Refactor struct trad_frame_saved_regs

The following patch drops the overloading going on with the trad_frame_saved_reg
struct and defines a new struct with a KIND enum and a union of different
fields.

The new struct looks like this:

struct trad_frame_saved_reg
 {
  setters/getters

  ...

private:

  trad_frame_saved_reg_kind m_kind;

  union {
    LONGEST value;
    int realreg;
    LONGEST addr;
    const gdb_byte *value_bytes;
  } m_reg;
};

And the enums look like this:

/* Describes the kind of encoding a stored register has.  */
enum class trad_frame_saved_reg_kind
{
  /* Register value is unknown.  */
  UNKNOWN = 0,
  /* Register value is a constant.  */
  VALUE,
  /* Register value is in another register.  */
  REALREG,
  /* Register value is at an address.  */
  ADDR,
  /* Register value is a sequence of bytes.  */
  VALUE_BYTES
};

The patch also adds setters/getters and updates all the users of the old
struct.

It is worth mentioning that due to the previous overloaded nature of the
fields, some tdep files like to store negative offsets and indexes in the ADDR
field, so I kept the ADDR as LONGEST instead of CORE_ADDR. Those cases may
be better supported by a new enum entry.

I have not addressed those cases in this patch to prevent unwanted breakage,
given I have no way to test some of the targets. But it would be nice to
clean those up eventually.

The change to frame-unwind.* is to constify the parameter being passed to the
unwinding functions, given we now accept a "const gdb_byte *" for value bytes.

Tested on aarch64-linux/Ubuntu 20.04/18.04 and by building GDB with
--enable-targets=all.

gdb/ChangeLog:

2021-01-04  Luis Machado  <luis.machado@linaro.org>

	Update all users of trad_frame_saved_reg to use the new member
	functions.

	Remote all struct keywords from declarations of trad_frame_saved_reg
	types, except on forward declarations.

	* aarch64-tdep.c: Update.
	* alpha-mdebug-tdep.c: Update.
	* alpha-tdep.c: Update.
	* arc-tdep.c: Update.
	* arm-tdep.c: Update.
	* avr-tdep.c: Update.
	* cris-tdep.c: Update.
	* csky-tdep.c: Update.
	* frv-tdep.c: Update.
	* hppa-linux-tdep.c: Update.
	* hppa-tdep.c: Update.
	* hppa-tdep.h: Update.
	* lm32-tdep.c: Update.
	* m32r-linux-tdep.c: Update.
	* m32r-tdep.c: Update.
	* m68hc11-tdep.c: Update.
	* mips-tdep.c: Update.
	* moxie-tdep.c: Update.
	* riscv-tdep.c: Update.
	* rs6000-tdep.c: Update.
	* s390-linux-tdep.c: Update.
	* s390-tdep.c: Update.
	* score-tdep.c: Update.
	* sparc-netbsd-tdep.c: Update.
	* sparc-sol2-tdep.c: Update.
	* sparc64-fbsd-tdep.c: Update.
	* sparc64-netbsd-tdep.c: Update.
	* sparc64-obsd-tdep.c: Update.
	* sparc64-sol2-tdep.c: Update.
	* tilegx-tdep.c: Update.
	* v850-tdep.c: Update.
	* vax-tdep.c: Update.

	* frame-unwind.c (frame_unwind_got_bytes): Make parameter const.
	* frame-unwind.h (frame_unwind_got_bytes): Likewise.

	* trad-frame.c: Update.
	Remove TF_REG_* enum.
	(trad_frame_alloc_saved_regs): Add a static assertion to check for
	a trivially-constructible struct.
	(trad_frame_reset_saved_regs): Adjust to use member function.
	(trad_frame_value_p): Likewise.
	(trad_frame_addr_p): Likewise.
	(trad_frame_realreg_p): Likewise.
	(trad_frame_value_bytes_p): Likewise.
	(trad_frame_set_value): Likewise.
	(trad_frame_set_realreg): Likewise.
	(trad_frame_set_addr): Likewise.
	(trad_frame_set_unknown): Likewise.
	(trad_frame_set_value_bytes): Likewise.
	(trad_frame_get_prev_register): Likewise.
	* trad-frame.h: Update.
	(trad_frame_saved_reg_kind): New enum.
	(struct trad_frame_saved_reg) <addr, realreg, data>: Remove.
	<m_kind, m_reg>: New member fields.
	<set_value, set_realreg, set_addr, set_unknown, set_value_bytes>
	<kind, value, realreg, addr, value_bytes, is_value, is_realreg>
	<is_addr, is_unknown, is_value_bytes>: New member functions.

