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tree-ssa-forwprop.c
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tree-ssa-forwprop.c
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/* Forward propagation of expressions for single use variables.
Copyright (C) 2004, 2005, 2007, 2008, 2009, 2010, 2011
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/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "tm_p.h"
#include "basic-block.h"
#include "timevar.h"
#include "tree-pretty-print.h"
#include "tree-flow.h"
#include "tree-pass.h"
#include "tree-dump.h"
#include "langhooks.h"
#include "flags.h"
#include "gimple.h"
#include "expr.h"
/* This pass propagates the RHS of assignment statements into use
sites of the LHS of the assignment. It's basically a specialized
form of tree combination. It is hoped all of this can disappear
when we have a generalized tree combiner.
One class of common cases we handle is forward propagating a single use
variable into a COND_EXPR.
bb0:
x = a COND b;
if (x) goto ... else goto ...
Will be transformed into:
bb0:
if (a COND b) goto ... else goto ...
Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
Or (assuming c1 and c2 are constants):
bb0:
x = a + c1;
if (x EQ/NEQ c2) goto ... else goto ...
Will be transformed into:
bb0:
if (a EQ/NEQ (c2 - c1)) goto ... else goto ...
Similarly for x = a - c1.
Or
bb0:
x = !a
if (x) goto ... else goto ...
Will be transformed into:
bb0:
if (a == 0) goto ... else goto ...
Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
For these cases, we propagate A into all, possibly more than one,
COND_EXPRs that use X.
Or
bb0:
x = (typecast) a
if (x) goto ... else goto ...
Will be transformed into:
bb0:
if (a != 0) goto ... else goto ...
(Assuming a is an integral type and x is a boolean or x is an
integral and a is a boolean.)
Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
For these cases, we propagate A into all, possibly more than one,
COND_EXPRs that use X.
In addition to eliminating the variable and the statement which assigns
a value to the variable, we may be able to later thread the jump without
adding insane complexity in the dominator optimizer.
Also note these transformations can cascade. We handle this by having
a worklist of COND_EXPR statements to examine. As we make a change to
a statement, we put it back on the worklist to examine on the next
iteration of the main loop.
A second class of propagation opportunities arises for ADDR_EXPR
nodes.
ptr = &x->y->z;
res = *ptr;
Will get turned into
res = x->y->z;
Or
ptr = (type1*)&type2var;
res = *ptr
Will get turned into (if type1 and type2 are the same size
and neither have volatile on them):
res = VIEW_CONVERT_EXPR<type1>(type2var)
Or
ptr = &x[0];
ptr2 = ptr + <constant>;
Will get turned into
ptr2 = &x[constant/elementsize];
Or
ptr = &x[0];
offset = index * element_size;
offset_p = (pointer) offset;
ptr2 = ptr + offset_p
Will get turned into:
ptr2 = &x[index];
Or
ssa = (int) decl
res = ssa & 1
Provided that decl has known alignment >= 2, will get turned into
res = 0
We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
{NOT_EXPR,NEG_EXPR}.
This will (of course) be extended as other needs arise. */
static bool forward_propagate_addr_expr (tree name, tree rhs);
/* Set to true if we delete EH edges during the optimization. */
static bool cfg_changed;
static tree rhs_to_tree (tree type, gimple stmt);
/* Get the next statement we can propagate NAME's value into skipping
trivial copies. Returns the statement that is suitable as a
propagation destination or NULL_TREE if there is no such one.
This only returns destinations in a single-use chain. FINAL_NAME_P
if non-NULL is written to the ssa name that represents the use. */
static gimple
get_prop_dest_stmt (tree name, tree *final_name_p)
{
use_operand_p use;
gimple use_stmt;
do {
/* If name has multiple uses, bail out. */
if (!single_imm_use (name, &use, &use_stmt))
return NULL;
/* If this is not a trivial copy, we found it. */
if (!gimple_assign_ssa_name_copy_p (use_stmt)
|| gimple_assign_rhs1 (use_stmt) != name)
break;
/* Continue searching uses of the copy destination. */
name = gimple_assign_lhs (use_stmt);
} while (1);
if (final_name_p)
*final_name_p = name;
return use_stmt;
}
/* Get the statement we can propagate from into NAME skipping
trivial copies. Returns the statement which defines the
propagation source or NULL_TREE if there is no such one.
