strlen_pass Class Reference

Inheritance diagram for strlen_pass:

Collaboration diagram for strlen_pass:

Public Types
enum	reachability { ALL_BLOCKS , REACHABLE_BLOCKS , REACHABLE_BLOCKS_PRESERVING_FLAGS }

Public Member Functions
	strlen_pass (function *fun, cdi_direction direction)
	~strlen_pass ()
edge	before_dom_children (basic_block) final override
void	after_dom_children (basic_block) final override
bool	check_and_optimize_stmt (bool *cleanup_eh)
bool	check_and_optimize_call (bool *zero_write)
bool	handle_assign (tree lhs, bool *zero_write)
bool	handle_store (bool *zero_write)
void	handle_pointer_plus ()
void	handle_builtin_strlen ()
void	handle_builtin_strchr ()
void	handle_builtin_strcpy (built_in_function)
void	handle_integral_assign (bool *cleanup_eh)
void	handle_builtin_stxncpy_strncat (bool append_p)
void	handle_builtin_memcpy (built_in_function bcode)
void	handle_builtin_strcat (built_in_function bcode)
void	handle_builtin_strncat (built_in_function)
bool	handle_builtin_memset (bool *zero_write)
bool	handle_builtin_memcmp ()
bool	handle_builtin_string_cmp ()
void	handle_alloc_call (built_in_function)
void	maybe_warn_overflow (gimple *stmt, bool call_lhs, tree len, strinfo *si=NULL, bool plus_one=false, bool rawmem=false)
void	maybe_warn_overflow (gimple *stmt, bool call_lhs, unsigned HOST_WIDE_INT len, strinfo *si=NULL, bool plus_one=false, bool rawmem=false)
void	adjust_last_stmt (strinfo *si, gimple *stmt, bool is_strcat)
tree	strxcmp_eqz_result (gimple *stmt, tree arg1, int idx1, tree arg2, int idx2, unsigned HOST_WIDE_INT bound, unsigned HOST_WIDE_INT len[2], unsigned HOST_WIDE_INT *psize)
bool	count_nonzero_bytes (tree expr_or_type, gimple *stmt, unsigned lenrange[3], bool *nulterm, bool *allnul, bool *allnonnul)
bool	count_nonzero_bytes (tree exp, tree vuse, gimple *stmt, unsigned HOST_WIDE_INT offset, unsigned HOST_WIDE_INT nbytes, unsigned lenrange[3], bool *nulterm, bool *allnul, bool *allnonnul, ssa_name_limit_t &snlim)
bool	count_nonzero_bytes_addr (tree exp, tree vuse, gimple *stmt, unsigned HOST_WIDE_INT offset, unsigned HOST_WIDE_INT nbytes, unsigned lenrange[3], bool *nulterm, bool *allnul, bool *allnonnul, ssa_name_limit_t &snlim)
bool	get_len_or_size (gimple *stmt, tree arg, int idx, unsigned HOST_WIDE_INT lenrng[2], unsigned HOST_WIDE_INT *size, bool *nulterm)
void	walk (basic_block)

Data Fields
pointer_query	ptr_qry
gimple_stmt_iterator	m_gsi
bool	m_cleanup_cfg

Static Public Attributes
static const edge	STOP = (edge)-1

Private Member Functions
bool	bb_reachable (struct function *, basic_block)
void	propagate_unreachable_to_edges (basic_block, FILE *, dump_flags_t)

Private Attributes
enum cdi_direction	m_dom_direction: 2
enum reachability	m_reachability: 2
bool	m_user_bb_to_rpo
basic_block	m_unreachable_dom
int *	m_bb_to_rpo

Member Enumeration Documentation

reachability

enum dom_walker::reachability

inherited

Enumerator
ALL_BLOCKS
REACHABLE_BLOCKS
REACHABLE_BLOCKS_PRESERVING_FLAGS

Constructor & Destructor Documentation

strlen_pass()

strlen_pass::strlen_pass ( function * fun, cdi_direction direction )

inline

~strlen_pass()

strlen_pass::~strlen_pass

(

)

Release pointer_query cache.   

References pointer_query::flush_cache(), and ptr_qry.

Member Function Documentation

adjust_last_stmt()

void strlen_pass::adjust_last_stmt	(	strinfo *	si,
		gimple *	stmt,
		bool	is_strcat )

If the last .MEM setter statement before STMT is
memcpy (x, y, strlen (y) + 1), the only .MEM use of it is STMT
and STMT is known to overwrite x[strlen (x)], adjust the last memcpy to
just memcpy (x, y, strlen (y)).  SI must be the zero length
strinfo.   

