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/* Conditional constant propagation pass for the GNU compiler.
Copyright (C) 2000-2015 Free Software Foundation, Inc.
Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org>
Adapted to GIMPLE trees by Diego Novillo <dnovillo@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/>. */
/* Conditional constant propagation (CCP) is based on the SSA
propagation engine (tree-ssa-propagate.c). Constant assignments of
the form VAR = CST are propagated from the assignments into uses of
VAR, which in turn may generate new constants. The simulation uses
a four level lattice to keep track of constant values associated
with SSA names. Given an SSA name V_i, it may take one of the
following values:
UNINITIALIZED -> the initial state of the value. This value
is replaced with a correct initial value
the first time the value is used, so the
rest of the pass does not need to care about
it. Using this value simplifies initialization
of the pass, and prevents us from needlessly
scanning statements that are never reached.
UNDEFINED -> V_i is a local variable whose definition
has not been processed yet. Therefore we
don't yet know if its value is a constant
or not.
CONSTANT -> V_i has been found to hold a constant
value C.
VARYING -> V_i cannot take a constant value, or if it
does, it is not possible to determine it
at compile time.
The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node:
1- In ccp_visit_stmt, we are interested in assignments whose RHS
evaluates into a constant and conditional jumps whose predicate
evaluates into a boolean true or false. When an assignment of
the form V_i = CONST is found, V_i's lattice value is set to
CONSTANT and CONST is associated with it. This causes the
propagation engine to add all the SSA edges coming out the
assignment into the worklists, so that statements that use V_i
can be visited.
If the statement is a conditional with a constant predicate, we
mark the outgoing edges as executable or not executable
depending on the predicate's value. This is then used when
visiting PHI nodes to know when a PHI argument can be ignored.
2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the
same constant C, then the LHS of the PHI is set to C. This
evaluation is known as the "meet operation". Since one of the
goals of this evaluation is to optimistically return constant
values as often as possible, it uses two main short cuts:
- If an argument is flowing in through a non-executable edge, it
is ignored. This is useful in cases like this:
if (PRED)
a_9 = 3;
else
a_10 = 100;
a_11 = PHI (a_9, a_10)
If PRED is known to always evaluate to false, then we can
assume that a_11 will always take its value from a_10, meaning
that instead of consider it VARYING (a_9 and a_10 have
different values), we can consider it CONSTANT 100.
- If an argument has an UNDEFINED value, then it does not affect
the outcome of the meet operation. If a variable V_i has an
UNDEFINED value, it means that either its defining statement
hasn't been visited yet or V_i has no defining statement, in
which case the original symbol 'V' is being used
uninitialized. Since 'V' is a local variable, the compiler
may assume any initial value for it.
After propagation, every variable V_i that ends up with a lattice
value of CONSTANT will have the associated constant value in the
array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for
final substitution and folding.
This algorithm uses wide-ints at the max precision of the target.
This means that, with one uninteresting exception, variables with
UNSIGNED types never go to VARYING because the bits above the
precision of the type of the variable are always zero. The
uninteresting case is a variable of UNSIGNED type that has the
maximum precision of the target. Such variables can go to VARYING,
but this causes no loss of infomation since these variables will
never be extended.
References:
Constant propagation with conditional branches,
Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
Building an Optimizing Compiler,
Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
Advanced Compiler Design and Implementation,
Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "hash-set.h"
#include "machmode.h"
#include "vec.h"
#include "double-int.h"
#include "input.h"
#include "alias.h"
#include "symtab.h"
#include "wide-int.h"
#include "inchash.h"
#include "real.h"
#include "tree.h"
#include "fold-const.h"
#include "stor-layout.h"
#include "flags.h"
#include "tm_p.h"
#include "predict.h"
#include "hard-reg-set.h"
#include "input.h"
#include "function.h"
#include "dominance.h"
#include "cfg.h"
#include "basic-block.h"
#include "gimple-pretty-print.h"
#include "hash-table.h"
#include "tree-ssa-alias.h"
#include "internal-fn.h"
#include "gimple-fold.h"
#include "tree-eh.h"
#include "gimple-expr.h"
#include "is-a.h"
#include "gimple.h"
#include "gimplify.h"
#include "gimple-iterator.h"
#include "gimple-ssa.h"
#include "tree-cfg.h"
#include "tree-phinodes.h"
#include "ssa-iterators.h"
#include "stringpool.h"
#include "tree-ssanames.h"
#include "tree-pass.h"
#include "tree-ssa-propagate.h"
#include "value-prof.h"
#include "langhooks.h"
#include "target.h"
#include "diagnostic-core.h"
#include "dbgcnt.h"
#include "params.h"
#include "wide-int-print.h"
#include "builtins.h"
#include "tree-chkp.h"
/* Possible lattice values. */
typedef enum
{
UNINITIALIZED,
UNDEFINED,
CONSTANT,
VARYING
} ccp_lattice_t;
struct ccp_prop_value_t {
/* Lattice value. */
ccp_lattice_t lattice_val;
/* Propagated value. */
tree value;
/* Mask that applies to the propagated value during CCP. For X
with a CONSTANT lattice value X & ~mask == value & ~mask. The
zero bits in the mask cover constant values. The ones mean no
information. */
widest_int mask;
};
/* Array of propagated constant values. After propagation,
CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
the constant is held in an SSA name representing a memory store
(i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
memory reference used to store (i.e., the LHS of the assignment
doing the store). */
static ccp_prop_value_t *const_val;
static unsigned n_const_val;
static void canonicalize_value (ccp_prop_value_t *);
static bool ccp_fold_stmt (gimple_stmt_iterator *);
/* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
static void
dump_lattice_value (FILE *outf, const char *prefix, ccp_prop_value_t val)
{
switch (val.lattice_val)
{
case UNINITIALIZED:
fprintf (outf, "%sUNINITIALIZED", prefix);
break;
case UNDEFINED:
fprintf (outf, "%sUNDEFINED", prefix);
break;
case VARYING:
fprintf (outf, "%sVARYING", prefix);
break;
case CONSTANT:
if (TREE_CODE (val.value) != INTEGER_CST
|| val.mask == 0)
{
fprintf (outf, "%sCONSTANT ", prefix);
print_generic_expr (outf, val.value, dump_flags);
}
else
{
widest_int cval = wi::bit_and_not (wi::to_widest (val.value),
val.mask);
fprintf (outf, "%sCONSTANT ", prefix);
print_hex (cval, outf);
fprintf (outf, " (");
print_hex (val.mask, outf);
fprintf (outf, ")");
}
break;
default:
gcc_unreachable ();
}
}
/* Print lattice value VAL to stderr. */
void debug_lattice_value (ccp_prop_value_t val);
DEBUG_FUNCTION void
debug_lattice_value (ccp_prop_value_t val)
{
dump_lattice_value (stderr, "", val);
fprintf (stderr, "\n");
}
/* Extend NONZERO_BITS to a full mask, with the upper bits being set. */
static widest_int
extend_mask (const wide_int &nonzero_bits)
{
return (wi::mask <widest_int> (wi::get_precision (nonzero_bits), true)
| widest_int::from (nonzero_bits, UNSIGNED));
}
/* Compute a default value for variable VAR and store it in the
CONST_VAL array. The following rules are used to get default
values:
1- Global and static variables that are declared constant are
considered CONSTANT.
2- Any other value is considered UNDEFINED. This is useful when
considering PHI nodes. PHI arguments that are undefined do not
change the constant value of the PHI node, which allows for more
constants to be propagated.
3- Variables defined by statements other than assignments and PHI
nodes are considered VARYING.
