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/* Predictive commoning.
Copyright (C) 2005-2017 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 3, or (at your option) any
later version.
GCC is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
/* This file implements the predictive commoning optimization. Predictive
commoning can be viewed as CSE around a loop, and with some improvements,
as generalized strength reduction-- i.e., reusing values computed in
earlier iterations of a loop in the later ones. So far, the pass only
handles the most useful case, that is, reusing values of memory references.
If you think this is all just a special case of PRE, you are sort of right;
however, concentrating on loops is simpler, and makes it possible to
incorporate data dependence analysis to detect the opportunities, perform
loop unrolling to avoid copies together with renaming immediately,
and if needed, we could also take register pressure into account.
Let us demonstrate what is done on an example:
for (i = 0; i < 100; i++)
{
a[i+2] = a[i] + a[i+1];
b[10] = b[10] + i;
c[i] = c[99 - i];
d[i] = d[i + 1];
}
1) We find data references in the loop, and split them to mutually
independent groups (i.e., we find components of a data dependence
graph). We ignore read-read dependences whose distance is not constant.
(TODO -- we could also ignore antidependences). In this example, we
find the following groups:
a[i]{read}, a[i+1]{read}, a[i+2]{write}
b[10]{read}, b[10]{write}
c[99 - i]{read}, c[i]{write}
d[i + 1]{read}, d[i]{write}
2) Inside each of the group, we verify several conditions:
a) all the references must differ in indices only, and the indices
must all have the same step
b) the references must dominate loop latch (and thus, they must be
ordered by dominance relation).
c) the distance of the indices must be a small multiple of the step
We are then able to compute the difference of the references (# of
iterations before they point to the same place as the first of them).
Also, in case there are writes in the loop, we split the groups into
chains whose head is the write whose values are used by the reads in
the same chain. The chains are then processed independently,
making the further transformations simpler. Also, the shorter chains
need the same number of registers, but may require lower unrolling
factor in order to get rid of the copies on the loop latch.
In our example, we get the following chains (the chain for c is invalid).
a[i]{read,+0}, a[i+1]{read,-1}, a[i+2]{write,-2}
b[10]{read,+0}, b[10]{write,+0}
d[i + 1]{read,+0}, d[i]{write,+1}
3) For each read, we determine the read or write whose value it reuses,
together with the distance of this reuse. I.e. we take the last
reference before it with distance 0, or the last of the references
with the smallest positive distance to the read. Then, we remove
the references that are not used in any of these chains, discard the
empty groups, and propagate all the links so that they point to the
single root reference of the chain (adjusting their distance
appropriately). Some extra care needs to be taken for references with
step 0. In our example (the numbers indicate the distance of the
reuse),
a[i] --> (*) 2, a[i+1] --> (*) 1, a[i+2] (*)
b[10] --> (*) 1, b[10] (*)
4) The chains are combined together if possible. If the corresponding
elements of two chains are always combined together with the same
operator, we remember just the result of this combination, instead
of remembering the values separately. We may need to perform
reassociation to enable combining, for example
e[i] + f[i+1] + e[i+1] + f[i]
can be reassociated as
(e[i] + f[i]) + (e[i+1] + f[i+1])
and we can combine the chains for e and f into one chain.
5) For each root reference (end of the chain) R, let N be maximum distance
of a reference reusing its value. Variables R0 up to RN are created,
together with phi nodes that transfer values from R1 .. RN to
R0 .. R(N-1).
Initial values are loaded to R0..R(N-1) (in case not all references
must necessarily be accessed and they may trap, we may fail here;
TODO sometimes, the loads could be guarded by a check for the number
of iterations). Values loaded/stored in roots are also copied to
RN. Other reads are replaced with the appropriate variable Ri.
Everything is put to SSA form.
As a small improvement, if R0 is dead after the root (i.e., all uses of
the value with the maximum distance dominate the root), we can avoid
creating RN and use R0 instead of it.
In our example, we get (only the parts concerning a and b are shown):
for (i = 0; i < 100; i++)
{
f = phi (a[0], s);
s = phi (a[1], f);
x = phi (b[10], x);
f = f + s;
a[i+2] = f;
x = x + i;
b[10] = x;
}
6) Factor F for unrolling is determined as the smallest common multiple of
(N + 1) for each root reference (N for references for that we avoided
creating RN). If F and the loop is small enough, loop is unrolled F
times. The stores to RN (R0) in the copies of the loop body are
periodically replaced with R0, R1, ... (R1, R2, ...), so that they can
be coalesced and the copies can be eliminated.
TODO -- copy propagation and other optimizations may change the live
ranges of the temporary registers and prevent them from being coalesced;
this may increase the register pressure.
In our case, F = 2 and the (main loop of the) result is
for (i = 0; i < ...; i += 2)
{
f = phi (a[0], f);
s = phi (a[1], s);
x = phi (b[10], x);
f = f + s;
a[i+2] = f;
x = x + i;
b[10] = x;
s = s + f;
a[i+3] = s;
x = x + i;
b[10] = x;
}
TODO -- stores killing other stores can be taken into account, e.g.,
for (i = 0; i < n; i++)
{
a[i] = 1;
a[i+2] = 2;
}
can be replaced with
t0 = a[0];
t1 = a[1];
for (i = 0; i < n; i++)
{
a[i] = 1;
t2 = 2;
t0 = t1;
t1 = t2;
}
a[n] = t0;
a[n+1] = t1;
The interesting part is that this would generalize store motion; still, since
sm is performed elsewhere, it does not seem that important.
Predictive commoning can be generalized for arbitrary computations (not
just memory loads), and also nontrivial transfer functions (e.g., replacing
i * i with ii_last + 2 * i + 1), to generalize strength reduction. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "rtl.h"
#include "tree.h"
#include "gimple.h"
#include "predict.h"
#include "tree-pass.h"
#include "ssa.h"
#include "gimple-pretty-print.h"
#include "alias.h"
#include "fold-const.h"
#include "cfgloop.h"
#include "tree-eh.h"
#include "gimplify.h"
#include "gimple-iterator.h"
#include "gimplify-me.h"
#include "tree-ssa-loop-ivopts.h"
#include "tree-ssa-loop-manip.h"
#include "tree-ssa-loop-niter.h"
#include "tree-ssa-loop.h"
#include "tree-into-ssa.h"
#include "tree-dfa.h"
#include "tree-ssa.h"
#include "tree-data-ref.h"
#include "tree-scalar-evolution.h"
#include "params.h"
#include "tree-affine.h"
#include "builtins.h"
/* The maximum number of iterations between the considered memory
references. */
#define MAX_DISTANCE (target_avail_regs < 16 ? 4 : 8)
/* Data references (or phi nodes that carry data reference values across
loop iterations). */
typedef struct dref_d
{
/* The reference itself. */
struct data_reference *ref;
/* The statement in that the reference appears. */
gimple *stmt;
/* In case that STMT is a phi node, this field is set to the SSA name
defined by it in replace_phis_by_defined_names (in order to avoid
pointing to phi node that got reallocated in the meantime). */
tree name_defined_by_phi;
/* Distance of the reference from the root of the chain (in number of
iterations of the loop). */
unsigned distance;
/* Number of iterations offset from the first reference in the component. */
widest_int offset;
/* Number of the reference in a component, in dominance ordering. */
unsigned pos;
/* True if the memory reference is always accessed when the loop is
entered. */
unsigned always_accessed : 1;
} *dref;
/* Type of the chain of the references. */
enum chain_type
{
/* The addresses of the references in the chain are constant. */
CT_INVARIANT,
/* There are only loads in the chain. */
CT_LOAD,
/* Root of the chain is store, the rest are loads. */
CT_STORE_LOAD,
/* A combination of two chains. */
CT_COMBINATION
};
/* Chains of data references. */
typedef struct chain
{
/* Type of the chain. */
enum chain_type type;
