forked from illumos/gcc
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tree-ssa-reassoc.c
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tree-ssa-reassoc.c
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/* Reassociation for trees.
Copyright (C) 2005, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
Contributed by Daniel Berlin <dan@dberlin.org>
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/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "ggc.h"
#include "tree.h"
#include "basic-block.h"
#include "diagnostic.h"
#include "tree-inline.h"
#include "tree-flow.h"
#include "gimple.h"
#include "tree-dump.h"
#include "timevar.h"
#include "tree-iterator.h"
#include "tree-pass.h"
#include "alloc-pool.h"
#include "vec.h"
#include "langhooks.h"
#include "pointer-set.h"
#include "cfgloop.h"
#include "flags.h"
/* This is a simple global reassociation pass. It is, in part, based
on the LLVM pass of the same name (They do some things more/less
than we do, in different orders, etc).
It consists of five steps:
1. Breaking up subtract operations into addition + negate, where
it would promote the reassociation of adds.
2. Left linearization of the expression trees, so that (A+B)+(C+D)
becomes (((A+B)+C)+D), which is easier for us to rewrite later.
During linearization, we place the operands of the binary
expressions into a vector of operand_entry_t
3. Optimization of the operand lists, eliminating things like a +
-a, a & a, etc.
4. Rewrite the expression trees we linearized and optimized so
they are in proper rank order.
5. Repropagate negates, as nothing else will clean it up ATM.
A bit of theory on #4, since nobody seems to write anything down
about why it makes sense to do it the way they do it:
We could do this much nicer theoretically, but don't (for reasons
explained after how to do it theoretically nice :P).
In order to promote the most redundancy elimination, you want
binary expressions whose operands are the same rank (or
preferably, the same value) exposed to the redundancy eliminator,
for possible elimination.
So the way to do this if we really cared, is to build the new op
tree from the leaves to the roots, merging as you go, and putting the
new op on the end of the worklist, until you are left with one
thing on the worklist.
IE if you have to rewrite the following set of operands (listed with
rank in parentheses), with opcode PLUS_EXPR:
a (1), b (1), c (1), d (2), e (2)
We start with our merge worklist empty, and the ops list with all of
those on it.
You want to first merge all leaves of the same rank, as much as
possible.
So first build a binary op of
mergetmp = a + b, and put "mergetmp" on the merge worklist.
Because there is no three operand form of PLUS_EXPR, c is not going to
be exposed to redundancy elimination as a rank 1 operand.
So you might as well throw it on the merge worklist (you could also
consider it to now be a rank two operand, and merge it with d and e,
but in this case, you then have evicted e from a binary op. So at
least in this situation, you can't win.)
Then build a binary op of d + e
mergetmp2 = d + e
and put mergetmp2 on the merge worklist.
so merge worklist = {mergetmp, c, mergetmp2}
Continue building binary ops of these operations until you have only
one operation left on the worklist.
So we have
build binary op
mergetmp3 = mergetmp + c
worklist = {mergetmp2, mergetmp3}
mergetmp4 = mergetmp2 + mergetmp3
worklist = {mergetmp4}
because we have one operation left, we can now just set the original
statement equal to the result of that operation.
This will at least expose a + b and d + e to redundancy elimination
as binary operations.
For extra points, you can reuse the old statements to build the
mergetmps, since you shouldn't run out.
So why don't we do this?
Because it's expensive, and rarely will help. Most trees we are
reassociating have 3 or less ops. If they have 2 ops, they already
will be written into a nice single binary op. If you have 3 ops, a
single simple check suffices to tell you whether the first two are of the
same rank. If so, you know to order it
mergetmp = op1 + op2
newstmt = mergetmp + op3
instead of
mergetmp = op2 + op3
newstmt = mergetmp + op1
If all three are of the same rank, you can't expose them all in a
single binary operator anyway, so the above is *still* the best you
can do.