References cfun, compute_objsize(), DECL_FUNCTION_CODE(), strinfo::first, gcc_assert, get_next_strinfo(), get_strinfo(), gimple_assign_rhs1(), gimple_assign_rhs2(), gimple_assign_rhs_code(), gimple_call_arg(), gimple_call_fndecl(), gimple_call_set_arg(), gimple_vuse(), gsi_for_stmt(), gsi_remove(), has_single_use(), integer_onep(), integer_zerop(), is_gimple_assign(), last, laststmt, laststmt_struct::len, NULL, NULL_TREE, ptr_qry, release_defs(), si, SSA_NAME_DEF_STMT, laststmt_struct::stmt, stmt_could_throw_p(), laststmt_struct::stridx, TREE_CODE, tree_fits_uhwi_p(), tree_int_cst_lt(), tree_to_uhwi(), unlink_stmt_vdef(), update_stmt(), valid_builtin_call(), verify_related_strinfos(), and zero_length_string_p().

Referenced by handle_builtin_memcpy(), handle_builtin_strcat(), handle_builtin_strcpy(), and handle_store().

after_dom_children()

void strlen_pass::after_dom_children ( basic_block bb )

finaloverridevirtual

Callback for walk_dominator_tree.  Free strinfo vector if it is
owned by the current bb, clear bb->aux.   

Reimplemented from dom_walker.

References basic_block_def::aux, free_strinfo(), i, NULL, si, stridx_to_strinfo, vec_free(), vec_safe_iterate(), and vec_safe_length().

bb_reachable()

bool dom_walker::bb_reachable ( struct function * fun, basic_block bb )

privateinherited

Return TRUE if BB is reachable, false otherwise.   

References dom_walker::ALL_BLOCKS, CDI_DOMINATORS, dominated_by_p(), ENTRY_BLOCK_PTR_FOR_FN, FOR_EACH_EDGE, dom_walker::m_reachability, dom_walker::m_unreachable_dom, and basic_block_def::preds.

Referenced by dom_walker::walk().

before_dom_children()

edge strlen_pass::before_dom_children ( basic_block bb )

finaloverridevirtual

Callback for walk_dominator_tree.  Attempt to optimize various
string ops by remembering string lengths pointed by pointer SSA_NAMEs.   

Reimplemented from dom_walker.

References basic_block_def::aux, BITMAP_ALLOC, BITMAP_FREE, CDI_DOMINATORS, check_and_optimize_stmt(), pointer_query::depth, do_invalidate(), free_strinfo(), get_immediate_dominator(), get_stridx(), gimple_phi_arg_def(), gimple_phi_num_args(), gimple_phi_result(), gimple_purge_dead_eh_edges(), gsi_end_p(), gsi_next(), gsi_start_bb(), gsi_start_phis(), i, m_cleanup_cfg, m_gsi, NULL, POINTER_TYPE_P, ptr_qry, si, SSA_NAME_VERSION, ssa_ver_to_stridx, stridx_to_strinfo, strinfo_shared(), TREE_TYPE, vec_safe_iterate(), vec_safe_length(), virtual_operand_p(), and visited.

check_and_optimize_call()

bool strlen_pass::check_and_optimize_call

(

bool *

zero_write

)

Check the built-in call at GSI for validity and optimize it.
Uses RVALS to determine range information.
Return true to let the caller advance *GSI to the next statement
in the basic block and false otherwise.   

References BUILT_IN_NORMAL, DECL_FUNCTION_CODE(), gimple_call_builtin_p(), gimple_call_fndecl(), gimple_call_fntype(), gimple_call_lhs(), gsi_stmt(), handle_alloc_call(), handle_assign(), handle_builtin_memcmp(), handle_builtin_memcpy(), handle_builtin_memset(), handle_builtin_strcat(), handle_builtin_strchr(), handle_builtin_strcpy(), handle_builtin_string_cmp(), handle_builtin_strlen(), handle_builtin_strncat(), handle_builtin_stxncpy_strncat(), handle_printf_call(), lookup_attribute(), m_gsi, ptr_qry, strlen_optimize, TYPE_ATTRIBUTES, and valid_builtin_call().

Referenced by check_and_optimize_stmt().

check_and_optimize_stmt()

bool strlen_pass::check_and_optimize_stmt

(

bool *

cleanup_eh

)

Attempt to check for validity of the performed access a single statement
at *GSI using string length knowledge, and to optimize it.
If the given basic block needs clean-up of EH, CLEANUP_EH is set to
true.  Return true to let the caller advance *GSI to the next statement
in the basic block and false otherwise.   

References check_and_optimize_call(), dyn_cast(), fold_strstr_to_strncmp(), get_stridx(), gimple_assign_cast_p(), gimple_assign_lhs(), gimple_assign_rhs1(), gimple_assign_rhs_code(), gimple_assign_single_p(), gimple_clobber_p(), gimple_cond_code(), gimple_cond_lhs(), gimple_cond_rhs(), gimple_vdef(), gsi_stmt(), handle_assign(), handle_integral_assign(), handle_pointer_plus(), INTEGRAL_TYPE_P, is_gimple_assign(), is_gimple_call(), m_gsi, maybe_invalidate(), POINTER_TYPE_P, SSA_NAME_VERSION, ssa_ver_to_stridx, strlen_optimize, TREE_CODE, TREE_SIDE_EFFECTS, and TREE_TYPE.

