Reimplement 'assume' processing pass.

Rework the assume pass to work properly and fail conservatively when it
does.  Also move it to its own file.

	PR tree-optimization/117287
	gcc/
	* Makefile.in (IBJS): Add tree-assume.o
	* gimple-range.cc (assume_query::assume_range_p): Remove.
	(assume_query::range_of_expr): Remove.
	(assume_query::assume_query): Move to tree-assume.cc.
	(assume_query::~assume_query): Remove.
	(assume_query::calculate_op): Move to tree-assume.cc.
	(assume_query::calculate_phi): Likewise.
	(assume_query::check_taken_edge): Remove.
	(assume_query::calculate_stmt): Move to tree-assume.cc.
	(assume_query::dump): Remove.
	* gimple-range.h (class assume_query): Move to tree-assume.cc
	* tree-assume.cc: New
	* tree-vrp.cc (struct pass_data_assumptions): Move to tree-assume.cc.
	(class pass_assumptions): Likewise.
	(make_pass_assumptions): Likewise.

	gcc/testsuite/
	* g++.dg/cpp23/pr117287-attr.C: New.
This commit is contained in:
Andrew MacLeod 2024-10-28 10:19:27 -04:00
parent fe22e18c1b
commit 62420dbd10
6 changed files with 408 additions and 271 deletions

View File

@ -1703,6 +1703,7 @@ OBJS = \
sanopt.o \
sancov.o \
simple-diagnostic-path.o \
tree-assume.o \
tree-call-cdce.o \
tree-cfg.o \
tree-cfgcleanup.o \