4- Initial values of variables that are not GIMPLE registers are
considered VARYING. */
static ccp_prop_value_t
get_default_value (tree var)
{
ccp_prop_value_t val = { UNINITIALIZED, NULL_TREE, 0 };
gimple stmt;
stmt = SSA_NAME_DEF_STMT (var);
if (gimple_nop_p (stmt))
{
/* Variables defined by an empty statement are those used
before being initialized. If VAR is a local variable, we
can assume initially that it is UNDEFINED, otherwise we must
consider it VARYING. */
if (!virtual_operand_p (var)
&& TREE_CODE (SSA_NAME_VAR (var)) == VAR_DECL)
val.lattice_val = UNDEFINED;
else
{
val.lattice_val = VARYING;
val.mask = -1;
if (flag_tree_bit_ccp)
{
wide_int nonzero_bits = get_nonzero_bits (var);
if (nonzero_bits != -1)
{
val.lattice_val = CONSTANT;
val.value = build_zero_cst (TREE_TYPE (var));
val.mask = extend_mask (nonzero_bits);
}
}
}
}
else if (is_gimple_assign (stmt))
{
tree cst;
if (gimple_assign_single_p (stmt)
&& DECL_P (gimple_assign_rhs1 (stmt))
&& (cst = get_symbol_constant_value (gimple_assign_rhs1 (stmt))))
{
val.lattice_val = CONSTANT;
val.value = cst;
}
else
{
/* Any other variable defined by an assignment is considered
UNDEFINED. */
val.lattice_val = UNDEFINED;
}
}
else if ((is_gimple_call (stmt)
&& gimple_call_lhs (stmt) != NULL_TREE)
|| gimple_code (stmt) == GIMPLE_PHI)
{
/* A variable defined by a call or a PHI node is considered
UNDEFINED. */
val.lattice_val = UNDEFINED;
}
else
{
/* Otherwise, VAR will never take on a constant value. */
val.lattice_val = VARYING;
val.mask = -1;
}
return val;
}
/* Get the constant value associated with variable VAR. */
static inline ccp_prop_value_t *
get_value (tree var)
{
ccp_prop_value_t *val;
if (const_val == NULL
|| SSA_NAME_VERSION (var) >= n_const_val)
return NULL;
val = &const_val[SSA_NAME_VERSION (var)];
if (val->lattice_val == UNINITIALIZED)
*val = get_default_value (var);
canonicalize_value (val);
return val;
}
/* Return the constant tree value associated with VAR. */
static inline tree
get_constant_value (tree var)
{
ccp_prop_value_t *val;
if (TREE_CODE (var) != SSA_NAME)
{
if (is_gimple_min_invariant (var))
return var;
return NULL_TREE;
}
val = get_value (var);
if (val
&& val->lattice_val == CONSTANT
&& (TREE_CODE (val->value) != INTEGER_CST
|| val->mask == 0))
return val->value;
return NULL_TREE;
}
/* Sets the value associated with VAR to VARYING. */
static inline void
set_value_varying (tree var)
{
ccp_prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
val->lattice_val = VARYING;
val->value = NULL_TREE;
val->mask = -1;
}
/* For integer constants, make sure to drop TREE_OVERFLOW. */
static void
canonicalize_value (ccp_prop_value_t *val)
{
if (val->lattice_val != CONSTANT)
return;
if (TREE_OVERFLOW_P (val->value))
val->value = drop_tree_overflow (val->value);
}
/* Return whether the lattice transition is valid. */
static bool
valid_lattice_transition (ccp_prop_value_t old_val, ccp_prop_value_t new_val)
{
/* Lattice transitions must always be monotonically increasing in
value. */
if (old_val.lattice_val < new_val.lattice_val)
return true;
if (old_val.lattice_val != new_val.lattice_val)
return false;
if (!old_val.value && !new_val.value)
return true;
/* Now both lattice values are CONSTANT. */
/* Allow transitioning from PHI <&x, not executable> == &x
to PHI <&x, &y> == common alignment. */
if (TREE_CODE (old_val.value) != INTEGER_CST
&& TREE_CODE (new_val.value) == INTEGER_CST)
return true;
/* Bit-lattices have to agree in the still valid bits. */
if (TREE_CODE (old_val.value) == INTEGER_CST
&& TREE_CODE (new_val.value) == INTEGER_CST)
return (wi::bit_and_not (wi::to_widest (old_val.value), new_val.mask)
== wi::bit_and_not (wi::to_widest (new_val.value), new_val.mask));
/* Otherwise constant values have to agree. */
if (operand_equal_p (old_val.value, new_val.value, 0))
return true;
/* At least the kinds and types should agree now. */
if (TREE_CODE (old_val.value) != TREE_CODE (new_val.value)
|| !types_compatible_p (TREE_TYPE (old_val.value),
TREE_TYPE (new_val.value)))
return false;
/* For floats and !HONOR_NANS allow transitions from (partial) NaN
to non-NaN. */
tree type = TREE_TYPE (new_val.value);
if (SCALAR_FLOAT_TYPE_P (type)
&& !HONOR_NANS (type))
{
if (REAL_VALUE_ISNAN (TREE_REAL_CST (old_val.value)))
return true;
}
else if (VECTOR_FLOAT_TYPE_P (type)
&& !HONOR_NANS (type))
{
for (unsigned i = 0; i < VECTOR_CST_NELTS (old_val.value); ++i)
if (!REAL_VALUE_ISNAN
(TREE_REAL_CST (VECTOR_CST_ELT (old_val.value, i)))
&& !operand_equal_p (VECTOR_CST_ELT (old_val.value, i),
VECTOR_CST_ELT (new_val.value, i), 0))
return false;
return true;
}
else if (COMPLEX_FLOAT_TYPE_P (type)
&& !HONOR_NANS (type))
{
if (!REAL_VALUE_ISNAN (TREE_REAL_CST (TREE_REALPART (old_val.value)))
&& !operand_equal_p (TREE_REALPART (old_val.value),
TREE_REALPART (new_val.value), 0))
return false;
if (!REAL_VALUE_ISNAN (TREE_REAL_CST (TREE_IMAGPART (old_val.value)))
&& !operand_equal_p (TREE_IMAGPART (old_val.value),
TREE_IMAGPART (new_val.value), 0))
return false;
return true;
}
return false;
}
/* Set the value for variable VAR to NEW_VAL. Return true if the new
value is different from VAR's previous value. */
static bool
set_lattice_value (tree var, ccp_prop_value_t new_val)
{
/* We can deal with old UNINITIALIZED values just fine here. */
ccp_prop_value_t *old_val = &const_val[SSA_NAME_VERSION (var)];
canonicalize_value (&new_val);
/* We have to be careful to not go up the bitwise lattice
represented by the mask.
??? This doesn't seem to be the best place to enforce this. */
if (new_val.lattice_val == CONSTANT
&& old_val->lattice_val == CONSTANT
&& TREE_CODE (new_val.value) == INTEGER_CST
&& TREE_CODE (old_val->value) == INTEGER_CST)
{
widest_int diff = (wi::to_widest (new_val.value)
^ wi::to_widest (old_val->value));
new_val.mask = new_val.mask | old_val->mask | diff;
}
gcc_checking_assert (valid_lattice_transition (*old_val, new_val));
/* If *OLD_VAL and NEW_VAL are the same, return false to inform the
caller that this was a non-transition. */
if (old_val->lattice_val != new_val.lattice_val
|| (new_val.lattice_val == CONSTANT
&& TREE_CODE (new_val.value) == INTEGER_CST
&& (TREE_CODE (old_val->value) != INTEGER_CST
|| new_val.mask != old_val->mask)))
{
/* ??? We would like to delay creation of INTEGER_CSTs from
partially constants here. */
if (dump_file && (dump_flags & TDF_DETAILS))
{
dump_lattice_value (dump_file, "Lattice value changed to ", new_val);
fprintf (dump_file, ". Adding SSA edges to worklist.\n");
}
*old_val = new_val;
gcc_assert (new_val.lattice_val != UNINITIALIZED);
return true;
}
return false;
}
static ccp_prop_value_t get_value_for_expr (tree, bool);
static ccp_prop_value_t bit_value_binop (enum tree_code, tree, tree, tree);
static void bit_value_binop_1 (enum tree_code, tree, widest_int *, widest_int *,
tree, const widest_int &, const widest_int &,
tree, const widest_int &, const widest_int &);
/* Return a widest_int that can be used for bitwise simplifications
from VAL. */
static widest_int
value_to_wide_int (ccp_prop_value_t val)
{
if (val.value
&& TREE_CODE (val.value) == INTEGER_CST)
return wi::to_widest (val.value);
return 0;
}
/* Return the value for the address expression EXPR based on alignment
information. */
static ccp_prop_value_t
get_value_from_alignment (tree expr)
{
tree type = TREE_TYPE (expr);
ccp_prop_value_t val;
unsigned HOST_WIDE_INT bitpos;
unsigned int align;
gcc_assert (TREE_CODE (expr) == ADDR_EXPR);
get_pointer_alignment_1 (expr, &align, &bitpos);
val.mask = (POINTER_TYPE_P (type) || TYPE_UNSIGNED (type)
? wi::mask <widest_int> (TYPE_PRECISION (type), false)
: -1).and_not (align / BITS_PER_UNIT - 1);
val.lattice_val = val.mask == -1 ? VARYING : CONSTANT;
if (val.lattice_val == CONSTANT)
val.value = build_int_cstu (type, bitpos / BITS_PER_UNIT);
else
val.value = NULL_TREE;
return val;
}
/* Return the value for the tree operand EXPR. If FOR_BITS_P is true
return constant bits extracted from alignment information for
invariant addresses. */
static ccp_prop_value_t
get_value_for_expr (tree expr, bool for_bits_p)
{
ccp_prop_value_t val;
if (TREE_CODE (expr) == SSA_NAME)
{
val = *get_value (expr);
if (for_bits_p
&& val.lattice_val == CONSTANT
&& TREE_CODE (val.value) == ADDR_EXPR)
val = get_value_from_alignment (val.value);
}
else if (is_gimple_min_invariant (expr)
&& (!for_bits_p || TREE_CODE (expr) != ADDR_EXPR))
{
val.lattice_val = CONSTANT;
val.value = expr;
val.mask = 0;
canonicalize_value (&val);
}
else if (TREE_CODE (expr) == ADDR_EXPR)
val = get_value_from_alignment (expr);
else
{
val.lattice_val = VARYING;
val.mask = -1;
val.value = NULL_TREE;
}
return val;
}
/* Return the likely CCP lattice value for STMT.
If STMT has no operands, then return CONSTANT.
Else if undefinedness of operands of STMT cause its value to be
undefined, then return UNDEFINED.
Else if any operands of STMT are constants, then return CONSTANT.
Else return VARYING. */
static ccp_lattice_t
likely_value (gimple stmt)
{
bool has_constant_operand, has_undefined_operand, all_undefined_operands;
tree use;
ssa_op_iter iter;
unsigned i;
enum gimple_code code = gimple_code (stmt);
/* This function appears to be called only for assignments, calls,
conditionals, and switches, due to the logic in visit_stmt. */
gcc_assert (code == GIMPLE_ASSIGN
|| code == GIMPLE_CALL
|| code == GIMPLE_COND
|| code == GIMPLE_SWITCH);
/* If the statement has volatile operands, it won't fold to a
constant value. */
if (gimple_has_volatile_ops (stmt))
return VARYING;
/* Arrive here for more complex cases. */
has_constant_operand = false;
has_undefined_operand = false;
all_undefined_operands = true;
FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
{
ccp_prop_value_t *val = get_value (use);
if (val->lattice_val == UNDEFINED)
has_undefined_operand = true;
else
all_undefined_operands = false;
if (val->lattice_val == CONSTANT)
has_constant_operand = true;
}
/* There may be constants in regular rhs operands. For calls we
have to ignore lhs, fndecl and static chain, otherwise only
the lhs. */
for (i = (is_gimple_call (stmt) ? 2 : 0) + gimple_has_lhs (stmt);
i < gimple_num_ops (stmt); ++i)
{
tree op = gimple_op (stmt, i);
if (!op || TREE_CODE (op) == SSA_NAME)
continue;
if (is_gimple_min_invariant (op))
has_constant_operand = true;
}
if (has_constant_operand)
all_undefined_operands = false;
if (has_undefined_operand
&& code == GIMPLE_CALL
&& gimple_call_internal_p (stmt))
switch (gimple_call_internal_fn (stmt))
{
/* These 3 builtins use the first argument just as a magic
way how to find out a decl uid. */
case IFN_GOMP_SIMD_LANE:
case IFN_GOMP_SIMD_VF:
case IFN_GOMP_SIMD_LAST_LANE:
has_undefined_operand = false;
break;
default:
break;
}
/* If the operation combines operands like COMPLEX_EXPR make sure to
not mark the result UNDEFINED if only one part of the result is
undefined. */
if (has_undefined_operand && all_undefined_operands)
return UNDEFINED;
else if (code == GIMPLE_ASSIGN && has_undefined_operand)
{
switch (gimple_assign_rhs_code (stmt))
{
/* Unary operators are handled with all_undefined_operands. */
case PLUS_EXPR:
case MINUS_EXPR:
case POINTER_PLUS_EXPR:
/* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
Not bitwise operators, one VARYING operand may specify the
result completely. Not logical operators for the same reason.