Referenced by before_dom_children().

count_nonzero_bytes() [1/2]

bool strlen_pass::count_nonzero_bytes	(	tree	exp,
		tree	vuse,
		gimple *	stmt,
		unsigned HOST_WIDE_INT	offset,
		unsigned HOST_WIDE_INT	nbytes,
		unsigned	lenrange[3],
		bool *	nulterm,
		bool *	allnul,
		bool *	allnonnul,
		ssa_name_limit_t &	snlim )

Recursively determine the minimum and maximum number of leading nonzero
bytes in the representation of EXP at memory state VUSE and set
LENRANGE[0] and LENRANGE[1] to each.
Sets LENRANGE[2] to the total size of the access (which may be less
than LENRANGE[1] when what's being referenced by EXP is a pointer
rather than an array).
Sets *NULTERM if the representation contains a zero byte, sets *ALLNUL
if all the bytes are zero, and *ALLNONNUL is all are nonzero.
OFFSET and NBYTES are the offset into the representation and
the size of the access to it determined from an ADDR_EXPR (i.e.,
a pointer) or MEM_REF or zero for other expressions.
Uses RVALS to determine range information.
Avoids recursing deeper than the limits in SNLIM allow.
Returns true on success and false otherwise.   

References build_int_cst(), CHAR_BIT, char_type_node, CONSTRUCTOR_ELT, CONSTRUCTOR_ELTS, CONSTRUCTOR_NELTS, count_nonzero_bytes(), count_nonzero_bytes_addr(), ctor_for_folding(), DECL_P, error_mark_node, exp(), FOR_EACH_CONSTRUCTOR_ELT, g, gimple_assign_rhs1(), gimple_assign_single_p(), gimple_phi_arg_def(), gimple_phi_num_args(), i, INT_MAX, int_size_in_bytes(), native_encode_expr(), ssa_name_limit_t::next_phi(), nonzero_bytes_for_type(), NULL, offset, SSA_NAME_DEF_STMT, TREE_CODE, tree_expr_nonzero_p(), tree_fits_uhwi_p(), TREE_OPERAND, TREE_STRING_LENGTH, TREE_STRING_POINTER, tree_to_uhwi(), TREE_TYPE, TYPE_MODE, TYPE_PRECISION, TYPE_SIZE_UNIT, VAR_P, and VECTOR_TYPE_P.

count_nonzero_bytes() [2/2]

bool strlen_pass::count_nonzero_bytes	(	tree	expr_or_type,
		gimple *	stmt,
		unsigned	lenrange[3],
		bool *	nulterm,
		bool *	allnul,
		bool *	allnonnul )

Same as above except with an implicit SSA_NAME limit.  When EXPR_OR_TYPE
is a type rather than an expression use its size to compute the range.
RVALS is used to determine ranges of dynamically computed string lengths
(the results of strlen).   

References count_nonzero_bytes(), gimple_vuse(), nonzero_bytes_for_type(), and TYPE_P.

Referenced by count_nonzero_bytes(), count_nonzero_bytes(), count_nonzero_bytes_addr(), handle_integral_assign(), and handle_store().

count_nonzero_bytes_addr()

bool strlen_pass::count_nonzero_bytes_addr	(	tree	exp,
		tree	vuse,
		gimple *	stmt,
		unsigned HOST_WIDE_INT	offset,
		unsigned HOST_WIDE_INT	nbytes,
		unsigned	lenrange[3],
		bool *	nulterm,
		bool *	allnul,
		bool *	allnonnul,
		ssa_name_limit_t &	snlim )

Like count_nonzero_bytes, but instead of counting bytes in EXP, count
bytes that are pointed to by EXP, which should be a pointer.   

References count_nonzero_bytes(), count_nonzero_bytes_addr(), exp(), g, get_stridx(), get_strinfo(), gimple_phi_arg_def(), gimple_phi_num_args(), gimple_vuse(), i, irange::lower_bound(), ssa_name_limit_t::next_phi(), offset, ptr_qry, range_query::range_of_expr(), pointer_query::rvals, si, SSA_NAME_DEF_STMT, generic_wide_int< storage >::to_uhwi(), TREE_CODE, tree_fits_shwi_p(), TREE_OPERAND, tree_to_shwi(), vrange::undefined_p(), irange::upper_bound(), and vrange::varying_p().

Referenced by count_nonzero_bytes(), and count_nonzero_bytes_addr().

get_len_or_size()

bool strlen_pass::get_len_or_size	(	gimple *	stmt,
		tree	arg,
		int	idx,
		unsigned HOST_WIDE_INT	lenrng[2],
		unsigned HOST_WIDE_INT *	size,
		bool *	nulterm )

Given strinfo IDX for ARG, sets LENRNG[] to the range of lengths
of the string(s) referenced by ARG if it can be determined.
If the length cannot be determined, sets *SIZE to the size of
the array the string is stored in, if any.  If no such array is
known, sets *SIZE to -1.  When the strings are nul-terminated sets
*NULTERM to true, otherwise to false.  When nonnull uses RVALS to
determine range information. Returns true on success.   