/* For combination chains, the operator and the two chains that are
combined, and the type of the result. */
enum tree_code op;
tree rslt_type;
struct chain *ch1, *ch2;
/* The references in the chain. */
vec<dref> refs;
/* The maximum distance of the reference in the chain from the root. */
unsigned length;
/* The variables used to copy the value throughout iterations. */
vec<tree> vars;
/* Initializers for the variables. */
vec<tree> inits;
/* True if there is a use of a variable with the maximal distance
that comes after the root in the loop. */
unsigned has_max_use_after : 1;
/* True if all the memory references in the chain are always accessed. */
unsigned all_always_accessed : 1;
/* True if this chain was combined together with some other chain. */
unsigned combined : 1;
} *chain_p;
/* Describes the knowledge about the step of the memory references in
the component. */
enum ref_step_type
{
/* The step is zero. */
RS_INVARIANT,
/* The step is nonzero. */
RS_NONZERO,
/* The step may or may not be nonzero. */
RS_ANY
};
/* Components of the data dependence graph. */
struct component
{
/* The references in the component. */
vec<dref> refs;
/* What we know about the step of the references in the component. */
enum ref_step_type comp_step;
/* Next component in the list. */
struct component *next;
};
/* Bitmap of ssa names defined by looparound phi nodes covered by chains. */
static bitmap looparound_phis;
/* Cache used by tree_to_aff_combination_expand. */
static hash_map<tree, name_expansion *> *name_expansions;
/* Dumps data reference REF to FILE. */
extern void dump_dref (FILE *, dref);
void
dump_dref (FILE *file, dref ref)
{
if (ref->ref)
{
fprintf (file, " ");
print_generic_expr (file, DR_REF (ref->ref), TDF_SLIM);
fprintf (file, " (id %u%s)\n", ref->pos,
DR_IS_READ (ref->ref) ? "" : ", write");
fprintf (file, " offset ");
print_decs (ref->offset, file);
fprintf (file, "\n");
fprintf (file, " distance %u\n", ref->distance);
}
else
{
if (gimple_code (ref->stmt) == GIMPLE_PHI)
fprintf (file, " looparound ref\n");
else
fprintf (file, " combination ref\n");
fprintf (file, " in statement ");
print_gimple_stmt (file, ref->stmt, 0, TDF_SLIM);
fprintf (file, "\n");
fprintf (file, " distance %u\n", ref->distance);
}
}
/* Dumps CHAIN to FILE. */
extern void dump_chain (FILE *, chain_p);
void
dump_chain (FILE *file, chain_p chain)
{
dref a;
const char *chain_type;
unsigned i;
tree var;
switch (chain->type)
{
case CT_INVARIANT:
chain_type = "Load motion";
break;
case CT_LOAD:
chain_type = "Loads-only";
break;
case CT_STORE_LOAD:
chain_type = "Store-loads";
break;
case CT_COMBINATION:
chain_type = "Combination";
break;
default:
gcc_unreachable ();
}
fprintf (file, "%s chain %p%s\n", chain_type, (void *) chain,
chain->combined ? " (combined)" : "");
if (chain->type != CT_INVARIANT)
fprintf (file, " max distance %u%s\n", chain->length,
chain->has_max_use_after ? "" : ", may reuse first");
if (chain->type == CT_COMBINATION)
{
fprintf (file, " equal to %p %s %p in type ",
(void *) chain->ch1, op_symbol_code (chain->op),
(void *) chain->ch2);
print_generic_expr (file, chain->rslt_type, TDF_SLIM);
fprintf (file, "\n");
}
if (chain->vars.exists ())
{
fprintf (file, " vars");
FOR_EACH_VEC_ELT (chain->vars, i, var)
{
fprintf (file, " ");
print_generic_expr (file, var, TDF_SLIM);
}
fprintf (file, "\n");
}
if (chain->inits.exists ())
{
fprintf (file, " inits");
FOR_EACH_VEC_ELT (chain->inits, i, var)
{
fprintf (file, " ");
print_generic_expr (file, var, TDF_SLIM);
}
fprintf (file, "\n");
}
fprintf (file, " references:\n");
FOR_EACH_VEC_ELT (chain->refs, i, a)
dump_dref (file, a);
fprintf (file, "\n");
}
/* Dumps CHAINS to FILE. */
extern void dump_chains (FILE *, vec<chain_p> );
void
dump_chains (FILE *file, vec<chain_p> chains)
{
chain_p chain;
unsigned i;
FOR_EACH_VEC_ELT (chains, i, chain)
dump_chain (file, chain);
}
/* Dumps COMP to FILE. */
extern void dump_component (FILE *, struct component *);
void
dump_component (FILE *file, struct component *comp)
{
dref a;
unsigned i;
fprintf (file, "Component%s:\n",
comp->comp_step == RS_INVARIANT ? " (invariant)" : "");
FOR_EACH_VEC_ELT (comp->refs, i, a)
dump_dref (file, a);
fprintf (file, "\n");
}
/* Dumps COMPS to FILE. */
extern void dump_components (FILE *, struct component *);
void
dump_components (FILE *file, struct component *comps)
{
struct component *comp;
for (comp = comps; comp; comp = comp->next)
dump_component (file, comp);
}
/* Frees a chain CHAIN. */
static void
release_chain (chain_p chain)
{
dref ref;
unsigned i;
if (chain == NULL)
return;
FOR_EACH_VEC_ELT (chain->refs, i, ref)
free (ref);
chain->refs.release ();
chain->vars.release ();
chain->inits.release ();
free (chain);
}
/* Frees CHAINS. */
static void
release_chains (vec<chain_p> chains)
{
unsigned i;
chain_p chain;
FOR_EACH_VEC_ELT (chains, i, chain)
release_chain (chain);
chains.release ();
}
/* Frees a component COMP. */
static void
release_component (struct component *comp)
{
comp->refs.release ();
free (comp);
}
/* Frees list of components COMPS. */
static void
release_components (struct component *comps)
{
struct component *act, *next;
for (act = comps; act; act = next)
{
next = act->next;
release_component (act);
}
}
/* Finds a root of tree given by FATHERS containing A, and performs path
shortening. */
static unsigned
component_of (unsigned fathers[], unsigned a)
{
unsigned root, n;
for (root = a; root != fathers[root]; root = fathers[root])
continue;
for (; a != root; a = n)
{
n = fathers[a];
fathers[a] = root;
}
return root;
}
/* Join operation for DFU. FATHERS gives the tree, SIZES are sizes of the
components, A and B are components to merge. */
static void
merge_comps (unsigned fathers[], unsigned sizes[], unsigned a, unsigned b)
{
unsigned ca = component_of (fathers, a);
unsigned cb = component_of (fathers, b);
if (ca == cb)
return;
if (sizes[ca] < sizes[cb])
{
sizes[cb] += sizes[ca];
fathers[ca] = cb;
}
else
{
sizes[ca] += sizes[cb];
fathers[cb] = ca;
}
}
/* Returns true if A is a reference that is suitable for predictive commoning
in the innermost loop that contains it. REF_STEP is set according to the
step of the reference A. */
static bool
suitable_reference_p (struct data_reference *a, enum ref_step_type *ref_step)
{
tree ref = DR_REF (a), step = DR_STEP (a);
if (!step
|| TREE_THIS_VOLATILE (ref)
|| !is_gimple_reg_type (TREE_TYPE (ref))
|| tree_could_throw_p (ref))
return false;
if (integer_zerop (step))
*ref_step = RS_INVARIANT;
else if (integer_nonzerop (step))
*ref_step = RS_NONZERO;
else
*ref_step = RS_ANY;
return true;
}
/* Stores DR_OFFSET (DR) + DR_INIT (DR) to OFFSET. */
static void
aff_combination_dr_offset (struct data_reference *dr, aff_tree *offset)
{
tree type = TREE_TYPE (DR_OFFSET (dr));
aff_tree delta;
tree_to_aff_combination_expand (DR_OFFSET (dr), type, offset,
&name_expansions);
aff_combination_const (&delta, type, wi::to_widest (DR_INIT (dr)));
aff_combination_add (offset, &delta);
}
/* Determines number of iterations of the innermost enclosing loop before B
refers to exactly the same location as A and stores it to OFF. If A and
B do not have the same step, they never meet, or anything else fails,
returns false, otherwise returns true. Both A and B are assumed to
satisfy suitable_reference_p. */
static bool
determine_offset (struct data_reference *a, struct data_reference *b,
widest_int *off)
{
aff_tree diff, baseb, step;
tree typea, typeb;
/* Check that both the references access the location in the same type. */
typea = TREE_TYPE (DR_REF (a));
typeb = TREE_TYPE (DR_REF (b));
if (!useless_type_conversion_p (typeb, typea))
return false;
/* Check whether the base address and the step of both references is the
same. */
if (!operand_equal_p (DR_STEP (a), DR_STEP (b), 0)
|| !operand_equal_p (DR_BASE_ADDRESS (a), DR_BASE_ADDRESS (b), 0))
return false;
if (integer_zerop (DR_STEP (a)))
{
/* If the references have loop invariant address, check that they access
exactly the same location. */
*off = 0;
return (operand_equal_p (DR_OFFSET (a), DR_OFFSET (b), 0)
&& operand_equal_p (DR_INIT (a), DR_INIT (b), 0));
}
/* Compare the offsets of the addresses, and check whether the difference
is a multiple of step. */
aff_combination_dr_offset (a, &diff);
