrays (struct loops *loops, struct loop *loop)
|
{
|
{
|
struct mem_ref_group *refs;
|
struct mem_ref_group *refs;
|
unsigned ahead, ninsns, unroll_factor;
|
unsigned ahead, ninsns, unroll_factor;
|
struct tree_niter_desc desc;
|
struct tree_niter_desc desc;
|
bool unrolled = false;
|
bool unrolled = false;
|
|
|
/* Step 1: gather the memory references. */
|
/* Step 1: gather the memory references. */
|
refs = gather_memory_references (loop);
|
refs = gather_memory_references (loop);
|
|
|
/* Step 2: estimate the reuse effects. */
|
/* Step 2: estimate the reuse effects. */
|
prune_by_reuse (refs);
|
prune_by_reuse (refs);
|
|
|
if (!anything_to_prefetch_p (refs))
|
if (!anything_to_prefetch_p (refs))
|
goto fail;
|
goto fail;
|
|
|
/* Step 3: determine the ahead and unroll factor. */
|
/* Step 3: determine the ahead and unroll factor. */
|
|
|
/* FIXME: We should use not size of the loop, but the average number of
|
/* FIXME: We should use not size of the loop, but the average number of
|
instructions executed per iteration of the loop. */
|
instructions executed per iteration of the loop. */
|
ninsns = tree_num_loop_insns (loop);
|
ninsns = tree_num_loop_insns (loop);
|
ahead = (PREFETCH_LATENCY + ninsns - 1) / ninsns;
|
ahead = (PREFETCH_LATENCY + ninsns - 1) / ninsns;
|
unroll_factor = determine_unroll_factor (loop, refs, ahead, ninsns,
|
unroll_factor = determine_unroll_factor (loop, refs, ahead, ninsns,
|
&desc);
|
&desc);
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, "Ahead %d, unroll factor %d\n", ahead, unroll_factor);
|
fprintf (dump_file, "Ahead %d, unroll factor %d\n", ahead, unroll_factor);
|
|
|
/* If the loop rolls less than the required unroll factor, prefetching
|
/* If the loop rolls less than the required unroll factor, prefetching
|
is useless. */
|
is useless. */
|
if (unroll_factor > 1
|
if (unroll_factor > 1
|
&& cst_and_fits_in_hwi (desc.niter)
|
&& cst_and_fits_in_hwi (desc.niter)
|
&& (unsigned HOST_WIDE_INT) int_cst_value (desc.niter) < unroll_factor)
|
&& (unsigned HOST_WIDE_INT) int_cst_value (desc.niter) < unroll_factor)
|
goto fail;
|
goto fail;
|
|
|
/* Step 4: what to prefetch? */
|
/* Step 4: what to prefetch? */
|
if (!schedule_prefetches (refs, unroll_factor, ahead))
|
if (!schedule_prefetches (refs, unroll_factor, ahead))
|
goto fail;
|
goto fail;
|
|
|
/* Step 5: unroll the loop. TODO -- peeling of first and last few
|
/* Step 5: unroll the loop. TODO -- peeling of first and last few
|
iterations so that we do not issue superfluous prefetches. */
|
iterations so that we do not issue superfluous prefetches. */
|
if (unroll_factor != 1)
|
if (unroll_factor != 1)
|
{
|
{
|
tree_unroll_loop (loops, loop, unroll_factor,
|
tree_unroll_loop (loops, loop, unroll_factor,
|
single_dom_exit (loop), &desc);
|
single_dom_exit (loop), &desc);
|
unrolled = true;
|
unrolled = true;
|
}
|
}
|
|
|
/* Step 6: issue the prefetches. */
|
/* Step 6: issue the prefetches. */
|
issue_prefetches (refs, unroll_factor, ahead);
|
issue_prefetches (refs, unroll_factor, ahead);
|
|
|
fail:
|
fail:
|
release_mem_refs (refs);
|
release_mem_refs (refs);
|
return unrolled;
|
return unrolled;
|
}
|
}
|
|
|
/* Issue prefetch instructions for array references in LOOPS. */
|
/* Issue prefetch instructions for array references in LOOPS. */
|
|
|
unsigned int
|
unsigned int
|
tree_ssa_prefetch_arrays (struct loops *loops)
|
tree_ssa_prefetch_arrays (struct loops *loops)
|
{
|
{
|
unsigned i;
|
unsigned i;
|
struct loop *loop;
|
struct loop *loop;
|
bool unrolled = false;
|
bool unrolled = false;
|
int todo_flags = 0;
|
int todo_flags = 0;
|
|
|
if (!HAVE_prefetch
|
if (!HAVE_prefetch
|
/* It is possible to ask compiler for say -mtune=i486 -march=pentium4.
