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Fix inter-procedural EAF flags propagation with respect to !binds_to_current_def_p 

While proofreading the code for handling EAF flags of !binds_to_current_def_p I
noticed that the interprocedural dataflow actually ignores the flag possibly
introducing wrong code on quite complex interposable functions in non-trivial
recursion cycles (or at ltrans partition boundary).

This patch unifies the flags changes to single place (remove_useless_eaf_flags)
and does extend modref_merge_call_site_flags to do the right thing.

lto-bootstrapped/regtested x86_64-linux.  Plan to commit it today after bit
more testing (firefox/clang build).

gcc/ChangeLog:

	* gimple.c (gimple_call_arg_flags): Use interposable_eaf_flags.
	(gimple_call_retslot_flags): Likewise.
	(gimple_call_static_chain_flags): Likewise.
	* ipa-modref.c (remove_useless_eaf_flags): Do not remove everything for
	NOVOPS.
	(modref_summary::useful_p): Likewise.
	(modref_summary_lto::useful_p): Likewise.
	(analyze_parms): Do not give up on NOVOPS.
	(analyze_function): When dumping report chnages in EAF flags
	between IPA and local pass.
	(modref_merge_call_site_flags): Compute implicit eaf flags
	based on callee ecf_flags and fnspec; if the function does not
	bind to current defs use interposable_eaf_flags.
	(modref_propagate_flags_in_scc): Update.
	* ipa-modref.h (interposable_eaf_flags): New function.
This commit is contained in:
Jan Hubicka 2021-11-07 18:20:45 +01:00
parent a28cfe4920
commit f6f704fd10
3 changed files with 203 additions and 55 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
gcc/gimple.c
View File

@ -1595,17 +1595,7 @@ gimple_call_arg_flags (const gcall *stmt, unsigned 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;
modref_flags |= EAF_NOESCAPE;
}
if ((modref_flags & EAF_NOREAD) && !(flags & EAF_NOREAD))
modref_flags &= ~EAF_NOREAD;
if ((modref_flags & EAF_DIRECT) && !(flags & EAF_DIRECT))
modref_flags &= ~EAF_DIRECT;
}
modref_flags = interposable_eaf_flags (modref_flags, flags);
if (dbg_cnt (ipa_mod_ref_pta))
flags |= modref_flags;
}
@ -1633,13 +1623,7 @@ gimple_call_retslot_flags (const gcall *stmt)
/* 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;
modref_flags |= EAF_NOESCAPE;
}
}
modref_flags = interposable_eaf_flags (modref_flags, flags);
if (dbg_cnt (ipa_mod_ref_pta))
flags |= modref_flags;
}
@ -1665,19 +1649,9 @@ gimple_call_static_chain_flags (const gcall *stmt)
{
int modref_flags = summary->static_chain_flags;
/* We have possibly optimized out load. Be conservative here. */
/* ??? Nested functions should always bind to current def. */
if (!node->binds_to_current_def_p ())
{
if ((modref_flags & EAF_UNUSED) && !(flags & EAF_UNUSED))
{
modref_flags &= ~EAF_UNUSED;
modref_flags |= EAF_NOESCAPE;
}
if ((modref_flags & EAF_NOREAD) && !(flags & EAF_NOREAD))
modref_flags &= ~EAF_NOREAD;
if ((modref_flags & EAF_DIRECT) && !(flags & EAF_DIRECT))
modref_flags &= ~EAF_DIRECT;
}
modref_flags = interposable_eaf_flags (modref_flags, flags);
if (dbg_cnt (ipa_mod_ref_pta))
flags |= modref_flags;
}

