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Detect EAF flags in ipa-modref

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A minimal patch for the EAF flags discovery.  It works only in local ipa-modref
and gives up on cyclic SSA graphs.  It improves pt_solution_includes
disambiguations twice.

gcc/Changelog:

	* gimple.c: Include ipa-modref-tree.h and ipa-modref.h.
	(gimple_call_arg_flags): Use modref to determine flags.
	* ipa-modref.c: Include gimple-ssa.h, tree-phinodes.h,
	tree-ssa-operands.h, stringpool.h and tree-ssanames.h.
	(analyze_ssa_name_flags): Declare.
	(modref_summary::useful_p): Summary is also useful if arg flags are
	known.
	(dump_eaf_flags): New function.
	(modref_summary::dump): Use it.
	(get_modref_function_summary): Be read for current_function_decl
	being NULL.
	(memory_access_to): New function.
	(deref_flags): New function.
	(call_lhs_flags): New function.
	(analyze_parms): New function.
	(analyze_function): Use it.
	* ipa-modref.h (struct modref_summary): Add arg_flags.
	* doc/invoke.texi (ipa-modref-max-depth): Document.
	* params.opt (ipa-modref-max-depth): New param.
This commit is contained in:
Jan Hubicka 2020-11-14 13:52:36 +01:00
parent 2873c8af66
commit 520d5ad337
5 changed files with 414 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
gcc/doc/invoke.texi
View File

@ -13008,6 +13008,10 @@ memory locations using the mod/ref information. This parameter ought to be
bigger than @option{--param ipa-modref-max-bases} and @option{--param
ipa-modref-max-refs}.
@item ipa-modref-max-depth
Specified the maximum depth of DFS walk used by modref escape analysis.
Setting to 0 disables the analysis completely.
@item profile-func-internal-id
A parameter to control whether to use function internal id in profile
database lookup. If the value is 0, the compiler uses an id that

53
gcc/gimple.c
View File

@ -46,6 +46,8 @@ along with GCC; see the file COPYING3. If not see
#include "asan.h"
#include "langhooks.h"
#include "attr-fnspec.h"
#include "ipa-modref-tree.h"
#include "ipa-modref.h"
/* All the tuples have their operand vector (if present) at the very bottom
@ -1528,24 +1530,45 @@ int
gimple_call_arg_flags (const gcall *stmt, unsigned arg)
{
attr_fnspec fnspec = gimple_call_fnspec (stmt);
if (!fnspec.known_p ())
return 0;
int flags = 0;
if (!fnspec.arg_specified_p (arg))
;
else if (!fnspec.arg_used_p (arg))
flags = EAF_UNUSED;
else
if (fnspec.known_p ())
{
if (fnspec.arg_direct_p (arg))
flags |= EAF_DIRECT;
if (fnspec.arg_noescape_p (arg))
flags |= EAF_NOESCAPE;
if (fnspec.arg_readonly_p (arg))
flags |= EAF_NOCLOBBER;
if (!fnspec.arg_specified_p (arg))
;
else if (!fnspec.arg_used_p (arg))
flags = EAF_UNUSED;
else
{
if (fnspec.arg_direct_p (arg))
flags |= EAF_DIRECT;
if (fnspec.arg_noescape_p (arg))
flags |= EAF_NOESCAPE;
if (fnspec.arg_readonly_p (arg))
flags |= EAF_NOCLOBBER;
}
}
tree callee = gimple_call_fndecl (stmt);
if (callee)
{
cgraph_node *node = cgraph_node::get (callee);
modref_summary *summary = node ? get_modref_function_summary (node)
: NULL;
if (summary && summary->arg_flags.length () > arg)
{
int modref_flags = summary->arg_flags[arg];
/* We have possibly optimized out load. Be conservative here. */
if (!node->binds_to_current_def_p ())
{
if ((modref_flags & EAF_UNUSED) && !(flags & EAF_UNUSED))
modref_flags &= ~EAF_UNUSED;
if ((modref_flags & EAF_DIRECT) && !(flags & EAF_DIRECT))
modref_flags &= ~EAF_DIRECT;
}
flags |= modref_flags;
}
}
return flags;
}

