Add support to GDB for the Renesas rl78 architecture.

1 files changed, 1035 insertions, 0 deletions

diff --git a/gdb/rl78-tdep.c b/gdb/rl78-tdep.c
new file mode 100644
index 0000000..6e4d784
--- /dev/null
+++ b/gdb/rl78-tdep.c
@@ -0,0 +1,1035 @@
+/* Target-dependent code for the Renesas RL78 for GDB, the GNU debugger.
+
+   Copyright (C) 2011-2012 Free Software Foundation, Inc.
+
+   Contributed by Red Hat, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "arch-utils.h"
+#include "prologue-value.h"
+#include "target.h"
+#include "regcache.h"
+#include "opcode/rl78.h"
+#include "dis-asm.h"
+#include "gdbtypes.h"
+#include "frame.h"
+#include "frame-unwind.h"
+#include "frame-base.h"
+#include "value.h"
+#include "gdbcore.h"
+#include "dwarf2-frame.h"
+
+#include "elf/rl78.h"
+#include "elf-bfd.h"
+
+/* Register Banks.  */
+
+enum
+{
+  RL78_BANK0 = 0,
+  RL78_BANK1 = 1,
+  RL78_BANK2 = 2,
+  RL78_BANK3 = 3,
+  RL78_NUMBANKS = 4,
+  RL78_REGS_PER_BANK = 8
+};
+
+/* Register Numbers.  */
+
+enum
+{
+  /* All general purpose registers are 8 bits wide.  */
+  RL78_BANK0_R0_REGNUM = 0,
+  RL78_BANK0_R1_REGNUM,
+  RL78_BANK0_R2_REGNUM,
+  RL78_BANK0_R3_REGNUM,
+  RL78_BANK0_R4_REGNUM,
+  RL78_BANK0_R5_REGNUM,
+  RL78_BANK0_R6_REGNUM,
+  RL78_BANK0_R7_REGNUM,
+
+  RL78_BANK1_R0_REGNUM,
+  RL78_BANK1_R1_REGNUM,
+  RL78_BANK1_R2_REGNUM,
+  RL78_BANK1_R3_REGNUM,
+  RL78_BANK1_R4_REGNUM,
+  RL78_BANK1_R5_REGNUM,
+  RL78_BANK1_R6_REGNUM,
+  RL78_BANK1_R7_REGNUM,
+
+  RL78_BANK2_R0_REGNUM,
+  RL78_BANK2_R1_REGNUM,
+  RL78_BANK2_R2_REGNUM,
+  RL78_BANK2_R3_REGNUM,
+  RL78_BANK2_R4_REGNUM,
+  RL78_BANK2_R5_REGNUM,
+  RL78_BANK2_R6_REGNUM,
+  RL78_BANK2_R7_REGNUM,
+
+  RL78_BANK3_R0_REGNUM,
+  RL78_BANK3_R1_REGNUM,
+  RL78_BANK3_R2_REGNUM,
+  RL78_BANK3_R3_REGNUM,
+  RL78_BANK3_R4_REGNUM,
+  RL78_BANK3_R5_REGNUM,
+  RL78_BANK3_R6_REGNUM,
+  RL78_BANK3_R7_REGNUM,
+
+  RL78_PSW_REGNUM,	/* 8 bits */
+  RL78_ES_REGNUM,	/* 8 bits */
+  RL78_CS_REGNUM,	/* 8 bits */
+  RL78_PC_REGNUM,	/* 20 bits; we'll use 32 bits for it.  */
+
+  /* Fixed address SFRs (some of those above are SFRs too.) */
+  RL78_SPL_REGNUM,	/* 8 bits; lower half of SP */
+  RL78_SPH_REGNUM,	/* 8 bits; upper half of SP */
+  RL78_PMC_REGNUM,	/* 8 bits */
+  RL78_MEM_REGNUM,	/* 8 bits ?? */
+
+  RL78_NUM_REGS,
+
+  /* Pseudo registers.  */
+  RL78_BANK0_RP0_REGNUM = RL78_NUM_REGS,
+  RL78_BANK0_RP1_REGNUM,
+  RL78_BANK0_RP2_REGNUM,
+  RL78_BANK0_RP3_REGNUM,
+
+  RL78_BANK1_RP0_REGNUM,
+  RL78_BANK1_RP1_REGNUM,
+  RL78_BANK1_RP2_REGNUM,
+  RL78_BANK1_RP3_REGNUM,
+
+  RL78_BANK2_RP0_REGNUM,
+  RL78_BANK2_RP1_REGNUM,
+  RL78_BANK2_RP2_REGNUM,
+  RL78_BANK2_RP3_REGNUM,
+
+  RL78_BANK3_RP0_REGNUM,
+  RL78_BANK3_RP1_REGNUM,
+  RL78_BANK3_RP2_REGNUM,
+  RL78_BANK3_RP3_REGNUM,
+
+  RL78_SP_REGNUM,
+
+  RL78_X_REGNUM,
+  RL78_A_REGNUM,
+  RL78_C_REGNUM,
+  RL78_B_REGNUM,
+  RL78_E_REGNUM,
+  RL78_D_REGNUM,
+  RL78_L_REGNUM,
+  RL78_H_REGNUM,
+
+  RL78_AX_REGNUM,
+  RL78_BC_REGNUM,
+  RL78_DE_REGNUM,
+  RL78_HL_REGNUM,
+  RL78_NUM_TOTAL_REGS,
+  RL78_NUM_PSEUDO_REGS = RL78_NUM_TOTAL_REGS - RL78_NUM_REGS
+};
+
+/* Architecture specific data.  */
+
+struct gdbarch_tdep
+{
+  /* The ELF header flags specify the multilib used.  */
+  int elf_flags;
+
+  struct type *rl78_void,
+              *rl78_uint8,
+	      *rl78_int8,
+	      *rl78_uint16,