Not COMPLEX_EXPR as one VARYING operand makes the result partly
not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
the undefined operand may be promoted. */
return UNDEFINED;
case ADDR_EXPR:
/* If any part of an address is UNDEFINED, like the index
of an ARRAY_EXPR, then treat the result as UNDEFINED. */
return UNDEFINED;
default:
;
}
}
/* If there was an UNDEFINED operand but the result may be not UNDEFINED
fall back to CONSTANT. During iteration UNDEFINED may still drop
to CONSTANT. */
if (has_undefined_operand)
return CONSTANT;
/* We do not consider virtual operands here -- load from read-only
memory may have only VARYING virtual operands, but still be
constant. */
if (has_constant_operand
|| gimple_references_memory_p (stmt))
return CONSTANT;
return VARYING;
}
/* Returns true if STMT cannot be constant. */
static bool
surely_varying_stmt_p (gimple stmt)
{
/* If the statement has operands that we cannot handle, it cannot be
constant. */
if (gimple_has_volatile_ops (stmt))
return true;
/* If it is a call and does not return a value or is not a
builtin and not an indirect call or a call to function with
assume_aligned/alloc_align attribute, it is varying. */
if (is_gimple_call (stmt))
{
tree fndecl, fntype = gimple_call_fntype (stmt);
if (!gimple_call_lhs (stmt)
|| ((fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
&& !DECL_BUILT_IN (fndecl)
&& !lookup_attribute ("assume_aligned",
TYPE_ATTRIBUTES (fntype))
&& !lookup_attribute ("alloc_align",
TYPE_ATTRIBUTES (fntype))))
return true;
}
/* Any other store operation is not interesting. */
else if (gimple_vdef (stmt))
return true;
/* Anything other than assignments and conditional jumps are not
interesting for CCP. */
if (gimple_code (stmt) != GIMPLE_ASSIGN
&& gimple_code (stmt) != GIMPLE_COND
&& gimple_code (stmt) != GIMPLE_SWITCH
&& gimple_code (stmt) != GIMPLE_CALL)
return true;
return false;
}
/* Initialize local data structures for CCP. */
static void
ccp_initialize (void)
{
basic_block bb;
n_const_val = num_ssa_names;
const_val = XCNEWVEC (ccp_prop_value_t, n_const_val);
/* Initialize simulation flags for PHI nodes and statements. */
FOR_EACH_BB_FN (bb, cfun)
{
gimple_stmt_iterator i;
for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
{
gimple stmt = gsi_stmt (i);
bool is_varying;
/* If the statement is a control insn, then we do not
want to avoid simulating the statement once. Failure
to do so means that those edges will never get added. */
if (stmt_ends_bb_p (stmt))
is_varying = false;
else
is_varying = surely_varying_stmt_p (stmt);
if (is_varying)
{
tree def;
ssa_op_iter iter;
/* If the statement will not produce a constant, mark
all its outputs VARYING. */
FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
set_value_varying (def);
}
prop_set_simulate_again (stmt, !is_varying);
}
}
/* Now process PHI nodes. We never clear the simulate_again flag on
phi nodes, since we do not know which edges are executable yet,
except for phi nodes for virtual operands when we do not do store ccp. */
FOR_EACH_BB_FN (bb, cfun)
{
gphi_iterator i;
for (i = gsi_start_phis (bb); !gsi_end_p (i); gsi_next (&i))
{
gphi *phi = i.phi ();
if (virtual_operand_p (gimple_phi_result (phi)))
prop_set_simulate_again (phi, false);
else
prop_set_simulate_again (phi, true);
}
}
}
/* Debug count support. Reset the values of ssa names
VARYING when the total number ssa names analyzed is
beyond the debug count specified. */
static void
do_dbg_cnt (void)
{
unsigned i;
for (i = 0; i < num_ssa_names; i++)
{
if (!dbg_cnt (ccp))
{
const_val[i].lattice_val = VARYING;
const_val[i].mask = -1;
const_val[i].value = NULL_TREE;
}
}
}
/* Do final substitution of propagated values, cleanup the flowgraph and
free allocated storage.
Return TRUE when something was optimized. */
static bool
ccp_finalize (void)
{
bool something_changed;
unsigned i;
do_dbg_cnt ();
/* Derive alignment and misalignment information from partially
constant pointers in the lattice or nonzero bits from partially
constant integers. */
for (i = 1; i < num_ssa_names; ++i)
{
tree name = ssa_name (i);
ccp_prop_value_t *val;
unsigned int tem, align;
if (!name
|| (!POINTER_TYPE_P (TREE_TYPE (name))
&& (!INTEGRAL_TYPE_P (TREE_TYPE (name))
/* Don't record nonzero bits before IPA to avoid
using too much memory. */
|| first_pass_instance)))
continue;
val = get_value (name);
if (val->lattice_val != CONSTANT
|| TREE_CODE (val->value) != INTEGER_CST)
continue;
if (POINTER_TYPE_P (TREE_TYPE (name)))
{
/* Trailing mask bits specify the alignment, trailing value
bits the misalignment. */
tem = val->mask.to_uhwi ();
align = (tem & -tem);
if (align > 1)
set_ptr_info_alignment (get_ptr_info (name), align,
(TREE_INT_CST_LOW (val->value)
& (align - 1)));
}
else
{
unsigned int precision = TYPE_PRECISION (TREE_TYPE (val->value));
wide_int nonzero_bits = wide_int::from (val->mask, precision,
UNSIGNED) | val->value;
nonzero_bits &= get_nonzero_bits (name);
set_nonzero_bits (name, nonzero_bits);
}
}
/* Perform substitutions based on the known constant values. */
something_changed = substitute_and_fold (get_constant_value,
ccp_fold_stmt, true);
free (const_val);
const_val = NULL;
return something_changed;;
}
/* Compute the meet operator between *VAL1 and *VAL2. Store the result
in VAL1.
any M UNDEFINED = any
any M VARYING = VARYING
Ci M Cj = Ci if (i == j)
Ci M Cj = VARYING if (i != j)
*/
static void
ccp_lattice_meet (ccp_prop_value_t *val1, ccp_prop_value_t *val2)
{
if (val1->lattice_val == UNDEFINED)
{
/* UNDEFINED M any = any */
*val1 = *val2;
}
else if (val2->lattice_val == UNDEFINED)
{
/* any M UNDEFINED = any
Nothing to do. VAL1 already contains the value we want. */
;
}
else if (val1->lattice_val == VARYING
|| val2->lattice_val == VARYING)
{
/* any M VARYING = VARYING. */
val1->lattice_val = VARYING;
val1->mask = -1;
val1->value = NULL_TREE;
}
else if (val1->lattice_val == CONSTANT
&& val2->lattice_val == CONSTANT
&& TREE_CODE (val1->value) == INTEGER_CST
&& TREE_CODE (val2->value) == INTEGER_CST)
{
/* Ci M Cj = Ci if (i == j)
Ci M Cj = VARYING if (i != j)
For INTEGER_CSTs mask unequal bits. If no equal bits remain,
drop to varying. */
val1->mask = (val1->mask | val2->mask
| (wi::to_widest (val1->value)
^ wi::to_widest (val2->value)));
if (val1->mask == -1)
{
val1->lattice_val = VARYING;
val1->value = NULL_TREE;
}
}
else if (val1->lattice_val == CONSTANT
&& val2->lattice_val == CONSTANT
&& simple_cst_equal (val1->value, val2->value) == 1)
{
/* Ci M Cj = Ci if (i == j)
Ci M Cj = VARYING if (i != j)
VAL1 already contains the value we want for equivalent values. */
}
else if (val1->lattice_val == CONSTANT
&& val2->lattice_val == CONSTANT
&& (TREE_CODE (val1->value) == ADDR_EXPR
|| TREE_CODE (val2->value) == ADDR_EXPR))
{
/* When not equal addresses are involved try meeting for
alignment. */
ccp_prop_value_t tem = *val2;
if (TREE_CODE (val1->value) == ADDR_EXPR)
*val1 = get_value_for_expr (val1->value, true);
if (TREE_CODE (val2->value) == ADDR_EXPR)
tem = get_value_for_expr (val2->value, true);
ccp_lattice_meet (val1, &tem);
}
else
{
/* Any other combination is VARYING. */
val1->lattice_val = VARYING;
val1->mask = -1;
val1->value = NULL_TREE;
}
}
/* Loop through the PHI_NODE's parameters for BLOCK and compare their
lattice values to determine PHI_NODE's lattice value. The value of a
PHI node is determined calling ccp_lattice_meet with all the arguments
of the PHI node that are incoming via executable edges. */
static enum ssa_prop_result
ccp_visit_phi_node (gphi *phi)
{
unsigned i;
ccp_prop_value_t *old_val, new_val;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "\nVisiting PHI node: ");
print_gimple_stmt (dump_file, phi, 0, dump_flags);
}
old_val = get_value (gimple_phi_result (phi));
switch (old_val->lattice_val)
{
case VARYING:
return SSA_PROP_VARYING;
case CONSTANT:
new_val = *old_val;
break;
case UNDEFINED:
new_val.lattice_val = UNDEFINED;
new_val.value = NULL_TREE;
break;
default:
gcc_unreachable ();
}
for (i = 0; i < gimple_phi_num_args (phi); i++)
{
/* Compute the meet operator over all the PHI arguments flowing
through executable edges. */
edge e = gimple_phi_arg_edge (phi, i);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file,
"\n Argument #%d (%d -> %d %sexecutable)\n",
i, e->src->index, e->dest->index,
(e->flags & EDGE_EXECUTABLE) ? "" : "not ");
}
/* If the incoming edge is executable, Compute the meet operator for
the existing value of the PHI node and the current PHI argument. */
if (e->flags & EDGE_EXECUTABLE)
{
tree arg = gimple_phi_arg (phi, i)->def;
ccp_prop_value_t arg_val = get_value_for_expr (arg, false);
ccp_lattice_meet (&new_val, &arg_val);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "\t");
print_generic_expr (dump_file, arg, dump_flags);
dump_lattice_value (dump_file, "\tValue: ", arg_val);
fprintf (dump_file, "\n");
}
if (new_val.lattice_val == VARYING)
break;
}
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
fprintf (dump_file, "\n\n");
}
/* Make the transition to the new value. */
if (set_lattice_value (gimple_phi_result (phi), new_val))
{
if (new_val.lattice_val == VARYING)
return SSA_PROP_VARYING;
else
return SSA_PROP_INTERESTING;
}
else
return SSA_PROP_NOT_INTERESTING;
}
/* Return the constant value for OP or OP otherwise. */
static tree
valueize_op (tree op)
{
if (TREE_CODE (op) == SSA_NAME)
{
tree tem = get_constant_value (op);
if (tem)
return tem;
}
return op;
}
/* Return the constant value for OP, but signal to not follow SSA
edges if the definition may be simulated again. */
static tree
valueize_op_1 (tree op)
{
if (TREE_CODE (op) == SSA_NAME)
{
/* If the definition may be simulated again we cannot follow
this SSA edge as the SSA propagator does not necessarily
re-visit the use. */
gimple def_stmt = SSA_NAME_DEF_STMT (op);
if (!gimple_nop_p (def_stmt)
&& prop_simulate_again_p (def_stmt))
return NULL_TREE;
tree tem = get_constant_value (op);
if (tem)
return tem;
}
return op;
}
/* CCP specific front-end to the non-destructive constant folding
routines.
