Report vectorization problems via a new opt_problem class

This is v3 of the patch; previous versions were:
  v2: https://gcc.gnu.org/ml/gcc-patches/2018-07/msg00446.html
  v1: https://gcc.gnu.org/ml/gcc-patches/2018-06/msg01462.html

This patch introduces a class opt_problem, along with wrapper
classes for bool (opt_result) and for pointers (e.g. opt_loop_vec_info
for loop_vec_info).

opt_problem instances are created when an optimization problem
is encountered, but only if dump_enabled_p.  They are manually
propagated up the callstack, and are manually reported at the
"top level" of an optimization if dumping is enabled, to give the user
a concise summary of the problem *after* the failure is reported.
In particular, the location of the problematic statement is
captured and emitted, rather than just the loop's location.

For example:

no-vfa-vect-102.c:24:3: missed: couldn't vectorize loop
no-vfa-vect-102.c:27:7: missed: statement clobbers memory: __asm__ __volatile__("" :  :  : "memory");

Changed in v3:
* This version bootstraps and passes regression testing (on
  x86_64-pc-linux-gnu).
* added selftests, to exercise the opt_problem machinery
* removed the "bool to opt_result" ctor, so that attempts to
  use e.g. return a bool from an opt_result-returning function
  will fail at compile time
* use formatted printing within opt_problem ctor to replace the
  various dump_printf_loc calls
* dropped i18n
* changed the sense of vect_analyze_data_ref_dependence's return
  value (see the ChangeLog)
* add MSG_PRIORITY_REEMITTED, so that -fopt-info can show the
  messages, without them messing up the counts in scan-tree-dump-times
  in DejaGnu tests

