The 2nd ping for the following patch:
https://gcc.gnu.org/pipermail/gcc-patches/2024-July/657150.html
thanks.
Qing
> On Jul 22, 2024, at 09:01, Qing Zhao <qing.z...@oracle.com> wrote:
>
> Hi, Richard,
>
> Could you please take a look at the patch and let me know any comment you
> have (especially on the middle-end part)?
>
> David, let me know if you have further comment and suggestions.
>
> Thanks a lot.
>
> Qing
>
>> On Jul 12, 2024, at 10:03, Qing Zhao <qing.z...@oracle.com> wrote:
>>
>> due to code duplication from jump threading [PR109071]
>> Control this with a new option -fdiagnostic-explain-harder.
>>
>> Compared to V1, the major difference are: (address David's comments)
>>
>> 1. Change the name of the option from:
>>
>> -fdiagnostic-try-to-explain-harder
>> To
>> -fdiagnostic-explain-harder
>>
>> 2. Sync the commit comments with the real output of the compilation message.
>>
>> 3. Add one more event in the end of the path to repeat the out-of-bound
>> issue.
>>
>> 4. Fixed the unnecessary changes in Makefile.in.
>>
>> 5. Add new copy_history_diagnostic_path.[cc|h] to implement a new
>> class copy_history_diagnostic_path : public diagnostic_path
>>
>> for copy_history_t.
>>
>> 6. Only building the rich locaiton and populating the path when warning_at
>> is called.
>>
>> There are two comments from David that I didn't addressed in this version:
>>
>> 1. Make regenerate-opt-urls.
>> will do this in a later version.
>>
>> 2. Add a ⚠️ emoji for the last event.
>> I didn't add this yet since I think the current message is clear enough.
>> might not worth the effort to add this emoji (it's not that straightforward
>> to add on).
>>
>> With this new version, the message emitted by GCC:
>>
>> $gcc -O2 -Wall -fdiagnostics-explain-harder -c -o t.o t.c
>> t.c: In function ‘sparx5_set’:
>> t.c:12:23: warning: array subscript 4 is above array bounds of ‘int[4]’
>> [-Warray-bounds=]
>> 12 | int *val = &sg->vals[index];
>> | ~~~~~~~~^~~~~~~
>> ‘sparx5_set’: events 1-2
>> 4 | if (*index >= 4)
>> | ^
>> | |
>> | (1) when the condition is evaluated to true
>> ......
>> 12 | int *val = &sg->vals[index];
>> | ~~~~~~~~~~~~~~~
>> | |
>> | (2) out of array bounds here
>> t.c:8:18: note: while referencing ‘vals’
>> 8 | struct nums {int vals[4];};
>> | ^~~~
>>
>> Bootstrapped and regression tested on both aarch64 and x86. no issues.
>>
>> Let me know any further comments and suggestions.
>>
>> thanks.
>>
>> Qing
>>
>> ==================================================
>> $ cat t.c
>> extern void warn(void);
>> static inline void assign(int val, int *regs, int *index)
>> {
>> if (*index >= 4)
>> warn();
>> *regs = val;
>> }
>> struct nums {int vals[4];};
>>
>> void sparx5_set (int *ptr, struct nums *sg, int index)
>> {
>> int *val = &sg->vals[index];
>>
>> assign(0, ptr, &index);
>> assign(*val, ptr, &index);
>> }
>>
>> $ gcc -Wall -O2 -c -o t.o t.c
>> t.c: In function ‘sparx5_set’:
>> t.c:12:23: warning: array subscript 4 is above array bounds of ‘int[4]’
>> [-Warray-bounds=]
>> 12 | int *val = &sg->vals[index];
>> | ~~~~~~~~^~~~~~~
>> t.c:8:18: note: while referencing ‘vals’
>> 8 | struct nums {int vals[4];};
>> | ^~~~
>>
>> In the above, Although the warning is correct in theory, the warning message
>> itself is confusing to the end-user since there is information that cannot
>> be connected to the source code directly.
>>
>> It will be a nice improvement to add more information in the warning message
>> to report where such index value come from.
>>
>> In order to achieve this, we add a new data structure copy_history to record
>> the condition and the transformation that triggered the code duplication.
>> Whenever there is a code duplication due to some specific transformations,
>> such as jump threading, loop switching, etc, a copy_history structure is
>> created and attached to the duplicated gimple statement.
>>
>> During array out-of-bound checking or other warning checking, the
>> copy_history
>> that was attached to the gimple statement is used to form a sequence of
>> diagnostic events that are added to the corresponding rich location to be
>> used
>> to report the warning message.
>>
>> This behavior is controled by the new option -fdiagnostic-explain-harder
>> which is off by default.
>>
>> With this change, by adding -fdiagnostic-explain-harder,
>> the warning message for the above testing case is now:
>>
>> $ gcc -Wall -O2 -fdiagnostics-explain-harder -c -o t.o t.c
>> t.c: In function ‘sparx5_set’:
>> t.c:12:23: warning: array subscript 4 is above array bounds of ‘int[4]’
>> [-Warray-bounds=]
>> 12 | int *val = &sg->vals[index];
>> | ~~~~~~~~^~~~~~~
>> ‘sparx5_set’: events 1-2
>> 4 | if (*index >= 4)
>> | ^
>> | |
>> | (1) when the condition is evaluated to true
>> ......