195
gcc/ipa-modref.c
View File

@ -291,9 +291,7 @@ modref_summary::~modref_summary ()
static int
remove_useless_eaf_flags (int eaf_flags, int ecf_flags, bool returns_void)
{
if (ecf_flags & ECF_NOVOPS)
return 0;
if (ecf_flags & ECF_CONST)
if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
eaf_flags &= ~implicit_const_eaf_flags;
else if (ecf_flags & ECF_PURE)
eaf_flags &= ~implicit_pure_eaf_flags;
@ -319,8 +317,6 @@ eaf_flags_useful_p (vec <eaf_flags_t> &flags, int ecf_flags)
bool
modref_summary::useful_p (int ecf_flags, bool check_flags)
{
if (ecf_flags & ECF_NOVOPS)
return false;
if (arg_flags.length () && !check_flags)
return true;
if (check_flags && eaf_flags_useful_p (arg_flags, ecf_flags))
@ -331,7 +327,7 @@ modref_summary::useful_p (int ecf_flags, bool check_flags)
if (check_flags
&& remove_useless_eaf_flags (static_chain_flags, ecf_flags, false))
return true;
if (ecf_flags & ECF_CONST)
if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
return false;
if (loads && !loads->every_base)
return true;
@ -405,8 +401,6 @@ modref_summary_lto::~modref_summary_lto ()
bool
modref_summary_lto::useful_p (int ecf_flags, bool check_flags)
{
if (ecf_flags & ECF_NOVOPS)
return false;
if (arg_flags.length () && !check_flags)
return true;
if (check_flags && eaf_flags_useful_p (arg_flags, ecf_flags))
@ -417,7 +411,7 @@ modref_summary_lto::useful_p (int ecf_flags, bool check_flags)
if (check_flags
&& remove_useless_eaf_flags (static_chain_flags, ecf_flags, false))
return true;
if (ecf_flags & ECF_CONST)
if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
return false;
if (loads && !loads->every_base)
return true;
@ -2321,10 +2315,6 @@ analyze_parms (modref_summary *summary, modref_summary_lto *summary_lto,
tree retslot = NULL;
tree static_chain = NULL;
/* For novops functions we have nothing to gain by EAF flags. */
if (ecf_flags & ECF_NOVOPS)
return;
/* If there is return slot, look up its SSA name. */
if (DECL_RESULT (current_function_decl)
&& DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
@ -2471,6 +2461,11 @@ analyze_function (function *f, bool ipa)
modref_summary *summary = NULL;
modref_summary_lto *summary_lto = NULL;
bool past_flags_known = false;
auto_vec <eaf_flags_t> past_flags;
int past_retslot_flags = 0;
int past_static_chain_flags = 0;
/* Initialize the summary.
If we run in local mode there is possibly pre-existing summary from
IPA pass. Dump it so it is easy to compare if mod-ref info has
@ -2490,6 +2485,11 @@ analyze_function (function *f, bool ipa)
fprintf (dump_file, "Past summary:\n");
optimization_summaries->get
(cgraph_node::get (f->decl))->dump (dump_file);
past_flags.reserve_exact (summary->arg_flags.length ());
past_flags.splice (summary->arg_flags);
past_retslot_flags = summary->retslot_flags;
past_static_chain_flags = summary->static_chain_flags;
past_flags_known = true;
}
optimization_summaries->remove (cgraph_node::get (f->decl));
}
@ -2630,6 +2630,108 @@ analyze_function (function *f, bool ipa)
if (summary_lto)
summary_lto->dump (dump_file);
dump_modref_edge_summaries (dump_file, fnode, 2);
/* To simplify debugging, compare IPA and local solutions. */
if (past_flags_known && summary)
{
size_t len = summary->arg_flags.length ();
if (past_flags.length () > len)
len = past_flags.length ();
for (size_t i = 0; i < len; i++)
{
int old_flags = i < past_flags.length () ? past_flags[i] : 0;
int new_flags = i < summary->arg_flags.length ()
? summary->arg_flags[i] : 0;
old_flags = remove_useless_eaf_flags
(old_flags, flags_from_decl_or_type (current_function_decl),
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))));
if (old_flags != new_flags)
{
if ((old_flags & ~new_flags) == 0)
fprintf (dump_file, " Flags for param %i improved:",
(int)i);
else if ((new_flags & ~old_flags) == 0)
fprintf (dump_file, " Flags for param %i worsened:",
(int)i);
else
fprintf (dump_file, " Flags for param %i changed:",
(int)i);
dump_eaf_flags (dump_file, old_flags, false);
fprintf (dump_file, " -> ");
dump_eaf_flags (dump_file, new_flags, true);
}
}
past_retslot_flags = remove_useless_eaf_flags
(past_retslot_flags,
flags_from_decl_or_type (current_function_decl),
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))));
if (past_retslot_flags != summary->retslot_flags)
{
if ((past_retslot_flags & ~summary->retslot_flags) == 0)
fprintf (dump_file, " Flags for retslot improved:");
else if ((summary->retslot_flags & ~past_retslot_flags) == 0)
fprintf (dump_file, " Flags for retslot worsened:");
else
fprintf (dump_file, " Flags for retslot changed:");
dump_eaf_flags (dump_file, past_retslot_flags, false);
fprintf (dump_file, " -> ");
dump_eaf_flags (dump_file, summary->retslot_flags, true);
}
past_static_chain_flags = remove_useless_eaf_flags
(past_static_chain_flags,
flags_from_decl_or_type (current_function_decl),
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))));
if (past_static_chain_flags != summary->static_chain_flags)
{
if ((past_static_chain_flags & ~summary->static_chain_flags) == 0)
fprintf (dump_file, " Flags for static chain improved:");
else if ((summary->static_chain_flags
& ~past_static_chain_flags) == 0)
fprintf (dump_file, " Flags for static chain worsened:");
else
fprintf (dump_file, " Flags for static chain changed:");
dump_eaf_flags (dump_file, past_static_chain_flags, false);