Attempt to simplify the RHS of STMT knowing that one or more
operands are constants.
If simplification is possible, return the simplified RHS,
otherwise return the original RHS or NULL_TREE. */
static tree
ccp_fold (gimple stmt)
{
location_t loc = gimple_location (stmt);
switch (gimple_code (stmt))
{
case GIMPLE_COND:
{
/* Handle comparison operators that can appear in GIMPLE form. */
tree op0 = valueize_op (gimple_cond_lhs (stmt));
tree op1 = valueize_op (gimple_cond_rhs (stmt));
enum tree_code code = gimple_cond_code (stmt);
return fold_binary_loc (loc, code, boolean_type_node, op0, op1);
}
case GIMPLE_SWITCH:
{
/* Return the constant switch index. */
return valueize_op (gimple_switch_index (as_a <gswitch *> (stmt)));
}
case GIMPLE_ASSIGN:
case GIMPLE_CALL:
return gimple_fold_stmt_to_constant_1 (stmt,
valueize_op, valueize_op_1);
default:
gcc_unreachable ();
}
}
/* Apply the operation CODE in type TYPE to the value, mask pair
RVAL and RMASK representing a value of type RTYPE and set
the value, mask pair *VAL and *MASK to the result. */
static void
bit_value_unop_1 (enum tree_code code, tree type,
widest_int *val, widest_int *mask,
tree rtype, const widest_int &rval, const widest_int &rmask)
{
switch (code)
{
case BIT_NOT_EXPR:
*mask = rmask;
*val = ~rval;
break;
case NEGATE_EXPR:
{
widest_int temv, temm;
/* Return ~rval + 1. */
bit_value_unop_1 (BIT_NOT_EXPR, type, &temv, &temm, type, rval, rmask);
bit_value_binop_1 (PLUS_EXPR, type, val, mask,
type, temv, temm, type, 1, 0);
break;
}
CASE_CONVERT:
{
signop sgn;
/* First extend mask and value according to the original type. */
sgn = TYPE_SIGN (rtype);
*mask = wi::ext (rmask, TYPE_PRECISION (rtype), sgn);
*val = wi::ext (rval, TYPE_PRECISION (rtype), sgn);
/* Then extend mask and value according to the target type. */
sgn = TYPE_SIGN (type);
*mask = wi::ext (*mask, TYPE_PRECISION (type), sgn);
*val = wi::ext (*val, TYPE_PRECISION (type), sgn);
break;
}
default:
*mask = -1;
break;
}
}
/* Apply the operation CODE in type TYPE to the value, mask pairs
R1VAL, R1MASK and R2VAL, R2MASK representing a values of type R1TYPE
and R2TYPE and set the value, mask pair *VAL and *MASK to the result. */
static void
bit_value_binop_1 (enum tree_code code, tree type,
widest_int *val, widest_int *mask,
tree r1type, const widest_int &r1val,
const widest_int &r1mask, tree r2type,
const widest_int &r2val, const widest_int &r2mask)
{
signop sgn = TYPE_SIGN (type);
int width = TYPE_PRECISION (type);
bool swap_p = false;
/* Assume we'll get a constant result. Use an initial non varying
value, we fall back to varying in the end if necessary. */
*mask = -1;
switch (code)
{
case BIT_AND_EXPR:
/* The mask is constant where there is a known not
set bit, (m1 | m2) & ((v1 | m1) & (v2 | m2)) */
*mask = (r1mask | r2mask) & (r1val | r1mask) & (r2val | r2mask);
*val = r1val & r2val;
break;
case BIT_IOR_EXPR:
/* The mask is constant where there is a known
set bit, (m1 | m2) & ~((v1 & ~m1) | (v2 & ~m2)). */
*mask = (r1mask | r2mask)
.and_not (r1val.and_not (r1mask) | r2val.and_not (r2mask));
*val = r1val | r2val;
break;
case BIT_XOR_EXPR:
/* m1 | m2 */
*mask = r1mask | r2mask;
*val = r1val ^ r2val;
break;
case LROTATE_EXPR:
case RROTATE_EXPR:
if (r2mask == 0)
{
widest_int shift = r2val;
if (shift == 0)
{
*mask = r1mask;
*val = r1val;
}
else
{
if (wi::neg_p (shift))
{
shift = -shift;
if (code == RROTATE_EXPR)
code = LROTATE_EXPR;
else
code = RROTATE_EXPR;
}
if (code == RROTATE_EXPR)
{
*mask = wi::rrotate (r1mask, shift, width);
*val = wi::rrotate (r1val, shift, width);
}
else
{
*mask = wi::lrotate (r1mask, shift, width);
*val = wi::lrotate (r1val, shift, width);
}
}
}
break;
case LSHIFT_EXPR:
case RSHIFT_EXPR:
/* ??? We can handle partially known shift counts if we know
its sign. That way we can tell that (x << (y | 8)) & 255
is zero. */
if (r2mask == 0)
{
widest_int shift = r2val;
if (shift == 0)
{
*mask = r1mask;
*val = r1val;
}
else
{
if (wi::neg_p (shift))
{
shift = -shift;
if (code == RSHIFT_EXPR)
code = LSHIFT_EXPR;
else
code = RSHIFT_EXPR;
}
if (code == RSHIFT_EXPR)
{
*mask = wi::rshift (wi::ext (r1mask, width, sgn), shift, sgn);
*val = wi::rshift (wi::ext (r1val, width, sgn), shift, sgn);
}
else
{
*mask = wi::ext (wi::lshift (r1mask, shift), width, sgn);
*val = wi::ext (wi::lshift (r1val, shift), width, sgn);
}
}
}
break;
case PLUS_EXPR:
case POINTER_PLUS_EXPR:
{
/* Do the addition with unknown bits set to zero, to give carry-ins of
zero wherever possible. */
widest_int lo = r1val.and_not (r1mask) + r2val.and_not (r2mask);
lo = wi::ext (lo, width, sgn);
/* Do the addition with unknown bits set to one, to give carry-ins of
one wherever possible. */
widest_int hi = (r1val | r1mask) + (r2val | r2mask);
hi = wi::ext (hi, width, sgn);
/* Each bit in the result is known if (a) the corresponding bits in
both inputs are known, and (b) the carry-in to that bit position
is known. We can check condition (b) by seeing if we got the same
result with minimised carries as with maximised carries. */
*mask = r1mask | r2mask | (lo ^ hi);
*mask = wi::ext (*mask, width, sgn);
/* It shouldn't matter whether we choose lo or hi here. */
*val = lo;
break;
}
case MINUS_EXPR:
{
widest_int temv, temm;
bit_value_unop_1 (NEGATE_EXPR, r2type, &temv, &temm,
r2type, r2val, r2mask);
bit_value_binop_1 (PLUS_EXPR, type, val, mask,
r1type, r1val, r1mask,
r2type, temv, temm);
break;
}
case MULT_EXPR:
{
/* Just track trailing zeros in both operands and transfer
them to the other. */
int r1tz = wi::ctz (r1val | r1mask);
int r2tz = wi::ctz (r2val | r2mask);
if (r1tz + r2tz >= width)
{
*mask = 0;
*val = 0;
}
else if (r1tz + r2tz > 0)
{
*mask = wi::ext (wi::mask <widest_int> (r1tz + r2tz, true),
width, sgn);
*val = 0;
}
break;
}
case EQ_EXPR:
case NE_EXPR:
{
widest_int m = r1mask | r2mask;
if (r1val.and_not (m) != r2val.and_not (m))
{
*mask = 0;
*val = ((code == EQ_EXPR) ? 0 : 1);
}
else
{
/* We know the result of a comparison is always one or zero. */
*mask = 1;
*val = 0;
}
break;
}
case GE_EXPR:
case GT_EXPR:
swap_p = true;
code = swap_tree_comparison (code);
/* Fall through. */
case LT_EXPR:
case LE_EXPR:
{
int minmax, maxmin;
const widest_int &o1val = swap_p ? r2val : r1val;
const widest_int &o1mask = swap_p ? r2mask : r1mask;
const widest_int &o2val = swap_p ? r1val : r2val;
const widest_int &o2mask = swap_p ? r1mask : r2mask;
