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, 35 insertions, 49 deletions

diff --git a/gdb/trad-frame.c b/gdb/trad-frame.c
index 2e98b79..17375e8 100644
--- a/gdb/trad-frame.c
+++ b/gdb/trad-frame.c
@@ -30,7 +30,7 @@ struct trad_frame_cache
 {
   struct frame_info *this_frame;
   CORE_ADDR this_base;
-  struct trad_frame_saved_reg *prev_regs;
+  trad_frame_saved_reg *prev_regs;
   struct frame_id this_id;
 };
 
@@ -49,23 +49,22 @@ trad_frame_cache_zalloc (struct frame_info *this_frame)
 
 void
 trad_frame_reset_saved_regs (struct gdbarch *gdbarch,
-			     struct trad_frame_saved_reg *regs)
+			     trad_frame_saved_reg *regs)
 {
   int numregs = gdbarch_num_cooked_regs (gdbarch);
+
   for (int regnum = 0; regnum < numregs; regnum++)
-    {
-      regs[regnum].realreg = regnum;
-      regs[regnum].addr = -1;
-      regs[regnum].data = nullptr;
-    }
+    regs[regnum].set_realreg (regnum);
 }
 
-struct trad_frame_saved_reg *
+trad_frame_saved_reg *
 trad_frame_alloc_saved_regs (struct gdbarch *gdbarch)
 {
+  gdb_static_assert (std::is_trivially_default_constructible<trad_frame_saved_reg>::value);
+
   int numregs = gdbarch_num_cooked_regs (gdbarch);
-  struct trad_frame_saved_reg *this_saved_regs
-    = FRAME_OBSTACK_CALLOC (numregs, struct trad_frame_saved_reg);
+  trad_frame_saved_reg *this_saved_regs
+    = FRAME_OBSTACK_CALLOC (numregs, trad_frame_saved_reg);
 
   trad_frame_reset_saved_regs (gdbarch, this_saved_regs);
   return this_saved_regs;
@@ -76,7 +75,7 @@ trad_frame_alloc_saved_regs (struct gdbarch *gdbarch)
    non-optimized frames, the technique is reliable (just need to check
    for all potential instruction sequences).  */
 
-struct trad_frame_saved_reg *
+trad_frame_saved_reg *
 trad_frame_alloc_saved_regs (struct frame_info *this_frame)
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
@@ -84,67 +83,57 @@ trad_frame_alloc_saved_regs (struct frame_info *this_frame)
   return trad_frame_alloc_saved_regs (gdbarch);
 }
 
-enum { TF_REG_VALUE = -1, TF_REG_UNKNOWN = -2, TF_REG_VALUE_BYTES = -3 };
-
 int
-trad_frame_value_p (struct trad_frame_saved_reg this_saved_regs[], int regnum)
+trad_frame_value_p (trad_frame_saved_reg this_saved_regs[], int regnum)
 {
-  return (this_saved_regs[regnum].realreg == TF_REG_VALUE);
+  return this_saved_regs[regnum].is_value ();
 }
 
 int
-trad_frame_addr_p (struct trad_frame_saved_reg this_saved_regs[], int regnum)
+trad_frame_addr_p (trad_frame_saved_reg this_saved_regs[], int regnum)
 {
-  return (this_saved_regs[regnum].realreg >= 0
-	  && this_saved_regs[regnum].addr != -1);
+  return this_saved_regs[regnum].is_addr ();
 }
 
 int
-trad_frame_realreg_p (struct trad_frame_saved_reg this_saved_regs[],
+trad_frame_realreg_p (trad_frame_saved_reg this_saved_regs[],
 		      int regnum)
 {
-  return (this_saved_regs[regnum].realreg >= 0
-	  && this_saved_regs[regnum].addr == -1);
+  return this_saved_regs[regnum].is_realreg ();
 }
 
 /* See trad-frame.h.  */
 
 bool
-trad_frame_value_bytes_p (struct trad_frame_saved_reg this_saved_regs[],
+trad_frame_value_bytes_p (trad_frame_saved_reg this_saved_regs[],
 			  int regnum)
 {
-  return (this_saved_regs[regnum].realreg == TF_REG_VALUE_BYTES
-	  && this_saved_regs[regnum].data != nullptr);
+  return this_saved_regs[regnum].is_value_bytes ();
 }
 
 void
-trad_frame_set_value (struct trad_frame_saved_reg this_saved_regs[],
+trad_frame_set_value (trad_frame_saved_reg this_saved_regs[],
 		      int regnum, LONGEST val)
 {
-  /* Make the REALREG invalid, indicating that the ADDR contains the
-     register's value.  */
-  this_saved_regs[regnum].realreg = TF_REG_VALUE;
-  this_saved_regs[regnum].addr = val;
+  this_saved_regs[regnum].set_value (val);
 }
 
