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, 10 insertions, 10 deletions

diff --git a/gdb/ppc64-tdep.c b/gdb/ppc64-tdep.c
index d415836..5797d55 100644
--- a/gdb/ppc64-tdep.c
+++ b/gdb/ppc64-tdep.c
@@ -85,7 +85,7 @@
    Return the function's entry point.  */
 
 static CORE_ADDR
-ppc64_plt_entry_point (frame_info_ptr frame, CORE_ADDR plt_off)
+ppc64_plt_entry_point (const frame_info_ptr &frame, CORE_ADDR plt_off)
 {
   struct gdbarch *gdbarch = get_frame_arch (frame);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
@@ -108,7 +108,7 @@ ppc64_plt_entry_point (frame_info_ptr frame, CORE_ADDR plt_off)
 }
 
 static CORE_ADDR
-ppc64_plt_pcrel_entry_point (frame_info_ptr frame, CORE_ADDR plt_off,
+ppc64_plt_pcrel_entry_point (const frame_info_ptr &frame, CORE_ADDR plt_off,
 			     CORE_ADDR pc)
 {
   struct gdbarch *gdbarch = get_frame_arch (frame);
@@ -546,7 +546,7 @@ static const struct ppc_insn_pattern ppc64_standard_linkage12[] =
    dynamic linker lazy symbol resolution stubs.)  */
 
 static CORE_ADDR
-ppc64_standard_linkage1_target (frame_info_ptr frame, unsigned int *insn)
+ppc64_standard_linkage1_target (const frame_info_ptr &frame, unsigned int *insn)
 {
   CORE_ADDR plt_off = ((ppc_insn_d_field (insn[0]) << 16)
 		       + ppc_insn_ds_field (insn[2]));
@@ -555,7 +555,7 @@ ppc64_standard_linkage1_target (frame_info_ptr frame, unsigned int *insn)
 }
 
 static CORE_ADDR
-ppc64_standard_linkage2_target (frame_info_ptr frame, unsigned int *insn)
+ppc64_standard_linkage2_target (const frame_info_ptr &frame, unsigned int *insn)
 {
   CORE_ADDR plt_off = ((ppc_insn_d_field (insn[1]) << 16)
 		       + ppc_insn_ds_field (insn[3]));
@@ -564,7 +564,7 @@ ppc64_standard_linkage2_target (frame_info_ptr frame, unsigned int *insn)
 }
 
 static CORE_ADDR
-ppc64_standard_linkage3_target (frame_info_ptr frame, unsigned int *insn)
+ppc64_standard_linkage3_target (const frame_info_ptr &frame, unsigned int *insn)
 {
   CORE_ADDR plt_off = ppc_insn_ds_field (insn[1]);
 
@@ -572,7 +572,7 @@ ppc64_standard_linkage3_target (frame_info_ptr frame, unsigned int *insn)
 }
 
 static CORE_ADDR
-ppc64_standard_linkage4_target (frame_info_ptr frame, unsigned int *insn)
+ppc64_standard_linkage4_target (const frame_info_ptr &frame, unsigned int *insn)
 {
   CORE_ADDR plt_off = ((ppc_insn_d_field (insn[1]) << 16)
 		       + ppc_insn_ds_field (insn[2]));
@@ -581,7 +581,7 @@ ppc64_standard_linkage4_target (frame_info_ptr frame, unsigned int *insn)
 }
 
 static CORE_ADDR
-ppc64_pcrel_linkage1_target (frame_info_ptr frame, unsigned int *insn,
+ppc64_pcrel_linkage1_target (const frame_info_ptr &frame, unsigned int *insn,
 			     CORE_ADDR pc)
 {
   /* insn[0] is for the std instruction.  */
@@ -591,7 +591,7 @@ ppc64_pcrel_linkage1_target (frame_info_ptr frame, unsigned int *insn,
 }
 
 static CORE_ADDR
-ppc64_pcrel_linkage2_target (frame_info_ptr frame, unsigned int *insn,
+ppc64_pcrel_linkage2_target (const frame_info_ptr &frame, unsigned int *insn,
 			     CORE_ADDR pc)
 {
   CORE_ADDR plt_off;
@@ -611,7 +611,7 @@ ppc64_pcrel_linkage2_target (frame_info_ptr frame, unsigned int *insn,
    check whether we are in the middle of a PLT stub.  */
 
 static CORE_ADDR
-ppc64_skip_trampoline_code_1 (frame_info_ptr frame, CORE_ADDR pc)
+ppc64_skip_trampoline_code_1 (const frame_info_ptr &frame, CORE_ADDR pc)
 {
 #define MAX(a,b) ((a) > (b) ? (a) : (b))
   unsigned int insns[MAX (MAX (MAX (ARRAY_SIZE (ppc64_standard_linkage1),
@@ -707,7 +707,7 @@ ppc64_skip_trampoline_code_1 (frame_info_ptr frame, CORE_ADDR pc)
    ppc_elfv2_skip_entrypoint.  */
 
 CORE_ADDR
-ppc64_skip_trampoline_code (frame_info_ptr frame, CORE_ADDR pc)
+ppc64_skip_trampoline_code (const frame_info_ptr &frame, CORE_ADDR pc)
 {
   struct gdbarch *gdbarch = get_frame_arch (frame);