Thus, this is what we do. When we have three ops left, we check to see
what order to put them in, and call it a day. As a nod to vector sum
reduction, we check if any of the ops are really a phi node that is a
destructive update for the associating op, and keep the destructive
update together for vector sum reduction recognition. */
/* Statistics */
static struct
{
int linearized;
int constants_eliminated;
int ops_eliminated;
int rewritten;
} reassociate_stats;
/* Operator, rank pair. */
typedef struct operand_entry
{
unsigned int rank;
tree op;
} *operand_entry_t;
static alloc_pool operand_entry_pool;
/* Starting rank number for a given basic block, so that we can rank
operations using unmovable instructions in that BB based on the bb
depth. */
static long *bb_rank;
/* Operand->rank hashtable. */
static struct pointer_map_t *operand_rank;
/* Look up the operand rank structure for expression E. */
static inline long
find_operand_rank (tree e)
{
void **slot = pointer_map_contains (operand_rank, e);
return slot ? (long) *slot : -1;
}
/* Insert {E,RANK} into the operand rank hashtable. */
static inline void
insert_operand_rank (tree e, long rank)
{
void **slot;
gcc_assert (rank > 0);
slot = pointer_map_insert (operand_rank, e);
gcc_assert (!*slot);
*slot = (void *) rank;
}
/* Given an expression E, return the rank of the expression. */
static long
get_rank (tree e)
{
/* Constants have rank 0. */
if (is_gimple_min_invariant (e))
return 0;
/* SSA_NAME's have the rank of the expression they are the result
of.
For globals and uninitialized values, the rank is 0.
For function arguments, use the pre-setup rank.
For PHI nodes, stores, asm statements, etc, we use the rank of
the BB.
For simple operations, the rank is the maximum rank of any of
its operands, or the bb_rank, whichever is less.
I make no claims that this is optimal, however, it gives good
results. */
if (TREE_CODE (e) == SSA_NAME)
{
gimple stmt;
long rank, maxrank;
int i, n;
if (TREE_CODE (SSA_NAME_VAR (e)) == PARM_DECL
&& SSA_NAME_IS_DEFAULT_DEF (e))
return find_operand_rank (e);
stmt = SSA_NAME_DEF_STMT (e);
if (gimple_bb (stmt) == NULL)
return 0;
if (!is_gimple_assign (stmt)
|| !ZERO_SSA_OPERANDS (stmt, SSA_OP_VIRTUAL_DEFS))
return bb_rank[gimple_bb (stmt)->index];
/* If we already have a rank for this expression, use that. */
rank = find_operand_rank (e);
if (rank != -1)
return rank;
/* Otherwise, find the maximum rank for the operands, or the bb
rank, whichever is less. */
rank = 0;
maxrank = bb_rank[gimple_bb(stmt)->index];
if (gimple_assign_single_p (stmt))
{
tree rhs = gimple_assign_rhs1 (stmt);
n = TREE_OPERAND_LENGTH (rhs);
if (n == 0)
rank = MAX (rank, get_rank (rhs));
else
{
for (i = 0;
i < n && TREE_OPERAND (rhs, i) && rank != maxrank; i++)
rank = MAX(rank, get_rank (TREE_OPERAND (rhs, i)));
}
}
else
{
n = gimple_num_ops (stmt);
for (i = 1; i < n && rank != maxrank; i++)
{
gcc_assert (gimple_op (stmt, i));
rank = MAX(rank, get_rank (gimple_op (stmt, i)));
}
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Rank for ");
print_generic_expr (dump_file, e, 0);
fprintf (dump_file, " is %ld\n", (rank + 1));
}
/* Note the rank in the hashtable so we don't recompute it. */
insert_operand_rank (e, (rank + 1));