If SINGLE_USE_ONLY is set considers only sources which have
a single use chain up to NAME. If SINGLE_USE_P is non-null,
it is set to whether the chain to NAME is a single use chain
or not. SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set. */
static gimple
get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
{
bool single_use = true;
do {
gimple def_stmt = SSA_NAME_DEF_STMT (name);
if (!has_single_use (name))
{
single_use = false;
if (single_use_only)
return NULL;
}
/* If name is defined by a PHI node or is the default def, bail out. */
if (!is_gimple_assign (def_stmt))
return NULL;
/* If def_stmt is not a simple copy, we possibly found it. */
if (!gimple_assign_ssa_name_copy_p (def_stmt))
{
tree rhs;
if (!single_use_only && single_use_p)
*single_use_p = single_use;
/* We can look through pointer conversions in the search
for a useful stmt for the comparison folding. */
rhs = gimple_assign_rhs1 (def_stmt);
if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))
&& TREE_CODE (rhs) == SSA_NAME
&& POINTER_TYPE_P (TREE_TYPE (gimple_assign_lhs (def_stmt)))
&& POINTER_TYPE_P (TREE_TYPE (rhs)))
name = rhs;
else
return def_stmt;
}
else
{
/* Continue searching the def of the copy source name. */
name = gimple_assign_rhs1 (def_stmt);
}
} while (1);
}
/* Checks if the destination ssa name in DEF_STMT can be used as
propagation source. Returns true if so, otherwise false. */
static bool
can_propagate_from (gimple def_stmt)
{
use_operand_p use_p;
ssa_op_iter iter;
gcc_assert (is_gimple_assign (def_stmt));
/* If the rhs has side-effects we cannot propagate from it. */
if (gimple_has_volatile_ops (def_stmt))
return false;
/* If the rhs is a load we cannot propagate from it. */
if (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_reference
|| TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_declaration)
return false;
/* Constants can be always propagated. */
if (gimple_assign_single_p (def_stmt)
&& is_gimple_min_invariant (gimple_assign_rhs1 (def_stmt)))
return true;
/* We cannot propagate ssa names that occur in abnormal phi nodes. */
FOR_EACH_SSA_USE_OPERAND (use_p, def_stmt, iter, SSA_OP_USE)
if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (use_p)))
return false;
/* If the definition is a conversion of a pointer to a function type,
then we can not apply optimizations as some targets require
function pointers to be canonicalized and in this case this
optimization could eliminate a necessary canonicalization. */
if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)))
{
tree rhs = gimple_assign_rhs1 (def_stmt);
if (POINTER_TYPE_P (TREE_TYPE (rhs))
&& TREE_CODE (TREE_TYPE (TREE_TYPE (rhs))) == FUNCTION_TYPE)
return false;
}
return true;
}
/* Remove a copy chain ending in NAME along the defs.
If NAME was replaced in its only use then this function can be used
to clean up dead stmts. Returns true if cleanup-cfg has to run. */
static bool
remove_prop_source_from_use (tree name)
{
gimple_stmt_iterator gsi;
gimple stmt;
bool cfg_changed = false;
do {
basic_block bb;
if (!has_zero_uses (name))
return cfg_changed;
stmt = SSA_NAME_DEF_STMT (name);
gsi = gsi_for_stmt (stmt);
bb = gimple_bb (stmt);
release_defs (stmt);
gsi_remove (&gsi, true);
cfg_changed |= gimple_purge_dead_eh_edges (bb);
name = (gimple_assign_copy_p (stmt)) ? gimple_assign_rhs1 (stmt) : NULL;
} while (name && TREE_CODE (name) == SSA_NAME);
return cfg_changed;
}
/* Return the rhs of a gimple_assign STMT in a form of a single tree,
converted to type TYPE.