View File

@ -700,200 +700,6 @@ disable_ranger (struct function *fun)
fun->x_range_query = NULL;
}
// ------------------------------------------------------------------------
// If there is a non-varying value associated with NAME, return true and the
// range in R.
bool
assume_query::assume_range_p (vrange &r, tree name)
{
if (global.get_range (r, name))
return !r.varying_p ();
return false;
}
// Query used by GORI to pick up any known value on entry to a block.
bool
assume_query::range_of_expr (vrange &r, tree expr, gimple *stmt)
{
if (!gimple_range_ssa_p (expr))
return get_tree_range (r, expr, stmt);
if (!global.get_range (r, expr))
r.set_varying (TREE_TYPE (expr));
return true;
}
// If the current function returns an integral value, and has a single return
// statement, it will calculate any SSA_NAMES it can determine ranges for
// assuming the function returns 1.
assume_query::assume_query ()
{
create_gori (0, param_vrp_switch_limit);
basic_block exit_bb = EXIT_BLOCK_PTR_FOR_FN (cfun);
if (single_pred_p (exit_bb))
{
basic_block bb = single_pred (exit_bb);
gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb);
if (gsi_end_p (gsi))
return;
gimple *s = gsi_stmt (gsi);
if (!is_a<greturn *> (s))
return;
greturn *gret = as_a<greturn *> (s);
tree op = gimple_return_retval (gret);
if (!gimple_range_ssa_p (op))
return;
tree lhs_type = TREE_TYPE (op);
if (!irange::supports_p (lhs_type))
return;
unsigned prec = TYPE_PRECISION (lhs_type);
int_range<2> lhs_range (lhs_type, wi::one (prec), wi::one (prec));
global.set_range (op, lhs_range);
gimple *def = SSA_NAME_DEF_STMT (op);
if (!def || gimple_get_lhs (def) != op)
return;
fur_stmt src (gret, this);
calculate_stmt (def, lhs_range, src);
}
}
assume_query::~assume_query ()
{
destroy_gori ();
}
// Evaluate operand OP on statement S, using the provided LHS range.
// If successful, set the range in the global table, then visit OP's def stmt.
void
assume_query::calculate_op (tree op, gimple *s, vrange &lhs, fur_source &src)
{
value_range op_range (TREE_TYPE (op));
if (gori ().compute_operand_range (op_range, s, lhs, op, src)
&& !op_range.varying_p ())
{
// Set the global range, merging if there is already a range.
global.merge_range (op, op_range);
gimple *def_stmt = SSA_NAME_DEF_STMT (op);
if (def_stmt && gimple_get_lhs (def_stmt) == op)
calculate_stmt (def_stmt, op_range, src);
}
}
// Evaluate PHI statement, using the provided LHS range.
// Check each constant argument predecessor if it can be taken
// provide LHS to any symbolic arguments, and process their def statements.
void
assume_query::calculate_phi (gphi *phi, vrange &lhs_range, fur_source &src)
{
for (unsigned x= 0; x < gimple_phi_num_args (phi); x++)
{
tree arg = gimple_phi_arg_def (phi, x);
value_range arg_range (TREE_TYPE (arg));
if (gimple_range_ssa_p (arg))
{
// A symbol arg will be the LHS value.
arg_range = lhs_range;
range_cast (arg_range, TREE_TYPE (arg));
if (!global.get_range (arg_range, arg))
{
global.set_range (arg, arg_range);
gimple *def_stmt = SSA_NAME_DEF_STMT (arg);
if (def_stmt && gimple_get_lhs (def_stmt) == arg)
calculate_stmt (def_stmt, arg_range, src);
}
}
else if (get_tree_range (arg_range, arg, NULL))
{
// If this is a constant value that differs from LHS, this
// edge cannot be taken.
arg_range.intersect (lhs_range);
if (arg_range.undefined_p ())
continue;
// Otherwise check the condition feeding this edge.
edge e = gimple_phi_arg_edge (phi, x);
check_taken_edge (e, src);
}
}
}
// If an edge is known to be taken, examine the outgoing edge to see
// if it carries any range information that can also be evaluated.
void
assume_query::check_taken_edge (edge e, fur_source &src)
{
gimple *stmt = gimple_outgoing_range_stmt_p (e->src);
if (stmt && is_a<gcond *> (stmt))
{
int_range<2> cond;
gcond_edge_range (cond, e);
calculate_stmt (stmt, cond, src);
}
}
// Evaluate statement S which produces range LHS_RANGE.
void
assume_query::calculate_stmt (gimple *s, vrange &lhs_range, fur_source &src)
{
gimple_range_op_handler handler (s);
if (handler)
{
tree op = gimple_range_ssa_p (handler.operand1 ());
if (op)
calculate_op (op, s, lhs_range, src);
op = gimple_range_ssa_p (handler.operand2 ());
if (op)
calculate_op (op, s, lhs_range, src);
}
else if (is_a<gphi *> (s))
{
calculate_phi (as_a<gphi *> (s), lhs_range, src);
// Don't further check predecessors of blocks with PHIs.
return;
}
// Even if the walk back terminates before the top, if this is a single
// predecessor block, see if the predecessor provided any ranges to get here.
if (single_pred_p (gimple_bb (s)))
check_taken_edge (single_pred_edge (gimple_bb (s)), src);
}
// Show everything that was calculated.
void
assume_query::dump (FILE *f)
{
fprintf (f, "Assumption details calculated:\n");
for (unsigned i = 0; i < num_ssa_names; i++)
{
tree name = ssa_name (i);
if (!name || !gimple_range_ssa_p (name))
continue;
tree type = TREE_TYPE (name);
if (!value_range::supports_type_p (type))
continue;
value_range assume_range (type);
if (assume_range_p (assume_range, name))
{
print_generic_expr (f, name, TDF_SLIM);
fprintf (f, " -> ");
assume_range.dump (f);
fputc ('\n', f);
}
}
fprintf (f, "------------------------------\n");
}
// ---------------------------------------------------------------------------
//
// The DOM based ranger assumes a single DOM walk through the IL, and is

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@ -82,23 +82,6 @@ extern gimple_ranger *enable_ranger (struct function *m,
bool use_imm_uses = true);
extern void disable_ranger (struct function *);
class assume_query : public range_query
{
public:
assume_query ();
~assume_query ();
bool assume_range_p (vrange &r, tree name);
virtual bool range_of_expr (vrange &r, tree expr, gimple * = NULL);
void dump (FILE *f);
protected:
void calculate_stmt (gimple *s, vrange &lhs_range, fur_source &src);
void calculate_op (tree op, gimple *s, vrange &lhs, fur_source &src);
void calculate_phi (gphi *phi, vrange &lhs_range, fur_source &src);
void check_taken_edge (edge e, fur_source &src);
ssa_lazy_cache global;
};
// DOM based ranger for fast VRP.
// This must be processed in DOM order, and does only basic range operations.