>> 12 | int *val = &sg->vals[index];
>> | ~~~~~~~~~~~~~~~
>> | |
>> | (2) out of array bounds here
>> t.c:8:18: note: while referencing ‘vals’
>> 8 | struct nums {int vals[4];};
>> | ^~~~
>>
>> gcc/ChangeLog:
>>
>> PR tree-optimization/109071
>>
>> * Makefile.in (OBJS): Add diagnostic-copy-history.o
>> and copy-history-diagnostic-path.o.
>> * gcc/common.opt (fdiagnostics-explain-harder): New option.
>> * gcc/doc/invoke.texi (fdiagnostics-explain-harder): Add
>> documentation for the new option.
>> * gimple-array-bounds.cc (build_rich_location_with_diagnostic_path):
>> New function.
>> (check_out_of_bounds_and_warn): Add one new parameter. Use rich
>> location with copy_history_diagnostic_path for warning_at.
>> (array_bounds_checker::check_array_ref): Use rich location with
>> copy_history_diagnostic_path for warning_at.
>> (array_bounds_checker::check_mem_ref): Add one new parameter.
>> Use rich location with copy_history_diagnostic_path for warning_at.
>> (array_bounds_checker::check_addr_expr): Use rich location with
>> copy_history_diagnostic_path for warning_at.
>> (array_bounds_checker::check_array_bounds): Call check_mem_ref with
>> one more parameter.
>> * gimple-array-bounds.h: Update prototype for check_mem_ref.
>> * gimple-iterator.cc (gsi_remove): (gsi_remove): Remove the copy
>> history when removing the gimple.
>> * toplev.cc (toplev::finalize): Call copy_history_finalize.
>> * tree-ssa-threadupdate.cc (set_copy_history_to_stmts_in_bb): New
>> function.
>> (back_jt_path_registry::duplicate_thread_path): Call the new function
>> to set copy history for every duplicated gimple.
>> * copy-history-diagnostic-path.cc: New file.
>> * copy-history-diagnostic-path.h: New file.
>> * diagnostic-copy-history.cc: New file.
>> * diagnostic-copy-history.h: New file.
>>
>> gcc/testsuite/ChangeLog:
>>
>> PR tree-optimization/109071
>>
>> * gcc.dg/pr109071.c: New test.
>> ---
>> gcc/Makefile.in | 2 +
>> gcc/common.opt | 4 +
>> gcc/copy-history-diagnostic-path.cc | 86 +++++++++++++++
>> gcc/copy-history-diagnostic-path.h | 87 +++++++++++++++
>> gcc/diagnostic-copy-history.cc | 163 ++++++++++++++++++++++++++++
>> gcc/diagnostic-copy-history.h | 80 ++++++++++++++
>> gcc/doc/invoke.texi | 7 ++
>> gcc/gimple-array-bounds.cc | 94 +++++++++++++---
>> gcc/gimple-array-bounds.h | 2 +-
>> gcc/gimple-iterator.cc | 3 +
>> gcc/testsuite/gcc.dg/pr109071.c | 43 ++++++++
>> gcc/toplev.cc | 3 +
>> gcc/tree-ssa-threadupdate.cc | 42 +++++++
>> 13 files changed, 598 insertions(+), 18 deletions(-)
>> create mode 100644 gcc/copy-history-diagnostic-path.cc
>> create mode 100644 gcc/copy-history-diagnostic-path.h
>> create mode 100644 gcc/diagnostic-copy-history.cc
>> create mode 100644 gcc/diagnostic-copy-history.h
>> create mode 100644 gcc/testsuite/gcc.dg/pr109071.c
>>
>> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
>> index 7d3ea27a6ab..f8bbfda845f 100644
>> --- a/gcc/Makefile.in
>> +++ b/gcc/Makefile.in
>> @@ -1436,6 +1436,8 @@ OBJS = \
>> df-problems.o \
>> df-scan.o \
>> dfp.o \
>> + diagnostic-copy-history.o \
>> + copy-history-diagnostic-path.o \
>> digraph.o \
>> dojump.o \
>> dominance.o \
>> diff --git a/gcc/common.opt b/gcc/common.opt
>> index a300470bbc5..714280390d9 100644
>> --- a/gcc/common.opt
>> +++ b/gcc/common.opt
>> @@ -1558,6 +1558,10 @@ fdiagnostics-minimum-margin-width=
>> Common Joined UInteger Var(diagnostics_minimum_margin_width) Init(6)
>> Set minimum width of left margin of source code when showing source.
>>
>> +fdiagnostics-explain-harder
>> +Common Var(flag_diagnostics_explain_harder)
>> +Collect and print more context information for diagnostics.
>> +
>> fdisable-
>> Common Joined RejectNegative Var(common_deferred_options) Defer
>> -fdisable-[tree|rtl|ipa]-<pass>=range1+range2 Disable an optimization pass.
>> diff --git a/gcc/copy-history-diagnostic-path.cc
>> b/gcc/copy-history-diagnostic-path.cc
>> new file mode 100644
>> index 00000000000..65e5c056165
>> --- /dev/null
>> +++ b/gcc/copy-history-diagnostic-path.cc
>> @@ -0,0 +1,86 @@
>> +/* Classes for implementing diagnostic paths for copy_history_t.