gcc/ChangeLog:
	* Makefile.in (OBJS): Add opt-problem.o.
	* dump-context.h: Include "selftest.h.
	(selftest::temp_dump_context): New forward decl.
	(class dump_context): Make friend of class
	selftest::temp_dump_context.
	(dump_context::dump_loc_immediate): New decl.
	(class dump_pretty_printer): Move here from dumpfile.c.
	(class temp_dump_context): Move to namespace selftest.
	(temp_dump_context::temp_dump_context): Add param
	"forcibly_enable_dumping".
	(selftest::verify_dumped_text):
	(ASSERT_DUMPED_TEXT_EQ): Move here from dumpfile.c.
	(selftest::verify_item):
	(ASSERT_IS_TEXT): Move here from dumpfile.c.
	(ASSERT_IS_TREE): Likewise.
	(ASSERT_IS_GIMPLE): Likewise.
	* dumpfile.c (dump_context::dump_loc): Move immediate dumping
	to...
	(dump_context::dump_loc_immediate): ...this new function.
	(class dump_pretty_printer): Move to dump-context.h.
	(dump_switch_p_1): Don't enable MSG_PRIORITY_REEMITTED.
	(opt_info_switch_p_1): Enable MSG_PRIORITY_REEMITTED.
	(temp_dump_context::temp_dump_context): Move to "selftest"
	namespace.  Add param "forcibly_enable_dumping", and use it to
	conditionalize the use of m_pp;
	(selftest::verify_dumped_text): Make non-static.
	(ASSERT_DUMPED_TEXT_EQ): Move to dump-context.h.
	(selftest::verify_item): Make non-static.
	(ASSERT_IS_TEXT): Move to dump-context.h.
	(ASSERT_IS_TREE): Likewise.
	(ASSERT_IS_GIMPLE): Likewise.
	(selftest::test_capture_of_dump_calls): Pass "true" for new
	param of temp_dump_context.
	* dumpfile.h (enum dump_flag): Add MSG_PRIORITY_REEMITTED, adding
	it to MSG_ALL_PRIORITIES.  Update values of TDF_COMPARE_DEBUG and
	TDF_COMPARE_DEBUG.
	* opt-problem.cc: New file.
	* opt-problem.h: New file.
	* optinfo-emit-json.cc
	(selftest::test_building_json_from_dump_calls): Pass "true" for
	new param of temp_dump_context.
	* optinfo.cc (optinfo_kind_to_dump_flag): New function.
	(optinfo::emit_for_opt_problem): New function.
	(optinfo::emit): Clarity which emit_item is used.
	* optinfo.h (optinfo::get_dump_location): New accessor.
	(optinfo::emit_for_opt_problem): New decl.
	(optinfo::emit): Make const.
	* selftest-run-tests.c (selftest::run_tests): Call
	selftest::opt_problem_cc_tests.
	* selftest.h (selftest::opt_problem_cc_tests): New decl.
	* tree-data-ref.c (dr_analyze_innermost): Convert return type from
	bool to opt_result, converting fprintf messages to
	opt_result::failure_at calls.  Add "stmt" param for use by the
	failure_at calls.
	(create_data_ref): Pass "stmt" to the dr_analyze_innermost call.
	(runtime_alias_check_p): Convert return type from bool to
	opt_result, converting dump_printf calls to
	opt_result::failure_at, using the statement DDR_A for their
	location.
	(find_data_references_in_stmt): Convert return type from bool to
	opt_result, converting "return false" to opt_result::failure_at
	with a new message.
	* tree-data-ref.h: Include "opt-problem.h".
	(dr_analyze_innermost): Convert return type from bool to opt_result,
	and add a const gimple * param.
	(find_data_references_in_stmt): Convert return type from bool to
	opt_result.
	(runtime_alias_check_p): Likewise.
	* tree-predcom.c (find_looparound_phi): Pass "init_stmt" to
	dr_analyze_innermost.
	* tree-vect-data-refs.c (vect_mark_for_runtime_alias_test):
	Convert return type from bool to opt_result, adding a message for
	the PARAM_VECT_MAX_VERSION_FOR_ALIAS_CHECKS zero case.
	(vect_analyze_data_ref_dependence): Convert return type from bool
	to opt_result.  Change sense of return type from "false"
	effectively meaning "no problems" to "false" meaning a problem,
	so that "return false" becomes "return opt_result::success".
	Convert "return true" calls to opt_result::failure_at, using
	the location of statement A rather than vect_location.
	(vect_analyze_data_ref_dependences): Convert return type from bool
	to opt_result.
	(verify_data_ref_alignment): Likewise, converting dump_printf_loc
	calls to opt_result::failure_at, using the stmt location rather
	than vect_location.