This should disappear, but is needed so we can combine expressions and use
the fold() interfaces. Long term, we need to develop folding and combine
routines that deal with gimple exclusively . */
static tree
rhs_to_tree (tree type, gimple stmt)
{
location_t loc = gimple_location (stmt);
enum tree_code code = gimple_assign_rhs_code (stmt);
if (get_gimple_rhs_class (code) == GIMPLE_TERNARY_RHS)
return fold_build3_loc (loc, code, type, gimple_assign_rhs1 (stmt),
gimple_assign_rhs2 (stmt),
gimple_assign_rhs3 (stmt));
else if (get_gimple_rhs_class (code) == GIMPLE_BINARY_RHS)
return fold_build2_loc (loc, code, type, gimple_assign_rhs1 (stmt),
gimple_assign_rhs2 (stmt));
else if (get_gimple_rhs_class (code) == GIMPLE_UNARY_RHS)
return build1 (code, type, gimple_assign_rhs1 (stmt));
else if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
return gimple_assign_rhs1 (stmt);
else
gcc_unreachable ();
}
/* Combine OP0 CODE OP1 in the context of a COND_EXPR. Returns
the folded result in a form suitable for COND_EXPR_COND or
NULL_TREE, if there is no suitable simplified form. If
INVARIANT_ONLY is true only gimple_min_invariant results are
considered simplified. */
static tree
combine_cond_expr_cond (location_t loc, enum tree_code code, tree type,
tree op0, tree op1, bool invariant_only)
{
tree t;
gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
t = fold_binary_loc (loc, code, type, op0, op1);
if (!t)
return NULL_TREE;
/* Require that we got a boolean type out if we put one in. */
gcc_assert (TREE_CODE (TREE_TYPE (t)) == TREE_CODE (type));
/* Canonicalize the combined condition for use in a COND_EXPR. */
t = canonicalize_cond_expr_cond (t);
/* Bail out if we required an invariant but didn't get one. */
if (!t || (invariant_only && !is_gimple_min_invariant (t)))
return NULL_TREE;
return t;
}
/* Propagate from the ssa name definition statements of COND_EXPR
in GIMPLE_COND statement STMT into the conditional if that simplifies it.
Returns zero if no statement was changed, one if there were
changes and two if cfg_cleanup needs to run.
This must be kept in sync with forward_propagate_into_cond. */
static int
forward_propagate_into_gimple_cond (gimple stmt)
{
int did_something = 0;
location_t loc = gimple_location (stmt);
do {
tree tmp = NULL_TREE;
tree name = NULL_TREE, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
gimple def_stmt;
bool single_use0_p = false, single_use1_p = false;
enum tree_code code = gimple_cond_code (stmt);
/* We can do tree combining on SSA_NAME and comparison expressions. */
if (TREE_CODE_CLASS (gimple_cond_code (stmt)) == tcc_comparison)
{
/* For comparisons use the first operand, that is likely to
simplify comparisons against constants. */
if (TREE_CODE (gimple_cond_lhs (stmt)) == SSA_NAME)
{
name = gimple_cond_lhs (stmt);
def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
if (def_stmt && can_propagate_from (def_stmt))
{
tree op1 = gimple_cond_rhs (stmt);
rhs0 = rhs_to_tree (TREE_TYPE (op1), def_stmt);
tmp = combine_cond_expr_cond (loc, code, boolean_type_node,
rhs0, op1, !single_use0_p);
}
}
/* If that wasn't successful, try the second operand. */
if (tmp == NULL_TREE
&& TREE_CODE (gimple_cond_rhs (stmt)) == SSA_NAME)
{
tree op0 = gimple_cond_lhs (stmt);
name = gimple_cond_rhs (stmt);
def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
if (!def_stmt || !can_propagate_from (def_stmt))
return did_something;
rhs1 = rhs_to_tree (TREE_TYPE (op0), def_stmt);
tmp = combine_cond_expr_cond (loc, code, boolean_type_node, op0,
rhs1, !single_use1_p);
}
/* If that wasn't successful either, try both operands. */
if (tmp == NULL_TREE
&& rhs0 != NULL_TREE
&& rhs1 != NULL_TREE)
tmp = combine_cond_expr_cond (loc, code, boolean_type_node, rhs0,
fold_convert_loc (loc,
TREE_TYPE (rhs0),
rhs1),
!(single_use0_p && single_use1_p));
}
if (tmp)
{
if (dump_file && tmp)
{
tree cond = build2 (gimple_cond_code (stmt),
boolean_type_node,
gimple_cond_lhs (stmt),
gimple_cond_rhs (stmt));
fprintf (dump_file, " Replaced '");
print_generic_expr (dump_file, cond, 0);
fprintf (dump_file, "' with '");
print_generic_expr (dump_file, tmp, 0);
fprintf (dump_file, "'\n");
}
gimple_cond_set_condition_from_tree (stmt, unshare_expr (tmp));
update_stmt (stmt);
/* Remove defining statements. */
if (remove_prop_source_from_use (name)
|| is_gimple_min_invariant (tmp))
did_something = 2;
else if (did_something == 0)
did_something = 1;
/* Continue combining. */
continue;
}
break;
} while (1);
return did_something;
}
/* Propagate from the ssa name definition statements of COND_EXPR
in the rhs of statement STMT into the conditional if that simplifies it.
