gdb: pass frames as `const frame_info_ptr &`

We currently pass frames to function by value, as `frame_info_ptr`.
This is somewhat expensive:

 - the size of `frame_info_ptr` is 64 bytes, which is a bit big to pass
   by value
 - the constructors and destructor link/unlink the object in the global
   `frame_info_ptr::frame_list` list.  This is an `intrusive_list`, so
   it's not so bad: it's just assigning a few points, there's no memory
   allocation as if it was `std::list`, but still it's useless to do
   that over and over.

As suggested by Tom Tromey, change many function signatures to accept
`const frame_info_ptr &` instead of `frame_info_ptr`.

Some functions reassign their `frame_info_ptr` parameter, like:

  void
  the_func (frame_info_ptr frame)
  {
    for (; frame != nullptr; frame = get_prev_frame (frame))
      {
        ...
      }
  }

I wondered what to do about them, do I leave them as-is or change them
(and need to introduce a separate local variable that can be
re-assigned).  I opted for the later for consistency.  It might not be
clear why some functions take `const frame_info_ptr &` while others take
`frame_info_ptr`.  Also, if a function took a `frame_info_ptr` because
it did re-assign its parameter, I doubt that we would think to change it
to `const frame_info_ptr &` should the implementation change such that
it doesn't need to take `frame_info_ptr` anymore.  It seems better to
have a simple rule and apply it everywhere.

Change-Id: I59d10addef687d157f82ccf4d54f5dde9a963fd0
Approved-By: Andrew Burgess <aburgess@redhat.com>

1 files changed, 23 insertions, 23 deletions

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index b97e215..d1d5486 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -268,7 +268,7 @@ class instruction_reader : public abstract_instruction_reader
 
 static CORE_ADDR
 aarch64_frame_unmask_lr (aarch64_gdbarch_tdep *tdep,
-			 frame_info_ptr this_frame, CORE_ADDR addr)
+			 const frame_info_ptr &this_frame, CORE_ADDR addr)
 {
   if (tdep->has_pauth ()
       && frame_unwind_register_unsigned (this_frame,
@@ -298,7 +298,7 @@ aarch64_frame_unmask_lr (aarch64_gdbarch_tdep *tdep,
 /* Implement the "get_pc_address_flags" gdbarch method.  */
 
 static std::string
-aarch64_get_pc_address_flags (frame_info_ptr frame, CORE_ADDR pc)
+aarch64_get_pc_address_flags (const frame_info_ptr &frame, CORE_ADDR pc)
 {
   if (pc != 0 && get_frame_pc_masked (frame))
     return "PAC";
@@ -995,7 +995,7 @@ aarch64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
    cache CACHE.  */
 
 static void
-aarch64_scan_prologue (frame_info_ptr this_frame,
+aarch64_scan_prologue (const frame_info_ptr &this_frame,
 		       struct aarch64_prologue_cache *cache)
 {
   CORE_ADDR block_addr = get_frame_address_in_block (this_frame);
@@ -1049,7 +1049,7 @@ aarch64_scan_prologue (frame_info_ptr this_frame,
    not available.  */
 
 static void
-aarch64_make_prologue_cache_1 (frame_info_ptr this_frame,
+aarch64_make_prologue_cache_1 (const frame_info_ptr &this_frame,
 			       struct aarch64_prologue_cache *cache)
 {
   CORE_ADDR unwound_fp;
@@ -1087,7 +1087,7 @@ aarch64_make_prologue_cache_1 (frame_info_ptr this_frame,
    *THIS_CACHE.  */
 
 static struct aarch64_prologue_cache *
-aarch64_make_prologue_cache (frame_info_ptr this_frame, void **this_cache)
+aarch64_make_prologue_cache (const frame_info_ptr &this_frame, void **this_cache)
 {
   struct aarch64_prologue_cache *cache;
 
