gdb: introduce FRAME_SCOPED_DEBUG_ENTER_EXIT

Introduce FRAME_SCOPED_DEBUG_ENTER_EXIT and use it to print enter/exit
messages in important frame-related functions.  I think this helps
understand which lower-level operations are done as part of which
higher-level operation.  And it helps visually skip over a higher-level
operation you are not interested in.

Here's an example, combined with some py-unwind messages:

    [frame] frame_unwind_find_by_frame: enter
      [frame] frame_unwind_find_by_frame: this_frame=0
      [frame] frame_unwind_try_unwinder: trying unwinder "dummy"
      [frame] frame_unwind_try_unwinder: no
      [frame] frame_unwind_try_unwinder: trying unwinder "dwarf2 tailcall"
      [frame] frame_unwind_try_unwinder: no
      [frame] frame_unwind_try_unwinder: trying unwinder "inline"
      [frame] frame_unwind_try_unwinder: no
      [frame] frame_unwind_try_unwinder: trying unwinder "jit"
      [frame] frame_unwind_try_unwinder: no
      [frame] frame_unwind_try_unwinder: trying unwinder "python"
      [py-unwind] pyuw_sniffer: enter
        [frame] frame_unwind_register_value: enter
          [frame] frame_unwind_register_value: frame=-1, regnum=7(rsp)
          [frame] frame_unwind_register_value:   -> register=7 bytes=[40ddffffff7f0000]
        [frame] frame_unwind_register_value: exit
        [py-unwind] pyuw_sniffer: frame=0, sp=0x7fffffffdd40, pc=0x5555555551ec
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_eq: l={stack=<sentinel>,!code,special=0x0000000000000000}, r={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_unwind_register_value: enter
          [frame] frame_unwind_register_value: frame=-1, regnum=6(rbp)
          [frame] frame_unwind_register_value:   -> register=6 bytes=[50ddffffff7f0000]
        [frame] frame_unwind_register_value: exit
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_eq: l={stack=<sentinel>,!code,special=0x0000000000000000}, r={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] get_prev_frame: enter
          [frame] get_prev_frame_always_1: enter
            [frame] get_prev_frame_always_1: this_frame=-1
            [frame] get_prev_frame_always_1:   -> {level=0,type=NORMAL_FRAME,unwind=0x5588ee3d17c0,pc=0x5555555551ec,id=<not computed>,func=<unknown>} // cached
          [frame] get_prev_frame_always_1: exit
        [frame] get_prev_frame: exit
        [frame] value_fetch_lazy_register: (frame=0, regnum=6(rbp), ...) -> register=6 bytes=[50ddffffff7f0000]
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_eq: l={stack=<sentinel>,!code,special=0x0000000000000000}, r={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_unwind_register_value: enter
          [frame] frame_unwind_register_value: frame=-1, regnum=7(rsp)
          [frame] frame_unwind_register_value:   -> register=7 bytes=[40ddffffff7f0000]
        [frame] frame_unwind_register_value: exit
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_eq: l={stack=<sentinel>,!code,special=0x0000000000000000}, r={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] get_prev_frame: enter
          [frame] get_prev_frame_always_1: enter
            [frame] get_prev_frame_always_1: this_frame=-1
            [frame] get_prev_frame_always_1:   -> {level=0,type=NORMAL_FRAME,unwind=0x5588ee3d1824,pc=0x5555555551ec,id=<not computed>,func=<unknown>} // cached
          [frame] get_prev_frame_always_1: exit
        [frame] get_prev_frame: exit
        [frame] value_fetch_lazy_register: (frame=0, regnum=7(rsp), ...) -> register=7 bytes=[40ddffffff7f0000]
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_eq: l={stack=<sentinel>,!code,special=0x0000000000000000}, r={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_unwind_register_value: enter
          [frame] frame_unwind_register_value: frame=-1, regnum=16(rip)
          [frame] frame_unwind_register_value:   -> register=16 bytes=[ec51555555550000]
        [frame] frame_unwind_register_value: exit
        [frame] frame_id_p: l={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] frame_id_eq: l={stack=<sentinel>,!code,special=0x0000000000000000}, r={stack=<sentinel>,!code,special=0x0000000000000000} -> 1
        [frame] get_prev_frame: enter
          [frame] get_prev_frame_always_1: enter
            [frame] get_prev_frame_always_1: this_frame=-1
            [frame] get_prev_frame_always_1:   -> {level=0,type=NORMAL_FRAME,unwind=0x5588ee3d1888,pc=0x5555555551ec,id=<not computed>,func=<unknown>} // cached
          [frame] get_prev_frame_always_1: exit
        [frame] get_prev_frame: exit
        [frame] value_fetch_lazy_register: (frame=0, regnum=16(rip), ...) -> register=16 bytes=[ec51555555550000]
        [py-unwind] pyuw_sniffer: frame claimed by unwinder test unwinder
      [py-unwind] pyuw_sniffer: exit
      [frame] frame_unwind_try_unwinder: yes
    [frame] frame_unwind_find_by_frame: exit

gdb/ChangeLog:

	* frame.h (FRAME_SCOPED_DEBUG_ENTER_EXIT): New.
	* frame.c (compute_frame_id, get_prev_frame_always_1,
	get_prev_frame): Use FRAME_SCOPED_DEBUG_ENTER_EXIT.
	* frame-unwind.c (frame_unwind_find_by_frame): Likewise.
	(frame_unwind_register_value): Likewise.