Returns zero if no statement was changed, one if there were
changes and two if cfg_cleanup needs to run.
This must be kept in sync with forward_propagate_into_gimple_cond. */
static int
forward_propagate_into_cond (gimple_stmt_iterator *gsi_p)
{
gimple stmt = gsi_stmt (*gsi_p);
location_t loc = gimple_location (stmt);
int did_something = 0;
do {
tree tmp = NULL_TREE;
tree cond = gimple_assign_rhs1 (stmt);
tree name, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
gimple def_stmt;
bool single_use0_p = false, single_use1_p = false;
/* We can do tree combining on SSA_NAME and comparison expressions. */
if (COMPARISON_CLASS_P (cond)
&& TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
{
/* For comparisons use the first operand, that is likely to
simplify comparisons against constants. */
name = TREE_OPERAND (cond, 0);
def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
if (def_stmt && can_propagate_from (def_stmt))
{
tree op1 = TREE_OPERAND (cond, 1);
rhs0 = rhs_to_tree (TREE_TYPE (op1), def_stmt);
tmp = combine_cond_expr_cond (loc, TREE_CODE (cond),
boolean_type_node,
rhs0, op1, !single_use0_p);
}
/* If that wasn't successful, try the second operand. */
if (tmp == NULL_TREE
&& TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
{
tree op0 = TREE_OPERAND (cond, 0);
name = TREE_OPERAND (cond, 1);
def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
if (!def_stmt || !can_propagate_from (def_stmt))
return did_something;
rhs1 = rhs_to_tree (TREE_TYPE (op0), def_stmt);
tmp = combine_cond_expr_cond (loc, TREE_CODE (cond),
boolean_type_node,
op0, rhs1, !single_use1_p);
}
/* If that wasn't successful either, try both operands. */
if (tmp == NULL_TREE
&& rhs0 != NULL_TREE
&& rhs1 != NULL_TREE)
tmp = combine_cond_expr_cond (loc, TREE_CODE (cond),
boolean_type_node,
rhs0,
fold_convert_loc (loc,
TREE_TYPE (rhs0),
rhs1),
!(single_use0_p && single_use1_p));
}
else if (TREE_CODE (cond) == SSA_NAME)
{
name = cond;
def_stmt = get_prop_source_stmt (name, true, NULL);
if (def_stmt || !can_propagate_from (def_stmt))
return did_something;
rhs0 = gimple_assign_rhs1 (def_stmt);
tmp = combine_cond_expr_cond (loc, NE_EXPR, boolean_type_node, rhs0,
build_int_cst (TREE_TYPE (rhs0), 0),
false);
}
if (tmp)
{
if (dump_file && tmp)
{
fprintf (dump_file, " Replaced '");
print_generic_expr (dump_file, cond, 0);
fprintf (dump_file, "' with '");
print_generic_expr (dump_file, tmp, 0);
fprintf (dump_file, "'\n");
}
gimple_assign_set_rhs_from_tree (gsi_p, unshare_expr (tmp));
stmt = gsi_stmt (*gsi_p);
update_stmt (stmt);
/* Remove defining statements. */
if (remove_prop_source_from_use (name)
|| is_gimple_min_invariant (tmp))
did_something = 2;
else if (did_something == 0)
did_something = 1;
/* Continue combining. */
continue;
}
break;
} while (1);
return did_something;
}
/* We've just substituted an ADDR_EXPR into stmt. Update all the
relevant data structures to match. */
static void
tidy_after_forward_propagate_addr (gimple stmt)
{
/* We may have turned a trapping insn into a non-trapping insn. */
if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
&& gimple_purge_dead_eh_edges (gimple_bb (stmt)))
cfg_changed = true;
if (TREE_CODE (gimple_assign_rhs1 (stmt)) == ADDR_EXPR)
recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1 (stmt));
}
/* DEF_RHS contains the address of the 0th element in an array.