return (rank + 1);
}
/* Globals, etc, are rank 0 */
return 0;
}
DEF_VEC_P(operand_entry_t);
DEF_VEC_ALLOC_P(operand_entry_t, heap);
/* We want integer ones to end up last no matter what, since they are
the ones we can do the most with. */
#define INTEGER_CONST_TYPE 1 << 3
#define FLOAT_CONST_TYPE 1 << 2
#define OTHER_CONST_TYPE 1 << 1
/* Classify an invariant tree into integer, float, or other, so that
we can sort them to be near other constants of the same type. */
static inline int
constant_type (tree t)
{
if (INTEGRAL_TYPE_P (TREE_TYPE (t)))
return INTEGER_CONST_TYPE;
else if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (t)))
return FLOAT_CONST_TYPE;
else
return OTHER_CONST_TYPE;
}
/* qsort comparison function to sort operand entries PA and PB by rank
so that the sorted array is ordered by rank in decreasing order. */
static int
sort_by_operand_rank (const void *pa, const void *pb)
{
const operand_entry_t oea = *(const operand_entry_t *)pa;
const operand_entry_t oeb = *(const operand_entry_t *)pb;
/* It's nicer for optimize_expression if constants that are likely
to fold when added/multiplied//whatever are put next to each
other. Since all constants have rank 0, order them by type. */
if (oeb->rank == 0 && oea->rank == 0)
return constant_type (oeb->op) - constant_type (oea->op);
/* Lastly, make sure the versions that are the same go next to each
other. We use SSA_NAME_VERSION because it's stable. */
if ((oeb->rank - oea->rank == 0)
&& TREE_CODE (oea->op) == SSA_NAME
&& TREE_CODE (oeb->op) == SSA_NAME)
return SSA_NAME_VERSION (oeb->op) - SSA_NAME_VERSION (oea->op);
return oeb->rank - oea->rank;
}
/* Add an operand entry to *OPS for the tree operand OP. */
static void
add_to_ops_vec (VEC(operand_entry_t, heap) **ops, tree op)
{
operand_entry_t oe = (operand_entry_t) pool_alloc (operand_entry_pool);
oe->op = op;
oe->rank = get_rank (op);
VEC_safe_push (operand_entry_t, heap, *ops, oe);
}
/* Return true if STMT is reassociable operation containing a binary
operation with tree code CODE, and is inside LOOP. */
static bool
is_reassociable_op (gimple stmt, enum tree_code code, struct loop *loop)
{
basic_block bb = gimple_bb (stmt);
if (gimple_bb (stmt) == NULL)
return false;
if (!flow_bb_inside_loop_p (loop, bb))
return false;
if (is_gimple_assign (stmt)
&& gimple_assign_rhs_code (stmt) == code
&& has_single_use (gimple_assign_lhs (stmt)))
return true;
return false;
}
/* Given NAME, if NAME is defined by a unary operation OPCODE, return the
operand of the negate operation. Otherwise, return NULL. */
static tree
get_unary_op (tree name, enum tree_code opcode)
{
gimple stmt = SSA_NAME_DEF_STMT (name);
if (!is_gimple_assign (stmt))
return NULL_TREE;
if (gimple_assign_rhs_code (stmt) == opcode)
return gimple_assign_rhs1 (stmt);
return NULL_TREE;
}
/* If CURR and LAST are a pair of ops that OPCODE allows us to
eliminate through equivalences, do so, remove them from OPS, and
return true. Otherwise, return false. */
static bool
eliminate_duplicate_pair (enum tree_code opcode,
VEC (operand_entry_t, heap) **ops,
bool *all_done,
unsigned int i,
operand_entry_t curr,
operand_entry_t last)
{
/* If we have two of the same op, and the opcode is & |, min, or max,
we can eliminate one of them.