|
/* It is possible to ask compiler for say -mtune=i486 -march=pentium4.
|
-mtune=i486 causes us having PREFETCH_BLOCK 0, since this is part
|
-mtune=i486 causes us having PREFETCH_BLOCK 0, since this is part
|
of processor costs and i486 does not have prefetch, but
|
of processor costs and i486 does not have prefetch, but
|
-march=pentium4 causes HAVE_prefetch to be true. Ugh. */
|
-march=pentium4 causes HAVE_prefetch to be true. Ugh. */
|
|| PREFETCH_BLOCK == 0)
|
|| PREFETCH_BLOCK == 0)
|
return 0;
|
return 0;
|
|
|
initialize_original_copy_tables ();
|
initialize_original_copy_tables ();
|
|
|
if (!built_in_decls[BUILT_IN_PREFETCH])
|
if (!built_in_decls[BUILT_IN_PREFETCH])
|
{
|
{
|
tree type = build_function_type (void_type_node,
|
tree type = build_function_type (void_type_node,
|
tree_cons (NULL_TREE,
|
tree_cons (NULL_TREE,
|
const_ptr_type_node,
|
const_ptr_type_node,
|
NULL_TREE));
|
NULL_TREE));
|
tree decl = lang_hooks.builtin_function ("__builtin_prefetch", type,
|
tree decl = lang_hooks.builtin_function ("__builtin_prefetch", type,
|
BUILT_IN_PREFETCH, BUILT_IN_NORMAL,
|
BUILT_IN_PREFETCH, BUILT_IN_NORMAL,
|
NULL, NULL_TREE);
|
NULL, NULL_TREE);
|
DECL_IS_NOVOPS (decl) = true;
|
DECL_IS_NOVOPS (decl) = true;
|
built_in_decls[BUILT_IN_PREFETCH] = decl;
|
built_in_decls[BUILT_IN_PREFETCH] = decl;
|
}
|
}
|
|
|
/* We assume that size of cache line is a power of two, so verify this
|
/* We assume that size of cache line is a power of two, so verify this
|
here. */
|
here. */
|
gcc_assert ((PREFETCH_BLOCK & (PREFETCH_BLOCK - 1)) == 0);
|
gcc_assert ((PREFETCH_BLOCK & (PREFETCH_BLOCK - 1)) == 0);
|
|
|
for (i = loops->num - 1; i > 0; i--)
|
for (i = loops->num - 1; i > 0; i--)
|
{
|
{
|
loop = loops->parray[i];
|
loop = loops->parray[i];
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, "Processing loop %d:\n", loop->num);
|
fprintf (dump_file, "Processing loop %d:\n", loop->num);
|
|
|
if (loop)
|
if (loop)
|
unrolled |= loop_prefetch_arrays (loops, loop);
|
unrolled |= loop_prefetch_arrays (loops, loop);
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, "\n\n");
|
fprintf (dump_file, "\n\n");
|
}
|
}
|
|
|
if (unrolled)
|
if (unrolled)
|
{
|
{
|
scev_reset ();
|
scev_reset ();
|
todo_flags |= TODO_cleanup_cfg;
|
todo_flags |= TODO_cleanup_cfg;
|
}
|
}
|
|
|
free_original_copy_tables ();
|
free_original_copy_tables ();
|
return todo_flags;
|
return todo_flags;
|
}
|
}
|
|
|