	(vect_verify_datarefs_alignment): Convert return type from bool
	to opt_result.
	(vect_enhance_data_refs_alignment): Likewise.  Split local "stat"
	into multiple more-tightly-scoped copies.
	(vect_analyze_data_refs_alignment): Convert return type from bool
	to opt_result.
	(vect_analyze_data_ref_accesses): Likewise, converting a
	"return false" to a "return opt_result::failure_at", adding a
	new message.
	(vect_prune_runtime_alias_test_list): Convert return type from
	bool to opt_result, converting dump_printf_loc to
	opt_result::failure_at.  Add a %G to show the pertinent statement,
	and use the stmt's location rather than vect_location.
	(vect_find_stmt_data_reference): Convert return type from
	bool to opt_result, converting dump_printf_loc to
	opt_result::failure_at, using stmt's location.
	(vect_analyze_data_refs):  Convert return type from bool to
	opt_result.  Convert "return false" to "return
	opt_result::failure_at", adding messages as needed.
	* tree-vect-loop.c (vect_determine_vf_for_stmt_1): Convert return
	type from bool to opt_result.
	(vect_determine_vf_for_stmt): Likewise.
	(vect_determine_vectorization_factor): Likewise, converting
	dump_printf_loc to opt_result::failure_at, using location of phi
	rather than vect_location.
	(vect_analyze_loop_form_1): Convert return type from bool to
	opt_result, converting dump_printf_loc calls, retaining the use of
	vect_location.
	(vect_analyze_loop_form): Convert return type from loop_vec_info
	to opt_loop_vec_info.
	(vect_analyze_loop_operations): Convert return type from bool to
	opt_result, converting dump_printf_loc calls, using the location
	of phi/stmt rather than vect_location where available.  Convert
	various "return false" to "return opt_result::failure_at" with
	"unsupported phi" messages.
	(vect_get_datarefs_in_loop): Convert return type from bool to
	opt_result.  Add a message for the
	PARAM_LOOP_MAX_DATAREFS_FOR_DATADEPS failure.
	(vect_analyze_loop_2): Convert return type from bool to
	opt_result.  Ensure "ok" is set to a opt_result::failure_at before
	each "goto again;", adding new messages where needed.
	Add "unsupported grouped {store|load}" messages.
	(vect_analyze_loop): Convert return type from loop_vec_info to
	opt_loop_vec_info.
	* tree-vect-slp.c (vect_analyze_slp): Convert return type from
	bool to opt_result.
	* tree-vect-stmts.c (process_use): Likewise, converting
	dump_printf_loc call and using stmt location, rather than
	vect_location.
	(vect_mark_stmts_to_be_vectorized): Likeise.
	(vect_analyze_stmt): Likewise, adding a %G.
	(vect_get_vector_types_for_stmt): Convert return type from bool to
	opt_result, converting dump_printf_loc calls and using stmt
	location, rather than vect_location.
	(vect_get_mask_type_for_stmt): Convert return type from tree to
	opt_tree, converting dump_printf_loc calls and using stmt location.
	* tree-vectorizer.c: Include "opt-problem.h.
	(try_vectorize_loop_1): Flag "Analyzing loop at" dump message as
	MSG_PRIORITY_INTERNALS.  Convert local "loop_vinfo" from
	loop_vec_info to opt_loop_vec_info.  If if fails, and dumping is
	enabled, use it to report at the top level "couldn't vectorize
	loop" followed by the problem.
	* tree-vectorizer.h (opt_loop_vec_info): New typedef.
	(vect_mark_stmts_to_be_vectorized): Convert return type from bool
	to opt_result.
	(vect_analyze_stmt): Likewise.
	(vect_get_vector_types_for_stmt): Likewise.
	(tree vect_get_mask_type_for_stmt): Likewise.
	(vect_analyze_data_ref_dependences): Likewise.
	(vect_enhance_data_refs_alignment): Likewise.
	(vect_analyze_data_refs_alignment): Likewise.
	(vect_verify_datarefs_alignment): Likewise.
	(vect_analyze_data_ref_accesses): Likewise.
	(vect_prune_runtime_alias_test_list): Likewise.
	(vect_find_stmt_data_reference): Likewise.
	(vect_analyze_data_refs): Likewise.
	(vect_analyze_loop): Convert return type from loop_vec_info to
	opt_loop_vec_info.
	(vect_analyze_loop_form): Likewise.
	(vect_analyze_slp): Convert return type from bool to opt_result.

