tree-optimization/99407 - DSE with data-ref analysis
Commit Message
The following resolves the issue that DSE cannot handle references
with variable offsets well when identifying possible uses of a store.
Instead of just relying on ref_maybe_used_by_stmt_p we use data-ref
analysis, making sure to perform that at most once per stmt. The
new mode is only exercised by the DSE pass before loop optimization
as specified by a new pass parameter and when expensive optimizations
are enabled, so it's disabled below -O2.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/99407
* tree-ssa-dse.c (dse_stmt_to_dr_map): New global.
(dse_classify_store): Use data-ref analysis to disambiguate more uses.
(pass_dse::use_dr_analysis_p): New pass parameter.
(pass_dse::set_pass_param): Implement.
(pass_dse::execute): Allocate and deallocate dse_stmt_to_dr_map.
* gcc.dg/vect/tsvc/vect-tsvc-s243.c: Remove XFAIL.
---
gcc/passes.def | 2 +-
.../gcc.dg/vect/tsvc/vect-tsvc-s243.c | 2 +-
gcc/tree-ssa-dse.cc | 51 ++++++++++++++++++-
3 files changed, 52 insertions(+), 3 deletions(-)
@@ -263,7 +263,7 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_sancov);
NEXT_PASS (pass_asan);
NEXT_PASS (pass_tsan);
- NEXT_PASS (pass_dse);
+ NEXT_PASS (pass_dse, true /* use DR analysis */);
NEXT_PASS (pass_dce);
/* Pass group that runs when 1) enabled, 2) there are loops
in the function. Make sure to run pass_fix_loops before
@@ -38,4 +38,4 @@ int main (int argc, char **argv)
return 0;
}
-/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" } } */
@@ -18,6 +18,7 @@ along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#include "config.h"
+#define INCLUDE_MEMORY
#include "system.h"
#include "coretypes.h"
#include "backend.h"
@@ -45,6 +46,8 @@ along with GCC; see the file COPYING3. If not see
#include "ipa-modref.h"
#include "target.h"
#include "tree-ssa-loop-niter.h"
+#include "cfgloop.h"
+#include "tree-data-ref.h"
/* This file implements dead store elimination.
@@ -937,6 +940,10 @@ contains_phi_arg (gphi *phi, tree arg)
return false;
}
+/* Hash map of the memory use in a GIMPLE assignment to its
+ data reference. If NULL data-ref analysis isn't used. */
+static hash_map<gimple *, data_reference_p> *dse_stmt_to_dr_map;
+
/* A helper of dse_optimize_stmt.
Given a GIMPLE_ASSIGN in STMT that writes to REF, classify it
according to downstream uses and defs. Sets *BY_CLOBBER_P to true
@@ -951,6 +958,8 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
gimple *temp;
int cnt = 0;
auto_bitmap visited;
+ std::unique_ptr<data_reference, void(*)(data_reference_p)>
+ dra (nullptr, free_data_ref);
if (by_clobber_p)
*by_clobber_p = true;
@@ -1019,6 +1028,28 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
/* If the statement is a use the store is not dead. */
else if (ref_maybe_used_by_stmt_p (use_stmt, ref))
{
+ if (dse_stmt_to_dr_map
+ && ref->ref
+ && is_gimple_assign (use_stmt))
+ {
+ if (!dra)
+ dra.reset (create_data_ref (NULL, NULL, ref->ref, stmt,
+ false, false));
+ bool existed_p;
+ data_reference_p &drb
+ = dse_stmt_to_dr_map->get_or_insert (use_stmt, &existed_p);
+ if (!existed_p)
+ drb = create_data_ref (NULL, NULL,
+ gimple_assign_rhs1 (use_stmt),
+ use_stmt, false, false);
+ if (!dr_may_alias_p (dra.get (), drb, NULL))
+ {
+ if (gimple_vdef (use_stmt))
+ defs.safe_push (use_stmt);
+ continue;
+ }
+ }
+
/* Handle common cases where we can easily build an ao_ref
structure for USE_STMT and in doing so we find that the
references hit non-live bytes and thus can be ignored.
@@ -1535,14 +1566,21 @@ class pass_dse : public gimple_opt_pass
{
public:
pass_dse (gcc::context *ctxt)
- : gimple_opt_pass (pass_data_dse, ctxt)
+ : gimple_opt_pass (pass_data_dse, ctxt), use_dr_analysis_p (false)
{}
/* opt_pass methods: */
opt_pass * clone () final override { return new pass_dse (m_ctxt); }
+ void set_pass_param (unsigned n, bool param) final override
+ {
+ gcc_assert (n == 0);
+ use_dr_analysis_p = param;
+ }
bool gate (function *) final override { return flag_tree_dse != 0; }
unsigned int execute (function *) final override;
+private:
+ bool use_dr_analysis_p;
}; // class pass_dse
unsigned int
@@ -1554,6 +1592,8 @@ pass_dse::execute (function *fun)
need_eh_cleanup = BITMAP_ALLOC (NULL);
need_ab_cleanup = BITMAP_ALLOC (NULL);
auto_sbitmap live_bytes (param_dse_max_object_size);
+ if (flag_expensive_optimizations && use_dr_analysis_p)
+ dse_stmt_to_dr_map = new hash_map<gimple *, data_reference_p>;
renumber_gimple_stmt_uids (fun);
@@ -1644,6 +1684,15 @@ pass_dse::execute (function *fun)
if (released_def)
free_numbers_of_iterations_estimates (fun);
+ if (flag_expensive_optimizations && use_dr_analysis_p)
+ {
+ for (auto i = dse_stmt_to_dr_map->begin ();
+ i != dse_stmt_to_dr_map->end (); ++i)
+ free_data_ref ((*i).second);
+ delete dse_stmt_to_dr_map;
+ dse_stmt_to_dr_map = NULL;
+ }
+
return todo;
}