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@ -0,0 +1,38 @@
// P1774R8 - Portable assumptions
// { dg-do run { target c++23 } }
// { dg-options "-O2 --param=logical-op-non-short-circuit=0" }
// Test the we can optimize based on conditions in assume.
static inline bool
foo (unsigned x)
{
return x == 4 || x == 5 || x == 9 || x == 10;
}
int v;
[[gnu::noipa]] void
bar (const char *p)
{
if (p[0] != (v ? 'a' : 'b') || p[1])
__builtin_abort ();
}
[[gnu::noipa]] void
baz (unsigned x)
{
bool a = x == 5;
[[assume (foo (x))]];
bar (a ? "a" : "b");
}
int
main ()
{
baz (4);
v = 1;
baz (5);
v = 0;
baz (9);
baz (10);
}

369
gcc/tree-assume.cc Normal file
View File

@ -0,0 +1,369 @@
/* Support for C++23 ASSUME keyword functionailty.
Copyright (C) 2023-2024 Free Software Foundation, Inc.
Contributed by Andrew MacLeod <amacleod@redhat.com>.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "basic-block.h"
#include "bitmap.h"
#include "options.h"
#include "function.h"
#include "cfg.h"
#include "tree.h"
#include "gimple.h"
#include "tree-pass.h"
#include "ssa.h"
#include "gimple-iterator.h"
#include "gimple-range.h"
#include "tree-dfa.h"
// An assume query utilizes the current range query to implelemtn the assume
// keyword.
// For any return value of 1 from the function, it attempts to determine
// which paths leads to a 1 value being returned. On those paths, what
// the ranges of any ssa_names listed in bitmap P (usually the parm list for
// the function) are, and combined them all.
// These ranges are then set as the global ranges for those parms in this
// function.
// Other functions which then refer to this function in an assume builtin
// will then pick up these ranges for the paramters via the inferred range
// mechanism.
// See gimple-range-infer.cc::gimple_infer_range::check_assume_func ()
//
// my_func (int x)
// {
// <...>
// assume [[(x == 1 || x ==4))]]
// if (x ==3)
//
// a small temporary assume function consisting of
// assume_f1 (int x) { return x == 1 || x == 4; }
// is constructed by the front end, and optimzed, at the very end of
// optimization, instead of generating code, we instead invoke the assume pass
// which uses this query to set the the global value of parm x to [1,1][4,4]
//
// Meanwhile., my_Fund has been rewritten to be:
//
// my_func (int x_2)
// {
// <...>
// assume_builtin_call assume_f1 (x_2);
// if (x_2 == 3)
//
// When ranger is processing the assume_builtin_call, it looks up the global
// value of the paramter in assume_f1, which is [1,1][4,4]. It then registers
// and inferred range at this statement setting the value x_2 to [1,1][4,4]
//
// Any uses of x_2 after this statement will now utilzie this inferred range.
//
// When VRP precoesses if (x_2 == 3), it picks up the inferred range, and
// determines that x_2 can never be 3, and will rewrite the branch to
// if (0 != 0)
class assume_query
{
public:
assume_query (function *f, bitmap p);
protected:
inline void process_stmts (gimple *s, vrange &lhs_range)
{
fur_depend src (s, get_range_query (m_func));
calculate_stmt (s, lhs_range, src);
update_parms (src);
}
void update_parms (fur_source &src);
void calculate_stmt (gimple *s, vrange &lhs_range, fur_source &src);
void calculate_op (tree op, gimple *s, vrange &lhs, fur_source &src);
void calculate_phi (gphi *phi, vrange &lhs_range);
ssa_lazy_cache m_path; // Values found on path
ssa_lazy_cache m_parms; // Cumulative parameter value calculated
bitmap &m_parm_list; // Parameter ssa-names list.
function *m_func;
};
// If function F returns a integral value, and has a single return
// statement, try to calculate the range of each value in P that leads
// to the return statement returning TRUE.
assume_query::assume_query (function *f, bitmap p) : m_parm_list (p),
m_func (f)
{
basic_block exit_bb = EXIT_BLOCK_PTR_FOR_FN (f);
// If there is more than one precessor to the exit block, bail.
if (!single_pred_p (exit_bb))
return;
basic_block bb = single_pred (exit_bb);
gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb);
if (gsi_end_p (gsi))
return;
gimple *s = gsi_stmt (gsi);
if (!is_a<greturn *> (s))
return;
// Check if the single return value is a symbolic and supported type.
greturn *gret = as_a<greturn *> (s);
tree op = gimple_return_retval (gret);
if (!gimple_range_ssa_p (op))
return;
tree lhs_type = TREE_TYPE (op);
if (!irange::supports_p (lhs_type))
return;
// Only values of interest are when the return value is 1. The defintion
// of the return value must be in the same block, or we have
// complicated flow control we don't understand, and just return.
unsigned prec = TYPE_PRECISION (lhs_type);
int_range<2> lhs_range (lhs_type, wi::one (prec), wi::one (prec));
gimple *def = SSA_NAME_DEF_STMT (op);
if (!def || gimple_get_lhs (def) != op || gimple_bb (def) != bb)
return;
// Determine if this is a PHI or a linear sequence to deal with.
if (is_a<gphi *> (def))
calculate_phi (as_a<gphi *> (def), lhs_range);
else
process_stmts (def, lhs_range);
if (dump_file)
fprintf (dump_file, "Assumptions :\n--------------\n");
// Now export any interesting values that were found.
bitmap_iterator bi;
unsigned x;
EXECUTE_IF_SET_IN_BITMAP (m_parm_list, 0, x, bi)
{
tree name = ssa_name (x);
tree type = TREE_TYPE (name);
value_range assume_range (type);
// Set the global range of NAME to anything calculated.
if (m_parms.get_range (assume_range, name) && !assume_range.varying_p ())
set_range_info (name, assume_range);
}
}
// This function Will update all the current value of interesting parameters.
// It tries, in order:
// a) a range found via path calculations.
// b) range of the parm at SRC point in the IL. (either edge or stmt)
// c) VARYING if those options fail.