USE_STMT uses type of DEF_RHS to compute the address of an
arbitrary element within the array. The (variable) byte offset
of the element is contained in OFFSET.
We walk back through the use-def chains of OFFSET to verify that
it is indeed computing the offset of an element within the array
and extract the index corresponding to the given byte offset.
We then try to fold the entire address expression into a form
&array[index].
If we are successful, we replace the right hand side of USE_STMT
with the new address computation. */
static bool
forward_propagate_addr_into_variable_array_index (tree offset,
tree def_rhs,
gimple_stmt_iterator *use_stmt_gsi)
{
tree index, tunit;
gimple offset_def, use_stmt = gsi_stmt (*use_stmt_gsi);
tree new_rhs, tmp;
if (TREE_CODE (TREE_OPERAND (def_rhs, 0)) == ARRAY_REF)
tunit = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)));
else if (TREE_CODE (TREE_TYPE (TREE_OPERAND (def_rhs, 0))) == ARRAY_TYPE)
tunit = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (TREE_TYPE (def_rhs))));
else
return false;
if (!host_integerp (tunit, 1))
return false;
/* Get the offset's defining statement. */
offset_def = SSA_NAME_DEF_STMT (offset);
/* Try to find an expression for a proper index. This is either a
multiplication expression by the element size or just the ssa name we came
along in case the element size is one. In that case, however, we do not
allow multiplications because they can be computing index to a higher
level dimension (PR 37861). */
if (integer_onep (tunit))
{
if (is_gimple_assign (offset_def)
&& gimple_assign_rhs_code (offset_def) == MULT_EXPR)
return false;
index = offset;
}
else
{
/* The statement which defines OFFSET before type conversion
must be a simple GIMPLE_ASSIGN. */
if (!is_gimple_assign (offset_def))
return false;
/* The RHS of the statement which defines OFFSET must be a
multiplication of an object by the size of the array elements.
This implicitly verifies that the size of the array elements
is constant. */
if (gimple_assign_rhs_code (offset_def) == MULT_EXPR
&& TREE_CODE (gimple_assign_rhs2 (offset_def)) == INTEGER_CST
&& tree_int_cst_equal (gimple_assign_rhs2 (offset_def), tunit))
{
/* The first operand to the MULT_EXPR is the desired index. */
index = gimple_assign_rhs1 (offset_def);
}
/* If we have idx * tunit + CST * tunit re-associate that. */
else if ((gimple_assign_rhs_code (offset_def) == PLUS_EXPR
|| gimple_assign_rhs_code (offset_def) == MINUS_EXPR)
&& TREE_CODE (gimple_assign_rhs1 (offset_def)) == SSA_NAME
&& TREE_CODE (gimple_assign_rhs2 (offset_def)) == INTEGER_CST
&& (tmp = div_if_zero_remainder (EXACT_DIV_EXPR,
gimple_assign_rhs2 (offset_def),
tunit)) != NULL_TREE)
{
gimple offset_def2 = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (offset_def));
if (is_gimple_assign (offset_def2)
&& gimple_assign_rhs_code (offset_def2) == MULT_EXPR
&& TREE_CODE (gimple_assign_rhs2 (offset_def2)) == INTEGER_CST
&& tree_int_cst_equal (gimple_assign_rhs2 (offset_def2), tunit))
{
index = fold_build2 (gimple_assign_rhs_code (offset_def),
TREE_TYPE (offset),
gimple_assign_rhs1 (offset_def2), tmp);
}
else
return false;
}
else
return false;
}
/* Replace the pointer addition with array indexing. */
index = force_gimple_operand_gsi (use_stmt_gsi, index, true, NULL_TREE,
true, GSI_SAME_STMT);
if (TREE_CODE (TREE_OPERAND (def_rhs, 0)) == ARRAY_REF)
{
new_rhs = unshare_expr (def_rhs);