References cfun, get_range_query(), get_range_strlen_dynamic(), get_strinfo(), HOST_WIDE_INT_M1U, HOST_WIDE_INT_MAX, integer_all_onesp(), max_object_size(), c_strlen_data::maxbound, c_strlen_data::maxlen, c_strlen_data::minlen, NULL, ptr_qry, r, si, TREE_CODE, tree_fits_uhwi_p(), and tree_to_uhwi().

Referenced by handle_builtin_string_cmp(), and strxcmp_eqz_result().

handle_alloc_call()

void strlen_pass::handle_alloc_call

(

built_in_function

bcode

)

Handle a call to an allocation function like alloca, malloc or calloc,
or an ordinary allocation function declared with attribute alloc_size.   

References build_int_cst(), gcc_assert, get_stridx(), gimple_call_lhs(), gsi_stmt(), m_gsi, new_stridx(), new_strinfo(), NULL_TREE, set_strinfo(), si, and size_type_node.

Referenced by check_and_optimize_call().

handle_assign()

bool strlen_pass::handle_assign	(	tree	lhs,
		bool *	zero_write )

Handle assignment statement at *GSI to LHS.  Set *ZERO_WRITE if
the assignment stores all zero bytes.   

References handle_store(), i, is_char_type(), TREE_CODE, TREE_OPERAND, and TREE_TYPE.

Referenced by check_and_optimize_call(), and check_and_optimize_stmt().

handle_builtin_memcmp()

bool strlen_pass::handle_builtin_memcmp

(

)

Handle a call to memcmp.  We try to handle small comparisons by
converting them to load and compare, and replacing the call to memcmp
with a __builtin_memcmp_eq call where possible.
return true when call is transformed, return false otherwise.   

References as_a(), boolean_type_node, build2_loc(), build_int_cst(), build_nonstandard_integer_type(), build_pointer_type_for_mode(), builtin_decl_explicit(), char_type_node, CHAR_TYPE_SIZE, fold_build2_loc(), fold_const_aggregate_ref(), fold_convert_loc(), gcc_assert, GET_MODE_BITSIZE(), GET_MODE_SIZE(), get_pointer_alignment(), gimple_call_arg(), gimple_call_lhs(), gimple_call_set_fndecl(), gimple_location(), gimplify_and_update_call_from_tree(), gsi_stmt(), int_mode_for_size(), known_eq, m_gsi, MIN, pow2p_hwi(), ptr_mode, targetm, tree_fits_uhwi_p(), tree_to_uhwi(), TREE_TYPE, type(), TYPE_MODE, use_in_zero_equality(), and word_mode.

Referenced by check_and_optimize_call().

handle_builtin_memcpy()

void strlen_pass::handle_builtin_memcpy

(

built_in_function

bcode

)

Handle a memcpy-like ({mem{,p}cpy,__mem{,p}cpy_chk}) call.
If strlen of the second argument is known and length of the third argument
is that plus one, strlen of the first argument is the same after this
call.  Uses RVALS to determine range information.   

References adjust_last_stmt(), adjust_related_strinfos(), build_int_cst(), strinfo::dont_invalidate, strinfo::endptr, find_equal_ptrs(), fold_build2_loc(), fold_convert_loc(), strinfo::full_string_p, gcc_unreachable, get_stridx(), get_strinfo(), gimple_assign_rhs1(), gimple_assign_rhs2(), gimple_assign_rhs_code(), gimple_call_arg(), gimple_call_lhs(), gimple_location(), gsi_stmt(), strinfo::idx, integer_onep(), integer_zerop(), is_gimple_assign(), laststmt, laststmt_struct::len, m_gsi, maybe_warn_overflow(), MIN, new_stridx(), new_strinfo(), strinfo::next, strinfo::nonzero_chars, NULL, NULL_TREE, strinfo::prev, set_strinfo(), si, size_type_node, SSA_NAME_DEF_STMT, SSA_NAME_VERSION, ssa_ver_to_stridx, laststmt_struct::stmt, strinfo::stmt, laststmt_struct::stridx, TREE_CODE, tree_fits_uhwi_p(), tree_int_cst_le(), tree_to_uhwi(), TREE_TYPE, unshare_strinfo(), and strinfo::writable.

Referenced by check_and_optimize_call().

handle_builtin_memset()

bool strlen_pass::handle_builtin_memset

(

bool *

zero_write

)

Handle a call to memset.
After a call to calloc, memset(,0,) is unnecessary.
memset(malloc(n),0,n) is calloc(n,1).
return true when the call is transformed, false otherwise.
When nonnull uses RVALS to determine range information.   

References strinfo::alloc, build_int_cst(), build_one_cst(), builtin_decl_implicit(), CHAR_TYPE_SIZE, DECL_FUNCTION_CODE(), strinfo::dont_invalidate, find_equal_ptrs(), fold_convert, strinfo::full_string_p, get_stridx(), get_strinfo(), gimple_build_assign(), gimple_call_arg(), gimple_call_fndecl(), gimple_call_lhs(), gsi_for_stmt(), gsi_remove(), gsi_replace(), gsi_stmt(), HOST_WIDE_INT_1U, integer_zerop(), is_gimple_call(), m_gsi, maybe_warn_overflow(), new_stridx(), new_strinfo(), strinfo::nonzero_chars, NULL, operand_equal_p(), ptr_qry, release_defs(), pointer_query::rvals, set_strinfo(), size_type_node, strinfo::stmt, wi::to_wide(), TREE_CODE, unlink_stmt_vdef(), update_gimple_call(), valid_builtin_call(), and strinfo::writable.