fprintf (dump_file, " -> ");
dump_eaf_flags (dump_file, summary->static_chain_flags, true);
}
}
else if (past_flags_known && !summary)
{
for (size_t i = 0; i < past_flags.length (); i++)
{
int old_flags = past_flags[i];
old_flags = remove_useless_eaf_flags
(old_flags, flags_from_decl_or_type (current_function_decl),
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))));
if (old_flags)
{
fprintf (dump_file, " Flags for param %i worsened:",
(int)i);
dump_eaf_flags (dump_file, old_flags, false);
fprintf (dump_file, " -> \n");
}
}
past_retslot_flags = remove_useless_eaf_flags
(past_retslot_flags,
flags_from_decl_or_type (current_function_decl),
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))));
if (past_retslot_flags)
{
fprintf (dump_file, " Flags for retslot worsened:");
dump_eaf_flags (dump_file, past_retslot_flags, false);
fprintf (dump_file, " ->\n");
}
past_static_chain_flags = remove_useless_eaf_flags
(past_static_chain_flags,
flags_from_decl_or_type (current_function_decl),
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))));
if (past_static_chain_flags)
{
fprintf (dump_file, " Flags for static chain worsened:");
dump_eaf_flags (dump_file, past_static_chain_flags, false);
fprintf (dump_file, " ->\n");
}
}
}
}
@ -4039,12 +4141,15 @@ modref_merge_call_site_flags (escape_summary *sum,
modref_summary *summary,
modref_summary_lto *summary_lto,
tree caller,
int ecf_flags)
cgraph_edge *e,
int caller_ecf_flags,
int callee_ecf_flags,
bool binds_to_current_def)
{
escape_entry *ee;
unsigned int i;
bool changed = false;
bool ignore_stores = ignore_stores_p (caller, ecf_flags);
bool ignore_stores = ignore_stores_p (caller, callee_ecf_flags);
/* If we have no useful info to propagate. */
if ((!cur_summary || !cur_summary->arg_flags.length ())
@ -4055,6 +4160,8 @@ modref_merge_call_site_flags (escape_summary *sum,
{
int flags = 0;
int flags_lto = 0;
/* Returning the value is already accounted to at local propagation. */
int implicit_flags = EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY;
if (summary && ee->arg < summary->arg_flags.length ())
flags = summary->arg_flags[ee->arg];
@ -4066,14 +4173,43 @@ modref_merge_call_site_flags (escape_summary *sum,
flags = deref_flags (flags, ignore_stores);
flags_lto = deref_flags (flags_lto, ignore_stores);
}
else if (ignore_stores)
if (ignore_stores)
implicit_flags |= ignore_stores_eaf_flags;
if (callee_ecf_flags & ECF_PURE)
implicit_flags |= implicit_pure_eaf_flags;
if (callee_ecf_flags & (ECF_CONST | ECF_NOVOPS))
implicit_flags |= implicit_const_eaf_flags;
class fnspec_summary *fnspec_sum = fnspec_summaries->get (e);
if (fnspec_sum)
{
flags |= ignore_stores_eaf_flags;
flags_lto |= ignore_stores_eaf_flags;
attr_fnspec fnspec (fnspec_sum->fnspec);
int fnspec_flags = 0;
if (fnspec.arg_specified_p (ee->arg))
{
if (!fnspec.arg_used_p (ee->arg))
fnspec_flags = EAF_UNUSED;
else
{
if (fnspec.arg_direct_p (ee->arg))
fnspec_flags |= EAF_DIRECT;
if (fnspec.arg_noescape_p (ee->arg))
fnspec_flags |= EAF_NOESCAPE | EAF_NODIRECTESCAPE;
if (fnspec.arg_readonly_p (ee->arg))
fnspec_flags |= EAF_NOCLOBBER;
}
}
implicit_flags |= fnspec_flags;
}
if (!ee->direct)
implicit_flags = deref_flags (implicit_flags, ignore_stores);
flags |= implicit_flags;
flags_lto |= implicit_flags;
if (!binds_to_current_def && (flags || flags_lto))
{
flags = interposable_eaf_flags (flags, implicit_flags);
flags_lto = interposable_eaf_flags (flags_lto, implicit_flags);
}
/* Returning the value is already accounted to at local propagation. */
flags |= ee->min_flags | EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY;
flags_lto |= ee->min_flags | EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY;
/* Noescape implies that value also does not escape directly.
Fnspec machinery does set both so compensate for this. */
if (flags & EAF_NOESCAPE)
@ -4095,7 +4231,7 @@ modref_merge_call_site_flags (escape_summary *sum,
if ((f & flags) != f)
{
f = remove_useless_eaf_flags
(f & flags, ecf_flags,
(f & flags, caller_ecf_flags,
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (caller))));
changed = true;
}
@ -4112,7 +4248,7 @@ modref_merge_call_site_flags (escape_summary *sum,
if ((f & flags_lto) != f)
{
f = remove_useless_eaf_flags
(f & flags_lto, ecf_flags,
(f & flags_lto, caller_ecf_flags,
VOID_TYPE_P (TREE_TYPE (TREE_TYPE (caller))));
changed = true;
}
@ -4146,6 +4282,7 @@ modref_propagate_flags_in_scc (cgraph_node *component_node)
if (!cur_summary && !cur_summary_lto)
continue;
int caller_ecf_flags = flags_from_decl_or_type (cur->decl);
if (dump_file)
fprintf (dump_file, " Processing %s%s%s\n",
@ -4164,7 +4301,11 @@ modref_propagate_flags_in_scc (cgraph_node *component_node)
changed |= modref_merge_call_site_flags
(sum, cur_summary, cur_summary_lto,
NULL, NULL,
node->decl, e->indirect_info->ecf_flags);
node->decl,
e,
caller_ecf_flags,
e->indirect_info->ecf_flags,
false);
}
if (!cur_summary && !cur_summary_lto)
@ -4216,7 +4357,11 @@ modref_propagate_flags_in_scc (cgraph_node *component_node)
changed |= modref_merge_call_site_flags
(sum, cur_summary, cur_summary_lto,
callee_summary, callee_summary_lto,
node->decl, ecf_flags);
node->decl,
callee_edge,
caller_ecf_flags,
ecf_flags,
callee->binds_to_current_def_p ());
if (dump_file && changed)
{
if (cur_summary)