If we have two of the same op, and the opcode is ^, we can
eliminate both of them. */
if (last && last->op == curr->op)
{
switch (opcode)
{
case MAX_EXPR:
case MIN_EXPR:
case BIT_IOR_EXPR:
case BIT_AND_EXPR:
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Equivalence: ");
print_generic_expr (dump_file, curr->op, 0);
fprintf (dump_file, " [&|minmax] ");
print_generic_expr (dump_file, last->op, 0);
fprintf (dump_file, " -> ");
print_generic_stmt (dump_file, last->op, 0);
}
VEC_ordered_remove (operand_entry_t, *ops, i);
reassociate_stats.ops_eliminated ++;
return true;
case BIT_XOR_EXPR:
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Equivalence: ");
print_generic_expr (dump_file, curr->op, 0);
fprintf (dump_file, " ^ ");
print_generic_expr (dump_file, last->op, 0);
fprintf (dump_file, " -> nothing\n");
}
reassociate_stats.ops_eliminated += 2;
if (VEC_length (operand_entry_t, *ops) == 2)
{
VEC_free (operand_entry_t, heap, *ops);
*ops = NULL;
add_to_ops_vec (ops, fold_convert (TREE_TYPE (last->op),
integer_zero_node));
*all_done = true;
}
else
{
VEC_ordered_remove (operand_entry_t, *ops, i-1);
VEC_ordered_remove (operand_entry_t, *ops, i-1);
}
return true;
default:
break;
}
}
return false;
}
/* If OPCODE is PLUS_EXPR, CURR->OP is really a negate expression,
look in OPS for a corresponding positive operation to cancel it
out. If we find one, remove the other from OPS, replace
OPS[CURRINDEX] with 0, and return true. Otherwise, return
false. */
static bool
eliminate_plus_minus_pair (enum tree_code opcode,
VEC (operand_entry_t, heap) **ops,
unsigned int currindex,
operand_entry_t curr)
{
tree negateop;
unsigned int i;
operand_entry_t oe;
if (opcode != PLUS_EXPR || TREE_CODE (curr->op) != SSA_NAME)
return false;
negateop = get_unary_op (curr->op, NEGATE_EXPR);
if (negateop == NULL_TREE)
return false;
/* Any non-negated version will have a rank that is one less than
the current rank. So once we hit those ranks, if we don't find
one, we can stop. */
for (i = currindex + 1;
VEC_iterate (operand_entry_t, *ops, i, oe)
&& oe->rank >= curr->rank - 1 ;
i++)
{
if (oe->op == negateop)
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Equivalence: ");
print_generic_expr (dump_file, negateop, 0);
fprintf (dump_file, " + -");
print_generic_expr (dump_file, oe->op, 0);
fprintf (dump_file, " -> 0\n");
}
VEC_ordered_remove (operand_entry_t, *ops, i);
add_to_ops_vec (ops, fold_convert(TREE_TYPE (oe->op),
integer_zero_node));
VEC_ordered_remove (operand_entry_t, *ops, currindex);
reassociate_stats.ops_eliminated ++;
return true;
}
}
return false;
}
/* If OPCODE is BIT_IOR_EXPR, BIT_AND_EXPR, and, CURR->OP is really a
bitwise not expression, look in OPS for a corresponding operand to
cancel it out. If we find one, remove the other from OPS, replace
OPS[CURRINDEX] with 0, and return true. Otherwise, return
false. */
static bool
eliminate_not_pairs (enum tree_code opcode,
VEC (operand_entry_t, heap) **ops,
unsigned int currindex,
operand_entry_t curr)
{
tree notop;
unsigned int i;
operand_entry_t oe;
if ((opcode != BIT_IOR_EXPR && opcode != BIT_AND_EXPR)
|| TREE_CODE (curr->op) != SSA_NAME)
return false;
notop = get_unary_op (curr->op, BIT_NOT_EXPR);
if (notop == NULL_TREE)
return false;
/* Any non-not version will have a rank that is one less than
the current rank. So once we hit those ranks, if we don't find
one, we can stop. */
for (i = currindex + 1;
VEC_iterate (operand_entry_t, *ops, i, oe)
&& oe->rank >= curr->rank - 1;
i++)
{
if (oe->op == notop)
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Equivalence: ");
print_generic_expr (dump_file, notop, 0);
if (opcode == BIT_AND_EXPR)