+	      *rl78_int16,
+	      *rl78_uint32,
+	      *rl78_int32,
+	      *rl78_data_pointer,
+	      *rl78_code_pointer;
+};
+
+/* This structure holds the results of a prologue analysis.  */
+
+struct rl78_prologue
+{
+  /* The offset from the frame base to the stack pointer --- always
+     zero or negative.
+
+     Calling this a "size" is a bit misleading, but given that the
+     stack grows downwards, using offsets for everything keeps one
+     from going completely sign-crazy: you never change anything's
+     sign for an ADD instruction; always change the second operand's
+     sign for a SUB instruction; and everything takes care of
+     itself.  */
+  int frame_size;
+
+  /* Non-zero if this function has initialized the frame pointer from
+     the stack pointer, zero otherwise.  */
+  int has_frame_ptr;
+
+  /* If has_frame_ptr is non-zero, this is the offset from the frame
+     base to where the frame pointer points.  This is always zero or
+     negative.  */
+  int frame_ptr_offset;
+
+  /* The address of the first instruction at which the frame has been
+     set up and the arguments are where the debug info says they are
+     --- as best as we can tell.  */
+  CORE_ADDR prologue_end;
+
+  /* reg_offset[R] is the offset from the CFA at which register R is
+     saved, or 1 if register R has not been saved.  (Real values are
+     always zero or negative.)  */
+  int reg_offset[RL78_NUM_TOTAL_REGS];
+};
+
+/* Implement the "register_type" gdbarch method.  */
+
+static struct type *
+rl78_register_type (struct gdbarch *gdbarch, int reg_nr)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
+  if (reg_nr == RL78_PC_REGNUM)
+    return tdep->rl78_code_pointer;
+  else if (reg_nr <= RL78_MEM_REGNUM
+           || (RL78_X_REGNUM <= reg_nr && reg_nr <= RL78_H_REGNUM))
+    return tdep->rl78_int8;
+  else
+    return tdep->rl78_data_pointer;
+}
+
+/* Implement the "register_name" gdbarch method.  */
+
+static const char *
+rl78_register_name (struct gdbarch *gdbarch, int regnr)
+{
+  static const char *const reg_names[] =
+  {
+    "bank0_r0",
+    "bank0_r1",
+    "bank0_r2",
+    "bank0_r3",
+    "bank0_r4",
+    "bank0_r5",
+    "bank0_r6",
+    "bank0_r7",
+
+    "bank1_r0",
+    "bank1_r1",
+    "bank1_r2",
+    "bank1_r3",
+    "bank1_r4",
+    "bank1_r5",
+    "bank1_r6",
+    "bank1_r7",
+
+    "bank2_r0",
+    "bank2_r1",
+    "bank2_r2",
+    "bank2_r3",
+    "bank2_r4",
+    "bank2_r5",
+    "bank2_r6",
+    "bank2_r7",
+
+    "bank3_r0",
+    "bank3_r1",
+    "bank3_r2",
+    "bank3_r3",
+    "bank3_r4",
+    "bank3_r5",
+    "bank3_r6",
+    "bank3_r7",
+
+    "psw",
+    "es",
+    "cs",
+    "pc",
+
+    "spl",
+    "sph",
+    "pmc",
+    "mem",
+
+    "bank0_rp0",
+    "bank0_rp1",
+    "bank0_rp2",
+    "bank0_rp3",
+
+    "bank1_rp0",
+    "bank1_rp1",
+    "bank1_rp2",
+    "bank1_rp3",
+
+    "bank2_rp0",
+    "bank2_rp1",
+    "bank2_rp2",
+    "bank2_rp3",
+
+    "bank3_rp0",
+    "bank3_rp1",
+    "bank3_rp2",
+    "bank3_rp3",
+
+    "sp",
+
+    "x",
+    "a",
+    "c",
+    "b",
+    "e",
+    "d",
+    "l",
+    "h",
+
+    "ax",
+    "bc",
+    "de",
+    "hl"
+  };
+
+  return reg_names[regnr];
+}
+
+/* Strip bits to form an instruction address.  (When fetching a
+   32-bit address from the stack, the high eight bits are garbage.
