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Improve handling of memory operands in ipa-icf 3/4 

this patch is based on Maritn's patch
https://gcc.gnu.org/legacy-ml/gcc-patches/2019-11/msg02633.html
however based on new code that track and compare memory accesses
so it can be implemented correctly.

As shown here
https://gcc.gnu.org/pipermail/gcc-patches/2020-November/558773.html
the most common reason for function body being streamed in but merging to fail
is the mismatch in base alias set.

This patch collect base and ref types ao_alias_ptr types, stream them to WPA
and at WPA time hash is produced. Now we can use alias_sets since these these
are assumed to be same as ltrans time alias sets. This is currently not always
true - but that is pre-existing issue.  I will try to produce a testcase and
make followup patch on this (that will stream out ODR types with TYPE_CANONICAL
that is !ODR as !ODR type). However for this patch this is not a problem since
the real alias sets are finer but definitly not coarser.

We may make it possible to use canonical type hash and save some streaming, but
I think it would be better to wait for next stage1 since it is not completely
trivial WRT ODR types: either we hash ODR type names and then hash values would
be too coarse for cases we got conflict betwen C and C++ type or we do not
stream and will again get into trouble with hash values being too weak. Tried
that - we get a lot of types that are struturally same but distinguished by
ODR names (from template instantiations).

As followup I will add code for merging with mismatched base alias sets.  This
makes the aforementioned problem about ODR names less pronounced but it is
still present on pointer loads/stores which requires REF alias set mismatches.

2020-11-13  Jan Hubicka  <hubicka@ucw.cz>
	    Martin Liska  <mliska@suse.cz>

	* ipa-icf.c: Include data-streamer.h and alias.h.
	(sem_function::sem_function): Initialize memory_access_types
	and m_alias_sets_hash.
	(sem_function::hash_stmt): For memory accesses and when going to
	do lto streaming add base and ref types into memory_access_types.
	(sem_item_optimizer::write_summary): Stream memory access types.
	(sem_item_optimizer::read_section): Likewise and also iniitalize
	m_alias_sets_hash.
	(sem_item_optimizer::execute): Call
	sem_item_optimizer::update_hash_by_memory_access_type.
	(sem_item_optimizer::update_hash_by_memory_access_type): Updat.
	* ipa-icf.h (sem_function): Add memory_access_types and
	m_alias_sets_hash.
This commit is contained in:
Jan Hubicka 2020-11-17 15:41:06 +01:00
parent 18dd295638
commit afa6adbd6c
2 changed files with 76 additions and 5 deletions
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71
gcc/ipa-icf.c
View File

