[PATCH v5 1/3] Fix handling of DW_AT_entry_pc of inlined subroutines

[Bernd Edlinger]

It may happen that the inline entry point is not the
start address of the first sub-range of an inline
function.

But the PC for a breakpoint on an inlined subroutine
is always the start address of the first sub-range.

This patch moves the sub-range starting at the entry
point to the first position of the block list.

Therefore the breakpoint on an inlined function
changes in rare cases from the start address of
the first sub-range to the real entry point.

There should always be a subrange that starts at the
entry point, even if that is an empty sub-range.
---
 gdb/dwarf2/read.c                       | 12 +++++++
 gdb/testsuite/gdb.base/inline-entry.c   | 39 ++++++++++++++++++++++
 gdb/testsuite/gdb.base/inline-entry.exp | 43 +++++++++++++++++++++++++
 3 files changed, 94 insertions(+)
 create mode 100644 gdb/testsuite/gdb.base/inline-entry.c
 create mode 100644 gdb/testsuite/gdb.base/inline-entry.exp

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 769ca91facc..95155a2ee59 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -11276,6 +11276,14 @@ dwarf2_record_block_ranges (struct die_info *die, struct block *block,
       if (die->tag != DW_TAG_compile_unit)
 	ranges_offset += cu->gnu_ranges_base;
 
+      CORE_ADDR entry_pc = (CORE_ADDR) -1;
+      if (die->tag == DW_TAG_inlined_subroutine)
+	{
+	  attr = dwarf2_attr (die, DW_AT_entry_pc, cu);
+	  if (attr != nullptr && !attr->form_is_constant ())
+	    entry_pc = per_objfile->relocate (attr->as_address ());
+	}
+
       std::vector<blockrange> blockvec;
       dwarf2_ranges_process (ranges_offset, cu, die->tag,
 	[&] (unrelocated_addr start, unrelocated_addr end)
@@ -11285,6 +11293,10 @@ dwarf2_record_block_ranges (struct die_info *die, struct block *block,
 	  cu->get_builder ()->record_block_range (block, abs_start,
 						  abs_end - 1);
 	  blockvec.emplace_back (abs_start, abs_end);
+	  /* This ensures that blockvec[0] is the one that starts
+	     at entry_pc, see block::entry_pc.  */
+	  if (entry_pc == abs_start && blockvec.size () > 1)
+	    std::swap (blockvec[0], blockvec[blockvec.size () - 1]);
 	});
 
       block->set_ranges (make_blockranges (objfile, blockvec));
diff --git a/gdb/testsuite/gdb.base/inline-entry.c b/gdb/testsuite/gdb.base/inline-entry.c
new file mode 100644
index 00000000000..bc36d8f9483
--- /dev/null
+++ b/gdb/testsuite/gdb.base/inline-entry.c
@@ -0,0 +1,39 @@
+/* Copyright 2024 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/>.  */
+
+volatile int global = 0;
+
+__attribute__((noinline, noclone)) void
+foo (int arg)
+{
+  global += arg;
+}
+
+inline __attribute__((always_inline)) int
+bar (int val)
+{
+  if (__builtin_expect(global == val, 0))
+    return 1;
+  foo (1);
+  return 1;
+}
+
+int
+main (void)
+{
+  if ((__builtin_expect(global, 0) && bar (1)) || bar (2))
+    return 1;
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/inline-entry.exp b/gdb/testsuite/gdb.base/inline-entry.exp
new file mode 100644
index 00000000000..20e112f7269
--- /dev/null
+++ b/gdb/testsuite/gdb.base/inline-entry.exp
@@ -0,0 +1,43 @@
+# Copyright 2024 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/>.
+
+standard_testfile .c
+
+if { [test_compiler_info gcc*] && ![supports_statement_frontiers] } {
+    untested "this test needs gcc with statement frontiers"
+    return -1
+}
+
+global srcfile testfile
+
+set options {debug nowarnings optimize=-O2}
+if { [supports_statement_frontiers] } {
+    lappend options additional_flags=-gstatement-frontiers
+}
+
+if { [prepare_for_testing "failed to prepare" $binfile \
+      $srcfile $options] } {
+    return -1
+}
+
+if ![runto_main] {
+    return
+}
+
+gdb_test "break bar" ".*Breakpoint 2 at .*" "break at bar"
+gdb_test "break foo" ".*Breakpoint 3 at .*" "break at foo"
+gdb_test "continue" ".*Breakpoint .* bar .*" "continue to bar"
+gdb_test "continue" ".*Breakpoint .* foo .*" "continue to foo"
+gdb_test "continue" ".* exited .*" "continue to exit"
-- 
2.39.2