372
gcc/ipa-modref.c
View File

@ -61,6 +61,15 @@ along with GCC; see the file COPYING3. If not see
#include "ipa-fnsummary.h"
#include "attr-fnspec.h"
#include "symtab-clones.h"
#include "gimple-ssa.h"
#include "tree-phinodes.h"
#include "tree-ssa-operands.h"
#include "ssa-iterators.h"
#include "stringpool.h"
#include "tree-ssanames.h"
static int analyze_ssa_name_flags (tree name,
vec<unsigned char> &known_flags, int depth);
/* We record fnspec specifiers for call edges since they depends on actual
gimple statements. */
@ -186,6 +195,8 @@ modref_summary::useful_p (int ecf_flags)
{
if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
return false;
if (arg_flags.length ())
return true;
if (loads && !loads->every_base)
return true;
if (ecf_flags & ECF_PURE)
@ -355,6 +366,22 @@ dump_lto_records (modref_records_lto *tt, FILE *out)
}
}
/* Dump EAF flags. */
static void
dump_eaf_flags (FILE *out, int flags)
{
if (flags & EAF_DIRECT)
fprintf (out, " direct");
if (flags & EAF_NOCLOBBER)
fprintf (out, " noclobber");
if (flags & EAF_NOESCAPE)
fprintf (out, " noescape");
if (flags & EAF_UNUSED)
fprintf (out, " unused");
fprintf (out, "\n");
}
/* Dump summary. */
void
@ -372,6 +399,15 @@ modref_summary::dump (FILE *out)
}
if (writes_errno)
fprintf (out, " Writes errno\n");
if (arg_flags.length ())
{
for (unsigned int i = 0; i < arg_flags.length (); i++)
if (arg_flags[i])
{
fprintf (out, " parm %i flags:", i);
dump_eaf_flags (out, arg_flags[i]);
}
}
}
/* Dump summary. */
@ -402,7 +438,8 @@ get_modref_function_summary (cgraph_node *func)
function. */
enum availability avail;
func = func->function_or_virtual_thunk_symbol
(&avail, cgraph_node::get (current_function_decl));
(&avail, current_function_decl ?
cgraph_node::get (current_function_decl) : NULL);
if (avail <= AVAIL_INTERPOSABLE)
return NULL;
@ -634,7 +671,7 @@ merge_call_side_effects (modref_summary *cur_summary,
cur_summary->loads->collapse ();
}
parm_map.safe_grow_cleared (gimple_call_num_args (stmt));
parm_map.safe_grow_cleared (gimple_call_num_args (stmt), true);
for (unsigned i = 0; i < gimple_call_num_args (stmt); i++)
{
parm_map[i] = parm_map_for_arg (stmt, i);
@ -1067,6 +1104,326 @@ remove_summary (bool lto, bool nolto, bool ipa)
" - modref done with result: not tracked.\n");
}
/* Return true if OP accesses memory pointed to by SSA_NAME. */
bool
memory_access_to (tree op, tree ssa_name)
{
tree base = get_base_address (op);
if (!base)
return false;
if (TREE_CODE (base) != MEM_REF && TREE_CODE (base) != TARGET_MEM_REF)
return false;
return TREE_OPERAND (base, 0) == ssa_name;
}
/* Consider statement val = *arg.
return EAF flags of ARG that can be determined from EAF flags of VAL
(which are known to be FLAGS). If IGNORE_STORES is true we can ignore
all stores to VAL, i.e. when handling noreturn function. */
static int
deref_flags (int flags, bool ignore_stores)
{
int ret = 0;
if (flags & EAF_UNUSED)
ret |= EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE;
else
{
if ((flags & EAF_NOCLOBBER) || ignore_stores)
ret |= EAF_NOCLOBBER;
if ((flags & EAF_NOESCAPE) || ignore_stores)
ret |= EAF_NOESCAPE;
}
return ret;
}
/* Call statements may return their parameters. Consider argument number
ARG of USE_STMT and determine flags that can needs to be cleared
in case pointer possibly indirectly references from ARG I is returned.
KNOWN_FLAGS and DEPTH are same as in analyze_ssa_name_flags. */
static int
call_lhs_flags (gcall *call, int arg,
vec<unsigned char> &known_flags, int depth)
{
/* If there is no return value, no flags are affected. */
if (!gimple_call_lhs (call))
return EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE | EAF_UNUSED;
/* If we know that function returns given argument and it is not ARG
we can still be happy. */
int flags = gimple_call_return_flags (call);
if ((flags & ERF_RETURNS_ARG)
&& (flags & ERF_RETURN_ARG_MASK) != arg)
return EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE | EAF_UNUSED;
/* If return value is SSA name determine its flags. */
if (TREE_CODE (gimple_call_lhs (call)) == SSA_NAME)
return analyze_ssa_name_flags
(gimple_call_lhs (call), known_flags,
depth + 1);