Referenced by check_and_optimize_call().

handle_builtin_strcat()

void strlen_pass::handle_builtin_strcat

(

built_in_function

bcode

)

Handle a strcat-like ({strcat,__strcat_chk}) call.
If strlen of the second argument is known, strlen of the first argument
is increased by the length of the second argument.  Furthermore, attempt
to convert it to memcpy/strcpy if the length of the first argument
is known.   

References adjust_last_stmt(), adjust_related_strinfos(), build_int_cst(), builtin_decl_explicit(), builtin_decl_implicit(), builtin_decl_implicit_p(), check_bounds_or_overlap(), strinfo::dont_invalidate, dump_file, dump_flags, strinfo::endptr, find_equal_ptrs(), fold_build2, fold_build2_loc(), fold_convert_loc(), force_gimple_operand_gsi(), strinfo::full_string_p, gcc_assert, gcc_unreachable, get_stridx(), get_strinfo(), get_string_length(), gimple_call_arg(), gimple_call_lhs(), gimple_location(), GSI_SAME_STMT, gsi_stmt(), strinfo::idx, laststmt, laststmt_struct::len, m_gsi, new_stridx(), new_strinfo(), strinfo::next, no_warning, strinfo::nonzero_chars, NULL, NULL_TREE, operand_equal_p(), print_gimple_stmt(), set_strinfo(), si, size_type_node, size_zero_node, sizetype, laststmt_struct::stmt, strinfo::stmt, laststmt_struct::stridx, suppress_warning(), TDF_DETAILS, TDF_SLIM, TREE_CHAIN, TREE_TYPE, TREE_VALUE, type(), TYPE_ARG_TYPES, unshare_expr(), unshare_strinfo(), update_gimple_call(), update_stmt(), and strinfo::writable.

Referenced by check_and_optimize_call().

handle_builtin_strchr()

void strlen_pass::handle_builtin_strchr

(

)

Handle a strchr call.  If strlen of the first argument is known, replace
the strchr (x, 0) call with the endptr or x + strlen, otherwise remember
that lhs of the call is endptr and strlen of the argument is endptr - x.   

References build_int_cst(), check_nul_terminated_array(), dump_file, dump_flags, find_equal_ptrs(), fold_build2_loc(), fold_convert_loc(), get_stridx(), get_strinfo(), get_string_length(), gimple_call_arg(), gimple_call_lhs(), gimple_location(), gimplify_and_update_call_from_tree(), gsi_stmt(), integer_zerop(), m_gsi, new_stridx(), new_strinfo(), NULL, NULL_TREE, print_gimple_stmt(), set_strinfo(), si, size_type_node, sizetype, SSA_NAME_OCCURS_IN_ABNORMAL_PHI, TDF_DETAILS, TDF_SLIM, TREE_CODE, TREE_TYPE, unshare_expr(), unshare_strinfo(), update_stmt(), useless_type_conversion_p(), and zero_length_string().

Referenced by check_and_optimize_call().

handle_builtin_strcpy()

void strlen_pass::handle_builtin_strcpy

(

built_in_function

bcode

)

Handle a strcpy-like ({st{r,p}cpy,__st{r,p}cpy_chk}) call.
If strlen of the second argument is known, strlen of the first argument
is the same after this call.  Furthermore, attempt to convert it to
memcpy.  Uses RVALS to determine range information.   

References adjust_last_stmt(), adjust_related_strinfos(), build_int_cst(), builtin_decl_explicit(), builtin_decl_implicit(), builtin_decl_implicit_p(), check_bounds_or_overlap(), strinfo::dont_invalidate, dump_file, dump_flags, strinfo::endptr, find_equal_ptrs(), fold_build2, fold_build2_loc(), fold_convert_loc(), force_gimple_operand_gsi(), strinfo::full_string_p, gcc_unreachable, get_stridx(), get_strinfo(), get_string_length(), gimple_call_arg(), gimple_call_lhs(), gimple_call_num_args(), gimple_location(), GSI_SAME_STMT, gsi_stmt(), strinfo::idx, integer_zerop(), laststmt, laststmt_struct::len, m_gsi, maybe_warn_overflow(), new_stridx(), new_strinfo(), strinfo::next, no_warning, strinfo::nonzero_chars, NULL, NULL_TREE, strinfo::prev, print_gimple_stmt(), strinfo::ptr, set_strinfo(), si, size_type_node, SSA_NAME_VERSION, ssa_ver_to_stridx, laststmt_struct::stmt, strinfo::stmt, laststmt_struct::stridx, suppress_warning(), TDF_DETAILS, TDF_SLIM, TREE_CHAIN, TREE_CODE, TREE_TYPE, TREE_VALUE, type(), TYPE_ARG_TYPES, unshare_expr(), unshare_strinfo(), update_gimple_call(), update_stmt(), verify_related_strinfos(), strinfo::writable, and zero_length_string().