fprintf (dump_file, " & ~");
else if (opcode == BIT_IOR_EXPR)
fprintf (dump_file, " | ~");
print_generic_expr (dump_file, oe->op, 0);
if (opcode == BIT_AND_EXPR)
fprintf (dump_file, " -> 0\n");
else if (opcode == BIT_IOR_EXPR)
fprintf (dump_file, " -> -1\n");
}
if (opcode == BIT_AND_EXPR)
oe->op = fold_convert (TREE_TYPE (oe->op), integer_zero_node);
else if (opcode == BIT_IOR_EXPR)
oe->op = build_low_bits_mask (TREE_TYPE (oe->op),
TYPE_PRECISION (TREE_TYPE (oe->op)));
reassociate_stats.ops_eliminated
+= VEC_length (operand_entry_t, *ops) - 1;
VEC_free (operand_entry_t, heap, *ops);
*ops = NULL;
VEC_safe_push (operand_entry_t, heap, *ops, oe);
return true;
}
}
return false;
}
/* Use constant value that may be present in OPS to try to eliminate
operands. Note that this function is only really used when we've
eliminated ops for other reasons, or merged constants. Across
single statements, fold already does all of this, plus more. There
is little point in duplicating logic, so I've only included the
identities that I could ever construct testcases to trigger. */
static void
eliminate_using_constants (enum tree_code opcode,
VEC(operand_entry_t, heap) **ops)
{
operand_entry_t oelast = VEC_last (operand_entry_t, *ops);
tree type = TREE_TYPE (oelast->op);
if (oelast->rank == 0
&& (INTEGRAL_TYPE_P (type) || FLOAT_TYPE_P (type)))
{
switch (opcode)
{
case BIT_AND_EXPR:
if (integer_zerop (oelast->op))
{
if (VEC_length (operand_entry_t, *ops) != 1)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Found & 0, removing all other ops\n");
reassociate_stats.ops_eliminated
+= VEC_length (operand_entry_t, *ops) - 1;
VEC_free (operand_entry_t, heap, *ops);
*ops = NULL;
VEC_safe_push (operand_entry_t, heap, *ops, oelast);
return;
}
}
else if (integer_all_onesp (oelast->op))
{
if (VEC_length (operand_entry_t, *ops) != 1)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Found & -1, removing\n");
VEC_pop (operand_entry_t, *ops);
reassociate_stats.ops_eliminated++;
}
}
break;
case BIT_IOR_EXPR:
if (integer_all_onesp (oelast->op))
{
if (VEC_length (operand_entry_t, *ops) != 1)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Found | -1, removing all other ops\n");
reassociate_stats.ops_eliminated
+= VEC_length (operand_entry_t, *ops) - 1;
VEC_free (operand_entry_t, heap, *ops);
*ops = NULL;
VEC_safe_push (operand_entry_t, heap, *ops, oelast);
return;
}
}
else if (integer_zerop (oelast->op))
{
if (VEC_length (operand_entry_t, *ops) != 1)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Found | 0, removing\n");
VEC_pop (operand_entry_t, *ops);
reassociate_stats.ops_eliminated++;
}
}
break;
case MULT_EXPR:
if (integer_zerop (oelast->op)
|| (FLOAT_TYPE_P (type)
&& !HONOR_NANS (TYPE_MODE (type))
&& !HONOR_SIGNED_ZEROS (TYPE_MODE (type))
&& real_zerop (oelast->op)))
{
if (VEC_length (operand_entry_t, *ops) != 1)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Found * 0, removing all other ops\n");
reassociate_stats.ops_eliminated
+= VEC_length (operand_entry_t, *ops) - 1;
VEC_free (operand_entry_t, heap, *ops);
*ops = NULL;
VEC_safe_push (operand_entry_t, heap, *ops, oelast);
return;
}
}
else if (integer_onep (oelast->op)
|| (FLOAT_TYPE_P (type)
&& !HONOR_SNANS (TYPE_MODE (type))
&& real_onep (oelast->op)))
{
if (VEC_length (operand_entry_t, *ops) != 1)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Found * 1, removing\n");
VEC_pop (operand_entry_t, *ops);
reassociate_stats.ops_eliminated++;
return;
}
}
break;
case BIT_XOR_EXPR:
case PLUS_EXPR:
case MINUS_EXPR:
if (integer_zerop (oelast->op)
|| (FLOAT_TYPE_P (type)
&& (opcode == PLUS_EXPR || opcode == MINUS_EXPR)
