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, 21 insertions, 19 deletions

diff --git a/gdb/hppa-tdep.c b/gdb/hppa-tdep.c
index 738f293..4f72565 100644
--- a/gdb/hppa-tdep.c
+++ b/gdb/hppa-tdep.c
@@ -1865,7 +1865,7 @@ hppa_find_unwind_entry_in_block (struct frame_info *this_frame)
 struct hppa_frame_cache
 {
   CORE_ADDR base;
-  struct trad_frame_saved_reg *saved_regs;
+  trad_frame_saved_reg *saved_regs;
 };
 
 static struct hppa_frame_cache *
@@ -2007,18 +2007,18 @@ hppa_frame_cache (struct frame_info *this_frame, void **this_cache)
 	if (inst == 0x6bc23fd9) /* stw rp,-0x14(sr0,sp) */
 	  {
 	    looking_for_rp = 0;
-	    cache->saved_regs[HPPA_RP_REGNUM].addr = -20;
+	    cache->saved_regs[HPPA_RP_REGNUM].set_addr (-20);
 	  }
 	else if (inst == 0x6bc23fd1) /* stw rp,-0x18(sr0,sp) */
 	  {
 	    looking_for_rp = 0;
-	    cache->saved_regs[HPPA_RP_REGNUM].addr = -24;
+	    cache->saved_regs[HPPA_RP_REGNUM].set_addr (-24);
 	  }
 	else if (inst == 0x0fc212c1 
 		 || inst == 0x73c23fe1) /* std rp,-0x10(sr0,sp) */
 	  {
 	    looking_for_rp = 0;
-	    cache->saved_regs[HPPA_RP_REGNUM].addr = -16;
+	    cache->saved_regs[HPPA_RP_REGNUM].set_addr (-16);
 	  }
 	
 	/* Check to see if we saved SP into the stack.  This also
@@ -2028,7 +2028,7 @@ hppa_frame_cache (struct frame_info *this_frame, void **this_cache)
 	    || (inst & 0xffffc00c) == 0x73c10008) /* std,ma r1,N(sr0,sp) */
 	  {
 	    looking_for_sp = 0;
-	    cache->saved_regs[HPPA_FP_REGNUM].addr = 0;
+	    cache->saved_regs[HPPA_FP_REGNUM].set_addr (0);
 	  }
 	else if (inst == 0x08030241) /* copy %r3, %r1 */
 	  {
@@ -2044,10 +2044,10 @@ hppa_frame_cache (struct frame_info *this_frame, void **this_cache)
 	    if ((inst >> 26) == 0x1b && hppa_extract_14 (inst) >= 0)
 	      /* stwm with a positive displacement is a _post_
 		 _modify_.  */
-	      cache->saved_regs[reg].addr = 0;
+	      cache->saved_regs[reg].set_addr (0);
 	    else if ((inst & 0xfc00000c) == 0x70000008)
 	      /* A std has explicit post_modify forms.  */
-	      cache->saved_regs[reg].addr = 0;
+	      cache->saved_regs[reg].set_addr (0);
 	    else
 	      {
 		CORE_ADDR offset;
@@ -2062,10 +2062,10 @@ hppa_frame_cache (struct frame_info *this_frame, void **this_cache)
 		
 		/* Handle code with and without frame pointers.  */
 		if (u->Save_SP)
-		  cache->saved_regs[reg].addr = offset;
+		  cache->saved_regs[reg].set_addr (offset);
 		else
-		  cache->saved_regs[reg].addr
-		    = (u->Total_frame_size << 3) + offset;
+		  cache->saved_regs[reg].set_addr ((u->Total_frame_size << 3)
+						   + offset);
 	      }
 	  }
 