 /* See trad-frame.h.  */
 
 void
-trad_frame_set_realreg (struct trad_frame_saved_reg this_saved_regs[],
+trad_frame_set_realreg (trad_frame_saved_reg this_saved_regs[],
 			int regnum, int realreg)
 {
-  this_saved_regs[regnum].realreg = realreg;
-  this_saved_regs[regnum].addr = -1;
+  this_saved_regs[regnum].set_realreg (realreg);
 }
 
 /* See trad-frame.h.  */
 
 void
-trad_frame_set_addr (struct trad_frame_saved_reg this_saved_regs[],
+trad_frame_set_addr (trad_frame_saved_reg this_saved_regs[],
 		     int regnum, CORE_ADDR addr)
 {
-  this_saved_regs[regnum].realreg = regnum;
-  this_saved_regs[regnum].addr = addr;
+  this_saved_regs[regnum].set_addr (addr);
 }
 
 void
@@ -227,26 +216,23 @@ trad_frame_set_reg_regmap (struct trad_frame_cache *this_trad_cache,
 }
 
 void
-trad_frame_set_unknown (struct trad_frame_saved_reg this_saved_regs[],
+trad_frame_set_unknown (trad_frame_saved_reg this_saved_regs[],
 			int regnum)
 {
-  /* Make the REALREG invalid, indicating that the value is not known.  */
-  this_saved_regs[regnum].realreg = TF_REG_UNKNOWN;
-  this_saved_regs[regnum].addr = -1;
+  this_saved_regs[regnum].set_unknown ();
 }
 
 /* See trad-frame.h.  */
 
 void
-trad_frame_set_value_bytes (struct trad_frame_saved_reg this_saved_regs[],
+trad_frame_set_value_bytes (trad_frame_saved_reg this_saved_regs[],
 			    int regnum, const gdb_byte *bytes,
 			    size_t size)
 {
-  this_saved_regs[regnum].realreg = TF_REG_VALUE_BYTES;
-
   /* Allocate the space and copy the data bytes.  */
-  this_saved_regs[regnum].data = FRAME_OBSTACK_CALLOC (size, gdb_byte);
-  memcpy (this_saved_regs[regnum].data, bytes, size);
+  gdb_byte *data = FRAME_OBSTACK_CALLOC (size, gdb_byte);
+  memcpy (data, bytes, size);
+  this_saved_regs[regnum].set_value_bytes (data);
 }
 
 /* See trad-frame.h.  */
@@ -266,24 +252,24 @@ trad_frame_set_reg_value_bytes (struct trad_frame_cache *this_trad_cache,
 
 struct value *
 trad_frame_get_prev_register (struct frame_info *this_frame,
-			      struct trad_frame_saved_reg this_saved_regs[],
+			      trad_frame_saved_reg this_saved_regs[],
 			      int regnum)
 {
   if (trad_frame_addr_p (this_saved_regs, regnum))
     /* The register was saved in memory.  */
     return frame_unwind_got_memory (this_frame, regnum,
-				    this_saved_regs[regnum].addr);
+				    this_saved_regs[regnum].addr ());
   else if (trad_frame_realreg_p (this_saved_regs, regnum))
     return frame_unwind_got_register (this_frame, regnum,
-				      this_saved_regs[regnum].realreg);
+				      this_saved_regs[regnum].realreg ());
   else if (trad_frame_value_p (this_saved_regs, regnum))
     /* The register's value is available.  */
     return frame_unwind_got_constant (this_frame, regnum,
-				      this_saved_regs[regnum].addr);
+				      this_saved_regs[regnum].value ());
   else if (trad_frame_value_bytes_p (this_saved_regs, regnum))
     /* The register's value is available as a sequence of bytes.  */
     return frame_unwind_got_bytes (this_frame, regnum,
-				   this_saved_regs[regnum].data);
+				   this_saved_regs[regnum].value_bytes ());
   else
     return frame_unwind_got_optimized (this_frame, regnum);
 }