/* If the most significant bits are not known we know nothing. */
if (wi::neg_p (o1mask) || wi::neg_p (o2mask))
break;
/* For comparisons the signedness is in the comparison operands. */
sgn = TYPE_SIGN (r1type);
/* If we know the most significant bits we know the values
value ranges by means of treating varying bits as zero
or one. Do a cross comparison of the max/min pairs. */
maxmin = wi::cmp (o1val | o1mask, o2val.and_not (o2mask), sgn);
minmax = wi::cmp (o1val.and_not (o1mask), o2val | o2mask, sgn);
if (maxmin < 0) /* o1 is less than o2. */
{
*mask = 0;
*val = 1;
}
else if (minmax > 0) /* o1 is not less or equal to o2. */
{
*mask = 0;
*val = 0;
}
else if (maxmin == minmax) /* o1 and o2 are equal. */
{
/* This probably should never happen as we'd have
folded the thing during fully constant value folding. */
*mask = 0;
*val = (code == LE_EXPR ? 1 : 0);
}
else
{
/* We know the result of a comparison is always one or zero. */
*mask = 1;
*val = 0;
}
break;
}
default:;
}
}
/* Return the propagation value when applying the operation CODE to
the value RHS yielding type TYPE. */
static ccp_prop_value_t
bit_value_unop (enum tree_code code, tree type, tree rhs)
{
ccp_prop_value_t rval = get_value_for_expr (rhs, true);
widest_int value, mask;
ccp_prop_value_t val;
if (rval.lattice_val == UNDEFINED)
return rval;
gcc_assert ((rval.lattice_val == CONSTANT
&& TREE_CODE (rval.value) == INTEGER_CST)
|| rval.mask == -1);
bit_value_unop_1 (code, type, &value, &mask,
TREE_TYPE (rhs), value_to_wide_int (rval), rval.mask);
if (mask != -1)
{
val.lattice_val = CONSTANT;
val.mask = mask;
/* ??? Delay building trees here. */
val.value = wide_int_to_tree (type, value);
}
else
{
val.lattice_val = VARYING;
val.value = NULL_TREE;
val.mask = -1;
}
return val;
}
/* Return the propagation value when applying the operation CODE to
the values RHS1 and RHS2 yielding type TYPE. */
static ccp_prop_value_t
bit_value_binop (enum tree_code code, tree type, tree rhs1, tree rhs2)
{
ccp_prop_value_t r1val = get_value_for_expr (rhs1, true);
ccp_prop_value_t r2val = get_value_for_expr (rhs2, true);
widest_int value, mask;
ccp_prop_value_t val;
if (r1val.lattice_val == UNDEFINED
|| r2val.lattice_val == UNDEFINED)
{
val.lattice_val = VARYING;
val.value = NULL_TREE;
val.mask = -1;
return val;
}
gcc_assert ((r1val.lattice_val == CONSTANT
&& TREE_CODE (r1val.value) == INTEGER_CST)
|| r1val.mask == -1);
gcc_assert ((r2val.lattice_val == CONSTANT
&& TREE_CODE (r2val.value) == INTEGER_CST)
|| r2val.mask == -1);
bit_value_binop_1 (code, type, &value, &mask,
TREE_TYPE (rhs1), value_to_wide_int (r1val), r1val.mask,
TREE_TYPE (rhs2), value_to_wide_int (r2val), r2val.mask);
if (mask != -1)
{
val.lattice_val = CONSTANT;
val.mask = mask;
/* ??? Delay building trees here. */
val.value = wide_int_to_tree (type, value);
}
else
{
val.lattice_val = VARYING;
val.value = NULL_TREE;
val.mask = -1;
}
return val;
}
/* Return the propagation value for __builtin_assume_aligned
and functions with assume_aligned or alloc_aligned attribute.
For __builtin_assume_aligned, ATTR is NULL_TREE,
for assume_aligned attribute ATTR is non-NULL and ALLOC_ALIGNED
is false, for alloc_aligned attribute ATTR is non-NULL and
ALLOC_ALIGNED is true. */
static ccp_prop_value_t
bit_value_assume_aligned (gimple stmt, tree attr, ccp_prop_value_t ptrval,
bool alloc_aligned)
{
tree align, misalign = NULL_TREE, type;
unsigned HOST_WIDE_INT aligni, misaligni = 0;
ccp_prop_value_t alignval;
widest_int value, mask;
ccp_prop_value_t val;
if (attr == NULL_TREE)
{
tree ptr = gimple_call_arg (stmt, 0);
type = TREE_TYPE (ptr);
ptrval = get_value_for_expr (ptr, true);
}
else
{
tree lhs = gimple_call_lhs (stmt);
type = TREE_TYPE (lhs);
}
if (ptrval.lattice_val == UNDEFINED)
return ptrval;
gcc_assert ((ptrval.lattice_val == CONSTANT
&& TREE_CODE (ptrval.value) == INTEGER_CST)
|| ptrval.mask == -1);
if (attr == NULL_TREE)
{
/* Get aligni and misaligni from __builtin_assume_aligned. */
align = gimple_call_arg (stmt, 1);
if (!tree_fits_uhwi_p (align))
return ptrval;
aligni = tree_to_uhwi (align);
if (gimple_call_num_args (stmt) > 2)
{
misalign = gimple_call_arg (stmt, 2);
if (!tree_fits_uhwi_p (misalign))
return ptrval;
misaligni = tree_to_uhwi (misalign);
}
}
else
{
/* Get aligni and misaligni from assume_aligned or
alloc_align attributes. */
if (TREE_VALUE (attr) == NULL_TREE)
return ptrval;
attr = TREE_VALUE (attr);
align = TREE_VALUE (attr);
if (!tree_fits_uhwi_p (align))
return ptrval;
aligni = tree_to_uhwi (align);
if (alloc_aligned)
{
if (aligni == 0 || aligni > gimple_call_num_args (stmt))
return ptrval;
align = gimple_call_arg (stmt, aligni - 1);
if (!tree_fits_uhwi_p (align))
return ptrval;
aligni = tree_to_uhwi (align);
}
else if (TREE_CHAIN (attr) && TREE_VALUE (TREE_CHAIN (attr)))
{
misalign = TREE_VALUE (TREE_CHAIN (attr));
if (!tree_fits_uhwi_p (misalign))
return ptrval;
misaligni = tree_to_uhwi (misalign);
}
}
if (aligni <= 1 || (aligni & (aligni - 1)) != 0 || misaligni >= aligni)
return ptrval;
align = build_int_cst_type (type, -aligni);
alignval = get_value_for_expr (align, true);
bit_value_binop_1 (BIT_AND_EXPR, type, &value, &mask,
type, value_to_wide_int (ptrval), ptrval.mask,
type, value_to_wide_int (alignval), alignval.mask);
if (mask != -1)
{
val.lattice_val = CONSTANT;
val.mask = mask;
gcc_assert ((mask.to_uhwi () & (aligni - 1)) == 0);
gcc_assert ((value.to_uhwi () & (aligni - 1)) == 0);
value |= misaligni;
/* ??? Delay building trees here. */
val.value = wide_int_to_tree (type, value);
}
else
{
val.lattice_val = VARYING;
val.value = NULL_TREE;
val.mask = -1;
}
return val;
}
/* Evaluate statement STMT.
Valid only for assignments, calls, conditionals, and switches. */
static ccp_prop_value_t
evaluate_stmt (gimple stmt)
{
ccp_prop_value_t val;
tree simplified = NULL_TREE;
ccp_lattice_t likelyvalue = likely_value (stmt);
bool is_constant = false;
unsigned int align;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "which is likely ");
switch (likelyvalue)
{
case CONSTANT:
fprintf (dump_file, "CONSTANT");
break;
case UNDEFINED:
fprintf (dump_file, "UNDEFINED");
break;
case VARYING:
fprintf (dump_file, "VARYING");
break;
default:;
}
fprintf (dump_file, "\n");
}
/* If the statement is likely to have a CONSTANT result, then try
to fold the statement to determine the constant value. */
/* FIXME. This is the only place that we call ccp_fold.