Change-Id: I45b69b4ed962e70572bc55b8adfb211483c1eeed

5 files changed, 29 insertions, 11 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index db55c09870b..699bf6fe568 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,13 @@
 2021-06-29  Simon Marchi  <simon.marchi@polymtl.ca>
 
+	* frame.h (FRAME_SCOPED_DEBUG_ENTER_EXIT): New.
+	* frame.c (compute_frame_id, get_prev_frame_always_1,
+	get_prev_frame): Use FRAME_SCOPED_DEBUG_ENTER_EXIT.
+	* frame-unwind.c (frame_unwind_find_by_frame): Likewise.
+	(frame_unwind_register_value): Likewise.
+
+2021-06-29  Simon Marchi  <simon.marchi@polymtl.ca>
+
 	* frame-unwind.h (struct frame_unwind) <name>: New.  Update
 	instances everywhere to include this field.
 	* frame-unwind.c (frame_unwind_try_unwinder,
diff --git a/gdb/frame-unwind.c b/gdb/frame-unwind.c
index 0fef2c1540e..3dc303a49ad 100644
--- a/gdb/frame-unwind.c
+++ b/gdb/frame-unwind.c
@@ -178,6 +178,7 @@ frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache,
 void
 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
 {
+  FRAME_SCOPED_DEBUG_ENTER_EXIT;
   frame_debug_printf ("this_frame=%d", frame_relative_level (this_frame));
 
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
diff --git a/gdb/frame.c b/gdb/frame.c
index 7b459680313..3f2d2700541 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -560,6 +560,8 @@ skip_tailcall_frames (struct frame_info *frame)
 static void
 compute_frame_id (struct frame_info *fi)
 {
+  FRAME_SCOPED_DEBUG_ENTER_EXIT;
+
   gdb_assert (fi->this_id.p == frame_id_status::NOT_COMPUTED);
 
   unsigned int entry_generation = get_frame_cache_generation ();
@@ -1215,12 +1217,10 @@ get_frame_register (struct frame_info *frame,
 struct value *
 frame_unwind_register_value (frame_info *next_frame, int regnum)
 {
-  struct gdbarch *gdbarch;
-  struct value *value;
+  FRAME_SCOPED_DEBUG_ENTER_EXIT;
 
   gdb_assert (next_frame != NULL);
-  gdbarch = frame_unwind_arch (next_frame);
-
+  gdbarch *gdbarch = frame_unwind_arch (next_frame);
   frame_debug_printf ("frame=%d, regnum=%d(%s)",
 		      next_frame->level, regnum,
 		      user_reg_map_regnum_to_name (gdbarch, regnum));
@@ -1230,9 +1230,9 @@ frame_unwind_register_value (frame_info *next_frame, int regnum)
     frame_unwind_find_by_frame (next_frame, &next_frame->prologue_cache);
 
   /* Ask this frame to unwind its register.  */
-  value = next_frame->unwind->prev_register (next_frame,
-					     &next_frame->prologue_cache,
-					     regnum);
+  value *value = next_frame->unwind->prev_register (next_frame,
+						    &next_frame->prologue_cache,
+						    regnum);
 
   if (frame_debug)
     {
@@ -2104,10 +2104,9 @@ get_prev_frame_if_no_cycle (struct frame_info *this_frame)
 static struct frame_info *
 get_prev_frame_always_1 (struct frame_info *this_frame)
 {
-  struct gdbarch *gdbarch;
+  FRAME_SCOPED_DEBUG_ENTER_EXIT;
 
   gdb_assert (this_frame != NULL);
-  gdbarch = get_frame_arch (this_frame);
 
   if (frame_debug)
     {
@@ -2117,6 +2116,8 @@ get_prev_frame_always_1 (struct frame_info *this_frame)
 	frame_debug_printf ("this_frame=nullptr");
     }
 
+  struct gdbarch *gdbarch = get_frame_arch (this_frame);
+
   /* Only try to do the unwind once.  */
   if (this_frame->prev_p)
     {
@@ -2419,6 +2420,8 @@ inside_entry_func (frame_info *this_frame)
 struct frame_info *
 get_prev_frame (struct frame_info *this_frame)
 {
+  FRAME_SCOPED_DEBUG_ENTER_EXIT;
+
   CORE_ADDR frame_pc;
   int frame_pc_p;
 
diff --git a/gdb/frame.h b/gdb/frame.h
index f8314ad66ce..0d2bc08a47b 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -71,6 +71,7 @@
 
 #include "language.h"
 #include "cli/cli-option.h"
+#include "gdbsupport/common-debug.h"
 
 struct symtab_and_line;
 struct frame_unwind;
@@ -221,6 +222,11 @@ extern bool frame_debug;
 #define frame_debug_printf(fmt, ...) \
   debug_prefixed_printf_cond (frame_debug, "frame", fmt, ##__VA_ARGS__)
 
+/* Print "frame" enter/exit debug statements.  */
+
+#define FRAME_SCOPED_DEBUG_ENTER_EXIT \
+  scoped_debug_enter_exit (frame_debug, "frame")
+
 /* Construct a frame ID.  The first parameter is the frame's constant
    stack address (typically the outer-bound), and the second the
    frame's constant code address (typically the entry point).
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-reg-undefined.exp b/gdb/testsuite/gdb.dwarf2/dw2-reg-undefined.exp
index 2473a41a0de..b1c28b2f41c 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-reg-undefined.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-reg-undefined.exp
@@ -79,8 +79,8 @@ for {set f 0} {$f < 3} {incr f} {
 # "not saved" and not "optimized out".
 gdb_test "set debug frame 1"
 gdb_test {print $rax} [multi_line \
-			{\[frame\] frame_unwind_register_value: frame=0, regnum=0\(rax\)} \
-			{\[frame\] frame_unwind_register_value:   -> <not saved>} \
+			{    \[frame\] frame_unwind_register_value: frame=0, regnum=0\(rax\)} \
+			{    \[frame\] frame_unwind_register_value:   -> <not saved>} \
 			{.*}]
 gdb_test "set debug frame 0"