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/* __builtin_object_size (ptr, object_size_type) computation
Copyright (C) 2004-2021 Free Software Foundation, Inc.
Contributed by Jakub Jelinek <jakub@redhat.com>
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 "backend.h"
#include "tree.h"
#include "gimple.h"
#include "tree-pass.h"
#include "ssa.h"
#include "gimple-pretty-print.h"
#include "fold-const.h"
#include "tree-object-size.h"
#include "gimple-fold.h"
#include "gimple-iterator.h"
#include "tree-cfg.h"
#include "stringpool.h"
#include "attribs.h"
struct object_size_info
{
int object_size_type;
unsigned char pass;
bool changed;
bitmap visited, reexamine;
unsigned int *depths;
unsigned int *stack, *tos;
};
static const unsigned HOST_WIDE_INT unknown[4] = {
HOST_WIDE_INT_M1U,
HOST_WIDE_INT_M1U,
0,
0
};
static tree compute_object_offset (const_tree, const_tree);
static bool addr_object_size (struct object_size_info *,
const_tree, int, unsigned HOST_WIDE_INT *);
static unsigned HOST_WIDE_INT alloc_object_size (const gcall *, int);
static tree pass_through_call (const gcall *);
static void collect_object_sizes_for (struct object_size_info *, tree);
static void expr_object_size (struct object_size_info *, tree, tree);
static bool merge_object_sizes (struct object_size_info *, tree, tree,
unsigned HOST_WIDE_INT);
static bool plus_stmt_object_size (struct object_size_info *, tree, gimple *);
static bool cond_expr_object_size (struct object_size_info *, tree, gimple *);
static void init_offset_limit (void);
static void check_for_plus_in_loops (struct object_size_info *, tree);
static void check_for_plus_in_loops_1 (struct object_size_info *, tree,
unsigned int);
/* object_sizes[0] is upper bound for number of bytes till the end of
the object.
object_sizes[1] is upper bound for number of bytes till the end of
the subobject (innermost array or field with address taken).
object_sizes[2] is lower bound for number of bytes till the end of
the object and object_sizes[3] lower bound for subobject. */
static vec<unsigned HOST_WIDE_INT> object_sizes[4];
/* Bitmaps what object sizes have been computed already. */
static bitmap computed[4];
/* Maximum value of offset we consider to be addition. */
static unsigned HOST_WIDE_INT offset_limit;
/* Initialize OFFSET_LIMIT variable. */
static void
init_offset_limit (void)
{
if (tree_fits_uhwi_p (TYPE_MAX_VALUE (sizetype)))
offset_limit = tree_to_uhwi (TYPE_MAX_VALUE (sizetype));
else
offset_limit = -1;
offset_limit /= 2;
}
/* Compute offset of EXPR within VAR. Return error_mark_node
if unknown. */
static tree
compute_object_offset (const_tree expr, const_tree var)
{
enum tree_code code = PLUS_EXPR;
tree base, off, t;
if (expr == var)
return size_zero_node;
switch (TREE_CODE (expr))
{
case COMPONENT_REF:
base = compute_object_offset (TREE_OPERAND (expr, 0), var);
if (base == error_mark_node)
return base;
t = TREE_OPERAND (expr, 1);
off = size_binop (PLUS_EXPR, DECL_FIELD_OFFSET (t),
size_int (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (t))
/ BITS_PER_UNIT));
break;
case REALPART_EXPR:
CASE_CONVERT:
case VIEW_CONVERT_EXPR:
case NON_LVALUE_EXPR:
return compute_object_offset (TREE_OPERAND (expr, 0), var);
case IMAGPART_EXPR:
base = compute_object_offset (TREE_OPERAND (expr, 0), var);
if (base == error_mark_node)
return base;
off = TYPE_SIZE_UNIT (TREE_TYPE (expr));
break;
case ARRAY_REF:
base = compute_object_offset (TREE_OPERAND (expr, 0), var);
if (base == error_mark_node)
return base;
t = TREE_OPERAND (expr, 1);
tree low_bound, unit_size;
low_bound = array_ref_low_bound (CONST_CAST_TREE (expr));
unit_size = array_ref_element_size (CONST_CAST_TREE (expr));
if (! integer_zerop (low_bound))
t = fold_build2 (MINUS_EXPR, TREE_TYPE (t), t, low_bound);
if (TREE_CODE (t) == INTEGER_CST && tree_int_cst_sgn (t) < 0)
{
code = MINUS_EXPR;
t = fold_build1 (NEGATE_EXPR, TREE_TYPE (t), t);
}
t = fold_convert (sizetype, t);
off = size_binop (MULT_EXPR, unit_size, t);
break;
case MEM_REF:
gcc_assert (TREE_CODE (TREE_OPERAND (expr, 0)) == ADDR_EXPR);
return wide_int_to_tree (sizetype, mem_ref_offset (expr));
default:
return error_mark_node;
}
return size_binop (code, base, off);
}
/* Returns the size of the object designated by DECL considering its
initializer if it either has one or if it would not affect its size,
otherwise the size of the object without the initializer when MIN
is true, else null. An object's initializer affects the object's
size if it's a struct type with a flexible array member. */
tree
decl_init_size (tree decl, bool min)
{
tree size = DECL_SIZE_UNIT (decl);
tree type = TREE_TYPE (decl);
if (TREE_CODE (type) != RECORD_TYPE)
return size;
tree last = last_field (type);
if (!last)
return size;
tree last_type = TREE_TYPE (last);
if (TREE_CODE (last_type) != ARRAY_TYPE
|| TYPE_SIZE (last_type))
return size;
/* Use TYPE_SIZE_UNIT; DECL_SIZE_UNIT sometimes reflects the size
of the initializer and sometimes doesn't. */
size = TYPE_SIZE_UNIT (type);
tree ref = build3 (COMPONENT_REF, type, decl, last, NULL_TREE);
tree compsize = component_ref_size (ref);
if (!compsize)
return min ? size : NULL_TREE;
/* The size includes tail padding and initializer elements. */
tree pos = byte_position (last);
size = fold_build2 (PLUS_EXPR, TREE_TYPE (size), pos, compsize);
return size;
}
/* Compute __builtin_object_size for PTR, which is a ADDR_EXPR.