Since likely_value never returns CONSTANT for calls, we will
not attempt to fold them, including builtins that may profit. */
if (likelyvalue == CONSTANT)
{
fold_defer_overflow_warnings ();
simplified = ccp_fold (stmt);
is_constant = simplified && is_gimple_min_invariant (simplified);
fold_undefer_overflow_warnings (is_constant, stmt, 0);
if (is_constant)
{
/* The statement produced a constant value. */
val.lattice_val = CONSTANT;
val.value = simplified;
val.mask = 0;
}
}
/* If the statement is likely to have a VARYING result, then do not
bother folding the statement. */
else if (likelyvalue == VARYING)
{
enum gimple_code code = gimple_code (stmt);
if (code == GIMPLE_ASSIGN)
{
enum tree_code subcode = gimple_assign_rhs_code (stmt);
/* Other cases cannot satisfy is_gimple_min_invariant
without folding. */
if (get_gimple_rhs_class (subcode) == GIMPLE_SINGLE_RHS)
simplified = gimple_assign_rhs1 (stmt);
}
else if (code == GIMPLE_SWITCH)
simplified = gimple_switch_index (as_a <gswitch *> (stmt));
else
/* These cannot satisfy is_gimple_min_invariant without folding. */
gcc_assert (code == GIMPLE_CALL || code == GIMPLE_COND);
is_constant = simplified && is_gimple_min_invariant (simplified);
if (is_constant)
{
/* The statement produced a constant value. */
val.lattice_val = CONSTANT;
val.value = simplified;
val.mask = 0;
}
}
/* Resort to simplification for bitwise tracking. */
if (flag_tree_bit_ccp
&& (likelyvalue == CONSTANT || is_gimple_call (stmt))
&& !is_constant)
{
enum gimple_code code = gimple_code (stmt);
val.lattice_val = VARYING;
val.value = NULL_TREE;
val.mask = -1;
if (code == GIMPLE_ASSIGN)
{
enum tree_code subcode = gimple_assign_rhs_code (stmt);
tree rhs1 = gimple_assign_rhs1 (stmt);
switch (get_gimple_rhs_class (subcode))
{
case GIMPLE_SINGLE_RHS:
if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
|| POINTER_TYPE_P (TREE_TYPE (rhs1)))
val = get_value_for_expr (rhs1, true);
break;
case GIMPLE_UNARY_RHS:
if ((INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
|| POINTER_TYPE_P (TREE_TYPE (rhs1)))
&& (INTEGRAL_TYPE_P (gimple_expr_type (stmt))
|| POINTER_TYPE_P (gimple_expr_type (stmt))))
val = bit_value_unop (subcode, gimple_expr_type (stmt), rhs1);
break;
case GIMPLE_BINARY_RHS:
if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
|| POINTER_TYPE_P (TREE_TYPE (rhs1)))
{
tree lhs = gimple_assign_lhs (stmt);
tree rhs2 = gimple_assign_rhs2 (stmt);
val = bit_value_binop (subcode,
TREE_TYPE (lhs), rhs1, rhs2);
}
break;
default:;
}
}
else if (code == GIMPLE_COND)
{
enum tree_code code = gimple_cond_code (stmt);
tree rhs1 = gimple_cond_lhs (stmt);
tree rhs2 = gimple_cond_rhs (stmt);
if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
|| POINTER_TYPE_P (TREE_TYPE (rhs1)))
val = bit_value_binop (code, TREE_TYPE (rhs1), rhs1, rhs2);
}
else if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
{
tree fndecl = gimple_call_fndecl (stmt);
switch (DECL_FUNCTION_CODE (fndecl))
{
case BUILT_IN_MALLOC:
case BUILT_IN_REALLOC:
case BUILT_IN_CALLOC:
case BUILT_IN_STRDUP:
case BUILT_IN_STRNDUP:
val.lattice_val = CONSTANT;
val.value = build_int_cst (TREE_TYPE (gimple_get_lhs (stmt)), 0);
val.mask = ~((HOST_WIDE_INT) MALLOC_ABI_ALIGNMENT
/ BITS_PER_UNIT - 1);
break;
case BUILT_IN_ALLOCA:
case BUILT_IN_ALLOCA_WITH_ALIGN:
align = (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_ALLOCA_WITH_ALIGN
? TREE_INT_CST_LOW (gimple_call_arg (stmt, 1))
: BIGGEST_ALIGNMENT);
val.lattice_val = CONSTANT;
val.value = build_int_cst (TREE_TYPE (gimple_get_lhs (stmt)), 0);
val.mask = ~((HOST_WIDE_INT) align / BITS_PER_UNIT - 1);
break;
/* These builtins return their first argument, unmodified. */
case BUILT_IN_MEMCPY:
case BUILT_IN_MEMMOVE:
case BUILT_IN_MEMSET:
case BUILT_IN_STRCPY:
case BUILT_IN_STRNCPY:
case BUILT_IN_MEMCPY_CHK:
case BUILT_IN_MEMMOVE_CHK:
case BUILT_IN_MEMSET_CHK:
case BUILT_IN_STRCPY_CHK:
case BUILT_IN_STRNCPY_CHK:
val = get_value_for_expr (gimple_call_arg (stmt, 0), true);
break;
case BUILT_IN_ASSUME_ALIGNED:
val = bit_value_assume_aligned (stmt, NULL_TREE, val, false);
break;
case BUILT_IN_ALIGNED_ALLOC:
{
tree align = get_constant_value (gimple_call_arg (stmt, 0));
if (align
&& tree_fits_uhwi_p (align))
{
unsigned HOST_WIDE_INT aligni = tree_to_uhwi (align);
if (aligni > 1
/* align must be power-of-two */
&& (aligni & (aligni - 1)) == 0)
{
val.lattice_val = CONSTANT;
val.value = build_int_cst (ptr_type_node, 0);
val.mask = -aligni;
}
}
break;
}
default:;
}
}
if (is_gimple_call (stmt) && gimple_call_lhs (stmt))
{
tree fntype = gimple_call_fntype (stmt);
if (fntype)
{
tree attrs = lookup_attribute ("assume_aligned",
TYPE_ATTRIBUTES (fntype));
if (attrs)
val = bit_value_assume_aligned (stmt, attrs, val, false);
attrs = lookup_attribute ("alloc_align",
TYPE_ATTRIBUTES (fntype));
if (attrs)
val = bit_value_assume_aligned (stmt, attrs, val, true);
}
}
is_constant = (val.lattice_val == CONSTANT);
}
if (flag_tree_bit_ccp
&& ((is_constant && TREE_CODE (val.value) == INTEGER_CST)
|| (!is_constant && likelyvalue != UNDEFINED))
&& gimple_get_lhs (stmt)
&& TREE_CODE (gimple_get_lhs (stmt)) == SSA_NAME)
{
tree lhs = gimple_get_lhs (stmt);
wide_int nonzero_bits = get_nonzero_bits (lhs);
if (nonzero_bits != -1)
{
if (!is_constant)
{
val.lattice_val = CONSTANT;
val.value = build_zero_cst (TREE_TYPE (lhs));
val.mask = extend_mask (nonzero_bits);
is_constant = true;
}
else
{
if (wi::bit_and_not (val.value, nonzero_bits) != 0)
val.value = wide_int_to_tree (TREE_TYPE (lhs),
nonzero_bits & val.value);
if (nonzero_bits == 0)
val.mask = 0;
else
val.mask = val.mask & extend_mask (nonzero_bits);
}
}
}
if (!is_constant)
{
/* The statement produced a nonconstant value. If the statement
had UNDEFINED operands, then the result of the statement
should be UNDEFINED. Otherwise, the statement is VARYING. */
if (likelyvalue == UNDEFINED)
{
val.lattice_val = likelyvalue;
val.mask = 0;
}
else
{
val.lattice_val = VARYING;
val.mask = -1;
}
val.value = NULL_TREE;
}
return val;
}
typedef hash_table<pointer_hash<gimple_statement_base> > gimple_htab;
/* Given a BUILT_IN_STACK_SAVE value SAVED_VAL, insert a clobber of VAR before
each matching BUILT_IN_STACK_RESTORE. Mark visited phis in VISITED. */
static void
insert_clobber_before_stack_restore (tree saved_val, tree var,
gimple_htab **visited)
{
gimple stmt;
gassign *clobber_stmt;
tree clobber;
imm_use_iterator iter;
gimple_stmt_iterator i;
gimple *slot;
FOR_EACH_IMM_USE_STMT (stmt, iter, saved_val)
if (gimple_call_builtin_p (stmt, BUILT_IN_STACK_RESTORE))
{
clobber = build_constructor (TREE_TYPE (var),
NULL);
TREE_THIS_VOLATILE (clobber) = 1;
clobber_stmt = gimple_build_assign (var, clobber);
i = gsi_for_stmt (stmt);
gsi_insert_before (&i, clobber_stmt, GSI_SAME_STMT);
}
else if (gimple_code (stmt) == GIMPLE_PHI)
{
if (!*visited)
*visited = new gimple_htab (10);
slot = (*visited)->find_slot (stmt, INSERT);
if (*slot != NULL)
continue;
*slot = stmt;
insert_clobber_before_stack_restore (gimple_phi_result (stmt), var,
visited);
}
else if (gimple_assign_ssa_name_copy_p (stmt))
insert_clobber_before_stack_restore (gimple_assign_lhs (stmt), var,
visited);
else if (chkp_gimple_call_builtin_p (stmt, BUILT_IN_CHKP_BNDRET))
continue;
else
gcc_assert (is_gimple_debug (stmt));
}
/* Advance the iterator to the previous non-debug gimple statement in the same
or dominating basic block. */
static inline void
gsi_prev_dom_bb_nondebug (gimple_stmt_iterator *i)
{
basic_block dom;
gsi_prev_nondebug (i);
while (gsi_end_p (*i))
{
dom = get_immediate_dominator (CDI_DOMINATORS, i->bb);
if (dom == NULL || dom == ENTRY_BLOCK_PTR_FOR_FN (cfun))
return;
*i = gsi_last_bb (dom);
}
}
/* Find a BUILT_IN_STACK_SAVE dominating gsi_stmt (I), and insert
a clobber of VAR before each matching BUILT_IN_STACK_RESTORE.
