RE: [PATCH] Accept functions with DW_AT_linkage_name present

["Sharma, Alok Kumar" <AlokKumar.Sharma@amd.com>]

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Thanks a lot.

Attached is the updated patch which I shall commit.

Regards,
Alok

-----Original Message-----
From: Tom Tromey <tom@tromey.com> 
Sent: Friday, May 20, 2022 9:43 PM
To: Sharma, Alok Kumar via Gdb-patches <gdb-patches@sourceware.org>
Cc: Tom Tromey <tom@tromey.com>; Sharma, Alok Kumar <AlokKumar.Sharma@amd.com>; George, Jini Susan <JiniSusan.George@amd.com>
Subject: Re: [PATCH] Accept functions with DW_AT_linkage_name present

[CAUTION: External Email]

>>>>> Sharma, Alok Kumar via Gdb-patches <gdb-patches@sourceware.org> writes:

> diff --git a/gdb/testsuite/gdb.threads/omp-task.c b/gdb/testsuite/gdb.threads/omp-task.c
> new file mode 100644
> index 00000000000..27aa3e805dc
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/omp-task.c
> @@ -0,0 +1,28 @@
> +#include <stdio.h>
> +#include <omp.h>

This file should have a copyright header.

This is ok with this change.

Tom

[-- Attachment #2: 0001-Accept-functions-with-DW_AT_linkage_name-present.patch --]
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From 00c95d7bdbd02b26dc22253917da876d07062dcc Mon Sep 17 00:00:00 2001
From: Alok Kumar Sharma <AlokKumar.Sharma@amd.com>
Date: Sun, 10 Apr 2022 18:50:01 +0530
Subject: [PATCH] Accept functions with DW_AT_linkage_name present

Currently GDB is not able to debug (Binary generated with Clang) variables
present in shared/private clause of OpenMP Task construct. Please note that
LLVM debugger LLDB is able to debug.

In case of OpenMP, compilers generate artificial functions which are not
present in actual program. This is done to apply parallelism to block of
code.

For non-artifical functions, DW_AT_name attribute should contains the name
exactly as present in actual program.
(Ref# http://wiki.dwarfstd.org/index.php?title=Best_Practices)
Since artificial functions are not present in actual program they not having
DW_AT_name and having DW_AT_linkage_name instead should be fine.

Currently GDB is invalidating any function not havnig DW_AT_name which is why
it is not able to debug OpenMP (Clang).

It should be fair to fallback to check DW_AT_linkage_name in case DW_AT_name
is absent.

Change-Id: I408af9be22c82409fb9e27a11639680673e2f7ef
---
 gdb/dwarf2/read.c                      | 16 +++++++-
 gdb/testsuite/gdb.threads/omp-task.c   | 49 +++++++++++++++++++++++++
 gdb/testsuite/gdb.threads/omp-task.exp | 51 ++++++++++++++++++++++++++
 3 files changed, 115 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.threads/omp-task.c
 create mode 100644 gdb/testsuite/gdb.threads/omp-task.exp

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index d146d525066..b7ad75e3a29 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -11926,6 +11926,8 @@ read_func_scope (struct die_info *die, struct dwarf2_cu *cu)
   baseaddr = objfile->text_section_offset ();
 
   name = dwarf2_name (die, cu);
+  if (name == nullptr)
+    name = dw2_linkage_name (die, cu);
 
   /* Ignore functions with missing or empty names.  These are actually
      illegal according to the DWARF standard.  */
@@ -18320,7 +18322,14 @@ cooked_indexer::index_dies (cutu_reader *reader,
 	     but not an ordinary name.  */
 	  if (name != nullptr)
 	    flags = flags & ~IS_MAIN;
-	  m_index_storage->add (this_die, abbrev->tag, flags | IS_LINKAGE,
+	  /* Set the IS_LINKAGE on for everything except when functions
+	     have linkage name present but name is absent.  */
+	  if (name != nullptr
+	      || (abbrev->tag != DW_TAG_subprogram
+	          && abbrev->tag != DW_TAG_inlined_subroutine
+	          && abbrev->tag != DW_TAG_entry_point))
+	    flags = flags | IS_LINKAGE;
+	  m_index_storage->add (this_die, abbrev->tag, flags,
 				linkage_name, nullptr, m_per_cu);
 	}
 
@@ -20597,6 +20606,11 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
   baseaddr = objfile->text_section_offset ();
 
   name = dwarf2_name (die, cu);
+  if (name == nullptr && (die->tag == DW_TAG_subprogram
+                          || die->tag == DW_TAG_inlined_subroutine
+                          || die->tag == DW_TAG_entry_point))
+    name = dw2_linkage_name (die, cu);
+
   if (name)
     {
       int suppress_add = 0;
diff --git a/gdb/testsuite/gdb.threads/omp-task.c b/gdb/testsuite/gdb.threads/omp-task.c
new file mode 100644
index 00000000000..bdeeae501cb
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/omp-task.c
@@ -0,0 +1,49 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2022 Free Software Foundation, Inc.
+
+   This program 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 of the License, or
+   (at your option) any later version.
+
+   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+   Tests which verify (or not) that GDB can access shared and private
+   clauses of OpenMP task construct.
+*/
+
+#include <stdio.h>
+#include <omp.h>
+
+int foo(int n) {
+  int share1 = 9, share2 = 11, share3 = 13, priv1, priv2, fpriv;
+  fpriv = n + 4;
+
+  if (n < 2)
+    return n;
+  else {
+#pragma omp task shared(share1, share2) private(priv1, priv2) firstprivate(fpriv) shared(share3)
+    {
+      priv1 = n;
+      priv2 = n + 2;
+      share2 += share3;
+      printf("share1 = %d, share2 = %d, share3 = %d\n", share1, share2, share3);
+      share1 = priv1 + priv2 + fpriv + foo(n - 1) + share2 + share3;
+    }
+#pragma omp taskwait
+    return share1 + share2 + share3;
+  }
+}
+
+int main() {
+  int n = 10;
+  printf("foo(%d) = %d\n", n, foo(n));
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/omp-task.exp b/gdb/testsuite/gdb.threads/omp-task.exp
new file mode 100644
index 00000000000..8f46658fe0d
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/omp-task.exp
@@ -0,0 +1,51 @@
+# Copyright 2022 Free Software Foundation, Inc.
+
+# This program 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 of the License, or
+# (at your option) any later version.
+#
+# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This file is part of the gdb testsuite.
+
+# Tests which verify (or not) that GDB can access shared and private
+# clauses of OpenMP task construct.
+
+standard_testfile
+
+set have_nested_function_support 0
+set opts {openmp debug}
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile $opts]} {
+    return -1
+}
+
+if {[info procs gdb_openmp_setup] != ""} {
+    if {[gdb_openmp_setup $binfile] != ""} {
+	untested "could not set up OpenMP environment"
+	return -1
+    }
+}
+
+if {![runto_main]} {
+    return -1
+}
+
+gdb_breakpoint [gdb_get_line_number "omp task shared"]
+gdb_test "continue" ".*Breakpoint 2.*" "continue 1"
+gdb_test "print share1" "= 9"
+gdb_test "print share2" "= 11"
+gdb_test "print share3" "= 13"
+gdb_test "disable 2" ".*"
+gdb_breakpoint [gdb_get_line_number "share1 = priv1"]
+gdb_test "continue" ".*Breakpoint 3.*" "continue 2"
+gdb_test "print priv1" "= 10"
+gdb_test "print priv2" "= 12"
+gdb_test "print fpriv" "= 14"
-- 
2.25.1