OBJECT_SIZE_TYPE is the second argument from __builtin_object_size.
If unknown, return unknown[object_size_type]. */
static bool
addr_object_size (struct object_size_info *osi, const_tree ptr,
int object_size_type, unsigned HOST_WIDE_INT *psize)
{
tree pt_var, pt_var_size = NULL_TREE, var_size, bytes;
gcc_assert (TREE_CODE (ptr) == ADDR_EXPR);
/* Set to unknown and overwrite just before returning if the size
could be determined. */
*psize = unknown[object_size_type];
pt_var = TREE_OPERAND (ptr, 0);
while (handled_component_p (pt_var))
pt_var = TREE_OPERAND (pt_var, 0);
if (!pt_var)
return false;
if (TREE_CODE (pt_var) == MEM_REF)
{
unsigned HOST_WIDE_INT sz;
if (!osi || (object_size_type & 1) != 0
|| TREE_CODE (TREE_OPERAND (pt_var, 0)) != SSA_NAME)
{
compute_builtin_object_size (TREE_OPERAND (pt_var, 0),
object_size_type & ~1, &sz);
}
else
{
tree var = TREE_OPERAND (pt_var, 0);
if (osi->pass == 0)
collect_object_sizes_for (osi, var);
if (bitmap_bit_p (computed[object_size_type],
SSA_NAME_VERSION (var)))
sz = object_sizes[object_size_type][SSA_NAME_VERSION (var)];
else
sz = unknown[object_size_type];
}
if (sz != unknown[object_size_type])
{
offset_int mem_offset;
if (mem_ref_offset (pt_var).is_constant (&mem_offset))
{
offset_int dsz = wi::sub (sz, mem_offset);
if (wi::neg_p (dsz))
sz = 0;
else if (wi::fits_uhwi_p (dsz))
sz = dsz.to_uhwi ();
else
sz = unknown[object_size_type];
}
else
sz = unknown[object_size_type];
}
if (sz != unknown[object_size_type] && sz < offset_limit)
pt_var_size = size_int (sz);
}
else if (DECL_P (pt_var))
{
pt_var_size = decl_init_size (pt_var, object_size_type & 2);
if (!pt_var_size)
return false;
}
else if (TREE_CODE (pt_var) == STRING_CST)
pt_var_size = TYPE_SIZE_UNIT (TREE_TYPE (pt_var));
else
return false;
if (pt_var_size)
{
/* Validate the size determined above. */
if (!tree_fits_uhwi_p (pt_var_size)
|| tree_to_uhwi (pt_var_size) >= offset_limit)
return false;
}
if (pt_var != TREE_OPERAND (ptr, 0))
{
tree var;
if (object_size_type & 1)
{
var = TREE_OPERAND (ptr, 0);
while (var != pt_var
&& TREE_CODE (var) != BIT_FIELD_REF
&& TREE_CODE (var) != COMPONENT_REF
&& TREE_CODE (var) != ARRAY_REF
&& TREE_CODE (var) != ARRAY_RANGE_REF
&& TREE_CODE (var) != REALPART_EXPR
&& TREE_CODE (var) != IMAGPART_EXPR)
var = TREE_OPERAND (var, 0);
if (var != pt_var && TREE_CODE (var) == ARRAY_REF)
var = TREE_OPERAND (var, 0);
if (! TYPE_SIZE_UNIT (TREE_TYPE (var))
|| ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var)))
|| (pt_var_size
&& tree_int_cst_lt (pt_var_size,
TYPE_SIZE_UNIT (TREE_TYPE (var)))))
var = pt_var;
else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF)
{
tree v = var;
/* For &X->fld, compute object size only if fld isn't the last
field, as struct { int i; char c[1]; } is often used instead
of flexible array member. */
while (v && v != pt_var)
switch (TREE_CODE (v))
{
case ARRAY_REF:
if (TYPE_SIZE_UNIT (TREE_TYPE (TREE_OPERAND (v, 0)))
&& TREE_CODE (TREE_OPERAND (v, 1)) == INTEGER_CST)
{
tree domain
= TYPE_DOMAIN (TREE_TYPE (TREE_OPERAND (v, 0)));
if (domain
&& TYPE_MAX_VALUE (domain)
&& TREE_CODE (TYPE_MAX_VALUE (domain))
== INTEGER_CST
&& tree_int_cst_lt (TREE_OPERAND (v, 1),
TYPE_MAX_VALUE (domain)))
{
v = NULL_TREE;
break;
}
}
v = TREE_OPERAND (v, 0);
break;
case REALPART_EXPR:
case IMAGPART_EXPR:
v = NULL_TREE;
break;
case COMPONENT_REF:
if (TREE_CODE (TREE_TYPE (v)) != ARRAY_TYPE)
{
v = NULL_TREE;
break;
}
while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
!= UNION_TYPE
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
!= QUAL_UNION_TYPE)
break;
else
v = TREE_OPERAND (v, 0);
if (TREE_CODE (v) == COMPONENT_REF
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
== RECORD_TYPE)
{
tree fld_chain = DECL_CHAIN (TREE_OPERAND (v, 1));
for (; fld_chain; fld_chain = DECL_CHAIN (fld_chain))