// The value is then unioned with any existing value, allowing for the
// cumulation of all ranges leading to the return that return 1.
void
assume_query::update_parms (fur_source &src)
{
// Merge any parameter values.
bitmap_iterator bi;
unsigned x;
EXECUTE_IF_SET_IN_BITMAP (m_parm_list, 0, x, bi)
{
tree name = ssa_name (x);
tree type = TREE_TYPE (name);
// Find a valu efrom calculations.
value_range glob_range (type);
if (!m_path.get_range (glob_range, name)
&& !src.get_operand (glob_range, name))
glob_range.set_varying (type);
// Find any current value of parm, and combine them.
value_range parm_range (type);
if (m_parms.get_range (parm_range, name))
glob_range.union_ (parm_range);
// Set this new value.
m_parms.set_range (name, glob_range);
}
// Now reset the path values for the next path.
m_path.clear ();
}
// Evaluate PHI statement, using the provided LHS range.
// Only process edge that are both taken and returns the LHS of the PHI.
void
assume_query::calculate_phi (gphi *phi, vrange &lhs_range)
{
for (unsigned x= 0; x < gimple_phi_num_args (phi); x++)
{
tree arg = gimple_phi_arg_def (phi, x);
value_range arg_range (TREE_TYPE (arg));
edge e = gimple_phi_arg_edge (phi, x);
value_range edge_range (TREE_TYPE (arg));
// If we can't get an edge range, be conservative and assume the
// edge can be taken.
// NOte this can be either an ssa_name or a constant.
if (get_range_query (m_func)->range_on_edge (edge_range, e, arg))
{
if (gimple_range_ssa_p (arg))
{
arg_range = lhs_range;
range_cast (arg_range, TREE_TYPE (arg));
// An SSA_NAME arg will start with the LHS value.
// Check the range of ARG on the edge leading here. If that range
// cannot be any value from the LHS of the PHI, then this branch
// will not be taken to return the LHS value and can be ignored.
arg_range.intersect (edge_range);
if (arg_range.undefined_p ())
continue;
// If the def is in the immediate preceeding block, process it
// with GORI to determine what values can produce this
// argument value. Otherwise there is more flow, so just query
// the edge for parm ranges and be conservative.
gimple *def_stmt = SSA_NAME_DEF_STMT (arg);
if (def_stmt && gimple_get_lhs (def_stmt) == arg
&& gimple_bb (def_stmt) == e->src)
{
process_stmts (def_stmt, arg_range);
continue;
}
// Fall through to process the edge.
}
else
{
// If this is a constant value that differs from LHS, this
// edge cannot be taken and we can ignore it. Otherwise fall
// thorugh and process the edge.
edge_range.intersect (lhs_range);
if (edge_range.undefined_p ())
continue;
}
}
// If this point is reached the edge needs processing.
fur_edge src (e, get_range_query (m_func));
update_parms (src);
}
}
// Evaluate operand OP on statement S, using the provided LHS range.
// If successful, set the range in path table, then visit OP's def stmt
// if it is in the same BB.
void
assume_query::calculate_op (tree op, gimple *s, vrange &lhs, fur_source &src)
{
basic_block bb = gimple_bb (s);
value_range op_range (TREE_TYPE (op));
if (src.gori () &&
src.gori ()->compute_operand_range (op_range, s, lhs, op, src)
&& !op_range.varying_p ())
{
// Set the global range, merging if there is already a range.
m_path.merge_range (op, op_range);
gimple *def_stmt = SSA_NAME_DEF_STMT (op);
// Terminate if the patway leads to a different block as we
// are not analyzing flow.
if (def_stmt && gimple_get_lhs (def_stmt) == op
&& gimple_bb (def_stmt) == bb)
calculate_stmt (def_stmt, op_range, src);
}
}
// Evaluate statement S which produces range LHS_RANGE. Use GORI to
// determine what values the operands can have to produce the LHS,
// and set these in the M_PATH table.
void
assume_query::calculate_stmt (gimple *s, vrange &lhs_range, fur_source &src)
{
gimple_range_op_handler handler (s);
if (handler)
{
tree op = gimple_range_ssa_p (handler.operand1 ());
if (op)
calculate_op (op, s, lhs_range, src);
op = gimple_range_ssa_p (handler.operand2 ());
if (op)
calculate_op (op, s, lhs_range, src);
}
}
namespace {
const pass_data pass_data_assumptions =
{
GIMPLE_PASS, /* type */
"assumptions", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_TREE_ASSUMPTIONS, /* tv_id */
PROP_ssa, /* properties_required */
PROP_assumptions_done, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
0, /* todo_flags_end */
};
class pass_assumptions : public gimple_opt_pass
{
public:
pass_assumptions (gcc::context *ctxt)
: gimple_opt_pass (pass_data_assumptions, ctxt)
{}
/* opt_pass methods: */
bool gate (function *fun) final override { return fun->assume_function; }
unsigned int execute (function *fun) final override
{
// Create a bitmap of all the paramters in this function.
// Invoke the assume_query to detemine what values these parameters
// have when the function returns TRUE, and set the globals value of
// those parameters in this function based on that. This will later be
// utilized by ranger when prcessing the builtin_assumer function.
auto_bitmap decls;
for (tree arg = DECL_ARGUMENTS (fun->decl); arg; arg = DECL_CHAIN (arg))
{
tree name = ssa_default_def (fun, arg);
if (!name || !gimple_range_ssa_p (name))
continue;
tree type = TREE_TYPE (name);
if (!value_range::supports_type_p (type))
continue;
bitmap_set_bit (decls, SSA_NAME_VERSION (name));
}
// If there are no parameters to map, simply return;
if (bitmap_empty_p (decls))
return TODO_discard_function;
enable_ranger (fun);
// This assume query will set any global values required.
assume_query query (fun, decls);
disable_ranger (fun);
return TODO_discard_function;
}
}; // class pass_assumptions
} // anon namespace
gimple_opt_pass *
make_pass_assumptions (gcc::context *ctx)
{
return new pass_assumptions (ctx);
}