aff_combination_dr_offset (b, &baseb);
aff_combination_scale (&baseb, -1);
aff_combination_add (&diff, &baseb);
tree_to_aff_combination_expand (DR_STEP (a), TREE_TYPE (DR_STEP (a)),
&step, &name_expansions);
return aff_combination_constant_multiple_p (&diff, &step, off);
}
/* Returns the last basic block in LOOP for that we are sure that
it is executed whenever the loop is entered. */
static basic_block
last_always_executed_block (struct loop *loop)
{
unsigned i;
vec<edge> exits = get_loop_exit_edges (loop);
edge ex;
basic_block last = loop->latch;
FOR_EACH_VEC_ELT (exits, i, ex)
last = nearest_common_dominator (CDI_DOMINATORS, last, ex->src);
exits.release ();
return last;
}
/* Splits dependence graph on DATAREFS described by DEPENDS to components. */
static struct component *
split_data_refs_to_components (struct loop *loop,
vec<data_reference_p> datarefs,
vec<ddr_p> depends)
{
unsigned i, n = datarefs.length ();
unsigned ca, ia, ib, bad;
unsigned *comp_father = XNEWVEC (unsigned, n + 1);
unsigned *comp_size = XNEWVEC (unsigned, n + 1);
struct component **comps;
struct data_reference *dr, *dra, *drb;
struct data_dependence_relation *ddr;
struct component *comp_list = NULL, *comp;
dref dataref;
basic_block last_always_executed = last_always_executed_block (loop);
FOR_EACH_VEC_ELT (datarefs, i, dr)
{
if (!DR_REF (dr))
{
/* A fake reference for call or asm_expr that may clobber memory;
just fail. */
goto end;
}
/* predcom pass isn't prepared to handle calls with data references. */
if (is_gimple_call (DR_STMT (dr)))
goto end;
dr->aux = (void *) (size_t) i;
comp_father[i] = i;
comp_size[i] = 1;
}
/* A component reserved for the "bad" data references. */
comp_father[n] = n;
comp_size[n] = 1;
FOR_EACH_VEC_ELT (datarefs, i, dr)
{
enum ref_step_type dummy;
if (!suitable_reference_p (dr, &dummy))
{
ia = (unsigned) (size_t) dr->aux;
merge_comps (comp_father, comp_size, n, ia);
}
}
FOR_EACH_VEC_ELT (depends, i, ddr)
{
widest_int dummy_off;
if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
continue;
dra = DDR_A (ddr);
drb = DDR_B (ddr);
ia = component_of (comp_father, (unsigned) (size_t) dra->aux);
ib = component_of (comp_father, (unsigned) (size_t) drb->aux);
if (ia == ib)
continue;
bad = component_of (comp_father, n);
/* If both A and B are reads, we may ignore unsuitable dependences. */
if (DR_IS_READ (dra) && DR_IS_READ (drb))
{
if (ia == bad || ib == bad
|| !determine_offset (dra, drb, &dummy_off))
continue;
}
/* If A is read and B write or vice versa and there is unsuitable
dependence, instead of merging both components into a component
that will certainly not pass suitable_component_p, just put the
read into bad component, perhaps at least the write together with
all the other data refs in it's component will be optimizable. */
else if (DR_IS_READ (dra) && ib != bad)
{
if (ia == bad)
continue;
else if (!determine_offset (dra, drb, &dummy_off))
{
merge_comps (comp_father, comp_size, bad, ia);
continue;
}
}
else if (DR_IS_READ (drb) && ia != bad)
{
if (ib == bad)
continue;
else if (!determine_offset (dra, drb, &dummy_off))
{
merge_comps (comp_father, comp_size, bad, ib);
continue;
}
}
merge_comps (comp_father, comp_size, ia, ib);
}
comps = XCNEWVEC (struct component *, n);
bad = component_of (comp_father, n);
FOR_EACH_VEC_ELT (datarefs, i, dr)
{
ia = (unsigned) (size_t) dr->aux;
ca = component_of (comp_father, ia);
if (ca == bad)
continue;
comp = comps[ca];
if (!comp)
{
comp = XCNEW (struct component);
comp->refs.create (comp_size[ca]);
comps[ca] = comp;
}
dataref = XCNEW (struct dref_d);
dataref->ref = dr;
dataref->stmt = DR_STMT (dr);
dataref->offset = 0;
dataref->distance = 0;
dataref->always_accessed
= dominated_by_p (CDI_DOMINATORS, last_always_executed,
gimple_bb (dataref->stmt));
dataref->pos = comp->refs.length ();
comp->refs.quick_push (dataref);
}
for (i = 0; i < n; i++)
{
comp = comps[i];
if (comp)
{
comp->next = comp_list;
comp_list = comp;
}
}
free (comps);
end:
free (comp_father);
free (comp_size);
return comp_list;
}
/* Returns true if the component COMP satisfies the conditions
described in 2) at the beginning of this file. LOOP is the current
loop. */
static bool
suitable_component_p (struct loop *loop, struct component *comp)
{
unsigned i;
dref a, first;
basic_block ba, bp = loop->header;
bool ok, has_write = false;
FOR_EACH_VEC_ELT (comp->refs, i, a)
{
ba = gimple_bb (a->stmt);
if (!just_once_each_iteration_p (loop, ba))
return false;
gcc_assert (dominated_by_p (CDI_DOMINATORS, ba, bp));
bp = ba;
if (DR_IS_WRITE (a->ref))
has_write = true;
}
first = comp->refs[0];
ok = suitable_reference_p (first->ref, &comp->comp_step);
gcc_assert (ok);
first->offset = 0;
for (i = 1; comp->refs.iterate (i, &a); i++)
{
if (!determine_offset (first->ref, a->ref, &a->offset))
return false;
enum ref_step_type a_step;
gcc_checking_assert (suitable_reference_p (a->ref, &a_step)
&& a_step == comp->comp_step);
}
/* If there is a write inside the component, we must know whether the
step is nonzero or not -- we would not otherwise be able to recognize
whether the value accessed by reads comes from the OFFSET-th iteration
or the previous one. */
if (has_write && comp->comp_step == RS_ANY)
return false;
return true;
}
/* Check the conditions on references inside each of components COMPS,
and remove the unsuitable components from the list. The new list
of components is returned. The conditions are described in 2) at
the beginning of this file. LOOP is the current loop. */
static struct component *
filter_suitable_components (struct loop *loop, struct component *comps)
{
struct component **comp, *act;
for (comp = &comps; *comp; )
{
act = *comp;
if (suitable_component_p (loop, act))
comp = &act->next;
else
{
dref ref;
unsigned i;
*comp = act->next;
FOR_EACH_VEC_ELT (act->refs, i, ref)
free (ref);
release_component (act);
}
}
return comps;
}
/* Compares two drefs A and B by their offset and position. Callback for
qsort. */
static int
order_drefs (const void *a, const void *b)
{
const dref *const da = (const dref *) a;
const dref *const db = (const dref *) b;
int offcmp = wi::cmps ((*da)->offset, (*db)->offset);
if (offcmp != 0)
return offcmp;
return (*da)->pos - (*db)->pos;
}
/* Returns root of the CHAIN. */
static inline dref
get_chain_root (chain_p chain)
{
return chain->refs[0];
}
/* Adds REF to the chain CHAIN. */
static void
add_ref_to_chain (chain_p chain, dref ref)
{
dref root = get_chain_root (chain);
gcc_assert (wi::les_p (root->offset, ref->offset));
widest_int dist = ref->offset - root->offset;
if (wi::leu_p (MAX_DISTANCE, dist))
{
free (ref);
return;
}
gcc_assert (wi::fits_uhwi_p (dist));
chain->refs.safe_push (ref);
ref->distance = dist.to_uhwi ();
if (ref->distance >= chain->length)
{
chain->length = ref->distance;
chain->has_max_use_after = false;
}
if (ref->distance == chain->length
&& ref->pos > root->pos)
chain->has_max_use_after = true;
chain->all_always_accessed &= ref->always_accessed;
}
/* Returns the chain for invariant component COMP. */
static chain_p
make_invariant_chain (struct component *comp)
{
chain_p chain = XCNEW (struct chain);
unsigned i;
dref ref;
chain->type = CT_INVARIANT;
chain->all_always_accessed = true;
FOR_EACH_VEC_ELT (comp->refs, i, ref)
{
chain->refs.safe_push (ref);
chain->all_always_accessed &= ref->always_accessed;
}
return chain;
}
/* Make a new chain rooted at REF. */
static chain_p
make_rooted_chain (dref ref)
{
chain_p chain = XCNEW (struct chain);
chain->type = DR_IS_READ (ref->ref) ? CT_LOAD : CT_STORE_LOAD;
chain->refs.safe_push (ref);
chain->all_always_accessed = ref->always_accessed;
ref->distance = 0;
return chain;
}
/* Returns true if CHAIN is not trivial. */
static bool
nontrivial_chain_p (chain_p chain)
{
return chain != NULL && chain->refs.length () > 1;
}
/* Returns the ssa name that contains the value of REF, or NULL_TREE if there
is no such name. */
static tree
name_for_ref (dref ref)
{
tree name;
if (is_gimple_assign (ref->stmt))
{
if (!ref->ref || DR_IS_READ (ref->ref))
name = gimple_assign_lhs (ref->stmt);
else
name = gimple_assign_rhs1 (ref->stmt);
}
else
name = PHI_RESULT (ref->stmt);
return (TREE_CODE (name) == SSA_NAME ? name : NULL_TREE);
}
/* Returns true if REF is a valid initializer for ROOT with given DISTANCE (in