TREE_OPERAND (TREE_OPERAND (new_rhs, 0), 1) = index;
}
else
{
new_rhs = build4 (ARRAY_REF, TREE_TYPE (TREE_TYPE (TREE_TYPE (def_rhs))),
unshare_expr (TREE_OPERAND (def_rhs, 0)),
index, integer_zero_node, NULL_TREE);
new_rhs = build_fold_addr_expr (new_rhs);
if (!useless_type_conversion_p (TREE_TYPE (gimple_assign_lhs (use_stmt)),
TREE_TYPE (new_rhs)))
{
new_rhs = force_gimple_operand_gsi (use_stmt_gsi, new_rhs, true,
NULL_TREE, true, GSI_SAME_STMT);
new_rhs = fold_convert (TREE_TYPE (gimple_assign_lhs (use_stmt)),
new_rhs);
}
}
gimple_assign_set_rhs_from_tree (use_stmt_gsi, new_rhs);
use_stmt = gsi_stmt (*use_stmt_gsi);
/* That should have created gimple, so there is no need to
record information to undo the propagation. */
fold_stmt_inplace (use_stmt);
tidy_after_forward_propagate_addr (use_stmt);
return true;
}
/* NAME is a SSA_NAME representing DEF_RHS which is of the form
ADDR_EXPR <whatever>.
Try to forward propagate the ADDR_EXPR into the use USE_STMT.
Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
node or for recovery of array indexing from pointer arithmetic.
Return true if the propagation was successful (the propagation can
be not totally successful, yet things may have been changed). */
static bool
forward_propagate_addr_expr_1 (tree name, tree def_rhs,
gimple_stmt_iterator *use_stmt_gsi,
bool single_use_p)
{
tree lhs, rhs, rhs2, array_ref;
gimple use_stmt = gsi_stmt (*use_stmt_gsi);
enum tree_code rhs_code;
bool res = true;
gcc_assert (TREE_CODE (def_rhs) == ADDR_EXPR);
lhs = gimple_assign_lhs (use_stmt);
rhs_code = gimple_assign_rhs_code (use_stmt);
rhs = gimple_assign_rhs1 (use_stmt);
/* Trivial cases. The use statement could be a trivial copy or a
useless conversion. Recurse to the uses of the lhs as copyprop does
not copy through different variant pointers and FRE does not catch
all useless conversions. Treat the case of a single-use name and
a conversion to def_rhs type separate, though. */
if (TREE_CODE (lhs) == SSA_NAME
&& ((rhs_code == SSA_NAME && rhs == name)
|| CONVERT_EXPR_CODE_P (rhs_code)))
{
/* Only recurse if we don't deal with a single use or we cannot
do the propagation to the current statement. In particular
we can end up with a conversion needed for a non-invariant
address which we cannot do in a single statement. */
if (!single_use_p
|| (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs))
&& (!is_gimple_min_invariant (def_rhs)
|| (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
&& POINTER_TYPE_P (TREE_TYPE (def_rhs))
&& (TYPE_PRECISION (TREE_TYPE (lhs))
> TYPE_PRECISION (TREE_TYPE (def_rhs)))))))
return forward_propagate_addr_expr (lhs, def_rhs);
gimple_assign_set_rhs1 (use_stmt, unshare_expr (def_rhs));
if (useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs)))
gimple_assign_set_rhs_code (use_stmt, TREE_CODE (def_rhs));
else
gimple_assign_set_rhs_code (use_stmt, NOP_EXPR);
return true;
}
/* Propagate through constant pointer adjustments. */
if (TREE_CODE (lhs) == SSA_NAME
&& rhs_code == POINTER_PLUS_EXPR
&& rhs == name
&& TREE_CODE (gimple_assign_rhs2 (use_stmt)) == INTEGER_CST)
{
tree new_def_rhs;
/* As we come here with non-invariant addresses in def_rhs we need
to make sure we can build a valid constant offsetted address
for further propagation. Simply rely on fold building that
and check after the fact. */
new_def_rhs = fold_build2 (MEM_REF, TREE_TYPE (TREE_TYPE (rhs)),