Referenced by check_and_optimize_call().

handle_builtin_string_cmp()

bool strlen_pass::handle_builtin_string_cmp

(

)

Optimize a call to strcmp or strncmp either by folding it to a constant
when possible or by transforming the latter to the former.  Warn about
calls where the length of one argument is greater than the size of
the array to which the other argument points if the latter's length
is not known.  Return true when the call has been transformed into
another and false otherwise.   

References as_a(), build_int_cst(), builtin_decl_implicit(), check_nul_terminated_array(), get_len_or_size(), get_stridx(), gimple_call_arg(), gimple_call_lhs(), gimple_call_num_args(), gsi_stmt(), HOST_WIDE_INT_M1U, HOST_WIDE_INT_MAX, integer_zero_node, integer_zerop(), m_gsi, maybe_warn_pointless_strcmp(), MIN, NULL_TREE, replace_call_with_value(), irange::set_nonzero(), set_range_info(), size_type_node, strxcmp_eqz_result(), tree_fits_shwi_p(), tree_to_shwi(), TREE_TYPE, update_gimple_call(), and use_in_zero_equality().

Referenced by check_and_optimize_call().

handle_builtin_strlen()

void strlen_pass::handle_builtin_strlen

(

)

Handle a strlen call.  If strlen of the argument is known, replace
the strlen call with the known value, otherwise remember that strlen
of the argument is stored in the lhs SSA_NAME.   

References adjust_related_strinfos(), build_int_cst(), DECL_FUNCTION_CODE(), dump_file, dump_flags, find_equal_ptrs(), fold_build2_loc(), fold_convert_loc(), gcc_assert, get_stridx(), get_strinfo(), get_string_length(), gimple_call_arg(), gimple_call_fndecl(), gimple_call_lhs(), gimple_location(), gimplify_and_update_call_from_tree(), gsi_stmt(), wi::gtu_p(), integer_zerop(), m_gsi, maybe_set_strlen_range(), new_stridx(), new_strinfo(), NULL, NULL_TREE, print_gimple_stmt(), ptrdiff_type_node, set_strinfo(), set_strlen_range(), si, SSA_NAME_OCCURS_IN_ABNORMAL_PHI, strlen_to_stridx, TDF_DETAILS, TDF_SLIM, wi::to_wide(), TREE_CODE, tree_int_cst_le(), tree_int_cst_lt(), TREE_TYPE, TYPE_MAX_VALUE, unshare_expr(), unshare_strinfo(), update_stmt(), and useless_type_conversion_p().

Referenced by check_and_optimize_call().

handle_builtin_strncat()

void strlen_pass::handle_builtin_strncat

(

built_in_function

)

Check the size argument to the built-in forms of stpncpy and strncpy
for out-of-bounds offsets or overlapping access, and to see if the
size argument is derived from a call to strlen() on the source argument,
and if so, issue an appropriate warning.   

References handle_builtin_stxncpy_strncat().

Referenced by check_and_optimize_call().

handle_builtin_stxncpy_strncat()

void strlen_pass::handle_builtin_stxncpy_strncat

(

bool

append_p

)

Check the arguments to the built-in forms of stpncpy, strncpy, and
strncat, for out-of-bounds offsets or overlapping access, and to see
if the size is derived from calling strlen() on the source argument,
and if so, issue the appropriate warning.
APPEND_P is true for strncat.   

References build_int_cst(), check_bounds_or_overlap(), fold_build2, strinfo::full_string_p, get_stridx(), get_strinfo(), gimple_call_alloc_size(), gimple_call_arg(), gimple_call_fndecl(), gimple_or_expr_nonartificial_location(), gsi_stmt(), inform(), is_strlen_related_p(), m_gsi, maybe_diag_stxncpy_trunc(), no_warning, strinfo::nonzero_chars, NULL, NULL_TREE, strinfo::ptr, SSA_NAME_DEF_STMT, strlen_to_stridx, suppress_warning(), TREE_CODE, TREE_TYPE, UNKNOWN_LOCATION, and warning_at().

Referenced by check_and_optimize_call(), and handle_builtin_strncat().

handle_integral_assign()

void strlen_pass::handle_integral_assign

(

bool *

cleanup_eh

)

Handle an assignment statement at *GSI to a LHS of integral type.
If GSI's basic block needs clean-up of EH, set *CLEANUP_EH to true.   

References build_int_cst(), cfun, char_type_node, count_nonzero_bytes(), dump_file, dump_flags, fold_strstr_to_strncmp(), get_addr_stridx(), get_range_query(), get_stridx(), get_strinfo(), gimple_assign_lhs(), gimple_assign_load_p(), gimple_assign_rhs1(), gimple_assign_rhs2(), gimple_assign_rhs_code(), gimple_assign_set_rhs_from_tree(), gimple_has_volatile_ops(), gimple_set_vuse(), gsi_stmt(), integer_zero_node, m_gsi, maybe_clean_or_replace_eh_stmt(), new_stridx(), new_strinfo(), NULL_TREE, print_gimple_stmt(), r, set_range_info(), set_strinfo(), si, sizetype, strlen_to_stridx, TDF_DETAILS, TDF_SLIM, wi::to_widest(), TREE_CODE, TREE_OPERAND, TREE_TYPE, TYPE_MODE, TYPE_PRECISION, UINT_MAX, and update_stmt().