@@ -1114,7 +1114,7 @@ aarch64_make_prologue_cache (frame_info_ptr this_frame, void **this_cache)
 /* Implement the "stop_reason" frame_unwind method.  */
 
 static enum unwind_stop_reason
-aarch64_prologue_frame_unwind_stop_reason (frame_info_ptr this_frame,
+aarch64_prologue_frame_unwind_stop_reason (const frame_info_ptr &this_frame,
 					   void **this_cache)
 {
   struct aarch64_prologue_cache *cache
@@ -1140,7 +1140,7 @@ aarch64_prologue_frame_unwind_stop_reason (frame_info_ptr this_frame,
    PC and the caller's SP when we were called.  */
 
 static void
-aarch64_prologue_this_id (frame_info_ptr this_frame,
+aarch64_prologue_this_id (const frame_info_ptr &this_frame,
 			  void **this_cache, struct frame_id *this_id)
 {
   struct aarch64_prologue_cache *cache
@@ -1155,7 +1155,7 @@ aarch64_prologue_this_id (frame_info_ptr this_frame,
 /* Implement the "prev_register" frame_unwind method.  */
 
 static struct value *
-aarch64_prologue_prev_register (frame_info_ptr this_frame,
+aarch64_prologue_prev_register (const frame_info_ptr &this_frame,
 				void **this_cache, int prev_regnum)
 {
   struct aarch64_prologue_cache *cache
@@ -1221,7 +1221,7 @@ static frame_unwind aarch64_prologue_unwind =
    *THIS_CACHE.  */
 
 static struct aarch64_prologue_cache *
-aarch64_make_stub_cache (frame_info_ptr this_frame, void **this_cache)
+aarch64_make_stub_cache (const frame_info_ptr &this_frame, void **this_cache)
 {
   struct aarch64_prologue_cache *cache;
 
@@ -1251,7 +1251,7 @@ aarch64_make_stub_cache (frame_info_ptr this_frame, void **this_cache)
 /* Implement the "stop_reason" frame_unwind method.  */
 
 static enum unwind_stop_reason
-aarch64_stub_frame_unwind_stop_reason (frame_info_ptr this_frame,
+aarch64_stub_frame_unwind_stop_reason (const frame_info_ptr &this_frame,
 				       void **this_cache)
 {
   struct aarch64_prologue_cache *cache
@@ -1266,7 +1266,7 @@ aarch64_stub_frame_unwind_stop_reason (frame_info_ptr this_frame,
 /* Our frame ID for a stub frame is the current SP and LR.  */
 
 static void
-aarch64_stub_this_id (frame_info_ptr this_frame,
+aarch64_stub_this_id (const frame_info_ptr &this_frame,
 		      void **this_cache, struct frame_id *this_id)
 {
   struct aarch64_prologue_cache *cache
@@ -1282,7 +1282,7 @@ aarch64_stub_this_id (frame_info_ptr this_frame,
 
 static int
 aarch64_stub_unwind_sniffer (const struct frame_unwind *self,
-			     frame_info_ptr this_frame,
+			     const frame_info_ptr &this_frame,
 			     void **this_prologue_cache)
 {
   CORE_ADDR addr_in_block;
@@ -1313,7 +1313,7 @@ static frame_unwind aarch64_stub_unwind =
 /* Return the frame base address of *THIS_FRAME.  */
 
 static CORE_ADDR
-aarch64_normal_frame_base (frame_info_ptr this_frame, void **this_cache)
+aarch64_normal_frame_base (const frame_info_ptr &this_frame, void **this_cache)
 {
   struct aarch64_prologue_cache *cache
     = aarch64_make_prologue_cache (this_frame, this_cache);
@@ -1334,7 +1334,7 @@ static frame_base aarch64_normal_base =
    *THIS_FRAME.  */
 
 static struct value *
-aarch64_dwarf2_prev_register (frame_info_ptr this_frame,
+aarch64_dwarf2_prev_register (const frame_info_ptr &this_frame,
 			      void **this_cache, int regnum)
 {
   gdbarch *arch = get_frame_arch (this_frame);
@@ -1361,7 +1361,7 @@ static const unsigned char op_lit1 = DW_OP_lit1;
 static void
 aarch64_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
 			       struct dwarf2_frame_state_reg *reg,
-			       frame_info_ptr this_frame)
+			       const frame_info_ptr &this_frame)
 {
   aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
@@ -2780,7 +2780,7 @@ aarch64_return_value (struct gdbarch *gdbarch, struct value *func_value,
 /* Implement the "get_longjmp_target" gdbarch method.  */
 