&& fold_real_zero_addition_p (type, oelast->op,
opcode == MINUS_EXPR)))
{
if (VEC_length (operand_entry_t, *ops) != 1)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Found [|^+] 0, removing\n");
VEC_pop (operand_entry_t, *ops);
reassociate_stats.ops_eliminated++;
return;
}
}
break;
default:
break;
}
}
}
static void linearize_expr_tree (VEC(operand_entry_t, heap) **, gimple,
bool, bool);
/* Structure for tracking and counting operands. */
typedef struct oecount_s {
int cnt;
enum tree_code oecode;
tree op;
} oecount;
DEF_VEC_O(oecount);
DEF_VEC_ALLOC_O(oecount,heap);
/* The heap for the oecount hashtable and the sorted list of operands. */
static VEC (oecount, heap) *cvec;
/* Hash function for oecount. */
static hashval_t
oecount_hash (const void *p)
{
const oecount *c = VEC_index (oecount, cvec, (size_t)p - 42);
return htab_hash_pointer (c->op) ^ (hashval_t)c->oecode;
}
/* Comparison function for oecount. */
static int
oecount_eq (const void *p1, const void *p2)
{
const oecount *c1 = VEC_index (oecount, cvec, (size_t)p1 - 42);
const oecount *c2 = VEC_index (oecount, cvec, (size_t)p2 - 42);
return (c1->oecode == c2->oecode
&& c1->op == c2->op);
}
/* Comparison function for qsort sorting oecount elements by count. */
static int
oecount_cmp (const void *p1, const void *p2)
{
const oecount *c1 = (const oecount *)p1;
const oecount *c2 = (const oecount *)p2;
return c1->cnt - c2->cnt;
}
/* Walks the linear chain with result *DEF searching for an operation
with operand OP and code OPCODE removing that from the chain. *DEF
is updated if there is only one operand but no operation left. */
static void
zero_one_operation (tree *def, enum tree_code opcode, tree op)
{
gimple stmt = SSA_NAME_DEF_STMT (*def);
do
{
tree name = gimple_assign_rhs1 (stmt);
/* If this is the operation we look for and one of the operands
is ours simply propagate the other operand into the stmts
single use. */
if (gimple_assign_rhs_code (stmt) == opcode
&& (name == op
|| gimple_assign_rhs2 (stmt) == op))
{
gimple use_stmt;
use_operand_p use;
gimple_stmt_iterator gsi;
if (name == op)
name = gimple_assign_rhs2 (stmt);
gcc_assert (has_single_use (gimple_assign_lhs (stmt)));
single_imm_use (gimple_assign_lhs (stmt), &use, &use_stmt);
if (gimple_assign_lhs (stmt) == *def)
*def = name;
SET_USE (use, name);
if (TREE_CODE (name) != SSA_NAME)
update_stmt (use_stmt);
gsi = gsi_for_stmt (stmt);
gsi_remove (&gsi, true);
release_defs (stmt);
return;
}
/* Continue walking the chain. */
gcc_assert (name != op
&& TREE_CODE (name) == SSA_NAME);
stmt = SSA_NAME_DEF_STMT (name);
}
while (1);
}
/* Builds one statement performing OP1 OPCODE OP2 using TMPVAR for
the result. Places the statement after the definition of either
OP1 or OP2. Returns the new statement. */
static gimple
build_and_add_sum (tree tmpvar, tree op1, tree op2, enum tree_code opcode)
{
gimple op1def = NULL, op2def = NULL;
gimple_stmt_iterator gsi;
tree op;
gimple sum;
/* Create the addition statement. */
sum = gimple_build_assign_with_ops (opcode, tmpvar, op1, op2);
op = make_ssa_name (tmpvar, sum);
gimple_assign_set_lhs (sum, op);
/* Find an insertion place and insert. */
if (TREE_CODE (op1) == SSA_NAME)
op1def = SSA_NAME_DEF_STMT (op1);
if (TREE_CODE (op2) == SSA_NAME)
op2def = SSA_NAME_DEF_STMT (op2);
if ((!op1def || gimple_nop_p (op1def))
&& (!op2def || gimple_nop_p (op2def)))
{
gsi = gsi_after_labels (single_succ (ENTRY_BLOCK_PTR));
gsi_insert_before (&gsi, sum, GSI_NEW_STMT);
}
else if ((!op1def || gimple_nop_p (op1def))
|| (op2def && !gimple_nop_p (op2def)
&& stmt_dominates_stmt_p (op1def, op2def)))
{
if (gimple_code (op2def) == GIMPLE_PHI)
{