Referenced by check_and_optimize_stmt().

handle_pointer_plus()

void strlen_pass::handle_pointer_plus

(

)

Handle a POINTER_PLUS_EXPR statement.
For p = "abcd" + 2; compute associated length, or if
p = q + off is pointing to a '\0' character of a string, call
zero_length_string on it.   

References strinfo::endptr, gcc_assert, get_stridx(), get_strinfo(), gimple_assign_lhs(), gimple_assign_rhs1(), gimple_assign_rhs2(), gimple_assign_set_rhs_with_ops(), gimple_assign_single_p(), gsi_stmt(), m_gsi, NULL, NULL_TREE, operand_equal_p(), si, SSA_NAME_DEF_STMT, SSA_NAME_VERSION, ssa_ver_to_stridx, TREE_CODE, tree_fits_uhwi_p(), tree_to_uhwi(), TREE_TYPE, update_stmt(), useless_type_conversion_p(), and zero_length_string().

Referenced by check_and_optimize_stmt().

handle_store()

bool strlen_pass::handle_store

(

bool *

zero_write

)

Handle a single or multibyte store other than by a built-in function,
either via a single character assignment or by multi-byte assignment
either via MEM_REF or via a type other than char (such as in
'*(int*)a = 12345').  Return true to let the caller advance *GSI to
the next statement in the basic block and false otherwise.   

References a, adjust_last_stmt(), adjust_related_strinfos(), build_fold_addr_expr, build_int_cst(), cfun, compare_nonzero_chars(), count_nonzero_bytes(), fold_build2_loc(), gcc_assert, get_addr_stridx(), get_stridx(), get_strinfo(), gimple_assign_lhs(), gimple_assign_rhs1(), gimple_call_lhs(), gimple_location(), gsi_next(), gsi_remove(), gsi_stmt(), HOST_WIDE_INT_M1U, initializer_zerop(), int_size_in_bytes(), is_gimple_assign(), is_gimple_call(), laststmt, laststmt_struct::len, m_gsi, maybe_warn_overflow(), new_addr_stridx(), new_stridx(), new_strinfo(), NULL, NULL_TREE, offset, ptr_qry, release_defs(), pointer_query::rvals, set_strinfo(), si, size_type_node, size_zero_node, SSA_NAME_OCCURS_IN_ABNORMAL_PHI, laststmt_struct::stmt, stmt_could_throw_p(), laststmt_struct::stridx, TREE_CODE, tree_fits_uhwi_p(), TREE_OPERAND, tree_to_uhwi(), TREE_TYPE, UINT_MAX, unlink_stmt_vdef(), and unshare_strinfo().

Referenced by handle_assign().

maybe_warn_overflow() [1/2]

void strlen_pass::maybe_warn_overflow	(	gimple *	stmt,
		bool	call_lhs,
		tree	len,
		strinfo *	si = NULL,
		bool	plus_one = false,
		bool	rawmem = false )

Diagnose buffer overflow by a STMT writing LEN + PLUS_ONE bytes,
either into a region allocated for the object SI when non-null,
or into an object designated by the LHS of STMT otherwise.
For a call STMT, when CALL_LHS is set use its left hand side
as the destination, otherwise use argument zero.
When nonnull uses RVALS to determine range information.
RAWMEM may be set by memcpy and other raw memory functions
to allow accesses across subobject boundaries.   

References access_write_only, BUILT_IN_NORMAL, compute_objsize(), gcc_assert, get_range(), gimple_assign_lhs(), gimple_call_arg(), gimple_call_builtin_p(), gimple_call_fndecl(), gimple_call_lhs(), gimple_or_expr_nonartificial_location(), access_ref::inform_access(), is_gimple_assign(), is_gimple_call(), is_strlen_related_p(), wi::leu_p(), max_object_size(), NULL_TREE, access_ref::offrng, ptr_qry, pointer_query::rvals, si, SIGNED, access_ref::size_remaining(), access_ref::sizrng, suppress_warning(), wi::to_offset(), UNSIGNED, warning_at(), warning_n(), and warning_suppressed_p().

Referenced by handle_builtin_memcpy(), handle_builtin_memset(), handle_builtin_strcpy(), handle_store(), and maybe_warn_overflow().

maybe_warn_overflow() [2/2]

void strlen_pass::maybe_warn_overflow	(	gimple *	stmt,
		bool	call_lhs,
		unsigned HOST_WIDE_INT	len,
		strinfo *	si = NULL,
		bool	plus_one = false,
		bool	rawmem = false )

Convenience wrapper for the above.   