>> + Copyright (C) 2024-2024 Free Software Foundation, Inc.
>> + Contributed by Qing Zhao<qing.z...@oracle.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 "function.h"
>> +#include "copy-history-diagnostic-path.h"
>> +
>> +bool
>> +copy_history_diagnostic_path::same_function_p (int event_idx_a,
>> + int event_idx_b) const
>> +{
>> + return (m_events[event_idx_a]->get_fndecl ()
>> + == m_events[event_idx_b]->get_fndecl ());
>> +}
>> +
>> +/* Add an event to this path at LOC within function FNDECL at
>> + stack depth DEPTH.
>> +
>> + Use m_context's printer to format FMT, as the text of the new
>> + event. */
>> +
>> +void
>> +copy_history_diagnostic_path::add_event (location_t loc, tree fndecl, int
>> depth,
>> + const char *fmt, ...)
>> +{
>> + pretty_printer *pp = m_event_pp;
>> + pp_clear_output_area (pp);
>> +
>> + rich_location rich_loc (line_table, UNKNOWN_LOCATION);
>> +
>> + va_list ap;
>> +
>> + va_start (ap, fmt);
>> +
>> + text_info ti (fmt, &ap, 0, nullptr, &rich_loc);
>> + pp_format (pp, &ti);
>> + pp_output_formatted_text (pp);
>> +
>> + va_end (ap);
>> +
>> + simple_diagnostic_event *new_event
>> + = new simple_diagnostic_event (loc, fndecl, depth, pp_formatted_text
>> (pp));
>> + m_events.safe_push (new_event);
>> +
>> + pp_clear_output_area (pp);
>> +
>> + return;
>> +}
>> +
>> +/* Populate the diagnostic_path from the copy_history. */
>> +void
>> +copy_history_diagnostic_path::populate_path_from_copy_history ()
>> +{
>> + if (!m_copy_history)
>> + return;
>> +
>> + for (copy_history_t cur_ch = m_copy_history; cur_ch;
>> + cur_ch = cur_ch->prev_copy)
>> + add_event (cur_ch->condition, cfun->decl, 1,
>> + "when the condition is evaluated to %s",
>> + cur_ch->is_true_path ? "true" : "false");
>> +
>> + /* Add an end of path warning event in the end of the path. */
>> + add_event (m_location, cfun->decl, 1,
>> + "out of array bounds here");
>> + return;
>> +}
>> diff --git a/gcc/copy-history-diagnostic-path.h
>> b/gcc/copy-history-diagnostic-path.h
>> new file mode 100644
>> index 00000000000..377e9136070
>> --- /dev/null
>> +++ b/gcc/copy-history-diagnostic-path.h
>> @@ -0,0 +1,87 @@
>> +/* Classes for implementing diagnostic paths for copy_history_t.
>> + Copyright (C) 2024-2024 Free Software Foundation, Inc.
>> + Contributed by Qing Zhao<qing.z...@oracle.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/>. */
>> +
>> +#ifndef GCC_COPY_HISTORY_DIAGNOSTIC_PATH_H
>> +#define GCC_COPY_HISTORY_DIAGNOSTIC_PATH_H
>> +
>> +#include "diagnostic-path.h"
>> +#include "simple-diagnostic-path.h"
>> +#include "diagnostic-copy-history.h"
>> +
>> +/* An implementation of diagnostic_path for copy_history_t, as a
>> + vector of simple_diagnostic_event instances. */
>> +
>> +class copy_history_diagnostic_path : public diagnostic_path
>> +{
>> + public:
>> + copy_history_diagnostic_path (pretty_printer *event_pp,
>> + copy_history_t cp_history,
>> + location_t loc)
>> + : diagnostic_path (),
>> + m_thread ("main"),
>> + m_event_pp (event_pp),
>> + m_copy_history (cp_history),
>> + m_location (loc)
>> + {}
>> +
>> + unsigned num_events () const final override
>> + {
>> + return m_events.length ();
>> + }
>> + const diagnostic_event & get_event (int idx) const final override
>> + {
>> + return *m_events[idx];
>> + }
>> + unsigned num_threads () const final override
>> + {
>> + return 1;
>> + }
>> + const diagnostic_thread &
>> + get_thread (diagnostic_thread_id_t) const final override
>> + {
>> + return m_thread;
>> + }
>> + bool
>> + same_function_p (int event_idx_a,
>> + int event_idx_b) const final override;
>> +
>> + void add_event (location_t loc, tree fndecl, int depth,
>> + const char *fmt, ...);
>> +
>> + void populate_path_from_copy_history ();
>> +
>> + private:
>> + simple_diagnostic_thread m_thread;
>> +
>> + /* The events that have occurred along this path. */
>> + auto_delete_vec<simple_diagnostic_event> m_events;
>> +
>> + pretty_printer *m_event_pp;
>> +
>> + /* The copy_history associated with this path. */
>> + copy_history_t m_copy_history;
>> +
>> + /* The location for the gimple statement where the
>> + diagnostic message emitted. */
>> + location_t m_location;
>> +
>> +};
>> +
>> +#endif /* ! GCC_COPY_HISTORY_DIAGNOSTIC_PATH_H */
>> diff --git a/gcc/diagnostic-copy-history.cc b/gcc/diagnostic-copy-history.cc
>> new file mode 100644
>> index 00000000000..2733d137622
>> --- /dev/null
>> +++ b/gcc/diagnostic-copy-history.cc
>> @@ -0,0 +1,163 @@
>> +/* Functions to handle copy history.