It is possible that BUILT_IN_STACK_SAVE cannot be find in a dominator when a
previous pass (such as DOM) duplicated it along multiple paths to a BB. In
that case the function gives up without inserting the clobbers. */
static void
insert_clobbers_for_var (gimple_stmt_iterator i, tree var)
{
gimple stmt;
tree saved_val;
gimple_htab *visited = NULL;
for (; !gsi_end_p (i); gsi_prev_dom_bb_nondebug (&i))
{
stmt = gsi_stmt (i);
if (!gimple_call_builtin_p (stmt, BUILT_IN_STACK_SAVE))
continue;
saved_val = gimple_call_lhs (stmt);
if (saved_val == NULL_TREE)
continue;
insert_clobber_before_stack_restore (saved_val, var, &visited);
break;
}
delete visited;
}
/* Detects a __builtin_alloca_with_align with constant size argument. Declares
fixed-size array and returns the address, if found, otherwise returns
NULL_TREE. */
static tree
fold_builtin_alloca_with_align (gimple stmt)
{
unsigned HOST_WIDE_INT size, threshold, n_elem;
tree lhs, arg, block, var, elem_type, array_type;
/* Get lhs. */
lhs = gimple_call_lhs (stmt);
if (lhs == NULL_TREE)
return NULL_TREE;
/* Detect constant argument. */
arg = get_constant_value (gimple_call_arg (stmt, 0));
if (arg == NULL_TREE
|| TREE_CODE (arg) != INTEGER_CST
|| !tree_fits_uhwi_p (arg))
return NULL_TREE;
size = tree_to_uhwi (arg);
/* Heuristic: don't fold large allocas. */
threshold = (unsigned HOST_WIDE_INT)PARAM_VALUE (PARAM_LARGE_STACK_FRAME);
/* In case the alloca is located at function entry, it has the same lifetime
as a declared array, so we allow a larger size. */
block = gimple_block (stmt);
if (!(cfun->after_inlining
&& block
&& TREE_CODE (BLOCK_SUPERCONTEXT (block)) == FUNCTION_DECL))
threshold /= 10;
if (size > threshold)
return NULL_TREE;
/* Declare array. */
elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
n_elem = size * 8 / BITS_PER_UNIT;
array_type = build_array_type_nelts (elem_type, n_elem);
var = create_tmp_var (array_type);
DECL_ALIGN (var) = TREE_INT_CST_LOW (gimple_call_arg (stmt, 1));
{
struct ptr_info_def *pi = SSA_NAME_PTR_INFO (lhs);
if (pi != NULL && !pi->pt.anything)
{
bool singleton_p;
unsigned uid;
singleton_p = pt_solution_singleton_p (&pi->pt, &uid);
gcc_assert (singleton_p);
SET_DECL_PT_UID (var, uid);
}
}
/* Fold alloca to the address of the array. */
return fold_convert (TREE_TYPE (lhs), build_fold_addr_expr (var));
}
/* Fold the stmt at *GSI with CCP specific information that propagating
and regular folding does not catch. */
static bool
ccp_fold_stmt (gimple_stmt_iterator *gsi)
{
gimple stmt = gsi_stmt (*gsi);
switch (gimple_code (stmt))
{
case GIMPLE_COND:
{
gcond *cond_stmt = as_a <gcond *> (stmt);
ccp_prop_value_t val;
/* Statement evaluation will handle type mismatches in constants
more gracefully than the final propagation. This allows us to
fold more conditionals here. */
val = evaluate_stmt (stmt);
if (val.lattice_val != CONSTANT
|| val.mask != 0)
return false;
if (dump_file)
{
fprintf (dump_file, "Folding predicate ");
print_gimple_expr (dump_file, stmt, 0, 0);
fprintf (dump_file, " to ");
print_generic_expr (dump_file, val.value, 0);
fprintf (dump_file, "\n");
}
if (integer_zerop (val.value))
gimple_cond_make_false (cond_stmt);
else
gimple_cond_make_true (cond_stmt);
return true;
}
case GIMPLE_CALL:
{
tree lhs = gimple_call_lhs (stmt);
int flags = gimple_call_flags (stmt);
tree val;
tree argt;
bool changed = false;
unsigned i;
/* If the call was folded into a constant make sure it goes
away even if we cannot propagate into all uses because of
type issues. */
if (lhs
&& TREE_CODE (lhs) == SSA_NAME
&& (val = get_constant_value (lhs))
/* Don't optimize away calls that have side-effects. */
&& (flags & (ECF_CONST|ECF_PURE)) != 0
&& (flags & ECF_LOOPING_CONST_OR_PURE) == 0)
{
tree new_rhs = unshare_expr (val);
bool res;
if (!useless_type_conversion_p (TREE_TYPE (lhs),
TREE_TYPE (new_rhs)))
new_rhs = fold_convert (TREE_TYPE (lhs), new_rhs);
res = update_call_from_tree (gsi, new_rhs);
gcc_assert (res);
return true;
}
/* Internal calls provide no argument types, so the extra laxity
for normal calls does not apply. */
if (gimple_call_internal_p (stmt))
return false;
/* The heuristic of fold_builtin_alloca_with_align differs before and
after inlining, so we don't require the arg to be changed into a
constant for folding, but just to be constant. */
if (gimple_call_builtin_p (stmt, BUILT_IN_ALLOCA_WITH_ALIGN))
{
tree new_rhs = fold_builtin_alloca_with_align (stmt);
if (new_rhs)
{
bool res = update_call_from_tree (gsi, new_rhs);
tree var = TREE_OPERAND (TREE_OPERAND (new_rhs, 0),0);
gcc_assert (res);
insert_clobbers_for_var (*gsi, var);
return true;
}
}
/* Propagate into the call arguments. Compared to replace_uses_in
this can use the argument slot types for type verification
instead of the current argument type. We also can safely
drop qualifiers here as we are dealing with constants anyway. */
argt = TYPE_ARG_TYPES (gimple_call_fntype (stmt));
for (i = 0; i < gimple_call_num_args (stmt) && argt;
++i, argt = TREE_CHAIN (argt))
{
tree arg = gimple_call_arg (stmt, i);
if (TREE_CODE (arg) == SSA_NAME
&& (val = get_constant_value (arg))
&& useless_type_conversion_p
(TYPE_MAIN_VARIANT (TREE_VALUE (argt)),
TYPE_MAIN_VARIANT (TREE_TYPE (val))))
{
gimple_call_set_arg (stmt, i, unshare_expr (val));
changed = true;
}
}
return changed;
}
case GIMPLE_ASSIGN:
{
tree lhs = gimple_assign_lhs (stmt);
tree val;
/* If we have a load that turned out to be constant replace it
as we cannot propagate into all uses in all cases. */
if (gimple_assign_single_p (stmt)
&& TREE_CODE (lhs) == SSA_NAME
&& (val = get_constant_value (lhs)))
{
tree rhs = unshare_expr (val);
if (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (rhs)))
rhs = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (lhs), rhs);
gimple_assign_set_rhs_from_tree (gsi, rhs);
return true;
}
return false;
}
default:
return false;
}
}
/* Visit the assignment statement STMT. Set the value of its LHS to the
value computed by the RHS and store LHS in *OUTPUT_P. If STMT
creates virtual definitions, set the value of each new name to that
of the RHS (if we can derive a constant out of the RHS).
Value-returning call statements also perform an assignment, and
are handled here. */
static enum ssa_prop_result
visit_assignment (gimple stmt, tree *output_p)
{
ccp_prop_value_t val;
enum ssa_prop_result retval;
tree lhs = gimple_get_lhs (stmt);
gcc_assert (gimple_code (stmt) != GIMPLE_CALL
|| gimple_call_lhs (stmt) != NULL_TREE);
if (gimple_assign_single_p (stmt)
&& gimple_assign_rhs_code (stmt) == SSA_NAME)
/* For a simple copy operation, we copy the lattice values. */
val = *get_value (gimple_assign_rhs1 (stmt));
else
/* Evaluate the statement, which could be
either a GIMPLE_ASSIGN or a GIMPLE_CALL. */
val = evaluate_stmt (stmt);
retval = SSA_PROP_NOT_INTERESTING;
/* Set the lattice value of the statement's output. */
if (TREE_CODE (lhs) == SSA_NAME)
{
/* If STMT is an assignment to an SSA_NAME, we only have one
value to set. */
if (set_lattice_value (lhs, val))
{
*output_p = lhs;
if (val.lattice_val == VARYING)
retval = SSA_PROP_VARYING;
else
retval = SSA_PROP_INTERESTING;
}
}
return retval;
}
/* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
if it can determine which edge will be taken. Otherwise, return
SSA_PROP_VARYING. */
static enum ssa_prop_result
visit_cond_stmt (gimple stmt, edge *taken_edge_p)
{
ccp_prop_value_t val;
basic_block block;
block = gimple_bb (stmt);
val = evaluate_stmt (stmt);
if (val.lattice_val != CONSTANT
|| val.mask != 0)
return SSA_PROP_VARYING;
/* Find which edge out of the conditional block will be taken and add it
to the worklist. If no single edge can be determined statically,
return SSA_PROP_VARYING to feed all the outgoing edges to the
propagation engine. */
*taken_edge_p = find_taken_edge (block, val.value);
if (*taken_edge_p)
return SSA_PROP_INTERESTING;
else
return SSA_PROP_VARYING;
}
/* Evaluate statement STMT. If the statement produces an output value and
its evaluation changes the lattice value of its output, return
SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
output value.
If STMT is a conditional branch and we can determine its truth
value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
value, return SSA_PROP_VARYING. */
static enum ssa_prop_result
ccp_visit_stmt (gimple stmt, edge *taken_edge_p, tree *output_p)
{
tree def;
ssa_op_iter iter;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "\nVisiting statement:\n");
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
}
switch (gimple_code (stmt))
{
case GIMPLE_ASSIGN:
/* If the statement is an assignment that produces a single
output value, evaluate its RHS to see if the lattice value of
its output has changed. */
return visit_assignment (stmt, output_p);
case GIMPLE_CALL:
/* A value-returning call also performs an assignment. */
if (gimple_call_lhs (stmt) != NULL_TREE)
return visit_assignment (stmt, output_p);
break;
case GIMPLE_COND:
case GIMPLE_SWITCH:
/* If STMT is a conditional branch, see if we can determine
which branch will be taken. */
/* FIXME. It appears that we should be able to optimize
computed GOTOs here as well. */
return visit_cond_stmt (stmt, taken_edge_p);
default:
break;
}
/* Any other kind of statement is not interesting for constant
propagation and, therefore, not worth simulating. */
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
/* Definitions made by statements other than assignments to
SSA_NAMEs represent unknown modifications to their outputs.
Mark them VARYING. */
FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
{
ccp_prop_value_t v = { VARYING, NULL_TREE, -1 };
set_lattice_value (def, v);
}
return SSA_PROP_VARYING;
}
/* Main entry point for SSA Conditional Constant Propagation. */
static unsigned int
do_ssa_ccp (void)
{
unsigned int todo = 0;
calculate_dominance_info (CDI_DOMINATORS);
ccp_initialize ();
ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
if (ccp_finalize ())
todo = (TODO_cleanup_cfg | TODO_update_ssa);
free_dominance_info (CDI_DOMINATORS);
return todo;
}
namespace {
const pass_data pass_data_ccp =
{
GIMPLE_PASS, /* type */
"ccp", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_TREE_CCP, /* tv_id */
( PROP_cfg | PROP_ssa ), /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_update_address_taken, /* todo_flags_finish */
};
class pass_ccp : public gimple_opt_pass
{
public:
pass_ccp (gcc::context *ctxt)
: gimple_opt_pass (pass_data_ccp, ctxt)
{}
/* opt_pass methods: */
opt_pass * clone () { return new pass_ccp (m_ctxt); }
virtual bool gate (function *) { return flag_tree_ccp != 0; }
virtual unsigned int execute (function *) { return do_ssa_ccp (); }
}; // class pass_ccp
} // anon namespace
gimple_opt_pass *
make_pass_ccp (gcc::context *ctxt)
{
return new pass_ccp (ctxt);
}
/* Try to optimize out __builtin_stack_restore. Optimize it out
if there is another __builtin_stack_restore in the same basic
block and no calls or ASM_EXPRs are in between, or if this block's
only outgoing edge is to EXIT_BLOCK and there are no calls or
ASM_EXPRs after this __builtin_stack_restore. */
static tree
optimize_stack_restore (gimple_stmt_iterator i)
{
tree callee;
gimple stmt;
basic_block bb = gsi_bb (i);
gimple call = gsi_stmt (i);
if (gimple_code (call) != GIMPLE_CALL
|| gimple_call_num_args (call) != 1
|| TREE_CODE (gimple_call_arg (call, 0)) != SSA_NAME
|| !POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call, 0))))
return NULL_TREE;
for (gsi_next (&i); !gsi_end_p (i); gsi_next (&i))
{
stmt = gsi_stmt (i);
if (gimple_code (stmt) == GIMPLE_ASM)
return NULL_TREE;
if (gimple_code (stmt) != GIMPLE_CALL)
continue;
callee = gimple_call_fndecl (stmt);
if (!callee
|| DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
/* All regular builtins are ok, just obviously not alloca. */
|| DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA
|| DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA_WITH_ALIGN)
return NULL_TREE;
if (DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE)
goto second_stack_restore;
}
if (!gsi_end_p (i))
return NULL_TREE;
/* Allow one successor of the exit block, or zero successors. */
switch (EDGE_COUNT (bb->succs))
{
case 0:
break;
case 1:
if (single_succ_edge (bb)->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
return NULL_TREE;
break;
default:
return NULL_TREE;
}
second_stack_restore:
/* If there's exactly one use, then zap the call to __builtin_stack_save.