iterations of the innermost enclosing loop). */
static bool
valid_initializer_p (struct data_reference *ref,
unsigned distance, struct data_reference *root)
{
aff_tree diff, base, step;
widest_int off;
/* Both REF and ROOT must be accessing the same object. */
if (!operand_equal_p (DR_BASE_ADDRESS (ref), DR_BASE_ADDRESS (root), 0))
return false;
/* The initializer is defined outside of loop, hence its address must be
invariant inside the loop. */
gcc_assert (integer_zerop (DR_STEP (ref)));
/* If the address of the reference is invariant, initializer must access
exactly the same location. */
if (integer_zerop (DR_STEP (root)))
return (operand_equal_p (DR_OFFSET (ref), DR_OFFSET (root), 0)
&& operand_equal_p (DR_INIT (ref), DR_INIT (root), 0));
/* Verify that this index of REF is equal to the root's index at
-DISTANCE-th iteration. */
aff_combination_dr_offset (root, &diff);
aff_combination_dr_offset (ref, &base);
aff_combination_scale (&base, -1);
aff_combination_add (&diff, &base);
tree_to_aff_combination_expand (DR_STEP (root), TREE_TYPE (DR_STEP (root)),
&step, &name_expansions);
if (!aff_combination_constant_multiple_p (&diff, &step, &off))
return false;
if (off != distance)
return false;
return true;
}
/* Finds looparound phi node of LOOP that copies the value of REF, and if its
initial value is correct (equal to initial value of REF shifted by one
iteration), returns the phi node. Otherwise, NULL_TREE is returned. ROOT
is the root of the current chain. */
static gphi *
find_looparound_phi (struct loop *loop, dref ref, dref root)
{
tree name, init, init_ref;
gphi *phi = NULL;
gimple *init_stmt;
edge latch = loop_latch_edge (loop);
struct data_reference init_dr;
gphi_iterator psi;
if (is_gimple_assign (ref->stmt))
{
if (DR_IS_READ (ref->ref))
name = gimple_assign_lhs (ref->stmt);
else
name = gimple_assign_rhs1 (ref->stmt);
}
else
name = PHI_RESULT (ref->stmt);
if (!name)
return NULL;
for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi))
{
phi = psi.phi ();
if (PHI_ARG_DEF_FROM_EDGE (phi, latch) == name)
break;
}
if (gsi_end_p (psi))
return NULL;
init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
if (TREE_CODE (init) != SSA_NAME)
return NULL;
init_stmt = SSA_NAME_DEF_STMT (init);
if (gimple_code (init_stmt) != GIMPLE_ASSIGN)
return NULL;
gcc_assert (gimple_assign_lhs (init_stmt) == init);
init_ref = gimple_assign_rhs1 (init_stmt);
if (!REFERENCE_CLASS_P (init_ref)
&& !DECL_P (init_ref))
return NULL;
/* Analyze the behavior of INIT_REF with respect to LOOP (innermost
loop enclosing PHI). */
memset (&init_dr, 0, sizeof (struct data_reference));
DR_REF (&init_dr) = init_ref;
DR_STMT (&init_dr) = phi;
if (!dr_analyze_innermost (&init_dr, loop))
return NULL;
if (!valid_initializer_p (&init_dr, ref->distance + 1, root->ref))
return NULL;
return phi;
}
/* Adds a reference for the looparound copy of REF in PHI to CHAIN. */
static void
insert_looparound_copy (chain_p chain, dref ref, gphi *phi)
{
dref nw = XCNEW (struct dref_d), aref;
unsigned i;
nw->stmt = phi;
nw->distance = ref->distance + 1;
nw->always_accessed = 1;
FOR_EACH_VEC_ELT (chain->refs, i, aref)
if (aref->distance >= nw->distance)
break;
chain->refs.safe_insert (i, nw);
if (nw->distance > chain->length)
{
chain->length = nw->distance;
chain->has_max_use_after = false;
}
}
/* For references in CHAIN that are copied around the LOOP (created previously
by PRE, or by user), add the results of such copies to the chain. This
enables us to remove the copies by unrolling, and may need less registers
(also, it may allow us to combine chains together). */
static void
add_looparound_copies (struct loop *loop, chain_p chain)
{
unsigned i;
dref ref, root = get_chain_root (chain);
gphi *phi;
FOR_EACH_VEC_ELT (chain->refs, i, ref)
{
phi = find_looparound_phi (loop, ref, root);
if (!phi)
continue;
bitmap_set_bit (looparound_phis, SSA_NAME_VERSION (PHI_RESULT (phi)));
insert_looparound_copy (chain, ref, phi);
}
}
/* Find roots of the values and determine distances in the component COMP.
The references are redistributed into CHAINS. LOOP is the current
loop. */
static void
determine_roots_comp (struct loop *loop,
struct component *comp,
vec<chain_p> *chains)
{
unsigned i;
dref a;
chain_p chain = NULL;
widest_int last_ofs = 0;
/* Invariants are handled specially. */
if (comp->comp_step == RS_INVARIANT)
{
chain = make_invariant_chain (comp);
chains->safe_push (chain);
return;
}
comp->refs.qsort (order_drefs);
FOR_EACH_VEC_ELT (comp->refs, i, a)
{
if (!chain || DR_IS_WRITE (a->ref)
|| wi::leu_p (MAX_DISTANCE, a->offset - last_ofs))
{
if (nontrivial_chain_p (chain))
{
add_looparound_copies (loop, chain);
chains->safe_push (chain);
}
else
release_chain (chain);
chain = make_rooted_chain (a);
last_ofs = a->offset;
continue;
}
add_ref_to_chain (chain, a);
}
if (nontrivial_chain_p (chain))
{
add_looparound_copies (loop, chain);
chains->safe_push (chain);
}
else
release_chain (chain);
}
/* Find roots of the values and determine distances in components COMPS, and
separates the references to CHAINS. LOOP is the current loop. */
static void
determine_roots (struct loop *loop,
struct component *comps, vec<chain_p> *chains)
{
struct component *comp;
for (comp = comps; comp; comp = comp->next)
determine_roots_comp (loop, comp, chains);
}
/* Replace the reference in statement STMT with temporary variable
NEW_TREE. If SET is true, NEW_TREE is instead initialized to the value of
the reference in the statement. IN_LHS is true if the reference
is in the lhs of STMT, false if it is in rhs. */
static void
replace_ref_with (gimple *stmt, tree new_tree, bool set, bool in_lhs)
{
tree val;
gassign *new_stmt;
gimple_stmt_iterator bsi, psi;
if (gimple_code (stmt) == GIMPLE_PHI)
{
gcc_assert (!in_lhs && !set);
val = PHI_RESULT (stmt);
bsi = gsi_after_labels (gimple_bb (stmt));
psi = gsi_for_stmt (stmt);
remove_phi_node (&psi, false);
/* Turn the phi node into GIMPLE_ASSIGN. */
new_stmt = gimple_build_assign (val, new_tree);
gsi_insert_before (&bsi, new_stmt, GSI_NEW_STMT);
return;
}
/* Since the reference is of gimple_reg type, it should only
appear as lhs or rhs of modify statement. */
gcc_assert (is_gimple_assign (stmt));
bsi = gsi_for_stmt (stmt);
/* If we do not need to initialize NEW_TREE, just replace the use of OLD. */
if (!set)
{
gcc_assert (!in_lhs);
gimple_assign_set_rhs_from_tree (&bsi, new_tree);
stmt = gsi_stmt (bsi);
update_stmt (stmt);
return;
}
if (in_lhs)
{
/* We have statement
OLD = VAL
If OLD is a memory reference, then VAL is gimple_val, and we transform
this to
OLD = VAL
NEW = VAL
Otherwise, we are replacing a combination chain,
VAL is the expression that performs the combination, and OLD is an
SSA name. In this case, we transform the assignment to
OLD = VAL
NEW = OLD
*/
val = gimple_assign_lhs (stmt);
if (TREE_CODE (val) != SSA_NAME)
{
val = gimple_assign_rhs1 (stmt);
gcc_assert (gimple_assign_single_p (stmt));
if (TREE_CLOBBER_P (val))
val = get_or_create_ssa_default_def (cfun, SSA_NAME_VAR (new_tree));
else
gcc_assert (gimple_assign_copy_p (stmt));
}
}
else
{
/* VAL = OLD
is transformed to
VAL = OLD
NEW = VAL */
val = gimple_assign_lhs (stmt);
}
new_stmt = gimple_build_assign (new_tree, unshare_expr (val));
gsi_insert_after (&bsi, new_stmt, GSI_NEW_STMT);
}
/* Returns a memory reference to DR in the ITER-th iteration of
the loop it was analyzed in. Append init stmts to STMTS. */
static tree
ref_at_iteration (data_reference_p dr, int iter, gimple_seq *stmts)
{
tree off = DR_OFFSET (dr);
tree coff = DR_INIT (dr);
tree ref = DR_REF (dr);
enum tree_code ref_code = ERROR_MARK;
tree ref_type = NULL_TREE;
tree ref_op1 = NULL_TREE;
tree ref_op2 = NULL_TREE;
if (iter == 0)
;
else if (TREE_CODE (DR_STEP (dr)) == INTEGER_CST)
coff = size_binop (PLUS_EXPR, coff,
size_binop (MULT_EXPR, DR_STEP (dr), ssize_int (iter)));
else
off = size_binop (PLUS_EXPR, off,
size_binop (MULT_EXPR, DR_STEP (dr), ssize_int (iter)));
/* While data-ref analysis punts on bit offsets it still handles
bitfield accesses at byte boundaries. Cope with that. Note that
if the bitfield object also starts at a byte-boundary we can simply
replicate the COMPONENT_REF, but we have to subtract the component's
byte-offset from the MEM_REF address first.