>> + Copyright (C) 2024-2024 Free Software Foundation, Inc.
>> + Contributed by Qing Zhao <qing.z...@oracle.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 "diagnostic-copy-history.h"
>> +
>> +/* A mapping from a gimple to a pointer to the copy history of it. */
>> +static copy_history_map_t *copy_history_map;
>> +
>> +/* Obstack for copy history. */
>> +static struct obstack copy_history_obstack;
>> +
>> +/* Create a new copy history. */
>> +
>> +copy_history_t
>> +create_copy_history (location_t condition,
>> + bool is_true_path,
>> + enum copy_reason reason,
>> + copy_history_t prev_copy)
>> +{
>> + static bool initialized = false;
>> +
>> + if (!initialized)
>> + {
>> + gcc_obstack_init (©_history_obstack);
>> + initialized = true;
>> + }
>> +
>> + copy_history_t copy_history
>> + = (copy_history_t) obstack_alloc (©_history_obstack,
>> + sizeof (struct copy_history));
>> + copy_history->condition = condition;
>> + copy_history->is_true_path = is_true_path;
>> + copy_history->reason = reason;
>> + copy_history->prev_copy = prev_copy;
>> + return copy_history;
>> +}
>> +
>> +/* Insert the copy history for the gimple STMT assuming the linked list
>> + of CP_HISTORY does not have duplications. It's the caller's
>> + responsibility to make sure that the linked list of CP_HISTORY does
>> + not have duplications. */
>> +
>> +void
>> +insert_copy_history (gimple *stmt, copy_history_t cp_history)
>> +{
>> + if (!copy_history_map)
>> + copy_history_map = new copy_history_map_t;
>> +
>> + copy_history_map->put (stmt, cp_history);
>> + return;
>> +}
>> +
>> +/* Get the copy history for the gimple STMT, return NULL when there is
>> + no associated copy history. */
>> +
>> +copy_history_t
>> +get_copy_history (gimple *stmt)
>> +{
>> + if (!copy_history_map)
>> + return NULL;
>> +
>> + if (const copy_history_t *cp_history_p = copy_history_map->get (stmt))
>> + return *cp_history_p;
>> +
>> + return NULL;
>> +}
>> +
>> +/* Remove the copy history for STMT. */
>> +
>> +void
>> +remove_copy_history (gimple *stmt)
>> +{
>> + if (!copy_history_map)
>> + return;
>> + copy_history_map->remove (stmt);
>> + return;
>> +}
>> +
>> +/* Check whether the cond_location, is_true_path and reason existed
>> + * in the OLD_COPY_HISTORY. */
>> +
>> +static bool
>> +is_copy_history_existed (location_t cond_location, bool is_true_path,
>> + enum copy_reason reason,
>> + copy_history_t old_copy_history)
>> +{
>> + for (copy_history_t cur_ch = old_copy_history; cur_ch;
>> + cur_ch = cur_ch->prev_copy)
>> + if ((cur_ch->condition == cond_location)
>> + && (cur_ch->is_true_path == is_true_path)
>> + && (cur_ch->reason == reason))
>> + return true;
>> +
>> + return false;
>> +}
>> +
>> +/* Set copy history for the gimple STMT. Return TRUE when a new copy
>> + * history is created and inserted. Otherwise return FALSE. */
>> +
>> +bool
>> +set_copy_history (gimple *stmt, location_t cond_location,
>> + bool is_true_path, enum copy_reason reason)
>> +{
>> +
>> + /* First, get the old copy history associated with this STMT. */
>> + copy_history_t old_cp_history = get_copy_history (stmt);
>> +
>> + /* If the current copy history is not in the STMT's copy history linked
>> + list yet, create the new copy history, put the old_copy_history as the
>> + prev_copy of it. */
>> + copy_history_t new_cp_history = NULL;
>> + if (!is_copy_history_existed (cond_location, is_true_path,
>> + reason, old_cp_history))
>> + new_cp_history
>> + = create_copy_history (cond_location, is_true_path,
>> + reason, old_cp_history);
>> +
>> + /* Insert the copy history into the hash map. */
>> + if (new_cp_history)
>> + {
>> + insert_copy_history (stmt, new_cp_history);
>> + return true;
>> + }
>> +
>> + return false;
>> +}
>> +
>> +/* Reset all state for diagnostic-copy-history.cc so that we can rerun the
>> + compiler within the same process. For use by toplev::finalize. */
>> +
>> +void
>> +copy_history_finalize (void)
>> +{
>> + if (copy_history_map)
>> + {
>> + delete copy_history_map;
>> + copy_history_map = NULL;
>> + }
>> + obstack_free (©_history_obstack, NULL);
>> + return;
>> +}
>> diff --git a/gcc/diagnostic-copy-history.h b/gcc/diagnostic-copy-history.h
>> new file mode 100644
>> index 00000000000..0c2c55a2a81
>> --- /dev/null
>> +++ b/gcc/diagnostic-copy-history.h
>> @@ -0,0 +1,80 @@
>> +/* Copy history associated with a gimple statement to record its history
>> + of duplications due to different transformations.