View File

@ -1353,60 +1353,6 @@ public:
const pass_data &data;
bool final_p;
}; // class pass_vrp
const pass_data pass_data_assumptions =
{
GIMPLE_PASS, /* type */
"assumptions", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_TREE_ASSUMPTIONS, /* tv_id */
PROP_ssa, /* properties_required */
PROP_assumptions_done, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
0, /* todo_flags_end */
};
class pass_assumptions : public gimple_opt_pass
{
public:
pass_assumptions (gcc::context *ctxt)
: gimple_opt_pass (pass_data_assumptions, ctxt)
{}
/* opt_pass methods: */
bool gate (function *fun) final override { return fun->assume_function; }
unsigned int execute (function *) final override
{
assume_query query;
if (dump_file)
fprintf (dump_file, "Assumptions :\n--------------\n");
for (tree arg = DECL_ARGUMENTS (cfun->decl); arg; arg = DECL_CHAIN (arg))
{
tree name = ssa_default_def (cfun, arg);
if (!name || !gimple_range_ssa_p (name))
continue;
tree type = TREE_TYPE (name);
if (!value_range::supports_type_p (type))
continue;
value_range assume_range (type);
// Set the global range of NAME to anything calculated.
if (query.assume_range_p (assume_range, name))
set_range_info (name, assume_range);
}
if (dump_file)
{
fputc ('\n', dump_file);
gimple_dump_cfg (dump_file, dump_flags & ~TDF_DETAILS);
if (dump_flags & TDF_DETAILS)
query.dump (dump_file);
}
return TODO_discard_function;
}
}; // class pass_assumptions
} // anon namespace
gimple_opt_pass *
@ -1426,9 +1372,3 @@ make_pass_fast_vrp (gcc::context *ctxt)
{
return new pass_vrp (ctxt, pass_data_fast_vrp);
}
gimple_opt_pass *
make_pass_assumptions (gcc::context *ctx)
{
return new pass_assumptions (ctx);
}