29
gcc/ipa-modref.h
View File

@ -58,4 +58,33 @@ static const int implicit_pure_eaf_flags = EAF_NOCLOBBER | EAF_NOESCAPE
static const int ignore_stores_eaf_flags = EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE
| EAF_NODIRECTESCAPE;
/* If function does not bind to current def (i.e. it is inline in comdat
section), the modref analysis may not match the behaviour of function
which will be later symbol interposed to. All side effects must match
however it is possible that the other function body contains more loads
which may trap.
MODREF_FLAGS are flags determined by analysis of function body while
FLAGS are flags known otherwise (i.e. by fnspec, pure/const attributes
etc.) */
static inline int
interposable_eaf_flags (int modref_flags, int flags)
{
/* If parameter was previously unused, we know it is only read
and its value is not used. */
if ((modref_flags & EAF_UNUSED) && !(flags & EAF_UNUSED))
{
modref_flags &= ~EAF_UNUSED;
modref_flags |= EAF_NOESCAPE | EAF_NOT_RETURNED
| EAF_NOT_RETURNED_DIRECTLY | EAF_NOCLOBBER;
}
/* We can not deterine that value is not read at all. */
if ((modref_flags & EAF_NOREAD) && !(flags & EAF_NOREAD))
modref_flags &= ~EAF_NOREAD;
/* Clear direct flags so we also know that value is possibly read
indirectly. */
if ((modref_flags & EAF_DIRECT) && !(flags & EAF_DIRECT))
modref_flags &= ~EAF_DIRECT;
return modref_flags;
}
#endif