>> + The copy history will be used to construct events for later diagnostic.
>> +
>> + Copyright (C) 2024-2024 Free Software Foundation, Inc.
>> + Contributed by Qing Zhao <qing.z...@oracle.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/>. */
>> +
>> +#ifndef DIAGNOSTIC_COPY_HISTORY_H_INCLUDED
>> +#define DIAGNOSTIC_COPY_HISTORY_H_INCLUDED
>> +
>> +#include "hash-map.h"
>> +#include "line-map.h"
>> +
>> +/* An enum for the reason why this copy is made. Right now, there are
>> + three reasons, we can add more if needed. */
>> +enum copy_reason {
>> + COPY_BY_THREAD_JUMP,
>> + COPY_BY_LOOP_UNSWITCH,
>> + COPY_BY_LOOP_UNROLL
>> +};
>> +
>> +/* This data structure records the information when a statement is
>> + duplicated during different transformations. Such information
>> + will be used by the later diagnostic messages to report more
>> + contexts of the warnings or errors. */
>> +struct copy_history {
>> + /* The location of the condition statement that triggered the code
>> + duplication. */
>> + location_t condition;
>> +
>> + /* Whether this copy is on the TRUE path of the condition. */
>> + bool is_true_path;
>> +
>> + /* The reason for the code duplication. */
>> + enum copy_reason reason;
>> +
>> + /* This statement itself might be a previous code duplication. */
>> + struct copy_history *prev_copy;
>> +};
>> +
>> +typedef struct copy_history *copy_history_t;
>> +
>> +/* Create a new copy history. */
>> +extern copy_history_t create_copy_history (location_t, bool,
>> + enum copy_reason, copy_history_t);
>> +
>> +typedef hash_map<gimple *, copy_history_t> copy_history_map_t;
>> +
>> +/* Get the copy history for the gimple STMT, return NULL when there is
>> + no associated copy history. */
>> +extern copy_history_t get_copy_history (gimple *);
>> +
>> +/* Remove the copy history for STMT from the copy_history_map. */
>> +extern void remove_copy_history (gimple *);
>> +
>> +/* Set copy history for the gimple STMT. */
>> +extern bool set_copy_history (gimple *, location_t,
>> + bool, enum copy_reason);
>> +
>> +/* Reset all state for diagnostic-copy-history.cc so that we can rerun the
>> + compiler within the same process. For use by toplev::finalize. */
>> +extern void copy_history_finalize (void);
>> +
>> +#endif // DIAGNOSTIC_COPY_HISTORY_H_INCLUDED
>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>> index b37c7af7a39..bb0c6a87523 100644
>> --- a/gcc/doc/invoke.texi
>> +++ b/gcc/doc/invoke.texi
>> @@ -321,6 +321,7 @@ Objective-C and Objective-C++ Dialects}.
>> -fdiagnostics-column-origin=@var{origin}
>> -fdiagnostics-escape-format=@r{[}unicode@r{|}bytes@r{]}
>> -fdiagnostics-text-art-charset=@r{[}none@r{|}ascii@r{|}unicode@r{|}emoji@r{]}}
>> +-fdiagnostics-explain-harder
>>
>> @item Warning Options
>> @xref{Warning Options,,Options to Request or Suppress Warnings}.
>> @@ -5518,6 +5519,12 @@ left margin.
>> This option controls the minimum width of the left margin printed by
>> @option{-fdiagnostics-show-line-numbers}. It defaults to 6.
>>
>> +@opindex fdiagnostics-explain-harder
>> +@item -fdiagnostics-explain-harder
>> +With this option, the compiler collects more context information for
>> +diagnostics and emits them to the users to provide more hints on how
>> +the diagnostics come from.
>> +
>> @opindex fdiagnostics-parseable-fixits
>> @item -fdiagnostics-parseable-fixits
>> Emit fix-it hints in a machine-parseable format, suitable for consumption
>> diff --git a/gcc/gimple-array-bounds.cc b/gcc/gimple-array-bounds.cc
>> index 1637a2fc4f4..ba98ab3b413 100644
>> --- a/gcc/gimple-array-bounds.cc
>> +++ b/gcc/gimple-array-bounds.cc
>> @@ -31,6 +31,9 @@ along with GCC; see the file COPYING3. If not see
>> #include "tree-dfa.h"
>> #include "fold-const.h"
>> #include "diagnostic-core.h"
>> +#include "simple-diagnostic-path.h"
>> +#include "diagnostic-copy-history.h"
>> +#include "copy-history-diagnostic-path.h"
>> #include "intl.h"
>> #include "tree-vrp.h"
>> #include "alloc-pool.h"
>> @@ -254,6 +257,25 @@ get_up_bounds_for_array_ref (tree ref, tree *decl,
>> return;
>> }
>>
>> +/* Build a rich location for LOCATION, and populate the diagonistic path
>> + for it. */
>> +
>> +static rich_location *
>> +build_rich_location_with_diagnostic_path (location_t location, gimple *stmt)
>> +{
>> + /* Generate a rich location for this location. */
>> + rich_location *richloc = new rich_location (line_table, location);
>> +
>> + copy_history_t cp_history = stmt ? get_copy_history (stmt) : NULL;
>> + copy_history_diagnostic_path *path
>> + = new copy_history_diagnostic_path (global_dc->printer,
>> + cp_history, location);
>> + path->populate_path_from_copy_history ();
>> +
>> + richloc->set_path (path);
>> + return richloc;
>> +}
>> +
>> /* Given the LOW_SUB_ORG, LOW_SUB and UP_SUB, and the computed UP_BOUND
>> and UP_BOUND_P1, check whether the array reference REF is out of bound.