1 files changed, 17 insertions, 16 deletions

diff --git a/gdb/avr-tdep.c b/gdb/avr-tdep.c
index 933af25..e9493f1 100644
--- a/gdb/avr-tdep.c
+++ b/gdb/avr-tdep.c
@@ -185,7 +185,7 @@ struct avr_unwind_cache
   int size;
   int prologue_type;
   /* Table indicating the location of each and every register.  */
-  struct trad_frame_saved_reg *saved_regs;
+  trad_frame_saved_reg *saved_regs;
 };
 
 struct gdbarch_tdep
@@ -672,14 +672,14 @@ avr_scan_prologue (struct gdbarch *gdbarch, CORE_ADDR pc_beg, CORE_ADDR pc_end,
 	{
 	  int from;
 
-	  info->saved_regs[AVR_FP_REGNUM + 1].addr = num_pushes;
+	  info->saved_regs[AVR_FP_REGNUM + 1].set_addr (num_pushes);
 	  if (num_pushes >= 2)
-	    info->saved_regs[AVR_FP_REGNUM].addr = num_pushes - 1;
+	    info->saved_regs[AVR_FP_REGNUM].set_addr (num_pushes - 1);
 
 	  i = 0;
 	  for (from = AVR_LAST_PUSHED_REGNUM + 1 - (num_pushes - 2);
 	       from <= AVR_LAST_PUSHED_REGNUM; ++from)
-	    info->saved_regs [from].addr = ++i;
+	    info->saved_regs [from].set_addr (++i);
 	}
       info->size = loc_size + num_pushes;
       info->prologue_type = AVR_PROLOGUE_CALL;
@@ -707,9 +707,9 @@ avr_scan_prologue (struct gdbarch *gdbarch, CORE_ADDR pc_beg, CORE_ADDR pc_end,
 	{
 	  info->prologue_type = AVR_PROLOGUE_INTR;
 	  vpc += sizeof (img);
-	  info->saved_regs[AVR_SREG_REGNUM].addr = 3;
-	  info->saved_regs[0].addr = 2;
-	  info->saved_regs[1].addr = 1;
+	  info->saved_regs[AVR_SREG_REGNUM].set_addr (3);
+	  info->saved_regs[0].set_addr (2);
+	  info->saved_regs[1].set_addr (1);
 	  info->size += 3;
 	}
       else if (len >= sizeof (img) - 2
@@ -717,9 +717,9 @@ avr_scan_prologue (struct gdbarch *gdbarch, CORE_ADDR pc_beg, CORE_ADDR pc_end,
 	{
 	  info->prologue_type = AVR_PROLOGUE_SIG;
 	  vpc += sizeof (img) - 2;
-	  info->saved_regs[AVR_SREG_REGNUM].addr = 3;
-	  info->saved_regs[0].addr = 2;
-	  info->saved_regs[1].addr = 1;
+	  info->saved_regs[AVR_SREG_REGNUM].set_addr (3);
+	  info->saved_regs[0].set_addr (2);
+	  info->saved_regs[1].set_addr (1);
 	  info->size += 2;
 	}
     }
@@ -735,7 +735,7 @@ avr_scan_prologue (struct gdbarch *gdbarch, CORE_ADDR pc_beg, CORE_ADDR pc_end,
 	  /* Bits 4-9 contain a mask for registers R0-R32.  */
 	  int regno = (insn & 0x1f0) >> 4;
 	  info->size++;
-	  info->saved_regs[regno].addr = info->size;
+	  info->saved_regs[regno].set_addr (info->size);
 	  scan_stage = 1;
 	}
       else
@@ -892,7 +892,7 @@ avr_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
   {
     CORE_ADDR prologue_end = pc;
     struct avr_unwind_cache info = {0};
-    struct trad_frame_saved_reg saved_regs[AVR_NUM_REGS];
+    trad_frame_saved_reg saved_regs[AVR_NUM_REGS];
 
     info.saved_regs = saved_regs;
     
@@ -1037,14 +1037,15 @@ avr_frame_unwind_cache (struct frame_info *this_frame,
   /* Adjust all the saved registers so that they contain addresses and not
      offsets.  */
   for (i = 0; i < gdbarch_num_regs (gdbarch) - 1; i++)
-    if (info->saved_regs[i].addr > 0)
-      info->saved_regs[i].addr = info->prev_sp - info->saved_regs[i].addr;
+    if (info->saved_regs[i].addr () > 0)
+      info->saved_regs[i].set_addr (info->prev_sp
+				    - info->saved_regs[i].addr ());
 
   /* Except for the main and startup code, the return PC is always saved on
      the stack and is at the base of the frame.  */
 
   if (info->prologue_type != AVR_PROLOGUE_MAIN)
-    info->saved_regs[AVR_PC_REGNUM].addr = info->prev_sp;
+    info->saved_regs[AVR_PC_REGNUM].set_addr (info->prev_sp);
 
   /* The previous frame's SP needed to be computed.  Save the computed
      value.  */
@@ -1132,7 +1133,7 @@ avr_frame_prev_register (struct frame_info *this_frame,
 	  struct gdbarch *gdbarch = get_frame_arch (this_frame);
 	  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 
-	  read_memory (info->saved_regs[AVR_PC_REGNUM].addr,
+	  read_memory (info->saved_regs[AVR_PC_REGNUM].addr (),
 		       buf, tdep->call_length);
 
 	  /* Extract the PC read from memory as a big-endian.  */