@ -66,6 +66,7 @@ along with GCC; see the file COPYING3. If not see
#include "coverage.h"
#include "gimple-pretty-print.h"
#include "data-streamer.h"
#include "tree-streamer.h"
#include "fold-const.h"
#include "calls.h"
#include "varasm.h"
@ -86,6 +87,7 @@ along with GCC; see the file COPYING3. If not see
#include "dbgcnt.h"
#include "tree-vector-builder.h"
#include "symtab-thunks.h"
#include "alias.h"
using namespace ipa_icf_gimple;
@ -227,14 +229,16 @@ hash_map<const_tree, hashval_t> sem_item::m_type_hash_cache;
/* Semantic function constructor that uses STACK as bitmap memory stack. */
sem_function::sem_function (bitmap_obstack *stack)
: sem_item (FUNC, stack), m_checker (NULL), m_compared_func (NULL)
: sem_item (FUNC, stack), memory_access_types (), m_alias_sets_hash (0),
m_checker (NULL), m_compared_func (NULL)
{
bb_sizes.create (0);
bb_sorted.create (0);
}
sem_function::sem_function (cgraph_node *node, bitmap_obstack *stack)
: sem_item (FUNC, node, stack), m_checker (NULL), m_compared_func (NULL)
: sem_item (FUNC, node, stack), memory_access_types (),
m_alias_sets_hash (0), m_checker (NULL), m_compared_func (NULL)
{
bb_sizes.create (0);
bb_sorted.create (0);
@ -1438,9 +1442,30 @@ sem_function::hash_stmt (gimple *stmt, inchash::hash &hstate)
/* All these statements are equivalent if their operands are. */
for (unsigned i = 0; i < gimple_num_ops (stmt); ++i)
m_checker->hash_operand (gimple_op (stmt, i), hstate, 0,
func_checker::get_operand_access_type
(&map, gimple_op (stmt, i)));
{
func_checker::operand_access_type
access_type = func_checker::get_operand_access_type
(&map, gimple_op (stmt, i));
m_checker->hash_operand (gimple_op (stmt, i), hstate, 0,
access_type);
/* For memory accesses when hasing for LTO stremaing record
base and ref alias ptr types so we can compare them at WPA
time without having to read actual function body. */
if (access_type == func_checker::OP_MEMORY
&& lto_streaming_expected_p ()
&& flag_strict_aliasing)
{
ao_ref ref;
ao_ref_init (&ref, gimple_op (stmt, i));
tree t = ao_ref_alias_ptr_type (&ref);
if (variably_modified_type_p (t, NULL_TREE))
memory_access_types.safe_push (t);
t = ao_ref_base_alias_ptr_type (&ref);
if (variably_modified_type_p (t, NULL_TREE))
memory_access_types.safe_push (t);
}
}
/* Consider nocf_check attribute in hash as it affects code
generation. */
if (code == GIMPLE_CALL
@ -2129,6 +2154,14 @@ sem_item_optimizer::write_summary (void)
streamer_write_uhwi_stream (ob->main_stream, node_ref);
streamer_write_uhwi (ob, (*item)->get_hash ());
if ((*item)->type == FUNC)
{
sem_function *fn = static_cast<sem_function *> (*item);
streamer_write_uhwi (ob, fn->memory_access_types.length ());
for (unsigned i = 0; i < fn->memory_access_types.length (); i++)
stream_write_tree (ob, fn->memory_access_types[i], true);
}
}
}
@ -2180,6 +2213,18 @@ sem_item_optimizer::read_section (lto_file_decl_data *file_data,
cgraph_node *cnode = dyn_cast <cgraph_node *> (node);
sem_function *fn = new sem_function (cnode, &m_bmstack);
unsigned count = streamer_read_uhwi (&ib_main);
inchash::hash hstate (0);
if (flag_incremental_link == INCREMENTAL_LINK_LTO)
fn->memory_access_types.reserve_exact (count);
for (unsigned i = 0; i < count; i++)
{
tree type = stream_read_tree (&ib_main, data_in);
hstate.add_int (get_deref_alias_set (type));
if (flag_incremental_link == INCREMENTAL_LINK_LTO)
fn->memory_access_types.quick_push (type);
}
fn->m_alias_sets_hash = hstate.end ();
fn->set_hash (hash);
m_items.safe_push (fn);
}
@ -2376,6 +2421,7 @@ sem_item_optimizer::execute (void)
build_graph ();
update_hash_by_addr_refs ();
update_hash_by_memory_access_type ();
build_hash_based_classes ();
if (dump_file)
@ -2513,6 +2559,21 @@ sem_item_optimizer::update_hash_by_addr_refs ()
m_items[i]->set_hash (m_items[i]->global_hash);
}
void
sem_item_optimizer::update_hash_by_memory_access_type ()
{
for (unsigned i = 0; i < m_items.length (); i++)
{
if (m_items[i]->type == FUNC)
{
sem_function *fn = static_cast<sem_function *> (m_items[i]);
inchash::hash hstate (fn->get_hash ());
hstate.add_int (fn->m_alias_sets_hash);
fn->set_hash (hstate.end ());
}
}
}
/* Congruence classes are built by hash value. */
void

10
gcc/ipa-icf.h
View File

@ -371,12 +371,19 @@ public:
/* GIMPLE codes hash value. */
hashval_t gcode_hash;
/* Vector of subpart of memory access types. */
vec<tree> memory_access_types;
/* Total number of SSA names used in the function. */
unsigned ssa_names_size;
/* Array of structures for all basic blocks. */
vec <ipa_icf_gimple::sem_bb *> bb_sorted;
/* Hash of canonical types used for memory references in the
function. */
hashval_t m_alias_sets_hash;
/* Return true if parameter I may be used. */
bool param_used_p (unsigned int i);
@ -541,6 +548,9 @@ private:
/* For each semantic item, append hash values of references. */
void update_hash_by_addr_refs ();
/* Update hash by canonical types of memory accesses. */
void update_hash_by_memory_access_type ();
/* Congruence classes are built by hash value. */
void build_hash_based_classes (void);