if (TREE_CODE (fld_chain) == FIELD_DECL)
break;
if (fld_chain)
{
v = NULL_TREE;
break;
}
v = TREE_OPERAND (v, 0);
}
while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
!= UNION_TYPE
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
!= QUAL_UNION_TYPE)
break;
else
v = TREE_OPERAND (v, 0);
if (v != pt_var)
v = NULL_TREE;
else
v = pt_var;
break;
default:
v = pt_var;
break;
}
if (v == pt_var)
var = pt_var;
}
}
else
var = pt_var;
if (var != pt_var)
var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
else if (!pt_var_size)
return false;
else
var_size = pt_var_size;
bytes = compute_object_offset (TREE_OPERAND (ptr, 0), var);
if (bytes != error_mark_node)
{
if (TREE_CODE (bytes) == INTEGER_CST
&& tree_int_cst_lt (var_size, bytes))
bytes = size_zero_node;
else
bytes = size_binop (MINUS_EXPR, var_size, bytes);
}
if (var != pt_var
&& pt_var_size
&& TREE_CODE (pt_var) == MEM_REF
&& bytes != error_mark_node)
{
tree bytes2 = compute_object_offset (TREE_OPERAND (ptr, 0), pt_var);
if (bytes2 != error_mark_node)
{
if (TREE_CODE (bytes2) == INTEGER_CST
&& tree_int_cst_lt (pt_var_size, bytes2))
bytes2 = size_zero_node;
else
bytes2 = size_binop (MINUS_EXPR, pt_var_size, bytes2);
bytes = size_binop (MIN_EXPR, bytes, bytes2);
}
}
}
else if (!pt_var_size)
return false;
else
bytes = pt_var_size;
if (tree_fits_uhwi_p (bytes))
{
*psize = tree_to_uhwi (bytes);
return true;
}
return false;
}
/* Compute __builtin_object_size for CALL, which is a GIMPLE_CALL.
Handles calls to functions declared with attribute alloc_size.
OBJECT_SIZE_TYPE is the second argument from __builtin_object_size.
If unknown, return unknown[object_size_type]. */
static unsigned HOST_WIDE_INT
alloc_object_size (const gcall *call, int object_size_type)
{
gcc_assert (is_gimple_call (call));
tree calltype;
if (tree callfn = gimple_call_fndecl (call))
calltype = TREE_TYPE (callfn);
else
calltype = gimple_call_fntype (call);
if (!calltype)
return unknown[object_size_type];
/* Set to positions of alloc_size arguments. */
int arg1 = -1, arg2 = -1;
tree alloc_size = lookup_attribute ("alloc_size",
TYPE_ATTRIBUTES (calltype));
if (alloc_size && TREE_VALUE (alloc_size))
{
tree p = TREE_VALUE (alloc_size);
arg1 = TREE_INT_CST_LOW (TREE_VALUE (p))-1;
if (TREE_CHAIN (p))
arg2 = TREE_INT_CST_LOW (TREE_VALUE (TREE_CHAIN (p)))-1;
}
if (arg1 < 0 || arg1 >= (int)gimple_call_num_args (call)
|| TREE_CODE (gimple_call_arg (call, arg1)) != INTEGER_CST
|| (arg2 >= 0
&& (arg2 >= (int)gimple_call_num_args (call)
|| TREE_CODE (gimple_call_arg (call, arg2)) != INTEGER_CST)))
return unknown[object_size_type];
tree bytes = NULL_TREE;
if (arg2 >= 0)
bytes = size_binop (MULT_EXPR,
fold_convert (sizetype, gimple_call_arg (call, arg1)),
fold_convert (sizetype, gimple_call_arg (call, arg2)));
else if (arg1 >= 0)
bytes = fold_convert (sizetype, gimple_call_arg (call, arg1));
if (bytes && tree_fits_uhwi_p (bytes))
return tree_to_uhwi (bytes);
return unknown[object_size_type];
}
/* If object size is propagated from one of function's arguments directly
to its return value, return that argument for GIMPLE_CALL statement CALL.
Otherwise return NULL. */
static tree
pass_through_call (const gcall *call)
{
unsigned rf = gimple_call_return_flags (call);
if (rf & ERF_RETURNS_ARG)
{
unsigned argnum = rf & ERF_RETURN_ARG_MASK;
if (argnum < gimple_call_num_args (call))
return gimple_call_arg (call, argnum);
}
/* __builtin_assume_aligned is intentionally not marked RET1. */
if (gimple_call_builtin_p (call, BUILT_IN_ASSUME_ALIGNED))
return gimple_call_arg (call, 0);
return NULL_TREE;
}
/* Compute __builtin_object_size value for PTR and set *PSIZE to
the resulting value. If the declared object is known and PDECL
is nonnull, sets *PDECL to the object's DECL. OBJECT_SIZE_TYPE
is the second argument to __builtin_object_size.