References build_int_cst(), maybe_warn_overflow(), si, and size_type_node.

propagate_unreachable_to_edges()

void dom_walker::propagate_unreachable_to_edges ( basic_block bb, FILE * dump_file, dump_flags_t dump_flags )

privateinherited

BB has been determined to be unreachable.  Propagate that property
to incoming and outgoing edges of BB as appropriate.   

References CDI_DOMINATORS, dominated_by_p(), dump_file, dump_flags, FOR_EACH_EDGE, basic_block_def::index, dom_walker::m_unreachable_dom, basic_block_def::preds, basic_block_def::succs, and TDF_DETAILS.

Referenced by dom_walker::walk().

strxcmp_eqz_result()

tree strlen_pass::strxcmp_eqz_result	(	gimple *	stmt,
		tree	arg1,
		int	idx1,
		tree	arg2,
		int	idx2,
		unsigned HOST_WIDE_INT	bound,
		unsigned HOST_WIDE_INT	len[2],
		unsigned HOST_WIDE_INT *	psize )

If IDX1 and IDX2 refer to strings A and B of unequal lengths, return
the result of 0 == strncmp (A, B, BOUND) (which is the same as strcmp
for a sufficiently large BOUND).  If the result is based on the length
of one string being greater than the longest string that would fit in
the array pointer to by the argument, set *PLEN and *PSIZE to
the corresponding length (or its complement when the string is known
to be at least as long and need not be nul-terminated) and size.
Otherwise return null.   

References get_len_or_size(), HOST_WIDE_INT_M1U, HOST_WIDE_INT_MAX, integer_one_node, integer_zero_node, and NULL_TREE.

Referenced by handle_builtin_string_cmp().

walk()

void dom_walker::walk ( basic_block bb )

inherited

Recursively walk the dominator tree.
BB is the basic block we are currently visiting.   

References dom_walker::after_dom_children(), dom_walker::bb_reachable(), dom_walker::before_dom_children(), CDI_DOMINATORS, cfun, dump_file, dump_flags, EDGE_COUNT, ENTRY_BLOCK_PTR_FOR_FN, EXIT_BLOCK_PTR_FOR_FN, first_dom_son(), FOR_EACH_EDGE, free(), i, last_basic_block_for_fn, dom_walker::m_bb_to_rpo, dom_walker::m_dom_direction, dom_walker::m_reachability, dom_walker::m_unreachable_dom, dom_walker::m_user_bb_to_rpo, n_basic_blocks_for_fn, next_dom_son(), NULL, pre_and_rev_post_order_compute(), basic_block_def::preds, dom_walker::propagate_unreachable_to_edges(), dom_walker::REACHABLE_BLOCKS, set_all_edges_as_executable(), sort_bbs_postorder(), dom_walker::STOP, basic_block_def::succs, and worklist.

Referenced by array_bounds_checker::check(), eliminate_with_rpo_vn(), find_comparisons(), get_non_trapping(), ipa_analyze_node(), ipcp_transform_function(), rewrite_blocks(), and substitute_and_fold_engine::substitute_and_fold().

Field Documentation

m_bb_to_rpo

int* dom_walker::m_bb_to_rpo

privateinherited

Referenced by dom_walker::walk(), and dom_walker::~dom_walker().

m_cleanup_cfg

bool strlen_pass::m_cleanup_cfg

Referenced by before_dom_children().

m_dom_direction

enum cdi_direction dom_walker::m_dom_direction

privateinherited

Referenced by dom_walker::walk().

m_gsi

gimple_stmt_iterator strlen_pass::m_gsi

Referenced by before_dom_children(), check_and_optimize_call(), check_and_optimize_stmt(), handle_alloc_call(), handle_builtin_memcmp(), handle_builtin_memcpy(), handle_builtin_memset(), handle_builtin_strcat(), handle_builtin_strchr(), handle_builtin_strcpy(), handle_builtin_string_cmp(), handle_builtin_strlen(), handle_builtin_stxncpy_strncat(), handle_integral_assign(), handle_pointer_plus(), and handle_store().

m_reachability

enum reachability dom_walker::m_reachability

privateinherited

Referenced by dom_walker::bb_reachable(), and dom_walker::walk().

m_unreachable_dom

basic_block dom_walker::m_unreachable_dom

privateinherited

Referenced by dom_walker::bb_reachable(), dom_walker::propagate_unreachable_to_edges(), and dom_walker::walk().

m_user_bb_to_rpo

bool dom_walker::m_user_bb_to_rpo

privateinherited

Referenced by dom_walker::walk(), and dom_walker::~dom_walker().

ptr_qry

pointer_query strlen_pass::ptr_qry

Referenced by adjust_last_stmt(), before_dom_children(), check_and_optimize_call(), count_nonzero_bytes_addr(), get_len_or_size(), handle_builtin_memset(), handle_store(), maybe_warn_overflow(), and ~strlen_pass().

STOP

const edge dom_walker::STOP = (edge)-1

staticinherited

Referenced by rewrite_update_dom_walker::before_dom_children(), and dom_walker::walk().

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The documentation for this class was generated from the following file:

• tree-ssa-strlen.cc