gcc/testsuite/ChangeLog:
	* gcc.dg/vect/nodump-vect-opt-info-2.c: New test.
	* gcc.dg/vect/vect-alias-check-4.c: Add "-fopt-info-vec-all" to
	dg-additional-options.  Add dg-message and dg-missed directives
	to verify that -fopt-info messages are written at the correct
	locations.

From-SVN: r264852

1 files changed, 335 insertions, 0 deletions

diff --git a/gcc/opt-problem.cc b/gcc/opt-problem.cc
new file mode 100644
index 00000000000..dad3a8c008b
--- /dev/null
+++ b/gcc/opt-problem.cc
@@ -0,0 +1,335 @@
+/* Rich optional information on why an optimization wasn't possible.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   Contributed by David Malcolm <dmalcolm@redhat.com>.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "backend.h"
+#include "tree.h"
+#include "gimple.h"
+#include "pretty-print.h"
+#include "opt-problem.h"
+#include "dump-context.h"
+#include "tree-pass.h"
+#include "selftest.h"
+
+/* opt_problem's ctor.
+
+   Use FMT and AP to emit a message to the "immediate" dump destinations
+   as if via:
+     dump_printf_loc (MSG_MISSED_OPTIMIZATION, loc, ...)
+
+   The optinfo_item instances are not emitted yet.  Instead, they
+   are retained internally so that the message can be replayed and
+   emitted when this problem is handled, higher up the call stack.  */
+
+opt_problem::opt_problem (const dump_location_t &loc,
+			  const char *fmt, va_list *ap)
+: m_optinfo (loc, OPTINFO_KIND_FAILURE, current_pass)
+{
+  /* We shouldn't be bothering to construct these objects if
+     dumping isn't enabled.  */
+  gcc_assert (dump_enabled_p ());
+
+  /* Update the singleton.  */
+  delete s_the_problem;
+  s_the_problem = this;
+
+  /* Print the location to the "immediate" dump destinations.  */
+  dump_context &dc = dump_context::get ();
+  dc.dump_loc (MSG_MISSED_OPTIMIZATION, loc);
+
+  /* Print the formatted string to this opt_problem's optinfo, dumping
+     the items to the "immediate" dump destinations, and storing items
+     for later retrieval.  */
+  {
+    dump_pretty_printer pp (&dump_context::get (), MSG_MISSED_OPTIMIZATION);
+
+    text_info text;
+    text.err_no = errno;
+    text.args_ptr = ap;
+    text.format_spec = fmt; /* No i18n is performed.  */
+
+    /* Phases 1 and 2, using pp_format.  */
+    pp_format (&pp, &text);
+
+    /* Phase 3: dump the items to the "immediate" dump destinations,
+       and storing them into m_optinfo for later retrieval.  */
+    pp.emit_items (&m_optinfo);
+  }
+}
+
+/* Emit this problem and delete it, clearing the current opt_problem.  */
+
+void
+opt_problem::emit_and_clear ()
+{
+  gcc_assert (this == s_the_problem);
+
+  m_optinfo.emit_for_opt_problem ();
+
+  delete this;
+  s_the_problem = NULL;
+}
+
+/* The singleton opt_problem *.  */
+
+opt_problem *opt_problem::s_the_problem;
+
+#if CHECKING_P
+
+namespace selftest {
+
+static opt_result
+function_that_succeeds ()
+{
+  return opt_result::success ();
+}
+
+/* Verify that opt_result::success works.  */
+
+static void
+test_opt_result_success ()
+{
+  /* Run all tests twice, with and then without dumping enabled.  */
+  for (int i = 0 ; i < 2; i++)
+    {
+      bool with_dumping = (i == 0);
+
+      temp_dump_context tmp (with_dumping, with_dumping,
+			     MSG_ALL_KINDS | MSG_ALL_PRIORITIES);
+
+      if (with_dumping)
+	gcc_assert (dump_enabled_p ());
+      else
+	gcc_assert (!dump_enabled_p ());
+
+      opt_result res = function_that_succeeds ();
+
+      /* Verify that "success" can be used as a "true" boolean.  */