Returns true on success and false when the object size could not
be determined. */
bool
compute_builtin_object_size (tree ptr, int object_size_type,
unsigned HOST_WIDE_INT *psize)
{
gcc_assert (object_size_type >= 0 && object_size_type <= 3);
/* Set to unknown and overwrite just before returning if the size
could be determined. */
*psize = unknown[object_size_type];
if (! offset_limit)
init_offset_limit ();
if (TREE_CODE (ptr) == ADDR_EXPR)
return addr_object_size (NULL, ptr, object_size_type, psize);
if (TREE_CODE (ptr) != SSA_NAME
|| !POINTER_TYPE_P (TREE_TYPE (ptr)))
return false;
if (computed[object_size_type] == NULL)
{
if (optimize || object_size_type & 1)
return false;
/* When not optimizing, rather than failing, make a small effort
to determine the object size without the full benefit of
the (costly) computation below. */
gimple *def = SSA_NAME_DEF_STMT (ptr);
if (gimple_code (def) == GIMPLE_ASSIGN)
{
tree_code code = gimple_assign_rhs_code (def);
if (code == POINTER_PLUS_EXPR)
{
tree offset = gimple_assign_rhs2 (def);
ptr = gimple_assign_rhs1 (def);
if (tree_fits_shwi_p (offset)
&& compute_builtin_object_size (ptr, object_size_type,
psize))
{
/* Return zero when the offset is out of bounds. */
unsigned HOST_WIDE_INT off = tree_to_shwi (offset);
*psize = off < *psize ? *psize - off : 0;
return true;
}
}
}
return false;
}
if (!bitmap_bit_p (computed[object_size_type], SSA_NAME_VERSION (ptr)))
{
struct object_size_info osi;
bitmap_iterator bi;
unsigned int i;
if (num_ssa_names > object_sizes[object_size_type].length ())
object_sizes[object_size_type].safe_grow (num_ssa_names, true);
if (dump_file)
{
fprintf (dump_file, "Computing %s %sobject size for ",
(object_size_type & 2) ? "minimum" : "maximum",
(object_size_type & 1) ? "sub" : "");
print_generic_expr (dump_file, ptr, dump_flags);
fprintf (dump_file, ":\n");
}
osi.visited = BITMAP_ALLOC (NULL);
osi.reexamine = BITMAP_ALLOC (NULL);
osi.object_size_type = object_size_type;
osi.depths = NULL;
osi.stack = NULL;
osi.tos = NULL;
/* First pass: walk UD chains, compute object sizes that
can be computed. osi.reexamine bitmap at the end will
contain what variables were found in dependency cycles
and therefore need to be reexamined. */
osi.pass = 0;
osi.changed = false;
collect_object_sizes_for (&osi, ptr);
/* Second pass: keep recomputing object sizes of variables
that need reexamination, until no object sizes are
increased or all object sizes are computed. */
if (! bitmap_empty_p (osi.reexamine))
{
bitmap reexamine = BITMAP_ALLOC (NULL);
/* If looking for minimum instead of maximum object size,
detect cases where a pointer is increased in a loop.
Although even without this detection pass 2 would eventually
terminate, it could take a long time. If a pointer is
increasing this way, we need to assume 0 object size.
E.g. p = &buf[0]; while (cond) p = p + 4; */
if (object_size_type & 2)
{
osi.depths = XCNEWVEC (unsigned int, num_ssa_names);
osi.stack = XNEWVEC (unsigned int, num_ssa_names);
osi.tos = osi.stack;
osi.pass = 1;
/* collect_object_sizes_for is changing
osi.reexamine bitmap, so iterate over a copy. */
bitmap_copy (reexamine, osi.reexamine);
EXECUTE_IF_SET_IN_BITMAP (reexamine, 0, i, bi)
if (bitmap_bit_p (osi.reexamine, i))
check_for_plus_in_loops (&osi, ssa_name (i));
free (osi.depths);
osi.depths = NULL;
free (osi.stack);
osi.stack = NULL;
osi.tos = NULL;
}
do
{
osi.pass = 2;
osi.changed = false;
/* collect_object_sizes_for is changing
osi.reexamine bitmap, so iterate over a copy. */
bitmap_copy (reexamine, osi.reexamine);
EXECUTE_IF_SET_IN_BITMAP (reexamine, 0, i, bi)
if (bitmap_bit_p (osi.reexamine, i))
{
collect_object_sizes_for (&osi, ssa_name (i));
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Reexamining ");
print_generic_expr (dump_file, ssa_name (i),
dump_flags);
fprintf (dump_file, "\n");
}
}
}
while (osi.changed);
BITMAP_FREE (reexamine);
}
EXECUTE_IF_SET_IN_BITMAP (osi.reexamine, 0, i, bi)
bitmap_set_bit (computed[object_size_type], i);
/* Debugging dumps. */
if (dump_file)
{
EXECUTE_IF_SET_IN_BITMAP (osi.visited, 0, i, bi)
if (object_sizes[object_size_type][i]
!= unknown[object_size_type])
{
print_generic_expr (dump_file, ssa_name (i),
dump_flags);
fprintf (dump_file,
": %s %sobject size "
HOST_WIDE_INT_PRINT_UNSIGNED "\n",
(object_size_type & 2) ? "minimum" : "maximum",
(object_size_type & 1) ? "sub" : "",
object_sizes[object_size_type][i]);
}
}
BITMAP_FREE (osi.reexamine);
BITMAP_FREE (osi.visited);
}
*psize = object_sizes[object_size_type][SSA_NAME_VERSION (ptr)];