>> When out of bounds, set OUT_OF_BOUND to true.
>> @@ -262,6 +284,7 @@ get_up_bounds_for_array_ref (tree ref, tree *decl,
>>
>> static bool
>> check_out_of_bounds_and_warn (location_t location, tree ref,
>> + gimple *stmt,
>> tree low_sub_org, tree low_sub, tree up_sub,
>> tree up_bound, tree up_bound_p1,
>> const irange *vr,
>> @@ -280,9 +303,13 @@ check_out_of_bounds_and_warn (location_t location, tree
>> ref,
>> {
>> *out_of_bound = true;
>> if (for_array_bound)
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript %E is outside array"
>> " bounds of %qT", low_sub_org, artype);
>> + }
>> }
>>
>> if (warned)
>> @@ -299,10 +326,14 @@ check_out_of_bounds_and_warn (location_t location,
>> tree ref,
>> {
>> *out_of_bound = true;
>> if (for_array_bound)
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript [%E, %E] is outside "
>> "array bounds of %qT",
>> low_sub, up_sub, artype);
>> + }
>> }
>> }
>> else if (up_bound
>> @@ -313,18 +344,26 @@ check_out_of_bounds_and_warn (location_t location,
>> tree ref,
>> {
>> *out_of_bound = true;
>> if (for_array_bound)
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript %E is above array bounds of %qT",
>> up_sub, artype);
>> + }
>> }
>> else if (TREE_CODE (low_sub) == INTEGER_CST
>> && tree_int_cst_lt (low_sub, low_bound))
>> {
>> *out_of_bound = true;
>> if (for_array_bound)
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript %E is below array bounds of %qT",
>> low_sub, artype);
>> + }
>> }
>> return warned;
>> }
>> @@ -388,21 +427,24 @@ array_bounds_checker::check_array_ref (location_t
>> location, tree ref,
>> }
>> }
>>
>> - warned = check_out_of_bounds_and_warn (location, ref,
>> + warned = check_out_of_bounds_and_warn (location, ref, stmt,
>> low_sub_org, low_sub, up_sub,
>> up_bound, up_bound_p1, &vr,
>> ignore_off_by_one, warn_array_bounds,
>> &out_of_bound);
>>
>> -
>> if (!warned && sam == special_array_member::int_0)
>> - warned = warning_at (location, OPT_Wzero_length_bounds,
>> + {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Wzero_length_bounds,
>> (TREE_CODE (low_sub) == INTEGER_CST
>> ? G_("array subscript %E is outside the bounds "
>> "of an interior zero-length array %qT")
>> : G_("array subscript %qE is outside the bounds "
>> "of an interior zero-length array %qT")),
>> low_sub, artype);
>> + }
>>
>> if (warned && dump_file && (dump_flags & TDF_DETAILS))
>> {
>> @@ -419,8 +461,10 @@ array_bounds_checker::check_array_ref (location_t
>> location, tree ref,
>> || sam == special_array_member::trail_n)
>> && DECL_NOT_FLEXARRAY (afield_decl))
>> {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> bool warned1
>> - = warning_at (location, OPT_Wstrict_flex_arrays,
>> + = warning_at (richloc, OPT_Wstrict_flex_arrays,
>> "trailing array %qT should not be used as "
>> "a flexible array member",
>> artype);
>> @@ -478,6 +522,7 @@ array_bounds_checker::check_array_ref (location_t
>> location, tree ref,
>>
>> bool
>> array_bounds_checker::check_mem_ref (location_t location, tree ref,
>> + gimple *stmt,
>> bool ignore_off_by_one)
>> {
>> if (warning_suppressed_p (ref, OPT_Warray_bounds_))
>> @@ -580,16 +625,24 @@ array_bounds_checker::check_mem_ref (location_t
>> location, tree ref,
>> if (lboob)
>> {
>> if (offrange[0] == offrange[1])
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript %wi is outside array bounds "
>> "of %qT",
>> offrange[0].to_shwi (), reftype);
>> + }
>> else
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + {
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript [%wi, %wi] is outside "
>> "array bounds of %qT",
>> offrange[0].to_shwi (),
>> offrange[1].to_shwi (), reftype);
>> + }
>> }
>> else if (uboob && !ignore_off_by_one)
>> {
>> @@ -599,8 +652,9 @@ array_bounds_checker::check_mem_ref (location_t
>> location, tree ref,
>> it were an untyped array of bytes. */
>> backtype = build_array_type_nelts (unsigned_char_type_node,
>> aref.sizrng[1].to_uhwi ());
>> -
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript %<%T[%wi]%> is partly "
>> "outside array bounds of %qT",
>> axstype, offrange[0].to_shwi (), backtype);
>> @@ -623,7 +677,9 @@ array_bounds_checker::check_mem_ref (location_t
>> location, tree ref,
>> {
>> HOST_WIDE_INT tmpidx = (aref.offmax[i] / eltsize).to_shwi ();
>>
>> - if (warning_at (location, OPT_Warray_bounds_,
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + if (warning_at (richloc, OPT_Warray_bounds_,