+      ASSERT_TRUE (res);
+
+      /* Verify the underlying opt_wrapper<bool>.  */
+      ASSERT_TRUE (res.get_result ());
+      ASSERT_EQ (res.get_problem (), NULL);
+
+      /* Nothing should have been dumped.  */
+      ASSERT_DUMPED_TEXT_EQ (tmp, "");
+      optinfo *info = tmp.get_pending_optinfo ();
+      ASSERT_EQ (info, NULL);
+    }
+}
+
+/* Example of a function that fails, with a non-trivial
+   pre-canned error message.  */
+
+static opt_result
+function_that_fails (const greturn *stmt)
+{
+  gcc_assert (stmt);
+  gcc_assert (gimple_return_retval (stmt));
+
+  AUTO_DUMP_SCOPE ("function_that_fails", stmt);
+
+  return opt_result::failure_at (stmt,
+				 "can't handle return type: %T for stmt: %G",
+				 TREE_TYPE (gimple_return_retval (stmt)),
+				 static_cast <const gimple *> (stmt));
+}
+
+/* Example of a function that indirectly fails.  */
+
+static opt_result
+function_that_indirectly_fails (const greturn *stmt)
+{
+  AUTO_DUMP_SCOPE ("function_that_indirectly_fails", stmt);
+
+  opt_result res = function_that_fails (stmt);
+  if (!res)
+    return res;
+  return opt_result::success ();
+}
+
+/* Verify that opt_result::failure_at works.
+   Simulate a failure handling a stmt at one location whilst considering
+   an optimization that's notionally at another location (as a microcosm
+   of e.g. a problematic statement within a loop that prevents loop
+   vectorization).  */
+
+static void
+test_opt_result_failure_at (const line_table_case &case_)
+{
+  /* Generate a location_t for testing.  */
+  line_table_test ltt (case_);
+  const line_map_ordinary *ord_map
+    = linemap_check_ordinary (linemap_add (line_table, LC_ENTER, false,
+					   "test.c", 0));
+  linemap_line_start (line_table, 5, 100);
+
+  /* A test location: "test.c:5:10".  */
+  const location_t line_5 = linemap_position_for_column (line_table, 10);
+
+  /* Another test location: "test.c:6:12".  */
+  const location_t line_6
+    = linemap_position_for_line_and_column (line_table, ord_map, 6, 12);
+
+  if (line_6 > LINE_MAP_MAX_LOCATION_WITH_COLS)
+    return;
+
+  /* Generate statements using "line_5" and "line_6" for testing.  */
+  greturn *stmt_at_5 = gimple_build_return (integer_one_node);
+  gimple_set_location (stmt_at_5, line_5);
+
+  greturn *stmt_at_6 = gimple_build_return (integer_zero_node);
+  gimple_set_location (stmt_at_6, line_6);
+
+  /* Run with and then without dumping enabled.  */
+  for (int i = 0; i < 2; i++)
+    {
+      bool with_dumping = (i == 0);
+
+      /* Run with all 4 combinations of
+	 with and without MSG_PRIORITY_INTERNALS and
+	 with and without MSG_PRIORITY_REEMITTED.  */
+      for (int j = 0; j < 4; j++)
+	{
+	  dump_flags_t filter = MSG_ALL_KINDS | MSG_PRIORITY_USER_FACING;
+	  if (j / 2)
+	    filter |= MSG_PRIORITY_INTERNALS;
+	  if (j % 2)
+	    filter |= MSG_PRIORITY_REEMITTED;
+
+	  temp_dump_context tmp (with_dumping, with_dumping, filter);
+
+	  if (with_dumping)
+	    gcc_assert (dump_enabled_p ());
+	  else
+	    gcc_assert (!dump_enabled_p ());
+
+	  /* Simulate attempting to optimize "stmt_at_6".  */
+	  opt_result res = function_that_indirectly_fails (stmt_at_6);
+
+	  /* Verify that "failure" can be used as a "false" boolean.  */
+	  ASSERT_FALSE (res);
+
+	  /* Verify the underlying opt_wrapper<bool>.  */
+	  ASSERT_FALSE (res.get_result ());
+	  opt_problem *problem = res.get_problem ();
+
+	  if (with_dumping)
+	    {
+	      ASSERT_NE (problem, NULL);
+	      ASSERT_EQ (problem->get_dump_location ().get_location_t (),