return *psize != unknown[object_size_type];
}
/* Compute object_sizes for PTR, defined to VALUE, which is not an SSA_NAME. */
static void
expr_object_size (struct object_size_info *osi, tree ptr, tree value)
{
int object_size_type = osi->object_size_type;
unsigned int varno = SSA_NAME_VERSION (ptr);
unsigned HOST_WIDE_INT bytes;
gcc_assert (object_sizes[object_size_type][varno]
!= unknown[object_size_type]);
gcc_assert (osi->pass == 0);
if (TREE_CODE (value) == WITH_SIZE_EXPR)
value = TREE_OPERAND (value, 0);
/* Pointer variables should have been handled by merge_object_sizes. */
gcc_assert (TREE_CODE (value) != SSA_NAME
|| !POINTER_TYPE_P (TREE_TYPE (value)));
if (TREE_CODE (value) == ADDR_EXPR)
addr_object_size (osi, value, object_size_type, &bytes);
else
bytes = unknown[object_size_type];
if ((object_size_type & 2) == 0)
{
if (object_sizes[object_size_type][varno] < bytes)
object_sizes[object_size_type][varno] = bytes;
}
else
{
if (object_sizes[object_size_type][varno] > bytes)
object_sizes[object_size_type][varno] = bytes;
}
}
/* Compute object_sizes for PTR, defined to the result of a call. */
static void
call_object_size (struct object_size_info *osi, tree ptr, gcall *call)
{
int object_size_type = osi->object_size_type;
unsigned int varno = SSA_NAME_VERSION (ptr);
unsigned HOST_WIDE_INT bytes;
gcc_assert (is_gimple_call (call));
gcc_assert (object_sizes[object_size_type][varno]
!= unknown[object_size_type]);
gcc_assert (osi->pass == 0);
bytes = alloc_object_size (call, object_size_type);
if ((object_size_type & 2) == 0)
{
if (object_sizes[object_size_type][varno] < bytes)
object_sizes[object_size_type][varno] = bytes;
}
else
{
if (object_sizes[object_size_type][varno] > bytes)
object_sizes[object_size_type][varno] = bytes;
}
}
/* Compute object_sizes for PTR, defined to an unknown value. */
static void
unknown_object_size (struct object_size_info *osi, tree ptr)
{
int object_size_type = osi->object_size_type;
unsigned int varno = SSA_NAME_VERSION (ptr);
unsigned HOST_WIDE_INT bytes;
gcc_assert (object_sizes[object_size_type][varno]
!= unknown[object_size_type]);
gcc_assert (osi->pass == 0);
bytes = unknown[object_size_type];
if ((object_size_type & 2) == 0)
{
if (object_sizes[object_size_type][varno] < bytes)
object_sizes[object_size_type][varno] = bytes;
}
else
{
if (object_sizes[object_size_type][varno] > bytes)
object_sizes[object_size_type][varno] = bytes;
}
}
/* Merge object sizes of ORIG + OFFSET into DEST. Return true if
the object size might need reexamination later. */
static bool
merge_object_sizes (struct object_size_info *osi, tree dest, tree orig,
unsigned HOST_WIDE_INT offset)
{
int object_size_type = osi->object_size_type;
unsigned int varno = SSA_NAME_VERSION (dest);
unsigned HOST_WIDE_INT orig_bytes;
if (object_sizes[object_size_type][varno] == unknown[object_size_type])
return false;
if (offset >= offset_limit)
{
object_sizes[object_size_type][varno] = unknown[object_size_type];
return false;
}
if (osi->pass == 0)
collect_object_sizes_for (osi, orig);
orig_bytes = object_sizes[object_size_type][SSA_NAME_VERSION (orig)];
if (orig_bytes != unknown[object_size_type])
orig_bytes = (offset > orig_bytes)
? HOST_WIDE_INT_0U : orig_bytes - offset;
if ((object_size_type & 2) == 0)
{
if (object_sizes[object_size_type][varno] < orig_bytes)
{
object_sizes[object_size_type][varno] = orig_bytes;
osi->changed = true;
}
}
else
{
if (object_sizes[object_size_type][varno] > orig_bytes)
{
object_sizes[object_size_type][varno] = orig_bytes;
osi->changed = true;
}
}
return bitmap_bit_p (osi->reexamine, SSA_NAME_VERSION (orig));
}
/* Compute object_sizes for VAR, defined to the result of an assignment
with operator POINTER_PLUS_EXPR. Return true if the object size might
need reexamination later. */
static bool
plus_stmt_object_size (struct object_size_info *osi, tree var, gimple *stmt)
{
int object_size_type = osi->object_size_type;
unsigned int varno = SSA_NAME_VERSION (var);
unsigned HOST_WIDE_INT bytes;
tree op0, op1;
if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
{
op0 = gimple_assign_rhs1 (stmt);
op1 = gimple_assign_rhs2 (stmt);
}
else if (gimple_assign_rhs_code (stmt) == ADDR_EXPR)
{
tree rhs = TREE_OPERAND (gimple_assign_rhs1 (stmt), 0);
gcc_assert (TREE_CODE (rhs) == MEM_REF);
op0 = TREE_OPERAND (rhs, 0);
op1 = TREE_OPERAND (rhs, 1);
}
else
gcc_unreachable ();
if (object_sizes[object_size_type][varno] == unknown[object_size_type])
return false;
/* Handle PTR + OFFSET here. */