>> "intermediate array offset %wi is outside array bounds "
>> "of %qT", tmpidx, reftype))
>> {
>> @@ -656,7 +712,7 @@ array_bounds_checker::check_addr_expr (location_t
>> location, tree t,
>> ignore_off_by_one = false;
>> }
>> else if (TREE_CODE (t) == MEM_REF)
>> - warned = check_mem_ref (location, t, ignore_off_by_one);
>> + warned = check_mem_ref (location, t, stmt, ignore_off_by_one);
>>
>> if (warned)
>> suppress_warning (t, OPT_Warray_bounds_);
>> @@ -702,7 +758,9 @@ array_bounds_checker::check_addr_expr (location_t
>> location, tree t,
>> dump_generic_expr (MSG_NOTE, TDF_SLIM, t);
>> fprintf (dump_file, "\n");
>> }
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript %wi is below "
>> "array bounds of %qT",
>> idx.to_shwi (), TREE_TYPE (tem));
>> @@ -716,7 +774,9 @@ array_bounds_checker::check_addr_expr (location_t
>> location, tree t,
>> dump_generic_expr (MSG_NOTE, TDF_SLIM, t);
>> fprintf (dump_file, "\n");
>> }
>> - warned = warning_at (location, OPT_Warray_bounds_,
>> + rich_location *richloc
>> + = build_rich_location_with_diagnostic_path (location, stmt);
>> + warned = warning_at (richloc, OPT_Warray_bounds_,
>> "array subscript %wu is above "
>> "array bounds of %qT",
>> idx.to_uhwi (), TREE_TYPE (tem));
>> @@ -811,7 +871,7 @@ array_bounds_checker::check_array_bounds (tree *tp, int
>> *walk_subtree,
>> warned = checker->check_array_ref (location, t, wi->stmt,
>> false/*ignore_off_by_one*/);
>> else if (TREE_CODE (t) == MEM_REF)
>> - warned = checker->check_mem_ref (location, t,
>> + warned = checker->check_mem_ref (location, t, wi->stmt,
>> false /*ignore_off_by_one*/);
>> else if (TREE_CODE (t) == ADDR_EXPR)
>> {
>> diff --git a/gcc/gimple-array-bounds.h b/gcc/gimple-array-bounds.h
>> index aa7ca8e9730..2d1d48d1e94 100644
>> --- a/gcc/gimple-array-bounds.h
>> +++ b/gcc/gimple-array-bounds.h
>> @@ -33,7 +33,7 @@ public:
>> private:
>> static tree check_array_bounds (tree *tp, int *walk_subtree, void *data);
>> bool check_array_ref (location_t, tree, gimple *, bool ignore_off_by_one);
>> - bool check_mem_ref (location_t, tree, bool ignore_off_by_one);
>> + bool check_mem_ref (location_t, tree, gimple *, bool ignore_off_by_one);
>> void check_addr_expr (location_t, tree, gimple *);
>> void get_value_range (irange &r, const_tree op, gimple *);
>>
>> diff --git a/gcc/gimple-iterator.cc b/gcc/gimple-iterator.cc
>> index 93646262eac..472a79360d7 100644
>> --- a/gcc/gimple-iterator.cc
>> +++ b/gcc/gimple-iterator.cc
>> @@ -33,6 +33,7 @@ along with GCC; see the file COPYING3. If not see
>> #include "tree-ssa.h"
>> #include "value-prof.h"
>> #include "gimplify.h"
>> +#include "diagnostic-copy-history.h"
>>
>>
>> /* Mark the statement STMT as modified, and update it. */
>> @@ -581,6 +582,8 @@ gsi_remove (gimple_stmt_iterator *i, bool
>> remove_permanently)
>> cfun->debug_marker_count--;
>> require_eh_edge_purge = remove_stmt_from_eh_lp (stmt);
>> gimple_remove_stmt_histograms (cfun, stmt);
>> + if (get_copy_history (stmt) != NULL)
>> + remove_copy_history (stmt);
>> }
>>
>> /* Update the iterator and re-wire the links in I->SEQ. */
>> diff --git a/gcc/testsuite/gcc.dg/pr109071.c
>> b/gcc/testsuite/gcc.dg/pr109071.c
>> new file mode 100644
>> index 00000000000..95ae576451e
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/pr109071.c
>> @@ -0,0 +1,43 @@
>> +/* PR tree-optimization/109071 need more context for -Warray-bounds warnings
>> + due to code duplication from jump threading. */
>> +/* { dg-options "-O2 -Wall -fdiagnostics-explain-harder" } */
>> +/* { dg-additional-options "-fdiagnostics-show-line-numbers
>> -fdiagnostics-path-format=inline-events -fdiagnostics-show-caret" } */
>> +/* { dg-enable-nn-line-numbers "" } */
>> +
>> +extern void warn(void);
>> +static inline void assign(int val, int *regs, int index)
>> +{
>> + if (index >= 4)
>> + warn();
>> + *regs = val;
>> +}
>> +struct nums {int vals[4];};
>> +
>> +void sparx5_set (int *ptr, struct nums *sg, int index)
>> +{
>> + int *val = &sg->vals[index]; /* { dg-warning "is above array bounds" } */
>> +
>> + assign(0, ptr, index);
>> + assign(*val, ptr, index);
>> +}
>> +/* { dg-begin-multiline-output "" }
>> + NN | int *val = &sg->vals[index];
>> + | ~~~~~~~~^~~~~~~
>> + 'sparx5_set': events 1-2
>> + NN | if (index >= 4)
>> + | ^
>> + | |
>> + | (1) when the condition is evaluated to true
>> +......
