[PATCH v11 06/10] gdb: Skip trampoline functions for the up command.

This change skips trampoline functions when the option
'skip-trampoline-functions' is set to 'on' for the up command.  Before this
change, GDB processes trampoline functions indicated by the compiler with
DIE "DW_AT_trampoline" and stops at the trampoline function for the 'up'
command.  For better user experience, all such frames can be
skipped and hidden from the user.

In this example the IFX compiler emits "DW_AT_trampoline" tag for the 'first'
and 'second' trampoline functions like following:

function second (x, y) result(z)
  integer, intent(in) :: x, y
  integer :: z
  z = x * y ! breakpt-up
end function second

function first (num1, num2) result(total)
  integer, intent(in) :: num1, num2
  integer  :: total
  total = second (num1 + 4, num2 * 3) ! first-breakpt
  total = total + 30
end function first

Related Dwarf:

0x0000013f:   DW_TAG_subprogram
                DW_AT_low_pc    (0x0000000000404350)
                DW_AT_high_pc   (0x000000000040435f)
                DW_AT_frame_base        (DW_OP_reg6 RBP)
                DW_AT_linkage_name      ("second_.t74p.t75p")
                DW_AT_name      ("second_.t74p.t75p")
                DW_AT_trampoline        ("second_")

0x0000015a:   DW_TAG_subprogram
                DW_AT_low_pc    (0x00000000004044a0)
                DW_AT_high_pc   (0x00000000004044af)
                DW_AT_frame_base        (DW_OP_reg6 RBP)
                DW_AT_linkage_name      ("first_.t104p.t105p")
                DW_AT_name      ("first_.t104p.t105p")
                DW_AT_trampoline        ("first_")

Before this change, the 'up' command output looks like:

'''
(gdb) up
\#1  0x0000000000405209 in second_.t74p.t75p () at test.f90:12
12      end function first
'''

After this change:

'''
(gdb) up
\#2  0x00000000004051e3 in first (num1=16, num2=3) at test.f90:10
10        total = second (num1 + 4, num2 * 3) ! first-breakpt
'''

The test gdb.fortran/func-trampoline.exp is updated for testing this change.
---
 gdb/doc/gdb.texinfo                           |  2 +-
 gdb/stack.c                                   |  7 +++++++
 gdb/testsuite/gdb.fortran/func-trampoline.exp | 12 ++++++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index b9dd6c14809..ee94ad09fd9 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -6772,7 +6772,7 @@ DWARF trampolines marked via DW_AT_trampoline are supported by this.
 When issuing a @code{backtrace}, if @code{skip-trampoline-functions} is set,
 @value{GDBN} will skip trampoline frames while printing the stack.
 
-When issuing a @code{finish} or @code{reverse-finish}, if
+When issuing a @code{finish}, @code{reverse-finish} or @code{up}, if
 @code{skip-trampoline-functions} is set, @value{GDBN} will skip trampoline
 frames while returning from the target function.
 
diff --git a/gdb/stack.c b/gdb/stack.c
index fa217ae9f6f..8b1644ddb6e 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -2636,6 +2636,13 @@ up_silently_base (const char *count_exp)
   frame = find_relative_frame (get_selected_frame ("No stack."), &count);
   if (count != 0 && count_exp == NULL)
     error (_("Initial frame selected; you cannot go up."));
+
+  if (skip_trampoline_functions)
+    {
+      for (int i = 0; (SAFE_TRAMPOLINE_CHAIN (i, frame)
+		       && in_trampoline_frame (frame)); ++i)
+	frame = get_prev_frame (frame);
+    }
   select_frame (frame);
 }
 
diff --git a/gdb/testsuite/gdb.fortran/func-trampoline.exp b/gdb/testsuite/gdb.fortran/func-trampoline.exp
index f330ac54ef2..ce9f14160aa 100644
--- a/gdb/testsuite/gdb.fortran/func-trampoline.exp
+++ b/gdb/testsuite/gdb.fortran/func-trampoline.exp
@@ -13,8 +13,8 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/> .
 
-# Test "backtrace", "backtrace -n" and "finish"  commands for functions with
-# trampoline calls.
+# Test "backtrace", "backtrace -n", "finish" and "up"  commands for
+# functions with trampoline calls.
 
 require allow_fortran_tests
 
@@ -97,4 +97,12 @@ foreach_with_prefix opt_level {O0 O2} {
 	    "${fill}first \\(num1=16, num2=3\\)${fill}" \
 	    "${fill}(\r\nValue returned is $valnum_re = 180)"]
     }
+
+    with_test_prefix "up" {
+	init_test $opt_level
+
+	gdb_test "up" [multi_line \
+	    "#$decimal.* $middle_desc" \
+	    "${fill}first = second \\(num1 \\+ 4, num2 \\* 3\\).*${fill}"]
+    }
 }
-- 
2.34.1

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