def_rhs,
fold_convert (ptr_type_node,
gimple_assign_rhs2 (use_stmt)));
if (TREE_CODE (new_def_rhs) == MEM_REF
&& !is_gimple_mem_ref_addr (TREE_OPERAND (new_def_rhs, 0)))
return false;
new_def_rhs = build_fold_addr_expr_with_type (new_def_rhs,
TREE_TYPE (rhs));
/* Recurse. If we could propagate into all uses of lhs do not
bother to replace into the current use but just pretend we did. */
if (TREE_CODE (new_def_rhs) == ADDR_EXPR
&& forward_propagate_addr_expr (lhs, new_def_rhs))
return true;
if (useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (new_def_rhs)))
gimple_assign_set_rhs_with_ops (use_stmt_gsi, TREE_CODE (new_def_rhs),
new_def_rhs, NULL_TREE);
else if (is_gimple_min_invariant (new_def_rhs))
gimple_assign_set_rhs_with_ops (use_stmt_gsi, NOP_EXPR,
new_def_rhs, NULL_TREE);
else
return false;
gcc_assert (gsi_stmt (*use_stmt_gsi) == use_stmt);
update_stmt (use_stmt);
return true;
}
/* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
ADDR_EXPR will not appear on the LHS. */
lhs = gimple_assign_lhs (use_stmt);
while (handled_component_p (lhs))
lhs = TREE_OPERAND (lhs, 0);
/* Now see if the LHS node is a MEM_REF using NAME. If so,
propagate the ADDR_EXPR into the use of NAME and fold the result. */
if (TREE_CODE (lhs) == MEM_REF
&& TREE_OPERAND (lhs, 0) == name)
{
tree def_rhs_base;
HOST_WIDE_INT def_rhs_offset;
/* If the address is invariant we can always fold it. */
if ((def_rhs_base = get_addr_base_and_unit_offset (TREE_OPERAND (def_rhs, 0),
&def_rhs_offset)))
{
double_int off = mem_ref_offset (lhs);
tree new_ptr;
off = double_int_add (off,
shwi_to_double_int (def_rhs_offset));
if (TREE_CODE (def_rhs_base) == MEM_REF)
{
off = double_int_add (off, mem_ref_offset (def_rhs_base));
new_ptr = TREE_OPERAND (def_rhs_base, 0);
}
else
new_ptr = build_fold_addr_expr (def_rhs_base);
TREE_OPERAND (lhs, 0) = new_ptr;
TREE_OPERAND (lhs, 1)
= double_int_to_tree (TREE_TYPE (TREE_OPERAND (lhs, 1)), off);
tidy_after_forward_propagate_addr (use_stmt);
/* Continue propagating into the RHS if this was not the only use. */
if (single_use_p)
return true;
}
/* If the LHS is a plain dereference and the value type is the same as
that of the pointed-to type of the address we can put the
dereferenced address on the LHS preserving the original alias-type. */
else if (gimple_assign_lhs (use_stmt) == lhs
&& useless_type_conversion_p
(TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
TREE_TYPE (gimple_assign_rhs1 (use_stmt))))
{
tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
tree new_offset, new_base, saved;
while (handled_component_p (*def_rhs_basep))
def_rhs_basep = &TREE_OPERAND (*def_rhs_basep, 0);
saved = *def_rhs_basep;
if (TREE_CODE (*def_rhs_basep) == MEM_REF)
{
new_base = TREE_OPERAND (*def_rhs_basep, 0);
new_offset
= int_const_binop (PLUS_EXPR, TREE_OPERAND (lhs, 1),
TREE_OPERAND (*def_rhs_basep, 1), 0);
}
else
{
new_base = build_fold_addr_expr (*def_rhs_basep);
new_offset = TREE_OPERAND (lhs, 1);
}
*def_rhs_basep = build2 (MEM_REF, TREE_TYPE (*def_rhs_basep),
new_base, new_offset);
gimple_assign_set_lhs (use_stmt,
unshare_expr (TREE_OPERAND (def_rhs, 0)));
*def_rhs_basep = saved;
tidy_after_forward_propagate_addr (use_stmt);
/* Continue propagating into the RHS if this was not the
only use. */
if (single_use_p)
return true;
}
else
/* We can have a struct assignment dereferencing our name twice.