>> + { dg-end-multiline-output "" } */
>> +
>> +/* { dg-begin-multiline-output "" }
>> + | ~~~~~~~~~~~~~~~
>> + | |
>> + | (2) out of array bounds here
>> + { dg-end-multiline-output "" } */
>> +
>> +/* { dg-begin-multiline-output "" }
>> + NN | struct nums {int vals[4];};
>> + | ^~~~
>> + { dg-end-multiline-output "" } */
>> diff --git a/gcc/toplev.cc b/gcc/toplev.cc
>> index f715f977b72..e9ae55f64be 100644
>> --- a/gcc/toplev.cc
>> +++ b/gcc/toplev.cc
>> @@ -41,6 +41,7 @@ along with GCC; see the file COPYING3. If not see
>> #include "cgraph.h"
>> #include "coverage.h"
>> #include "diagnostic.h"
>> +#include "diagnostic-copy-history.h"
>> #include "varasm.h"
>> #include "tree-inline.h"
>> #include "realmpfr.h" /* For GMP/MPFR/MPC versions, in print_version. */
>> @@ -2381,6 +2382,8 @@ toplev::finalize (void)
>> tree_cc_finalize ();
>> reginfo_cc_finalize ();
>>
>> + copy_history_finalize ();
>> +
>> /* save_decoded_options uses opts_obstack, so these must
>> be cleaned up together. */
>> obstack_free (&opts_obstack, NULL);
>> diff --git a/gcc/tree-ssa-threadupdate.cc b/gcc/tree-ssa-threadupdate.cc
>> index fa61ba9512b..9292f0c2aa1 100644
>> --- a/gcc/tree-ssa-threadupdate.cc
>> +++ b/gcc/tree-ssa-threadupdate.cc
>> @@ -36,6 +36,7 @@ along with GCC; see the file COPYING3. If not see
>> #include "tree-cfg.h"
>> #include "tree-vectorizer.h"
>> #include "tree-pass.h"
>> +#include "diagnostic-copy-history.h"
>>
>> /* Given a block B, update the CFG and SSA graph to reflect redirecting
>> one or more in-edges to B to instead reach the destination of an
>> @@ -2371,6 +2372,37 @@ back_jt_path_registry::adjust_paths_after_duplication
>> (unsigned curr_path_num)
>> }
>> }
>>
>> +/* Set copy history to all the stmts in the basic block BB based on
>> + the entry edge ENTRY and whether this basic block is on the true
>> + path of the condition in the destination of the edge ENTRY.
>> + Return TRUE when copy history are set, otherwise return FALSE. */
>> +
>> +static bool
>> +set_copy_history_to_stmts_in_bb (basic_block bb, edge entry, bool
>> is_true_path)
>> +{
>> + /* First, get the condition statement in the destination of the
>> + edge ENTRY. */
>> + basic_block cond_block = entry->dest;
>> + gimple *cond_stmt = NULL;
>> + gimple_stmt_iterator gsi;
>> + gsi = gsi_last_bb (cond_block);
>> + /* if the cond_block ends with a conditional statement, get it. */
>> + if (!gsi_end_p (gsi)
>> + && gsi_stmt (gsi)
>> + && (gimple_code (gsi_stmt (gsi)) == GIMPLE_COND))
>> + cond_stmt = gsi_stmt (gsi);
>> +
>> + if (!cond_stmt)
>> + return false;
>> +
>> + for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
>> + set_copy_history (gsi_stmt (gsi),
>> + gimple_location (cond_stmt),
>> + is_true_path,
>> + COPY_BY_THREAD_JUMP);
>> + return true;
>> +}
>> +
>> /* Duplicates a jump-thread path of N_REGION basic blocks.
>> The ENTRY edge is redirected to the duplicate of the region.
>>
>> @@ -2419,6 +2451,16 @@ back_jt_path_registry::duplicate_thread_path (edge
>> entry,
>> copy_bbs (region, n_region, region_copy, &exit, 1, &exit_copy, loop,
>> split_edge_bb_loc (entry), false);
>>
>> + /* Set the copy history for all the stmts in both original and copied
>> + basic blocks. The copied regions are in the true path. */
>> + if (flag_diagnostics_explain_harder)
>> + for (i = 0; i < n_region; i++)
>> + {
>> + set_copy_history_to_stmts_in_bb (region[i], entry, false);
>> + set_copy_history_to_stmts_in_bb (region_copy[i], entry, true);
>> + }
>> +
>> +
>> /* Fix up: copy_bbs redirects all edges pointing to copied blocks. The
>> following code ensures that all the edges exiting the jump-thread path
>> are
>> redirected back to the original code: these edges are exceptions
>> --
>> 2.31.1
>>
>