Otherwise we simply build a BIT_FIELD_REF knowing that the bits
start at offset zero. */
if (TREE_CODE (ref) == COMPONENT_REF
&& DECL_BIT_FIELD (TREE_OPERAND (ref, 1)))
{
unsigned HOST_WIDE_INT boff;
tree field = TREE_OPERAND (ref, 1);
tree offset = component_ref_field_offset (ref);
ref_type = TREE_TYPE (ref);
boff = tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field));
/* This can occur in Ada. See the comment in get_bit_range. */
if (boff % BITS_PER_UNIT != 0
|| !tree_fits_uhwi_p (offset))
{
ref_code = BIT_FIELD_REF;
ref_op1 = DECL_SIZE (field);
ref_op2 = bitsize_zero_node;
}
else
{
boff >>= LOG2_BITS_PER_UNIT;
boff += tree_to_uhwi (offset);
coff = size_binop (MINUS_EXPR, coff, ssize_int (boff));
ref_code = COMPONENT_REF;
ref_op1 = field;
ref_op2 = TREE_OPERAND (ref, 2);
ref = TREE_OPERAND (ref, 0);
}
}
tree addr = fold_build_pointer_plus (DR_BASE_ADDRESS (dr), off);
addr = force_gimple_operand_1 (unshare_expr (addr), stmts,
is_gimple_mem_ref_addr, NULL_TREE);
tree alias_ptr = fold_convert (reference_alias_ptr_type (ref), coff);
tree type = build_aligned_type (TREE_TYPE (ref),
get_object_alignment (ref));
ref = build2 (MEM_REF, type, addr, alias_ptr);
if (ref_type)
ref = build3 (ref_code, ref_type, ref, ref_op1, ref_op2);
return ref;
}
/* Get the initialization expression for the INDEX-th temporary variable
of CHAIN. */
static tree
get_init_expr (chain_p chain, unsigned index)
{
if (chain->type == CT_COMBINATION)
{
tree e1 = get_init_expr (chain->ch1, index);
tree e2 = get_init_expr (chain->ch2, index);
return fold_build2 (chain->op, chain->rslt_type, e1, e2);
}
else
return chain->inits[index];
}
/* Returns a new temporary variable used for the I-th variable carrying
value of REF. The variable's uid is marked in TMP_VARS. */
static tree
predcom_tmp_var (tree ref, unsigned i, bitmap tmp_vars)
{
tree type = TREE_TYPE (ref);
/* We never access the components of the temporary variable in predictive
commoning. */
tree var = create_tmp_reg (type, get_lsm_tmp_name (ref, i));
bitmap_set_bit (tmp_vars, DECL_UID (var));
return var;
}
/* Creates the variables for CHAIN, as well as phi nodes for them and
initialization on entry to LOOP. Uids of the newly created
temporary variables are marked in TMP_VARS. */
static void
initialize_root_vars (struct loop *loop, chain_p chain, bitmap tmp_vars)
{
unsigned i;
unsigned n = chain->length;
dref root = get_chain_root (chain);
bool reuse_first = !chain->has_max_use_after;
tree ref, init, var, next;
gphi *phi;
gimple_seq stmts;
edge entry = loop_preheader_edge (loop), latch = loop_latch_edge (loop);
/* If N == 0, then all the references are within the single iteration. And
since this is an nonempty chain, reuse_first cannot be true. */
gcc_assert (n > 0 || !reuse_first);
chain->vars.create (n + 1);
if (chain->type == CT_COMBINATION)
ref = gimple_assign_lhs (root->stmt);
else
ref = DR_REF (root->ref);
for (i = 0; i < n + (reuse_first ? 0 : 1); i++)
{
var = predcom_tmp_var (ref, i, tmp_vars);
chain->vars.quick_push (var);
}
if (reuse_first)
chain->vars.quick_push (chain->vars[0]);
FOR_EACH_VEC_ELT (chain->vars, i, var)
chain->vars[i] = make_ssa_name (var);
for (i = 0; i < n; i++)
{
var = chain->vars[i];
next = chain->vars[i + 1];
init = get_init_expr (chain, i);
init = force_gimple_operand (init, &stmts, true, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (entry, stmts);
phi = create_phi_node (var, loop->header);
add_phi_arg (phi, init, entry, UNKNOWN_LOCATION);
add_phi_arg (phi, next, latch, UNKNOWN_LOCATION);
}
}
/* Create the variables and initialization statement for root of chain
CHAIN. Uids of the newly created temporary variables are marked
in TMP_VARS. */
static void
initialize_root (struct loop *loop, chain_p chain, bitmap tmp_vars)
{
dref root = get_chain_root (chain);
bool in_lhs = (chain->type == CT_STORE_LOAD
|| chain->type == CT_COMBINATION);
initialize_root_vars (loop, chain, tmp_vars);
replace_ref_with (root->stmt,
chain->vars[chain->length],
true, in_lhs);
}
/* Initializes a variable for load motion for ROOT and prepares phi nodes and
initialization on entry to LOOP if necessary. The ssa name for the variable
is stored in VARS. If WRITTEN is true, also a phi node to copy its value
around the loop is created. Uid of the newly created temporary variable
is marked in TMP_VARS. INITS is the list containing the (single)
initializer. */
static void
initialize_root_vars_lm (struct loop *loop, dref root, bool written,
vec<tree> *vars, vec<tree> inits,
bitmap tmp_vars)
{
unsigned i;
tree ref = DR_REF (root->ref), init, var, next;
gimple_seq stmts;
gphi *phi;
edge entry = loop_preheader_edge (loop), latch = loop_latch_edge (loop);
/* Find the initializer for the variable, and check that it cannot
trap. */
init = inits[0];
vars->create (written ? 2 : 1);
var = predcom_tmp_var (ref, 0, tmp_vars);
vars->quick_push (var);
if (written)
vars->quick_push ((*vars)[0]);
FOR_EACH_VEC_ELT (*vars, i, var)
(*vars)[i] = make_ssa_name (var);
var = (*vars)[0];
init = force_gimple_operand (init, &stmts, written, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (entry, stmts);
if (written)
{
next = (*vars)[1];
phi = create_phi_node (var, loop->header);
add_phi_arg (phi, init, entry, UNKNOWN_LOCATION);
add_phi_arg (phi, next, latch, UNKNOWN_LOCATION);
}
else
{
gassign *init_stmt = gimple_build_assign (var, init);
gsi_insert_on_edge_immediate (entry, init_stmt);
}
}
/* Execute load motion for references in chain CHAIN. Uids of the newly
created temporary variables are marked in TMP_VARS. */
static void
execute_load_motion (struct loop *loop, chain_p chain, bitmap tmp_vars)
{
auto_vec<tree> vars;
dref a;
unsigned n_writes = 0, ridx, i;
tree var;
gcc_assert (chain->type == CT_INVARIANT);
gcc_assert (!chain->combined);
FOR_EACH_VEC_ELT (chain->refs, i, a)
if (DR_IS_WRITE (a->ref))
n_writes++;
/* If there are no reads in the loop, there is nothing to do. */
if (n_writes == chain->refs.length ())
return;
initialize_root_vars_lm (loop, get_chain_root (chain), n_writes > 0,
&vars, chain->inits, tmp_vars);
ridx = 0;
FOR_EACH_VEC_ELT (chain->refs, i, a)
{
bool is_read = DR_IS_READ (a->ref);
if (DR_IS_WRITE (a->ref))
{
n_writes--;
if (n_writes)
{
var = vars[0];
var = make_ssa_name (SSA_NAME_VAR (var));
vars[0] = var;
}
else
ridx = 1;
}
replace_ref_with (a->stmt, vars[ridx],
!is_read, !is_read);
}
}
/* Returns the single statement in that NAME is used, excepting
the looparound phi nodes contained in one of the chains. If there is no
such statement, or more statements, NULL is returned. */
static gimple *
single_nonlooparound_use (tree name)
{
use_operand_p use;
imm_use_iterator it;
gimple *stmt, *ret = NULL;
FOR_EACH_IMM_USE_FAST (use, it, name)
{
stmt = USE_STMT (use);
if (gimple_code (stmt) == GIMPLE_PHI)
{
/* Ignore uses in looparound phi nodes. Uses in other phi nodes
could not be processed anyway, so just fail for them. */
if (bitmap_bit_p (looparound_phis,
SSA_NAME_VERSION (PHI_RESULT (stmt))))
continue;
return NULL;
}
else if (is_gimple_debug (stmt))
continue;
else if (ret != NULL)
return NULL;
else
ret = stmt;
}
return ret;
}
/* Remove statement STMT, as well as the chain of assignments in that it is
used. */
static void
remove_stmt (gimple *stmt)
{
tree name;
gimple *next;
gimple_stmt_iterator psi;
if (gimple_code (stmt) == GIMPLE_PHI)
{
name = PHI_RESULT (stmt);
next = single_nonlooparound_use (name);
reset_debug_uses (stmt);
psi = gsi_for_stmt (stmt);
remove_phi_node (&psi, true);
if (!next
|| !gimple_assign_ssa_name_copy_p (next)
|| gimple_assign_rhs1 (next) != name)
return;
stmt = next;
}
while (1)
{
gimple_stmt_iterator bsi;
bsi = gsi_for_stmt (stmt);
name = gimple_assign_lhs (stmt);
gcc_assert (TREE_CODE (name) == SSA_NAME);
next = single_nonlooparound_use (name);
reset_debug_uses (stmt);
unlink_stmt_vdef (stmt);
gsi_remove (&bsi, true);
release_defs (stmt);
if (!next
|| !gimple_assign_ssa_name_copy_p (next)
|| gimple_assign_rhs1 (next) != name)
return;
stmt = next;
}
}
/* Perform the predictive commoning optimization for a chain CHAIN.