Note that we didn't propagate into the lhs to not falsely
claim we did when propagating into the rhs. */
res = false;
}
/* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
nodes from the RHS. */
rhs = gimple_assign_rhs1 (use_stmt);
if (TREE_CODE (rhs) == ADDR_EXPR)
rhs = TREE_OPERAND (rhs, 0);
while (handled_component_p (rhs))
rhs = TREE_OPERAND (rhs, 0);
/* Now see if the RHS node is a MEM_REF using NAME. If so,
propagate the ADDR_EXPR into the use of NAME and fold the result. */
if (TREE_CODE (rhs) == MEM_REF
&& TREE_OPERAND (rhs, 0) == name)
{
tree def_rhs_base;
HOST_WIDE_INT def_rhs_offset;
if ((def_rhs_base = get_addr_base_and_unit_offset (TREE_OPERAND (def_rhs, 0),
&def_rhs_offset)))
{
double_int off = mem_ref_offset (rhs);
tree new_ptr;
off = double_int_add (off,
shwi_to_double_int (def_rhs_offset));
if (TREE_CODE (def_rhs_base) == MEM_REF)
{
off = double_int_add (off, mem_ref_offset (def_rhs_base));
new_ptr = TREE_OPERAND (def_rhs_base, 0);
}
else
new_ptr = build_fold_addr_expr (def_rhs_base);
TREE_OPERAND (rhs, 0) = new_ptr;
TREE_OPERAND (rhs, 1)
= double_int_to_tree (TREE_TYPE (TREE_OPERAND (rhs, 1)), off);
fold_stmt_inplace (use_stmt);
tidy_after_forward_propagate_addr (use_stmt);
return res;
}
/* If the LHS is a plain dereference and the value type is the same as
that of the pointed-to type of the address we can put the
dereferenced address on the LHS preserving the original alias-type. */
else if (gimple_assign_rhs1 (use_stmt) == rhs
&& useless_type_conversion_p
(TREE_TYPE (gimple_assign_lhs (use_stmt)),
TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
{
tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
tree new_offset, new_base, saved;
while (handled_component_p (*def_rhs_basep))
def_rhs_basep = &TREE_OPERAND (*def_rhs_basep, 0);
saved = *def_rhs_basep;
if (TREE_CODE (*def_rhs_basep) == MEM_REF)
{
new_base = TREE_OPERAND (*def_rhs_basep, 0);
new_offset
= int_const_binop (PLUS_EXPR, TREE_OPERAND (rhs, 1),
TREE_OPERAND (*def_rhs_basep, 1), 0);
}
else
{
new_base = build_fold_addr_expr (*def_rhs_basep);
new_offset = TREE_OPERAND (rhs, 1);
}
*def_rhs_basep = build2 (MEM_REF, TREE_TYPE (*def_rhs_basep),
new_base, new_offset);
gimple_assign_set_rhs1 (use_stmt,
unshare_expr (TREE_OPERAND (def_rhs, 0)));
*def_rhs_basep = saved;
fold_stmt_inplace (use_stmt);
tidy_after_forward_propagate_addr (use_stmt);
return res;
}
}
/* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
is nothing to do. */
if (gimple_assign_rhs_code (use_stmt) != POINTER_PLUS_EXPR
|| gimple_assign_rhs1 (use_stmt) != name)
return false;
/* The remaining cases are all for turning pointer arithmetic into
array indexing. They only apply when we have the address of
element zero in an array. If that is not the case then there
is nothing to do. */
array_ref = TREE_OPERAND (def_rhs, 0);
if ((TREE_CODE (array_ref) != ARRAY_REF
|| TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
|| TREE_CODE (TREE_OPERAND (array_ref, 1)) != INTEGER_CST)
&& TREE_CODE (TREE_TYPE (array_ref)) != ARRAY_TYPE)
return false;