re PR target/92038 (Extremely inefficient x86_64 code for trivally copyable…

re PR target/92038 (Extremely inefficient x86_64 code for trivally copyable types passed in registers.)

	PR target/92038
	* gimple-ssa-store-merging.c (find_constituent_stores): For return
	value only, return non-NULL if there is a single non-clobber
	constituent store even if there are constituent clobbers and return
	one of clobber constituent stores if all constituent stores are
	clobbers.
	(split_group): Handle clobbers.
	(imm_store_chain_info::output_merged_store): When computing
	bzero_first, look after all clobbers at the start.  Don't count
	clobber stmts in orig_num_stmts, except if the first orig store is
	a clobber covering the whole area and split_stores cover the whole
	area, consider equal number of stmts ok.  Punt if split_stores
	contains only ->orig stores and their number plus number of original
	clobbers is equal to original number of stmts.  For ->orig, look past
	clobbers in the constituent stores.
	(imm_store_chain_info::output_merged_stores): Don't remove clobber
	stmts.
	(rhs_valid_for_store_merging_p): Don't return false for clobber stmt
	rhs.
	(store_valid_for_store_merging_p): Allow clobber stmts.
	(verify_clear_bit_region_be): Fix up a thinko in function comment.

	* g++.dg/opt/store-merging-1.C: New test.
	* g++.dg/opt/store-merging-2.C: New test.
	* g++.dg/opt/store-merging-3.C: New test.

From-SVN: r277963

gcc/ChangeLog

 2019-11-08  Jakub Jelinek  <jakub@redhat.com>
 
+	PR target/92038
+	* gimple-ssa-store-merging.c (find_constituent_stores): For return
+	value only, return non-NULL if there is a single non-clobber
+	constituent store even if there are constituent clobbers and return
+	one of clobber constituent stores if all constituent stores are
+	clobbers.
+	(split_group): Handle clobbers.
+	(imm_store_chain_info::output_merged_store): When computing
+	bzero_first, look after all clobbers at the start.  Don't count
+	clobber stmts in orig_num_stmts, except if the first orig store is
+	a clobber covering the whole area and split_stores cover the whole
+	area, consider equal number of stmts ok.  Punt if split_stores
+	contains only ->orig stores and their number plus number of original
+	clobbers is equal to original number of stmts.  For ->orig, look past
+	clobbers in the constituent stores.
+	(imm_store_chain_info::output_merged_stores): Don't remove clobber
+	stmts.
+	(rhs_valid_for_store_merging_p): Don't return false for clobber stmt
+	rhs.
+	(store_valid_for_store_merging_p): Allow clobber stmts.
+	(verify_clear_bit_region_be): Fix up a thinko in function comment.
+
 	PR c++/92384
 	* function.c (assign_parm_setup_block, assign_parm_setup_stack): Don't
 	copy TYPE_EMPTY_P arguments from data->entry_parm to data->stack_parm

gcc/testsuite/ChangeLog

 2019-11-08  Jakub Jelinek  <jakub@redhat.com>
 
+	PR target/92038
+	* g++.dg/opt/store-merging-1.C: New test.
+	* g++.dg/opt/store-merging-2.C: New test.
+	* g++.dg/opt/store-merging-3.C: New test.
+
 	PR c++/92384
 	* g++.dg/torture/pr92384.C: New test.
 

gcc/testsuite/g++.dg/opt/store-merging-1.C

+// PR target/92038
+// { dg-do compile { target int32 } }
+// { dg-require-effective-target store_merge }
+// { dg-options "-O2 -flifetime-dse=2 -fdump-tree-store-merging-details" }
+// { dg-final { scan-tree-dump "New sequence of \[12] stores to replace old one of 2 stores" "store-merging" } }
+
+struct S { S () : a (0), b (0) {} int a; char b; char c[3]; };
+void foo (struct S);
+void bar (void) { struct S s; foo (s); }

gcc/testsuite/g++.dg/opt/store-merging-2.C

+// PR target/92038
+// { dg-do compile { target int32 } }
+// { dg-require-effective-target store_merge }
+// { dg-options "-O2 -flifetime-dse=2 -fdump-tree-store-merging-details" }
+// { dg-final { scan-tree-dump "New sequence of 2 stores to replace old one of 3 stores" "store-merging" } }
+
+struct T { char a[128]; };
+struct S { S () : a () { a.a[12] = 0; a.a[13] = 1; a.a[14] = 0; a.a[15] = 6; } T a; };
+void foo (S &);
+void bar (void) { S s; foo (s); }

gcc/testsuite/g++.dg/opt/store-merging-3.C

+// PR target/92038
+// { dg-do compile }
+// { dg-options "-O2 -flifetime-dse=2" }
+
+struct A { A (int); int a; };
+struct B { B () : b(0) {} A b; };
+struct C { C () : c () {} bool c; B d; };
+void foo () { C d; }