if (TREE_CODE (op1) == INTEGER_CST
&& (TREE_CODE (op0) == SSA_NAME
|| TREE_CODE (op0) == ADDR_EXPR))
{
if (! tree_fits_uhwi_p (op1))
bytes = unknown[object_size_type];
else if (TREE_CODE (op0) == SSA_NAME)
return merge_object_sizes (osi, var, op0, tree_to_uhwi (op1));
else
{
unsigned HOST_WIDE_INT off = tree_to_uhwi (op1);
/* op0 will be ADDR_EXPR here. */
addr_object_size (osi, op0, object_size_type, &bytes);
if (bytes == unknown[object_size_type])
;
else if (off > offset_limit)
bytes = unknown[object_size_type];
else if (off > bytes)
bytes = 0;
else
bytes -= off;
}
}
else
bytes = unknown[object_size_type];
if ((object_size_type & 2) == 0)
{
if (object_sizes[object_size_type][varno] < bytes)
object_sizes[object_size_type][varno] = bytes;
}
else
{
if (object_sizes[object_size_type][varno] > bytes)
object_sizes[object_size_type][varno] = bytes;
}
return false;
}
/* Compute object_sizes for VAR, defined at STMT, which is
a COND_EXPR. Return true if the object size might need reexamination
later. */
static bool
cond_expr_object_size (struct object_size_info *osi, tree var, gimple *stmt)
{
tree then_, else_;
int object_size_type = osi->object_size_type;
unsigned int varno = SSA_NAME_VERSION (var);
bool reexamine = false;
gcc_assert (gimple_assign_rhs_code (stmt) == COND_EXPR);
if (object_sizes[object_size_type][varno] == unknown[object_size_type])
return false;
then_ = gimple_assign_rhs2 (stmt);
else_ = gimple_assign_rhs3 (stmt);
if (TREE_CODE (then_) == SSA_NAME)
reexamine |= merge_object_sizes (osi, var, then_, 0);
else
expr_object_size (osi, var, then_);
if (object_sizes[object_size_type][varno] == unknown[object_size_type])
return reexamine;
if (TREE_CODE (else_) == SSA_NAME)
reexamine |= merge_object_sizes (osi, var, else_, 0);
else
expr_object_size (osi, var, else_);
return reexamine;
}
/* Compute object sizes for VAR.
For ADDR_EXPR an object size is the number of remaining bytes
to the end of the object (where what is considered an object depends on
OSI->object_size_type).
For allocation GIMPLE_CALL like malloc or calloc object size is the size
of the allocation.
For POINTER_PLUS_EXPR where second operand is a constant integer,
object size is object size of the first operand minus the constant.
If the constant is bigger than the number of remaining bytes until the
end of the object, object size is 0, but if it is instead a pointer
subtraction, object size is unknown[object_size_type].
To differentiate addition from subtraction, ADDR_EXPR returns
unknown[object_size_type] for all objects bigger than half of the address
space, and constants less than half of the address space are considered
addition, while bigger constants subtraction.
For a memcpy like GIMPLE_CALL that always returns one of its arguments, the
object size is object size of that argument.
Otherwise, object size is the maximum of object sizes of variables
that it might be set to. */
static void
collect_object_sizes_for (struct object_size_info *osi, tree var)
{
int object_size_type = osi->object_size_type;
unsigned int varno = SSA_NAME_VERSION (var);
gimple *stmt;
bool reexamine;
if (bitmap_bit_p (computed[object_size_type], varno))
return;
if (osi->pass == 0)
{
if (bitmap_set_bit (osi->visited, varno))
{
object_sizes[object_size_type][varno]
= (object_size_type & 2) ? -1 : 0;
}
else
{
/* Found a dependency loop. Mark the variable for later
re-examination. */
bitmap_set_bit (osi->reexamine, varno);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Found a dependency loop at ");
print_generic_expr (dump_file, var, dump_flags);
fprintf (dump_file, "\n");
}
return;
}
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Visiting use-def links for ");
print_generic_expr (dump_file, var, dump_flags);
fprintf (dump_file, "\n");
}
stmt = SSA_NAME_DEF_STMT (var);
reexamine = false;
switch (gimple_code (stmt))
{
case GIMPLE_ASSIGN:
{
tree rhs = gimple_assign_rhs1 (stmt);
if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
|| (gimple_assign_rhs_code (stmt) == ADDR_EXPR
&& TREE_CODE (TREE_OPERAND (rhs, 0)) == MEM_REF))
reexamine = plus_stmt_object_size (osi, var, stmt);
else if (gimple_assign_rhs_code (stmt) == COND_EXPR)
reexamine = cond_expr_object_size (osi, var, stmt);
else if (gimple_assign_single_p (stmt)
|| gimple_assign_unary_nop_p (stmt))
{
if (TREE_CODE (rhs) == SSA_NAME
&& POINTER_TYPE_P (TREE_TYPE (rhs)))
reexamine = merge_object_sizes (osi, var, rhs, 0);
else
expr_object_size (osi, var, rhs);
}
else
unknown_object_size (osi, var);
break;
}
case GIMPLE_CALL:
