Detect EAF flags in ipa-modref
Jan Hubicka
hubicka@ucw.cz
Tue Nov 10 14:31:43 GMT 2020
Hi,
here is updaed patch.
Honza
Bootstrapped/regtested x86_64-linux, OK (after the fnspec fixes)?
2020-11-10 Jan Hubicka <hubicka@ucw.cz>
* 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.
gcc/testsuite/ChangeLog:
2020-11-10 Jan Hubicka <hubicka@ucw.cz>
* gcc.dg/torture/pta-ptrarith-1.c: Escape parametrs.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index d2a188d7c75..0bd76d2841e 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -12953,6 +12953,10 @@ 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
diff --git a/gcc/gimple.c b/gcc/gimple.c
index 1afed88e1f1..da90716aa23 100644
--- a/gcc/gimple.c
+++ b/gcc/gimple.c
@@ -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
@@ -1532,24 +1534,45 @@ 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;
}
diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index 3f46bebed3c..30e76580fb0 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -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;
}
}
}
@@ -1957,7 +2319,7 @@ 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++)
{
diff --git a/gcc/ipa-modref.h b/gcc/ipa-modref.h
index 31ceffa8d34..59872301cd6 100644
--- a/gcc/ipa-modref.h
+++ b/gcc/ipa-modref.h
@@ -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 ();
diff --git a/gcc/params.opt b/gcc/params.opt
index a33a371a395..70152bf59bb 100644
--- a/gcc/params.opt
+++ b/gcc/params.opt
@@ -931,6 +931,10 @@ 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.
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