Uids of the newly created temporary variables are marked in TMP_VARS.*/
static void
execute_pred_commoning_chain (struct loop *loop, chain_p chain,
bitmap tmp_vars)
{
unsigned i;
dref a;
tree var;
if (chain->combined)
{
/* For combined chains, just remove the statements that are used to
compute the values of the expression (except for the root one).
We delay this until after all chains are processed. */
}
else
{
/* For non-combined chains, set up the variables that hold its value,
and replace the uses of the original references by these
variables. */
initialize_root (loop, chain, tmp_vars);
for (i = 1; chain->refs.iterate (i, &a); i++)
{
var = chain->vars[chain->length - a->distance];
replace_ref_with (a->stmt, var, false, false);
}
}
}
/* Determines the unroll factor necessary to remove as many temporary variable
copies as possible. CHAINS is the list of chains that will be
optimized. */
static unsigned
determine_unroll_factor (vec<chain_p> chains)
{
chain_p chain;
unsigned factor = 1, af, nfactor, i;
unsigned max = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES);
FOR_EACH_VEC_ELT (chains, i, chain)
{
if (chain->type == CT_INVARIANT)
continue;
if (chain->combined)
{
/* For combined chains, we can't handle unrolling if we replace
looparound PHIs. */
dref a;
unsigned j;
for (j = 1; chain->refs.iterate (j, &a); j++)
if (gimple_code (a->stmt) == GIMPLE_PHI)
return 1;
continue;
}
/* The best unroll factor for this chain is equal to the number of
temporary variables that we create for it. */
af = chain->length;
if (chain->has_max_use_after)
af++;
nfactor = factor * af / gcd (factor, af);
if (nfactor <= max)
factor = nfactor;
}
return factor;
}
/* Perform the predictive commoning optimization for CHAINS.
Uids of the newly created temporary variables are marked in TMP_VARS. */
static void
execute_pred_commoning (struct loop *loop, vec<chain_p> chains,
bitmap tmp_vars)
{
chain_p chain;
unsigned i;
FOR_EACH_VEC_ELT (chains, i, chain)
{
if (chain->type == CT_INVARIANT)
execute_load_motion (loop, chain, tmp_vars);
else
execute_pred_commoning_chain (loop, chain, tmp_vars);
}
FOR_EACH_VEC_ELT (chains, i, chain)
{
if (chain->type == CT_INVARIANT)
;
else if (chain->combined)
{
/* For combined chains, just remove the statements that are used to
compute the values of the expression (except for the root one). */
dref a;
unsigned j;
for (j = 1; chain->refs.iterate (j, &a); j++)
remove_stmt (a->stmt);
}
}
update_ssa (TODO_update_ssa_only_virtuals);
}
/* For each reference in CHAINS, if its defining statement is
phi node, record the ssa name that is defined by it. */
static void
replace_phis_by_defined_names (vec<chain_p> chains)
{
chain_p chain;
dref a;
unsigned i, j;
FOR_EACH_VEC_ELT (chains, i, chain)
FOR_EACH_VEC_ELT (chain->refs, j, a)
{
if (gimple_code (a->stmt) == GIMPLE_PHI)
{
a->name_defined_by_phi = PHI_RESULT (a->stmt);
a->stmt = NULL;
}
}
}
/* For each reference in CHAINS, if name_defined_by_phi is not
NULL, use it to set the stmt field. */
static void
replace_names_by_phis (vec<chain_p> chains)
{
chain_p chain;
dref a;
unsigned i, j;
FOR_EACH_VEC_ELT (chains, i, chain)
FOR_EACH_VEC_ELT (chain->refs, j, a)
if (a->stmt == NULL)
{
a->stmt = SSA_NAME_DEF_STMT (a->name_defined_by_phi);
gcc_assert (gimple_code (a->stmt) == GIMPLE_PHI);
a->name_defined_by_phi = NULL_TREE;
}
}
/* Wrapper over execute_pred_commoning, to pass it as a callback
to tree_transform_and_unroll_loop. */
struct epcc_data
{
vec<chain_p> chains;
bitmap tmp_vars;
};
static void
execute_pred_commoning_cbck (struct loop *loop, void *data)
{
struct epcc_data *const dta = (struct epcc_data *) data;
/* Restore phi nodes that were replaced by ssa names before
tree_transform_and_unroll_loop (see detailed description in
tree_predictive_commoning_loop). */
replace_names_by_phis (dta->chains);
execute_pred_commoning (loop, dta->chains, dta->tmp_vars);
}
/* Base NAME and all the names in the chain of phi nodes that use it
on variable VAR. The phi nodes are recognized by being in the copies of
the header of the LOOP. */
static void
base_names_in_chain_on (struct loop *loop, tree name, tree var)
{
gimple *stmt, *phi;
imm_use_iterator iter;
replace_ssa_name_symbol (name, var);
while (1)
{
phi = NULL;
FOR_EACH_IMM_USE_STMT (stmt, iter, name)
{
if (gimple_code (stmt) == GIMPLE_PHI
&& flow_bb_inside_loop_p (loop, gimple_bb (stmt)))
{
phi = stmt;
BREAK_FROM_IMM_USE_STMT (iter);
}
}
if (!phi)
return;
name = PHI_RESULT (phi);
replace_ssa_name_symbol (name, var);
}
}
/* Given an unrolled LOOP after predictive commoning, remove the
register copies arising from phi nodes by changing the base
variables of SSA names. TMP_VARS is the set of the temporary variables
for those we want to perform this. */
static void
eliminate_temp_copies (struct loop *loop, bitmap tmp_vars)
{
edge e;
gphi *phi;
gimple *stmt;
tree name, use, var;
gphi_iterator psi;
e = loop_latch_edge (loop);
for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi))
{
phi = psi.phi ();
name = PHI_RESULT (phi);
var = SSA_NAME_VAR (name);
if (!var || !bitmap_bit_p (tmp_vars, DECL_UID (var)))
continue;
use = PHI_ARG_DEF_FROM_EDGE (phi, e);
gcc_assert (TREE_CODE (use) == SSA_NAME);
/* Base all the ssa names in the ud and du chain of NAME on VAR. */
stmt = SSA_NAME_DEF_STMT (use);
while (gimple_code (stmt) == GIMPLE_PHI
/* In case we could not unroll the loop enough to eliminate
all copies, we may reach the loop header before the defining
statement (in that case, some register copies will be present
in loop latch in the final code, corresponding to the newly
created looparound phi nodes). */
&& gimple_bb (stmt) != loop->header)
{
gcc_assert (single_pred_p (gimple_bb (stmt)));
use = PHI_ARG_DEF (stmt, 0);
stmt = SSA_NAME_DEF_STMT (use);
}
base_names_in_chain_on (loop, use, var);
}
}
/* Returns true if CHAIN is suitable to be combined. */
static bool
chain_can_be_combined_p (chain_p chain)
{
return (!chain->combined
&& (chain->type == CT_LOAD || chain->type == CT_COMBINATION));
}
/* Returns the modify statement that uses NAME. Skips over assignment
statements, NAME is replaced with the actual name used in the returned
statement. */
static gimple *
find_use_stmt (tree *name)
{
gimple *stmt;
tree rhs, lhs;
/* Skip over assignments. */
while (1)
{
stmt = single_nonlooparound_use (*name);
if (!stmt)
return NULL;
if (gimple_code (stmt) != GIMPLE_ASSIGN)
return NULL;
lhs = gimple_assign_lhs (stmt);
if (TREE_CODE (lhs) != SSA_NAME)
return NULL;
if (gimple_assign_copy_p (stmt))
{
rhs = gimple_assign_rhs1 (stmt);
if (rhs != *name)
return NULL;
*name = lhs;
}
else if (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
== GIMPLE_BINARY_RHS)
return stmt;
else
return NULL;
}
}
/* Returns true if we may perform reassociation for operation CODE in TYPE. */
static bool
may_reassociate_p (tree type, enum tree_code code)
{
if (FLOAT_TYPE_P (type)
&& !flag_unsafe_math_optimizations)
return false;
return (commutative_tree_code (code)
&& associative_tree_code (code));
}
/* If the operation used in STMT is associative and commutative, go through the
tree of the same operations and returns its root. Distance to the root
is stored in DISTANCE. */
static gimple *
find_associative_operation_root (gimple *stmt, unsigned *distance)