/* In the case of memory store we can do nothing. */
else
return 0;
}
/* Analyze EAF flags for SSA name NAME.
KNOWN_FLAGS is a cache for flags we already determined.
DEPTH is a recursion depth used to make debug output prettier. */
static int
analyze_ssa_name_flags (tree name, vec<unsigned char> &known_flags, int depth)
{
imm_use_iterator ui;
gimple *use_stmt;
int flags = EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE | EAF_UNUSED;
/* See if value is already computed. */
if (known_flags[SSA_NAME_VERSION (name)])
{
/* Punt on cycles for now, so we do not need dataflow. */
if (known_flags[SSA_NAME_VERSION (name)] == 1)
{
if (dump_file)
fprintf (dump_file,
"%*sGiving up on a cycle in SSA graph\n", depth * 4, "");
return 0;
}
return known_flags[SSA_NAME_VERSION (name)] - 2;
}
if (depth == param_modref_max_depth)
{
if (dump_file)
fprintf (dump_file,
"%*sGiving up on max depth\n", depth * 4, "");
return 0;
}
/* Recursion guard. */
known_flags[SSA_NAME_VERSION (name)] = 1;
if (dump_file)
{
fprintf (dump_file,
"%*sAnalyzing flags of ssa name: ", depth * 4, "");
print_generic_expr (dump_file, name);
fprintf (dump_file, "\n");
}
FOR_EACH_IMM_USE_STMT (use_stmt, ui, name)
{
if (flags == 0)
{
BREAK_FROM_IMM_USE_STMT (ui);
}
if (is_gimple_debug (use_stmt))
continue;
if (dump_file)
{
fprintf (dump_file, "%*s Analyzing stmt:", depth * 4, "");
print_gimple_stmt (dump_file, use_stmt, 0);
}
/* Gimple return may load the return value. */
if (greturn *ret = dyn_cast <greturn *> (use_stmt))
{
if (memory_access_to (gimple_return_retval (ret), name))
flags &= ~EAF_UNUSED;
}
/* Account for LHS store, arg loads and flags from callee function. */
else if (gcall *call = dyn_cast <gcall *> (use_stmt))
{
tree callee = gimple_call_fndecl (call);
/* Recursion would require bit of propagation; give up for now. */
if (callee && recursive_call_p (current_function_decl, callee))
flags = 0;
else
{
int ecf_flags = gimple_call_flags (call);
bool ignore_stores = ignore_stores_p (current_function_decl,
ecf_flags);
/* Handle *name = func (...). */
if (gimple_call_lhs (call)
&& memory_access_to (gimple_call_lhs (call), name))
flags &= ~(EAF_UNUSED | EAF_NOCLOBBER);
/* We do not track accesses to the static chain (we could)
so give up. */
if (gimple_call_chain (call)
&& (gimple_call_chain (call) == name))
flags = 0;
/* Handle all function parameters. */
for (unsigned i = 0; i < gimple_call_num_args (call); i++)
/* Name is directly passed to the callee. */
if (gimple_call_arg (call, i) == name)
{
if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
flags &= ignore_stores
? 0
: call_lhs_flags (call, i, known_flags, depth);
else
{
int call_flags = gimple_call_arg_flags (call, i);
if (ignore_stores)
call_flags |= EAF_NOCLOBBER | EAF_NOESCAPE;
else
call_flags &= call_lhs_flags (call, i,
known_flags, depth);
flags &= call_flags;
}
}
/* Name is dereferenced and passed to a callee. */
else if (memory_access_to (gimple_call_arg (call, i), name))
{
if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
flags &= ~EAF_UNUSED;
else
flags &= deref_flags (gimple_call_arg_flags (call, i),
ignore_stores);
if (!ignore_stores)
flags &= call_lhs_flags (call, i, known_flags, depth);
}
}
/* Only NOCLOBBER or DIRECT flags alone are not useful (see comments
in tree-ssa-alias.c). Give up earlier. */
if ((flags & ~(EAF_DIRECT | EAF_NOCLOBBER)) == 0)
flags = 0;
}
else if (gimple_assign_load_p (use_stmt))
{
gassign *assign = as_a <gassign *> (use_stmt);
/* Memory to memory copy. */
if (gimple_store_p (assign))
{
/* Handle *name = *exp. */
if (memory_access_to (gimple_assign_lhs (assign), name))
flags &= ~(EAF_UNUSED | EAF_NOCLOBBER);
/* Handle *lhs = *name.
We do not track memory locations, so assume that value
is used arbitrarily. */
if (memory_access_to (gimple_assign_rhs1 (assign), name))
flags = 0;
}
/* Handle lhs = *name. */
else if (memory_access_to (gimple_assign_rhs1 (assign), name))
flags &= deref_flags (analyze_ssa_name_flags
(gimple_assign_lhs (assign),
known_flags, depth + 1), false);
}
else if (gimple_store_p (use_stmt))
{
gassign *assign = dyn_cast <gassign *> (use_stmt);
/* Handle *lhs = name. */
if (assign && gimple_assign_rhs1 (assign) == name)