@@ -2095,12 +2095,12 @@ hppa_frame_cache (struct frame_info *this_frame, void **this_cache)
 		/* 1st HP CC FP register store.  After this
 		   instruction we've set enough state that the GCC and
 		   HPCC code are both handled in the same manner.  */
-		cache->saved_regs[reg + HPPA_FP4_REGNUM + 4].addr = 0;
+		cache->saved_regs[reg + HPPA_FP4_REGNUM + 4].set_addr (0);
 		fp_loc = 8;
 	      }
 	    else
 	      {
-		cache->saved_regs[reg + HPPA_FP0_REGNUM + 4].addr = fp_loc;
+		cache->saved_regs[reg + HPPA_FP0_REGNUM + 4].set_addr (fp_loc);
 		fp_loc += 8;
 	      }
 	  }
@@ -2251,7 +2251,8 @@ hppa_frame_cache (struct frame_info *this_frame, void **this_cache)
     for (reg = 0; reg < gdbarch_num_regs (gdbarch); reg++)
       {
 	if (trad_frame_addr_p (cache->saved_regs, reg))
-	  cache->saved_regs[reg].addr += cache->base;
+	  cache->saved_regs[reg].set_addr (cache->saved_regs[reg].addr ()
+					   + cache->base);
       }
   }
 
@@ -2357,13 +2358,13 @@ hppa_fallback_frame_cache (struct frame_info *this_frame, void **this_cache)
 	     stack.  */
 	  if (insn == 0x6bc23fd9) /* stw rp,-0x14(sr0,sp) */
 	    {
-	      cache->saved_regs[HPPA_RP_REGNUM].addr = -20;
+	      cache->saved_regs[HPPA_RP_REGNUM].set_addr (-20);
 	      found_rp = 1;
 	    }
 	  else if (insn == 0x0fc212c1
 		   || insn == 0x73c23fe1) /* std rp,-0x10(sr0,sp) */
 	    {
-	      cache->saved_regs[HPPA_RP_REGNUM].addr = -16;
+	      cache->saved_regs[HPPA_RP_REGNUM].set_addr (-16);
 	      found_rp = 1;
 	    }
 	}
@@ -2379,7 +2380,8 @@ hppa_fallback_frame_cache (struct frame_info *this_frame, void **this_cache)
 
   if (trad_frame_addr_p (cache->saved_regs, HPPA_RP_REGNUM))
     {
-      cache->saved_regs[HPPA_RP_REGNUM].addr += cache->base;
+      cache->saved_regs[HPPA_RP_REGNUM].set_addr (cache->saved_regs[HPPA_RP_REGNUM].addr ()
+						  + cache->base);
       cache->saved_regs[HPPA_PCOQ_HEAD_REGNUM] = 
 	cache->saved_regs[HPPA_RP_REGNUM];
     }
@@ -2428,7 +2430,7 @@ static const struct frame_unwind hppa_fallback_frame_unwind =
 struct hppa_stub_unwind_cache
 {
   CORE_ADDR base;
-  struct trad_frame_saved_reg *saved_regs;
+  trad_frame_saved_reg *saved_regs;
 };
 
 static struct hppa_stub_unwind_cache *
@@ -2447,7 +2449,7 @@ hppa_stub_frame_unwind_cache (struct frame_info *this_frame,
   info->base = get_frame_register_unsigned (this_frame, HPPA_SP_REGNUM);
 
   /* By default we assume that stubs do not change the rp.  */
-  info->saved_regs[HPPA_PCOQ_HEAD_REGNUM].realreg = HPPA_RP_REGNUM;
+  info->saved_regs[HPPA_PCOQ_HEAD_REGNUM].set_realreg (HPPA_RP_REGNUM);
 
   return info;
 }
@@ -2754,7 +2756,7 @@ hppa_find_global_pointer (struct gdbarch *gdbarch, struct value *function)
 
 struct value *
 hppa_frame_prev_register_helper (struct frame_info *this_frame,
-				 struct trad_frame_saved_reg saved_regs[],
+				 trad_frame_saved_reg saved_regs[],
 				 int regnum)
 {
   struct gdbarch *arch = get_frame_arch (this_frame);