{
tree lhs;
gimple *next;
enum tree_code code = gimple_assign_rhs_code (stmt);
tree type = TREE_TYPE (gimple_assign_lhs (stmt));
unsigned dist = 0;
if (!may_reassociate_p (type, code))
return NULL;
while (1)
{
lhs = gimple_assign_lhs (stmt);
gcc_assert (TREE_CODE (lhs) == SSA_NAME);
next = find_use_stmt (&lhs);
if (!next
|| gimple_assign_rhs_code (next) != code)
break;
stmt = next;
dist++;
}
if (distance)
*distance = dist;
return stmt;
}
/* Returns the common statement in that NAME1 and NAME2 have a use. If there
is no such statement, returns NULL_TREE. In case the operation used on
NAME1 and NAME2 is associative and commutative, returns the root of the
tree formed by this operation instead of the statement that uses NAME1 or
NAME2. */
static gimple *
find_common_use_stmt (tree *name1, tree *name2)
{
gimple *stmt1, *stmt2;
stmt1 = find_use_stmt (name1);
if (!stmt1)
return NULL;
stmt2 = find_use_stmt (name2);
if (!stmt2)
return NULL;
if (stmt1 == stmt2)
return stmt1;
stmt1 = find_associative_operation_root (stmt1, NULL);
if (!stmt1)
return NULL;
stmt2 = find_associative_operation_root (stmt2, NULL);
if (!stmt2)
return NULL;
return (stmt1 == stmt2 ? stmt1 : NULL);
}
/* Checks whether R1 and R2 are combined together using CODE, with the result
in RSLT_TYPE, in order R1 CODE R2 if SWAP is false and in order R2 CODE R1
if it is true. If CODE is ERROR_MARK, set these values instead. */
static bool
combinable_refs_p (dref r1, dref r2,
enum tree_code *code, bool *swap, tree *rslt_type)
{
enum tree_code acode;
bool aswap;
tree atype;
tree name1, name2;
gimple *stmt;
name1 = name_for_ref (r1);
name2 = name_for_ref (r2);
gcc_assert (name1 != NULL_TREE && name2 != NULL_TREE);
stmt = find_common_use_stmt (&name1, &name2);
if (!stmt
/* A simple post-dominance check - make sure the combination
is executed under the same condition as the references. */
|| (gimple_bb (stmt) != gimple_bb (r1->stmt)
&& gimple_bb (stmt) != gimple_bb (r2->stmt)))
return false;
acode = gimple_assign_rhs_code (stmt);
aswap = (!commutative_tree_code (acode)
&& gimple_assign_rhs1 (stmt) != name1);
atype = TREE_TYPE (gimple_assign_lhs (stmt));
if (*code == ERROR_MARK)
{
*code = acode;
*swap = aswap;
*rslt_type = atype;
return true;
}
return (*code == acode
&& *swap == aswap
&& *rslt_type == atype);
}
/* Remove OP from the operation on rhs of STMT, and replace STMT with
an assignment of the remaining operand. */
static void
remove_name_from_operation (gimple *stmt, tree op)
{
tree other_op;
gimple_stmt_iterator si;
gcc_assert (is_gimple_assign (stmt));
if (gimple_assign_rhs1 (stmt) == op)
other_op = gimple_assign_rhs2 (stmt);
else
other_op = gimple_assign_rhs1 (stmt);
si = gsi_for_stmt (stmt);
gimple_assign_set_rhs_from_tree (&si, other_op);
/* We should not have reallocated STMT. */
gcc_assert (gsi_stmt (si) == stmt);
update_stmt (stmt);
}
/* Reassociates the expression in that NAME1 and NAME2 are used so that they
are combined in a single statement, and returns this statement. Note the
statement is inserted before INSERT_BEFORE if it's not NULL. */
static gimple *
reassociate_to_the_same_stmt (tree name1, tree name2, gimple *insert_before)
{
gimple *stmt1, *stmt2, *root1, *root2, *s1, *s2;
gassign *new_stmt, *tmp_stmt;
tree new_name, tmp_name, var, r1, r2;
unsigned dist1, dist2;
enum tree_code code;
tree type = TREE_TYPE (name1);
gimple_stmt_iterator bsi;
stmt1 = find_use_stmt (&name1);
stmt2 = find_use_stmt (&name2);
root1 = find_associative_operation_root (stmt1, &dist1);
root2 = find_associative_operation_root (stmt2, &dist2);
code = gimple_assign_rhs_code (stmt1);
gcc_assert (root1 && root2 && root1 == root2
&& code == gimple_assign_rhs_code (stmt2));
/* Find the root of the nearest expression in that both NAME1 and NAME2
are used. */
r1 = name1;
s1 = stmt1;
r2 = name2;
s2 = stmt2;
while (dist1 > dist2)
{
s1 = find_use_stmt (&r1);
r1 = gimple_assign_lhs (s1);
dist1--;
}
while (dist2 > dist1)
{
s2 = find_use_stmt (&r2);
r2 = gimple_assign_lhs (s2);
dist2--;
}
while (s1 != s2)
{
s1 = find_use_stmt (&r1);
r1 = gimple_assign_lhs (s1);
s2 = find_use_stmt (&r2);
r2 = gimple_assign_lhs (s2);
}
/* Remove NAME1 and NAME2 from the statements in that they are used
currently. */
remove_name_from_operation (stmt1, name1);
remove_name_from_operation (stmt2, name2);
/* Insert the new statement combining NAME1 and NAME2 before S1, and
combine it with the rhs of S1. */
var = create_tmp_reg (type, "predreastmp");
new_name = make_ssa_name (var);
new_stmt = gimple_build_assign (new_name, code, name1, name2);
if (insert_before && stmt_dominates_stmt_p (insert_before, s1))
bsi = gsi_for_stmt (insert_before);
else
bsi = gsi_for_stmt (s1);
gsi_insert_before (&bsi, new_stmt, GSI_SAME_STMT);
var = create_tmp_reg (type, "predreastmp");
tmp_name = make_ssa_name (var);
/* Rhs of S1 may now be either a binary expression with operation
CODE, or gimple_val (in case that stmt1 == s1 or stmt2 == s1,
so that name1 or name2 was removed from it). */
tmp_stmt = gimple_build_assign (tmp_name, gimple_assign_rhs_code (s1),
gimple_assign_rhs1 (s1),
gimple_assign_rhs2 (s1));
bsi = gsi_for_stmt (s1);
gimple_assign_set_rhs_with_ops (&bsi, code, new_name, tmp_name);
s1 = gsi_stmt (bsi);
update_stmt (s1);
gsi_insert_before (&bsi, tmp_stmt, GSI_SAME_STMT);
return new_stmt;
}
/* Returns the statement that combines references R1 and R2. In case R1
and R2 are not used in the same statement, but they are used with an
associative and commutative operation in the same expression, reassociate
the expression so that they are used in the same statement. The combined
statement is inserted before INSERT_BEFORE if it's not NULL. */
static gimple *
stmt_combining_refs (dref r1, dref r2, gimple *insert_before)
{
gimple *stmt1, *stmt2;
tree name1 = name_for_ref (r1);
tree name2 = name_for_ref (r2);
stmt1 = find_use_stmt (&name1);
stmt2 = find_use_stmt (&name2);
if (stmt1 == stmt2)
return stmt1;
return reassociate_to_the_same_stmt (name1, name2, insert_before);
}
/* Tries to combine chains CH1 and CH2 together. If this succeeds, the
description of the new chain is returned, otherwise we return NULL. */
static chain_p
combine_chains (chain_p ch1, chain_p ch2)
{
dref r1, r2, nw;
enum tree_code op = ERROR_MARK;
bool swap = false;
chain_p new_chain;
int i, j, num;
gimple *root_stmt;
tree rslt_type = NULL_TREE;
if (ch1 == ch2)
return NULL;
if (ch1->length != ch2->length)
return NULL;
if (ch1->refs.length () != ch2->refs.length ())
return NULL;
for (i = 0; (ch1->refs.iterate (i, &r1)
&& ch2->refs.iterate (i, &r2)); i++)
{
if (r1->distance != r2->distance)
return NULL;
if (!combinable_refs_p (r1, r2, &op, &swap, &rslt_type))
return NULL;
}
ch1->combined = true;
ch2->combined = true;
if (swap)
std::swap (ch1, ch2);
new_chain = XCNEW (struct chain);
new_chain->type = CT_COMBINATION;
new_chain->op = op;
new_chain->ch1 = ch1;
new_chain->ch2 = ch2;
new_chain->rslt_type = rslt_type;
new_chain->length = ch1->length;
gimple *insert = NULL;
num = ch1->refs.length ();
i = (new_chain->length == 0) ? num - 1 : 0;
j = (new_chain->length == 0) ? -1 : 1;
/* For ZERO length chain, process refs in reverse order so that dominant
position is ready when it comes to the root ref.
