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/* A rich_location subclass that lazily populates a diagnostic_path
with diagnostic context events, but only if the path is actually to be
used.
Copyright (C) 2025 Free Software Foundation, Inc.
Contributed by Qing Zhao<qing.zhao@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/>. */
#define INCLUDE_MEMORY
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "tree.h"
#include "gimple.h"
#include "gimple-iterator.h"
#include "cfganal.h"
#include "tree-cfg.h"
#include "simple-diagnostic-path.h"
#include "diagnostic-context-rich-location.h"
/* Implemenation of the method make_inner_path of the class
lazy_diagnostic_context_path. */
std::unique_ptr<diagnostics::paths::path>
lazy_diagnostic_context_path::make_inner_path () const
{
auto path = std::make_unique<simple_diagnostic_path>
(m_logical_loc_mgr,
global_dc->get_reference_printer ());
if (!flag_diagnostics_show_context)
return path;
if (!m_stmt)
return path;
/* For the following more complicated code:
if (i < 10) // B2
{
if (is_day) // B3
__builtin_printf ("day"); // B4
else
__builtin_printf ("night"); // B5
if (i == -1) // B6
{
if (is_dollar) // B7
__builtin_printf ("dollar");// B8
else
__builtin_printf ("euro"); // B9
a[i] = -1; // B10 (warning here)
}
else
a[i] = i; // B11
}
else
a[i] = i + 1; // B12
it has the following CFG:
B2
/ \
V \
B3 \
/ \ \
V V \
B4 B5 V
\ / B12
V
B6
/ \
V V
B7 B11
/ \
V V
B8 B9
\ /
V
B10 (warning here)
If the STMT that has warning is in B10, the interesting conditions for
the diagnostic are:
depth=1: the condition stmt at B6, the edge from B6->B7;
depth=2: the condition stmt at B2, the edge from B2->B3;
In order to get the interesting conditions, the key to the heuristic
is to backtrace the immediate dominator block chain of the current
block B10, such as, B7, then B6, B3, B2.
In this basic block dominator chain, identify the single predecessor
edges, such as B6->B7, and B2->B3.
For each of the single predecessor edge, the interesting condition is
embedded in the single predecessor block, and the TRUE/FALSE of this
condition is embedded in the edge.
FIXME: We currently only handle GIMPLE_COND, might extend to GIMPLE_SWITCH
later. */
basic_block cur_bb = gimple_bb (m_stmt);
if (!cur_bb)
return path;
basic_block cond_bb = NULL;
int depth = 0;
do
{
/* Step 1. locate the immediate dominator of cur_bb. */
if (dom_info_available_p (cfun, CDI_DOMINATORS))
cond_bb = get_immediate_dominator (CDI_DOMINATORS, cur_bb);
if (!cond_bb)
return path;
/* Step 2. identify the single predecessor edge to locate the
conditional statement. */
if (single_pred_p (cur_bb))
{
gcc_assert (cond_bb == single_pred (cur_bb));
gimple *cond_stmt = NULL;
gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
/* Currently, we only hanlde GIMPLE_COND.
FIXME, will handle GIMPLE_SWITCH and other ctrl stmt later. */
if (gsi_stmt (gsi) && stmt_ends_bb_p (gsi_stmt (gsi)))
if (gimple_code (gsi_stmt (gsi)) == GIMPLE_COND)
cond_stmt = gsi_stmt (gsi);
/* If there is no conditional statement in the cond_bb, continue. */
if (!cond_stmt)
{
cur_bb = cond_bb;
continue;
}
depth++;
/* if there is no location information for the cond_stmt, we should
not add this event to confuse end user. */
if (cond_stmt
&& LOCATION_LOCUS (gimple_location (cond_stmt))
!= UNKNOWN_LOCATION)
{
/* Get the edge from the cond_bb to cur_bb, to determine whether
the stmt is on the taken path of the conditional statement. */
edge e = find_edge (cond_bb, cur_bb);
bool is_branch_taken = e->flags & EDGE_TRUE_VALUE;
path->add_event (gimple_location (cond_stmt), cfun->decl, 1,
"when the condition is evaluated to %s",
is_branch_taken ? "true" : "false");
}
}
cur_bb = cond_bb;
}
while (cond_bb != ENTRY_BLOCK_PTR_FOR_FN (cfun)
&& depth < flag_diagnostics_show_context);
/* Add an end of path warning event in the end of the path. */
if (path->num_events () > 0)
path->add_event (m_location, cfun->decl, 1,
"warning happens here");
return path;
}
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