 static int
-aarch64_get_longjmp_target (frame_info_ptr frame, CORE_ADDR *pc)
+aarch64_get_longjmp_target (const frame_info_ptr &frame, CORE_ADDR *pc)
 {
   CORE_ADDR jb_addr;
   gdb_byte buf[X_REGISTER_SIZE];
@@ -3105,7 +3105,7 @@ aarch64_pseudo_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
 /* Helper for aarch64_pseudo_read_value.  */
 
 static value *
-aarch64_pseudo_read_value_1 (frame_info_ptr next_frame,
+aarch64_pseudo_read_value_1 (const frame_info_ptr &next_frame,
 			     const int pseudo_reg_num, int raw_regnum_offset)
 {
   unsigned v_regnum = AARCH64_V0_REGNUM + raw_regnum_offset;
@@ -3197,7 +3197,7 @@ aarch64_za_offsets_from_regnum (struct gdbarch *gdbarch, int regnum)
 /* Given REGNUM, a SME pseudo-register number, return its value in RESULT.  */
 
 static value *
-aarch64_sme_pseudo_register_read (gdbarch *gdbarch, frame_info_ptr next_frame,
+aarch64_sme_pseudo_register_read (gdbarch *gdbarch, const frame_info_ptr &next_frame,
 				  const int pseudo_reg_num)
 {
   aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
@@ -3231,7 +3231,7 @@ aarch64_sme_pseudo_register_read (gdbarch *gdbarch, frame_info_ptr next_frame,
 /* Implement the "pseudo_register_read_value" gdbarch method.  */
 
 static value *
-aarch64_pseudo_read_value (gdbarch *gdbarch, frame_info_ptr next_frame,
+aarch64_pseudo_read_value (gdbarch *gdbarch, const frame_info_ptr &next_frame,
 			   const int pseudo_reg_num)
 {
   aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
@@ -3296,7 +3296,7 @@ aarch64_pseudo_read_value (gdbarch *gdbarch, frame_info_ptr next_frame,
 /* Helper for aarch64_pseudo_write.  */
 
 static void
-aarch64_pseudo_write_1 (gdbarch *gdbarch, frame_info_ptr next_frame,
+aarch64_pseudo_write_1 (gdbarch *gdbarch, const frame_info_ptr &next_frame,
 			int regnum_offset,
 			gdb::array_view<const gdb_byte> buf)
 {
@@ -3322,7 +3322,7 @@ aarch64_pseudo_write_1 (gdbarch *gdbarch, frame_info_ptr next_frame,
    pseudo-register.  */
 
 static void
-aarch64_sme_pseudo_register_write (gdbarch *gdbarch, frame_info_ptr next_frame,
+aarch64_sme_pseudo_register_write (gdbarch *gdbarch, const frame_info_ptr &next_frame,
 				   const int regnum,
 				   gdb::array_view<const gdb_byte> data)
 {
@@ -3364,7 +3364,7 @@ aarch64_sme_pseudo_register_write (gdbarch *gdbarch, frame_info_ptr next_frame,
 /* Implement the "pseudo_register_write" gdbarch method.  */
 
 static void
-aarch64_pseudo_write (gdbarch *gdbarch, frame_info_ptr next_frame,
+aarch64_pseudo_write (gdbarch *gdbarch, const frame_info_ptr &next_frame,
 		      const int pseudo_reg_num,
 		      gdb::array_view<const gdb_byte> buf)
 {
@@ -3437,7 +3437,7 @@ aarch64_pseudo_write (gdbarch *gdbarch, frame_info_ptr next_frame,
 /* Callback function for user_reg_add.  */
 
 static struct value *
-value_of_aarch64_user_reg (frame_info_ptr frame, const void *baton)
+value_of_aarch64_user_reg (const frame_info_ptr &frame, const void *baton)
 {
   const int *reg_p = (const int *) baton;