For non-ZERO length chain, process refs in order. See PR79663. */
for (; num > 0; num--, i += j)
{
r1 = ch1->refs[i];
r2 = ch2->refs[i];
nw = XCNEW (struct dref_d);
nw->distance = r1->distance;
/* For ZERO length chain, insert combined stmt of root ref at dominant
position. */
nw->stmt = stmt_combining_refs (r1, r2, i == 0 ? insert : NULL);
/* For ZERO length chain, record dominant position where combined stmt
of root ref should be inserted. In this case, though all root refs
dominate following ones, it's possible that combined stmt doesn't.
See PR70754. */
if (new_chain->length == 0
&& (insert == NULL || stmt_dominates_stmt_p (nw->stmt, insert)))
insert = nw->stmt;
new_chain->refs.safe_push (nw);
}
if (new_chain->length == 0)
{
/* Restore the order for ZERO length chain's refs. */
num = new_chain->refs.length () >> 1;
for (i = 0, j = new_chain->refs.length () - 1; i < num; i++, j--)
std::swap (new_chain->refs[i], new_chain->refs[j]);
/* For ZERO length chain, has_max_use_after must be true since root
combined stmt must dominates others. */
new_chain->has_max_use_after = true;
return new_chain;
}
new_chain->has_max_use_after = false;
root_stmt = get_chain_root (new_chain)->stmt;
for (i = 1; new_chain->refs.iterate (i, &nw); i++)
{
if (nw->distance == new_chain->length
&& !stmt_dominates_stmt_p (nw->stmt, root_stmt))
{
new_chain->has_max_use_after = true;
break;
}
}
return new_chain;
}
/* Try to combine the CHAINS. */
static void
try_combine_chains (vec<chain_p> *chains)
{
unsigned i, j;
chain_p ch1, ch2, cch;
auto_vec<chain_p> worklist;
FOR_EACH_VEC_ELT (*chains, i, ch1)
if (chain_can_be_combined_p (ch1))
worklist.safe_push (ch1);
while (!worklist.is_empty ())
{
ch1 = worklist.pop ();
if (!chain_can_be_combined_p (ch1))
continue;
FOR_EACH_VEC_ELT (*chains, j, ch2)
{
if (!chain_can_be_combined_p (ch2))
continue;
cch = combine_chains (ch1, ch2);
if (cch)
{
worklist.safe_push (cch);
chains->safe_push (cch);
break;
}
}
}
}
/* Prepare initializers for CHAIN in LOOP. Returns false if this is
impossible because one of these initializers may trap, true otherwise. */
static bool
prepare_initializers_chain (struct loop *loop, chain_p chain)
{
unsigned i, n = (chain->type == CT_INVARIANT) ? 1 : chain->length;
struct data_reference *dr = get_chain_root (chain)->ref;
tree init;
dref laref;
edge entry = loop_preheader_edge (loop);
/* Find the initializers for the variables, and check that they cannot
trap. */
chain->inits.create (n);
for (i = 0; i < n; i++)
chain->inits.quick_push (NULL_TREE);
/* If we have replaced some looparound phi nodes, use their initializers
instead of creating our own. */
FOR_EACH_VEC_ELT (chain->refs, i, laref)
{
if (gimple_code (laref->stmt) != GIMPLE_PHI)
continue;
gcc_assert (laref->distance > 0);
chain->inits[n - laref->distance]
= PHI_ARG_DEF_FROM_EDGE (laref->stmt, entry);
}
for (i = 0; i < n; i++)
{
gimple_seq stmts = NULL;
if (chain->inits[i] != NULL_TREE)
continue;
init = ref_at_iteration (dr, (int) i - n, &stmts);
if (!chain->all_always_accessed && tree_could_trap_p (init))
{
gimple_seq_discard (stmts);
return false;
}
if (stmts)
gsi_insert_seq_on_edge_immediate (entry, stmts);
chain->inits[i] = init;
}
return true;
}
/* Prepare initializers for CHAINS in LOOP, and free chains that cannot
be used because the initializers might trap. */
static void
prepare_initializers (struct loop *loop, vec<chain_p> chains)
{
chain_p chain;
unsigned i;
for (i = 0; i < chains.length (); )
{
chain = chains[i];
if (prepare_initializers_chain (loop, chain))
i++;
else
{
release_chain (chain);
chains.unordered_remove (i);
}
}
}
/* Performs predictive commoning for LOOP. Returns true if LOOP was
unrolled. */
static bool
tree_predictive_commoning_loop (struct loop *loop)
{
vec<data_reference_p> datarefs;
vec<ddr_p> dependences;
struct component *components;
vec<chain_p> chains = vNULL;
unsigned unroll_factor;
struct tree_niter_desc desc;
bool unroll = false;
edge exit;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Processing loop %d\n", loop->num);
/* Nothing for predicitive commoning if loop only iterates 1 time. */
if (get_max_loop_iterations_int (loop) == 0)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Loop iterates only 1 time, nothing to do.\n");
return false;
}
/* Find the data references and split them into components according to their
dependence relations. */
auto_vec<loop_p, 3> loop_nest;
dependences.create (10);
datarefs.create (10);
if (! compute_data_dependences_for_loop (loop, true, &loop_nest, &datarefs,
&dependences))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Cannot analyze data dependencies\n");
free_data_refs (datarefs);
free_dependence_relations (dependences);
return false;
}
if (dump_file && (dump_flags & TDF_DETAILS))
dump_data_dependence_relations (dump_file, dependences);
components = split_data_refs_to_components (loop, datarefs, dependences);
loop_nest.release ();
free_dependence_relations (dependences);
if (!components)
{
free_data_refs (datarefs);
free_affine_expand_cache (&name_expansions);
return false;
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Initial state:\n\n");
dump_components (dump_file, components);
}
/* Find the suitable components and split them into chains. */
components = filter_suitable_components (loop, components);
auto_bitmap tmp_vars;
looparound_phis = BITMAP_ALLOC (NULL);
determine_roots (loop, components, &chains);
release_components (components);
if (!chains.exists ())
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
"Predictive commoning failed: no suitable chains\n");
goto end;
}
prepare_initializers (loop, chains);
/* Try to combine the chains that are always worked with together. */
try_combine_chains (&chains);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Before commoning:\n\n");
dump_chains (dump_file, chains);
}
/* Determine the unroll factor, and if the loop should be unrolled, ensure
that its number of iterations is divisible by the factor. */
unroll_factor = determine_unroll_factor (chains);
scev_reset ();
unroll = (unroll_factor > 1
&& can_unroll_loop_p (loop, unroll_factor, &desc));
exit = single_dom_exit (loop);
/* Execute the predictive commoning transformations, and possibly unroll the
loop. */
if (unroll)
{
struct epcc_data dta;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Unrolling %u times.\n", unroll_factor);
dta.chains = chains;
dta.tmp_vars = tmp_vars;
update_ssa (TODO_update_ssa_only_virtuals);
/* Cfg manipulations performed in tree_transform_and_unroll_loop before
execute_pred_commoning_cbck is called may cause phi nodes to be
reallocated, which is a problem since CHAINS may point to these
statements. To fix this, we store the ssa names defined by the
phi nodes here instead of the phi nodes themselves, and restore
the phi nodes in execute_pred_commoning_cbck. A bit hacky. */
replace_phis_by_defined_names (chains);
tree_transform_and_unroll_loop (loop, unroll_factor, exit, &desc,
execute_pred_commoning_cbck, &dta);
eliminate_temp_copies (loop, tmp_vars);
}
else
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
"Executing predictive commoning without unrolling.\n");
execute_pred_commoning (loop, chains, tmp_vars);
}
end: ;
release_chains (chains);
free_data_refs (datarefs);
BITMAP_FREE (looparound_phis);
free_affine_expand_cache (&name_expansions);
return unroll;
}
/* Runs predictive commoning. */
unsigned
tree_predictive_commoning (void)
{
bool unrolled = false;
struct loop *loop;
unsigned ret = 0;
initialize_original_copy_tables ();
FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
if (optimize_loop_for_speed_p (loop))
{
unrolled |= tree_predictive_commoning_loop (loop);
}
if (unrolled)
{
scev_reset ();
ret = TODO_cleanup_cfg;
}
free_original_copy_tables ();
return ret;
}
/* Predictive commoning Pass. */
static unsigned
run_tree_predictive_commoning (struct function *fun)
{
if (number_of_loops (fun) <= 1)
return 0;
return tree_predictive_commoning ();
}
namespace {
const pass_data pass_data_predcom =
{
GIMPLE_PASS, /* type */
"pcom", /* name */
OPTGROUP_LOOP, /* optinfo_flags */
TV_PREDCOM, /* tv_id */
PROP_cfg, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_update_ssa_only_virtuals, /* todo_flags_finish */
};
class pass_predcom : public gimple_opt_pass
{
public:
pass_predcom (gcc::context *ctxt)
: gimple_opt_pass (pass_data_predcom, ctxt)
{}
/* opt_pass methods: */
virtual bool gate (function *) { return flag_predictive_commoning != 0; }
virtual unsigned int execute (function *fun)
{
return run_tree_predictive_commoning (fun);
}
}; // class pass_predcom
} // anon namespace
gimple_opt_pass *
make_pass_predcom (gcc::context *ctxt)
{
return new pass_predcom (ctxt);
}
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