{
if (dump_file)
fprintf (dump_file, "%*s ssa name saved to memory\n",
depth * 4, "");
flags = 0;
}
/* Handle *name = exp. */
else if (assign
&& memory_access_to (gimple_assign_lhs (assign), name))
flags &= ~(EAF_UNUSED | EAF_NOCLOBBER);
/* ASM statements etc. */
else if (!assign)
{
if (dump_file)
fprintf (dump_file, "%*s Unhandled store\n",
depth * 4, "");
flags = 0;
}
}
else if (gassign *assign = dyn_cast <gassign *> (use_stmt))
{
enum tree_code code = gimple_assign_rhs_code (assign);
/* See if operation is a merge as considered by
tree-ssa-structalias.c:find_func_aliases. */
if (!truth_value_p (code)
&& code != POINTER_DIFF_EXPR
&& (code != POINTER_PLUS_EXPR
|| gimple_assign_rhs1 (assign) == name))
flags &= analyze_ssa_name_flags
(gimple_assign_lhs (assign), known_flags,
depth + 1);
}
else if (gphi *phi = dyn_cast <gphi *> (use_stmt))
{
flags &= analyze_ssa_name_flags
(gimple_phi_result (phi), known_flags,
depth + 1);
}
/* Conditions are not considered escape points
by tree-ssa-structalias. */
else if (gimple_code (use_stmt) == GIMPLE_COND)
;
else
{
if (dump_file)
fprintf (dump_file, "%*s Unhandled stmt\n", depth * 4, "");
flags = 0;
}
if (dump_file)
{
fprintf (dump_file, "%*s current flags of ", depth * 4, "");
print_generic_expr (dump_file, name);
dump_eaf_flags (dump_file, flags);
}
}
if (dump_file)
{
fprintf (dump_file, "%*sflags of ssa name ", depth * 4, "");
print_generic_expr (dump_file, name);
dump_eaf_flags (dump_file, flags);
}
known_flags[SSA_NAME_VERSION (name)] = flags + 2;
return flags;
}
/* Determine EAF flags for function parameters. */
static void
analyze_parms (modref_summary *summary)
{
unsigned int parm_index = 0;
unsigned int count = 0;
for (tree parm = DECL_ARGUMENTS (current_function_decl); parm;
parm = TREE_CHAIN (parm))
count++;
if (!count)
return;
auto_vec<unsigned char> known_flags;
known_flags.safe_grow_cleared (num_ssa_names, true);
for (tree parm = DECL_ARGUMENTS (current_function_decl); parm; parm_index++,
parm = TREE_CHAIN (parm))
{
tree name = ssa_default_def (cfun, parm);
if (!name)
continue;
int flags = analyze_ssa_name_flags (name, known_flags, 0);
if (flags)
{
if (parm_index >= summary->arg_flags.length ())
summary->arg_flags.safe_grow_cleared (count, true);
summary->arg_flags[parm_index] = flags;
}
}
}
/* Analyze function F. IPA indicates whether we're running in local mode
(false) or the IPA mode (true). */
@ -1174,6 +1531,10 @@ analyze_function (function *f, bool ipa)
param_modref_max_accesses);
summary_lto->writes_errno = false;
}
if (!ipa)
analyze_parms (summary);
int ecf_flags = flags_from_decl_or_type (current_function_decl);
auto_vec <gimple *, 32> recursive_calls;
@ -1191,8 +1552,9 @@ analyze_function (function *f, bool ipa)
|| ((!summary || !summary->useful_p (ecf_flags))
&& (!summary_lto || !summary_lto->useful_p (ecf_flags))))
{
remove_summary (lto, nolto, ipa);
return;
collapse_loads (summary, summary_lto);
collapse_stores (summary, summary_lto);
break;
}
}
}
@ -1959,7 +2321,7 @@ compute_parm_map (cgraph_edge *callee_edge, vec<modref_parm_map> *parm_map)
: callee_edge->caller);
callee_pi = IPA_NODE_REF (callee);
(*parm_map).safe_grow_cleared (count);
(*parm_map).safe_grow_cleared (count, true);
for (i = 0; i < count; i++)
{

1
gcc/ipa-modref.h
View File

@ -29,6 +29,7 @@ struct GTY(()) modref_summary
/* Load and stores in function (transitively closed to all callees) */
modref_records *loads;
modref_records *stores;
auto_vec<unsigned char> GTY((skip)) arg_flags;
modref_summary ();
~modref_summary ();

4
gcc/params.opt
View File

@ -927,6 +927,10 @@ Maximum number of accesse stored in each modref reference.
Common Joined UInteger Var(param_modref_max_tests) Init(64)
Maximum number of tests performed by modref query.
-param=modref-max-depth=
Common Joined UInteger Var(param_modref_max_depth) Init(256)
Maximum depth of DFS walk used by modref escape analysis
-param=tm-max-aggregate-size=
Common Joined UInteger Var(param_tm_max_aggregate_size) Init(9) Param Optimization
Size in bytes after which thread-local aggregates should be instrumented with the logging functions instead of save/restore pairs.