If there are multiple uses, then the last one should remove the call.
In any case, whether the call to __builtin_stack_save can be removed
or not is irrelevant to removing the call to __builtin_stack_restore. */
if (has_single_use (gimple_call_arg (call, 0)))
{
gimple stack_save = SSA_NAME_DEF_STMT (gimple_call_arg (call, 0));
if (is_gimple_call (stack_save))
{
callee = gimple_call_fndecl (stack_save);
if (callee
&& DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
&& DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_SAVE)
{
gimple_stmt_iterator stack_save_gsi;
tree rhs;
stack_save_gsi = gsi_for_stmt (stack_save);
rhs = build_int_cst (TREE_TYPE (gimple_call_arg (call, 0)), 0);
update_call_from_tree (&stack_save_gsi, rhs);
}
}
}
/* No effect, so the statement will be deleted. */
return integer_zero_node;
}
/* If va_list type is a simple pointer and nothing special is needed,
optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
__builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
pointer assignment. */
static tree
optimize_stdarg_builtin (gimple call)
{
tree callee, lhs, rhs, cfun_va_list;
bool va_list_simple_ptr;
location_t loc = gimple_location (call);
if (gimple_code (call) != GIMPLE_CALL)
return NULL_TREE;
callee = gimple_call_fndecl (call);
cfun_va_list = targetm.fn_abi_va_list (callee);
va_list_simple_ptr = POINTER_TYPE_P (cfun_va_list)
&& (TREE_TYPE (cfun_va_list) == void_type_node
|| TREE_TYPE (cfun_va_list) == char_type_node);
switch (DECL_FUNCTION_CODE (callee))
{
case BUILT_IN_VA_START:
if (!va_list_simple_ptr
|| targetm.expand_builtin_va_start != NULL
|| !builtin_decl_explicit_p (BUILT_IN_NEXT_ARG))
return NULL_TREE;
if (gimple_call_num_args (call) != 2)
return NULL_TREE;
lhs = gimple_call_arg (call, 0);
if (!POINTER_TYPE_P (TREE_TYPE (lhs))
|| TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
!= TYPE_MAIN_VARIANT (cfun_va_list))
return NULL_TREE;
lhs = build_fold_indirect_ref_loc (loc, lhs);
rhs = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_NEXT_ARG),
1, integer_zero_node);
rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
case BUILT_IN_VA_COPY:
if (!va_list_simple_ptr)
return NULL_TREE;
if (gimple_call_num_args (call) != 2)
return NULL_TREE;
lhs = gimple_call_arg (call, 0);
if (!POINTER_TYPE_P (TREE_TYPE (lhs))
|| TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
!= TYPE_MAIN_VARIANT (cfun_va_list))
return NULL_TREE;
lhs = build_fold_indirect_ref_loc (loc, lhs);
rhs = gimple_call_arg (call, 1);
if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs))
!= TYPE_MAIN_VARIANT (cfun_va_list))
return NULL_TREE;
rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
case BUILT_IN_VA_END:
/* No effect, so the statement will be deleted. */
return integer_zero_node;
default:
gcc_unreachable ();
}
}
/* Attemp to make the block of __builtin_unreachable I unreachable by changing
the incoming jumps. Return true if at least one jump was changed. */
static bool
optimize_unreachable (gimple_stmt_iterator i)
{
basic_block bb = gsi_bb (i);
gimple_stmt_iterator gsi;
gimple stmt;
edge_iterator ei;
edge e;
bool ret;
if (flag_sanitize & SANITIZE_UNREACHABLE)
return false;
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
stmt = gsi_stmt (gsi);
if (is_gimple_debug (stmt))
continue;
if (glabel *label_stmt = dyn_cast <glabel *> (stmt))
{
/* Verify we do not need to preserve the label. */
if (FORCED_LABEL (gimple_label_label (label_stmt)))
return false;
continue;
}
/* Only handle the case that __builtin_unreachable is the first statement
in the block. We rely on DCE to remove stmts without side-effects
before __builtin_unreachable. */
if (gsi_stmt (gsi) != gsi_stmt (i))
return false;
}
ret = false;
FOR_EACH_EDGE (e, ei, bb->preds)
{
gsi = gsi_last_bb (e->src);
if (gsi_end_p (gsi))
continue;
stmt = gsi_stmt (gsi);
if (gcond *cond_stmt = dyn_cast <gcond *> (stmt))
{
if (e->flags & EDGE_TRUE_VALUE)
gimple_cond_make_false (cond_stmt);
else if (e->flags & EDGE_FALSE_VALUE)
gimple_cond_make_true (cond_stmt);
else
gcc_unreachable ();
update_stmt (cond_stmt);
}
else
{
/* Todo: handle other cases, f.i. switch statement. */
continue;
}
ret = true;
}
return ret;
}
/* A simple pass that attempts to fold all builtin functions. This pass
is run after we've propagated as many constants as we can. */
namespace {
const pass_data pass_data_fold_builtins =
{
GIMPLE_PASS, /* type */
"fab", /* 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 */
TODO_update_ssa, /* todo_flags_finish */
};
class pass_fold_builtins : public gimple_opt_pass
{
public:
pass_fold_builtins (gcc::context *ctxt)
: gimple_opt_pass (pass_data_fold_builtins, ctxt)
{}
/* opt_pass methods: */
opt_pass * clone () { return new pass_fold_builtins (m_ctxt); }
virtual unsigned int execute (function *);
}; // class pass_fold_builtins
unsigned int
pass_fold_builtins::execute (function *fun)
{
bool cfg_changed = false;
basic_block bb;
unsigned int todoflags = 0;
FOR_EACH_BB_FN (bb, fun)
{
gimple_stmt_iterator i;
for (i = gsi_start_bb (bb); !gsi_end_p (i); )
{
gimple stmt, old_stmt;
tree callee;
enum built_in_function fcode;
stmt = gsi_stmt (i);
if (gimple_code (stmt) != GIMPLE_CALL)
{
/* Remove all *ssaname_N ={v} {CLOBBER}; stmts,
after the last GIMPLE DSE they aren't needed and might
unnecessarily keep the SSA_NAMEs live. */
if (gimple_clobber_p (stmt))
{
tree lhs = gimple_assign_lhs (stmt);
if (TREE_CODE (lhs) == MEM_REF
&& TREE_CODE (TREE_OPERAND (lhs, 0)) == SSA_NAME)
{
unlink_stmt_vdef (stmt);
gsi_remove (&i, true);
release_defs (stmt);
continue;
}
}
gsi_next (&i);
continue;
}
callee = gimple_call_fndecl (stmt);
if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
{
gsi_next (&i);
continue;
}
fcode = DECL_FUNCTION_CODE (callee);
if (fold_stmt (&i))
;
else
{
tree result = NULL_TREE;
switch (DECL_FUNCTION_CODE (callee))
{
case BUILT_IN_CONSTANT_P:
/* Resolve __builtin_constant_p. If it hasn't been
folded to integer_one_node by now, it's fairly
certain that the value simply isn't constant. */
result = integer_zero_node;
break;
case BUILT_IN_ASSUME_ALIGNED:
/* Remove __builtin_assume_aligned. */
result = gimple_call_arg (stmt, 0);
break;
case BUILT_IN_STACK_RESTORE:
result = optimize_stack_restore (i);
if (result)
break;
gsi_next (&i);
continue;
case BUILT_IN_UNREACHABLE:
if (optimize_unreachable (i))
cfg_changed = true;
break;
case BUILT_IN_VA_START:
case BUILT_IN_VA_END:
case BUILT_IN_VA_COPY:
/* These shouldn't be folded before pass_stdarg. */
result = optimize_stdarg_builtin (stmt);
if (result)
break;
/* FALLTHRU */
default:;
}
if (!result)
{
gsi_next (&i);
continue;
}
if (!update_call_from_tree (&i, result))
gimplify_and_update_call_from_tree (&i, result);
}
todoflags |= TODO_update_address_taken;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Simplified\n ");
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
}
old_stmt = stmt;
stmt = gsi_stmt (i);
update_stmt (stmt);
if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)
&& gimple_purge_dead_eh_edges (bb))
cfg_changed = true;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "to\n ");
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
fprintf (dump_file, "\n");
}
/* Retry the same statement if it changed into another
builtin, there might be new opportunities now. */
if (gimple_code (stmt) != GIMPLE_CALL)
{
gsi_next (&i);
continue;
}
callee = gimple_call_fndecl (stmt);
if (!callee
|| DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
|| DECL_FUNCTION_CODE (callee) == fcode)
gsi_next (&i);
}
}
/* Delete unreachable blocks. */
if (cfg_changed)
todoflags |= TODO_cleanup_cfg;
return todoflags;
}
} // anon namespace
gimple_opt_pass *
make_pass_fold_builtins (gcc::context *ctxt)
{
return new pass_fold_builtins (ctxt);
}