{
gcall *call_stmt = as_a <gcall *> (stmt);
tree arg = pass_through_call (call_stmt);
if (arg)
{
if (TREE_CODE (arg) == SSA_NAME
&& POINTER_TYPE_P (TREE_TYPE (arg)))
reexamine = merge_object_sizes (osi, var, arg, 0);
else
expr_object_size (osi, var, arg);
}
else
call_object_size (osi, var, call_stmt);
break;
}
case GIMPLE_ASM:
/* Pointers defined by __asm__ statements can point anywhere. */
object_sizes[object_size_type][varno] = unknown[object_size_type];
break;
case GIMPLE_NOP:
if (SSA_NAME_VAR (var)
&& TREE_CODE (SSA_NAME_VAR (var)) == PARM_DECL)
expr_object_size (osi, var, SSA_NAME_VAR (var));
else
/* Uninitialized SSA names point nowhere. */
object_sizes[object_size_type][varno] = unknown[object_size_type];
break;
case GIMPLE_PHI:
{
unsigned i;
for (i = 0; i < gimple_phi_num_args (stmt); i++)
{
tree rhs = gimple_phi_arg (stmt, i)->def;
if (object_sizes[object_size_type][varno]
== unknown[object_size_type])
break;
if (TREE_CODE (rhs) == SSA_NAME)
reexamine |= merge_object_sizes (osi, var, rhs, 0);
else if (osi->pass == 0)
expr_object_size (osi, var, rhs);
}
break;
}
default:
gcc_unreachable ();
}
if (! reexamine
|| object_sizes[object_size_type][varno] == unknown[object_size_type])
{
bitmap_set_bit (computed[object_size_type], varno);
bitmap_clear_bit (osi->reexamine, varno);
}
else
{
bitmap_set_bit (osi->reexamine, varno);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Need to reexamine ");
print_generic_expr (dump_file, var, dump_flags);
fprintf (dump_file, "\n");
}
}
}
/* Helper function for check_for_plus_in_loops. Called recursively
to detect loops. */
static void
check_for_plus_in_loops_1 (struct object_size_info *osi, tree var,
unsigned int depth)
{
gimple *stmt = SSA_NAME_DEF_STMT (var);
unsigned int varno = SSA_NAME_VERSION (var);
if (osi->depths[varno])
{
if (osi->depths[varno] != depth)
{
unsigned int *sp;
/* Found a loop involving pointer addition. */
for (sp = osi->tos; sp > osi->stack; )
{
--sp;
bitmap_clear_bit (osi->reexamine, *sp);
bitmap_set_bit (computed[osi->object_size_type], *sp);
object_sizes[osi->object_size_type][*sp] = 0;
if (*sp == varno)
break;
}
}
return;
}
else if (! bitmap_bit_p (osi->reexamine, varno))
return;
osi->depths[varno] = depth;
*osi->tos++ = varno;
switch (gimple_code (stmt))
{
case GIMPLE_ASSIGN:
{
if ((gimple_assign_single_p (stmt)
|| gimple_assign_unary_nop_p (stmt))
&& TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)
{
tree rhs = gimple_assign_rhs1 (stmt);
check_for_plus_in_loops_1 (osi, rhs, depth);
}
else if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
{
tree basevar = gimple_assign_rhs1 (stmt);
tree cst = gimple_assign_rhs2 (stmt);
gcc_assert (TREE_CODE (cst) == INTEGER_CST);
check_for_plus_in_loops_1 (osi, basevar,
depth + !integer_zerop (cst));
}
else
gcc_unreachable ();
break;
}
case GIMPLE_CALL:
{
gcall *call_stmt = as_a <gcall *> (stmt);
tree arg = pass_through_call (call_stmt);
if (arg)
{
if (TREE_CODE (arg) == SSA_NAME)
check_for_plus_in_loops_1 (osi, arg, depth);
else
gcc_unreachable ();
}
break;
}
case GIMPLE_PHI:
{
unsigned i;
for (i = 0; i < gimple_phi_num_args (stmt); i++)
{
tree rhs = gimple_phi_arg (stmt, i)->def;
if (TREE_CODE (rhs) == SSA_NAME)
check_for_plus_in_loops_1 (osi, rhs, depth);
}
break;
}
default:
gcc_unreachable ();
}
osi->depths[varno] = 0;
osi->tos--;
}
/* Check if some pointer we are computing object size of is being increased
within a loop. If yes, assume all the SSA variables participating in
that loop have minimum object sizes 0. */
static void
check_for_plus_in_loops (struct object_size_info *osi, tree var)
{
gimple *stmt = SSA_NAME_DEF_STMT (var);
/* NOTE: In the pre-tuples code, we handled a CALL_EXPR here,
and looked for a POINTER_PLUS_EXPR in the pass-through
argument, if any. In GIMPLE, however, such an expression
is not a valid call operand. */
if (is_gimple_assign (stmt)
&& gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
{
tree basevar = gimple_assign_rhs1 (stmt);
tree cst = gimple_assign_rhs2 (stmt);
gcc_assert (TREE_CODE (cst) == INTEGER_CST);
if (integer_zerop (cst))
return;
osi->depths[SSA_NAME_VERSION (basevar)] = 1;
*osi->tos++ = SSA_NAME_VERSION (basevar);
check_for_plus_in_loops_1 (osi, var, 2);
osi->depths[SSA_NAME_VERSION (basevar)] = 0;
osi->tos--;
}
}
/* Initialize data structures for the object size computation. */
void
init_object_sizes (void)
{
int object_size_type;
if (computed[0])
return;
for (object_size_type = 0; object_size_type <= 3; object_size_type++)
{