gsi = gsi_after_labels (gimple_bb (op2def));
gsi_insert_before (&gsi, sum, GSI_NEW_STMT);
}
else
{
if (!stmt_ends_bb_p (op2def))
{
gsi = gsi_for_stmt (op2def);
gsi_insert_after (&gsi, sum, GSI_NEW_STMT);
}
else
{
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, gimple_bb (op2def)->succs)
if (e->flags & EDGE_FALLTHRU)
gsi_insert_on_edge_immediate (e, sum);
}
}
}
else
{
if (gimple_code (op1def) == GIMPLE_PHI)
{
gsi = gsi_after_labels (gimple_bb (op1def));
gsi_insert_before (&gsi, sum, GSI_NEW_STMT);
}
else
{
if (!stmt_ends_bb_p (op1def))
{
gsi = gsi_for_stmt (op1def);
gsi_insert_after (&gsi, sum, GSI_NEW_STMT);
}
else
{
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, gimple_bb (op1def)->succs)
if (e->flags & EDGE_FALLTHRU)
gsi_insert_on_edge_immediate (e, sum);
}
}
}
update_stmt (sum);
return sum;
}
/* Perform un-distribution of divisions and multiplications.
A * X + B * X is transformed into (A + B) * X and A / X + B / X
to (A + B) / X for real X.
The algorithm is organized as follows.
- First we walk the addition chain *OPS looking for summands that
are defined by a multiplication or a real division. This results
in the candidates bitmap with relevant indices into *OPS.
- Second we build the chains of multiplications or divisions for
these candidates, counting the number of occurences of (operand, code)
pairs in all of the candidates chains.
- Third we sort the (operand, code) pairs by number of occurence and
process them starting with the pair with the most uses.
* For each such pair we walk the candidates again to build a
second candidate bitmap noting all multiplication/division chains
that have at least one occurence of (operand, code).
* We build an alternate addition chain only covering these
candidates with one (operand, code) operation removed from their
multiplication/division chain.
* The first candidate gets replaced by the alternate addition chain
multiplied/divided by the operand.
* All candidate chains get disabled for further processing and
processing of (operand, code) pairs continues.
The alternate addition chains built are re-processed by the main
reassociation algorithm which allows optimizing a * x * y + b * y * x
to (a + b ) * x * y in one invocation of the reassociation pass. */
static bool
undistribute_ops_list (enum tree_code opcode,
VEC (operand_entry_t, heap) **ops, struct loop *loop)
{
unsigned int length = VEC_length (operand_entry_t, *ops);
operand_entry_t oe1;
unsigned i, j;
sbitmap candidates, candidates2;
unsigned nr_candidates, nr_candidates2;
sbitmap_iterator sbi0;
VEC (operand_entry_t, heap) **subops;
htab_t ctable;
bool changed = false;
if (length <= 1
|| opcode != PLUS_EXPR)
return false;
/* Build a list of candidates to process. */
candidates = sbitmap_alloc (length);
sbitmap_zero (candidates);
nr_candidates = 0;
for (i = 0; VEC_iterate (operand_entry_t, *ops, i, oe1); ++i)
{
enum tree_code dcode;
gimple oe1def;
if (TREE_CODE (oe1->op) != SSA_NAME)
continue;
oe1def = SSA_NAME_DEF_STMT (oe1->op);
if (!is_gimple_assign (oe1def))
continue;
dcode = gimple_assign_rhs_code (oe1def);
if ((dcode != MULT_EXPR
&& dcode != RDIV_EXPR)
|| !is_reassociable_op (oe1def, dcode, loop))
continue;
SET_BIT (candidates, i);
nr_candidates++;
}
if (nr_candidates < 2)
{
sbitmap_free (candidates);
return false;
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "searching for un-distribute opportunities ");
print_generic_expr (dump_file,
VEC_index (operand_entry_t, *ops,
sbitmap_first_set_bit (candidates))->op, 0);
fprintf (dump_file, " %d\n", nr_candidates);
}
/* Build linearized sub-operand lists and the counting table. */
cvec = NULL;