+			 line_6);
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)
+	      /* Verify that the problem captures the implementation location
+		 it was emitted from.  */
+	      const dump_impl_location_t &impl_location
+		= problem->get_dump_location ().get_impl_location ();
+	      ASSERT_STR_CONTAINS (impl_location.m_function,
+				   "function_that_fails");
+#endif
+
+	      /* Verify that the underlying dump items are retained in the
+		 opt_problem.  */
+	      const optinfo &info = problem->get_optinfo ();
+	      ASSERT_EQ (info.get_dump_location ().get_location_t (), line_6);
+	      ASSERT_EQ (info.num_items (), 4);
+	      ASSERT_IS_TEXT (info.get_item (0), "can't handle return type: ");
+	      ASSERT_IS_TREE (info.get_item (1), UNKNOWN_LOCATION, "int");
+	      ASSERT_IS_TEXT (info.get_item (2), " for stmt: ");
+	      ASSERT_IS_GIMPLE (info.get_item (3), line_6, "return 0;\n");
+
+	      /* ...but not in the dump_context's pending_optinfo.  */
+	      ASSERT_EQ (tmp.get_pending_optinfo (), NULL);
+
+	      /* Simulate emitting a high-level summary message, followed
+		 by the problem.  */
+	      dump_printf_loc (MSG_MISSED_OPTIMIZATION, stmt_at_5,
+			       "can't optimize loop\n");
+	      problem->emit_and_clear ();
+	      ASSERT_EQ (res.get_problem (), NULL);
+
+	      /* Verify that the error message was dumped (when the failure
+		 occurred).  We can't use a switch here as not all of the
+		 values are const expressions (using C++98).  */
+	      dump_flags_t effective_filter
+		= filter & (MSG_PRIORITY_INTERNALS | MSG_PRIORITY_REEMITTED);
+	      if (effective_filter
+		  == (MSG_PRIORITY_INTERNALS | MSG_PRIORITY_REEMITTED))
+		/* The -fopt-info-internals case.  */
+		ASSERT_DUMPED_TEXT_EQ
+		  (tmp,
+		   "test.c:6:12: note:  === function_that_indirectly_fails"
+		   " ===\n"
+		   "test.c:6:12: note:   === function_that_fails ===\n"
+		   "test.c:6:12: missed:   can't handle return type: int"
+		   " for stmt: return 0;\n"
+		   "test.c:5:10: missed: can't optimize loop\n"
+		   "test.c:6:12: missed: can't handle return type: int"
+		   " for stmt: return 0;\n");
+	      else if (effective_filter == MSG_PRIORITY_INTERNALS)
+		/* The default for dump files.  */
+		ASSERT_DUMPED_TEXT_EQ
+		  (tmp,
+		   "test.c:6:12: note:  === function_that_indirectly_fails"
+		   " ===\n"
+		   "test.c:6:12: note:   === function_that_fails ===\n"
+		   "test.c:6:12: missed:   can't handle return type: int"
+		     " for stmt: return 0;\n"
+		   "test.c:5:10: missed: can't optimize loop\n");
+	      else if (effective_filter == MSG_PRIORITY_REEMITTED)
+		/* The default when -fopt-info is enabled.  */
+		ASSERT_DUMPED_TEXT_EQ
+		  (tmp,
+		   "test.c:5:10: missed: can't optimize loop\n"
+		   "test.c:6:12: missed: can't handle return type: int"
+		   " for stmt: return 0;\n");
+	      else
+		{
+		  gcc_assert (effective_filter == 0);
+		  ASSERT_DUMPED_TEXT_EQ
+		    (tmp,
+		     "test.c:5:10: missed: can't optimize loop\n");
+		}
+	    }
+	  else
+	    {
+	      /* If dumping was disabled, then no problem should have been
+		 created, and nothing should have been dumped.  */
+	      ASSERT_EQ (problem, NULL);
+	      ASSERT_DUMPED_TEXT_EQ (tmp, "");
+	    }
+	}
+    }
+}
+
+/* Run all of the selftests within this file.  */
+
+void
+opt_problem_cc_tests ()
+{
+  test_opt_result_success ();
+  for_each_line_table_case (test_opt_result_failure_at);
+}
+
+} // namespace selftest
+
+#endif /* CHECKING_P */