object_sizes[object_size_type].safe_grow (num_ssa_names, true);
computed[object_size_type] = BITMAP_ALLOC (NULL);
}
init_offset_limit ();
}
/* Destroy data structures after the object size computation. */
void
fini_object_sizes (void)
{
int object_size_type;
for (object_size_type = 0; object_size_type <= 3; object_size_type++)
{
object_sizes[object_size_type].release ();
BITMAP_FREE (computed[object_size_type]);
}
}
/* Dummy valueize function. */
static tree
do_valueize (tree t)
{
return t;
}
static unsigned int
object_sizes_execute (function *fun, bool insert_min_max_p)
{
basic_block bb;
FOR_EACH_BB_FN (bb, fun)
{
gimple_stmt_iterator i;
for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
{
tree result;
gimple *call = gsi_stmt (i);
if (!gimple_call_builtin_p (call, BUILT_IN_OBJECT_SIZE))
continue;
init_object_sizes ();
/* If insert_min_max_p, only attempt to fold
__builtin_object_size (x, 1) and __builtin_object_size (x, 3),
and rather than folding the builtin to the constant if any,
create a MIN_EXPR or MAX_EXPR of the __builtin_object_size
call result and the computed constant. */
if (insert_min_max_p)
{
tree ost = gimple_call_arg (call, 1);
if (tree_fits_uhwi_p (ost))
{
unsigned HOST_WIDE_INT object_size_type = tree_to_uhwi (ost);
tree ptr = gimple_call_arg (call, 0);
tree lhs = gimple_call_lhs (call);
if ((object_size_type == 1 || object_size_type == 3)
&& (TREE_CODE (ptr) == ADDR_EXPR
|| TREE_CODE (ptr) == SSA_NAME)
&& lhs)
{
tree type = TREE_TYPE (lhs);
unsigned HOST_WIDE_INT bytes;
if (compute_builtin_object_size (ptr, object_size_type,
&bytes)
&& wi::fits_to_tree_p (bytes, type))
{
tree tem = make_ssa_name (type);
gimple_call_set_lhs (call, tem);
enum tree_code code
= object_size_type == 1 ? MIN_EXPR : MAX_EXPR;
tree cst = build_int_cstu (type, bytes);
gimple *g
= gimple_build_assign (lhs, code, tem, cst);
gsi_insert_after (&i, g, GSI_NEW_STMT);
update_stmt (call);
}
}
}
continue;
}
tree lhs = gimple_call_lhs (call);
if (!lhs)
continue;
result = gimple_fold_stmt_to_constant (call, do_valueize);
if (!result)
{
tree ost = gimple_call_arg (call, 1);
if (tree_fits_uhwi_p (ost))
{
unsigned HOST_WIDE_INT object_size_type = tree_to_uhwi (ost);
if (object_size_type < 2)
result = fold_convert (size_type_node,
integer_minus_one_node);
else if (object_size_type < 4)
result = build_zero_cst (size_type_node);
}
if (!result)
continue;
}
gcc_assert (TREE_CODE (result) == INTEGER_CST);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Simplified\n ");
print_gimple_stmt (dump_file, call, 0, dump_flags);
fprintf (dump_file, " to ");
print_generic_expr (dump_file, result);
fprintf (dump_file, "\n");
}
/* Propagate into all uses and fold those stmts. */
if (!SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
replace_uses_by (lhs, result);
else
replace_call_with_value (&i, result);
}
}
fini_object_sizes ();
return 0;
}
/* Simple pass to optimize all __builtin_object_size () builtins. */
namespace {
const pass_data pass_data_object_sizes =
{
GIMPLE_PASS, /* type */
"objsz", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_NONE, /* tv_id */
( PROP_cfg | PROP_ssa ), /* properties_required */
PROP_objsz, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
0, /* todo_flags_finish */
};
class pass_object_sizes : public gimple_opt_pass
{
public:
pass_object_sizes (gcc::context *ctxt)
: gimple_opt_pass (pass_data_object_sizes, ctxt)
{}
/* opt_pass methods: */
opt_pass * clone () { return new pass_object_sizes (m_ctxt); }
virtual unsigned int execute (function *fun)
{
return object_sizes_execute (fun, false);
}
}; // class pass_object_sizes
} // anon namespace
gimple_opt_pass *
make_pass_object_sizes (gcc::context *ctxt)
{
return new pass_object_sizes (ctxt);
}
/* Early version of pass to optimize all __builtin_object_size () builtins. */
namespace {
const pass_data pass_data_early_object_sizes =
{
GIMPLE_PASS, /* type */
"early_objsz", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_NONE, /* tv_id */
( PROP_cfg | PROP_ssa ), /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
0, /* todo_flags_finish */
};
class pass_early_object_sizes : public gimple_opt_pass
{
public:
pass_early_object_sizes (gcc::context *ctxt)
: gimple_opt_pass (pass_data_early_object_sizes, ctxt)
{}
/* opt_pass methods: */
virtual unsigned int execute (function *fun)
{
return object_sizes_execute (fun, true);
}
}; // class pass_object_sizes
} // anon namespace
gimple_opt_pass *
make_pass_early_object_sizes (gcc::context *ctxt)
{
return new pass_early_object_sizes (ctxt);
}