+   This function strips off those unused bits.)  */
+
+static CORE_ADDR
+rl78_make_instruction_address (CORE_ADDR addr)
+{
+  return addr & 0xffffff;
+}
+
+/* Set / clear bits necessary to make a data address.  */
+
+static CORE_ADDR
+rl78_make_data_address (CORE_ADDR addr)
+{
+  return (addr & 0xffff) | 0xf0000;
+}
+
+/* Implement the "pseudo_register_read" gdbarch method.  */
+
+static enum register_status
+rl78_pseudo_register_read (struct gdbarch *gdbarch,
+                           struct regcache *regcache,
+                           int reg, gdb_byte *buffer)
+{
+  enum register_status status;
+
+  if (RL78_BANK0_RP0_REGNUM <= reg && reg <= RL78_BANK3_RP3_REGNUM)
+    {
+      int raw_regnum = 2 * (reg - RL78_BANK0_RP0_REGNUM)
+                       + RL78_BANK0_R0_REGNUM;
+
+      status = regcache_raw_read (regcache, raw_regnum, buffer);
+      if (status == REG_VALID)
+	status = regcache_raw_read (regcache, raw_regnum + 1, buffer + 1);
+    }
+  else if (reg == RL78_SP_REGNUM)
+    {
+      status = regcache_raw_read (regcache, RL78_SPL_REGNUM, buffer);
+      if (status == REG_VALID)
+	status = regcache_raw_read (regcache, RL78_SPH_REGNUM, buffer + 1);
+    }
+  else if (RL78_X_REGNUM <= reg && reg <= RL78_H_REGNUM)
+    {
+      ULONGEST psw;
+
+      status = regcache_raw_read_unsigned (regcache, RL78_PSW_REGNUM, &psw);
+      if (status == REG_VALID)
+	{
+	  /* RSB0 is at bit 3; RSBS1 is at bit 5.  */
+	  int bank = ((psw >> 3) & 1) | ((psw >> 4) & 1);
+	  int raw_regnum = RL78_BANK0_R0_REGNUM + bank * RL78_REGS_PER_BANK
+	                   + (reg - RL78_X_REGNUM);
+	  status = regcache_raw_read (regcache, raw_regnum, buffer);
+	}
+    }
+  else if (RL78_AX_REGNUM <= reg && reg <= RL78_HL_REGNUM)
+    {
+      ULONGEST psw;
+
+      status = regcache_raw_read_unsigned (regcache, RL78_PSW_REGNUM, &psw);
+      if (status == REG_VALID)
+	{
+	  /* RSB0 is at bit 3; RSBS1 is at bit 5.  */
+	  int bank = ((psw >> 3) & 1) | ((psw >> 4) & 1);
+	  int raw_regnum = RL78_BANK0_R0_REGNUM + bank * RL78_REGS_PER_BANK
+	                   + 2 * (reg - RL78_AX_REGNUM);
+	  status = regcache_raw_read (regcache, raw_regnum, buffer);
+	  if (status == REG_VALID)
+	    status = regcache_raw_read (regcache, raw_regnum + 1,
+	                                buffer + 1);
+	}
+    }
+  else
+    gdb_assert_not_reached ("invalid pseudo register number");
+  return status;
+}
+
+/* Implement the "pseudo_register_write" gdbarch method.  */
+
+static void
+rl78_pseudo_register_write (struct gdbarch *gdbarch,
+                            struct regcache *regcache,
+                            int reg, const gdb_byte *buffer)
+{
+  if (RL78_BANK0_RP0_REGNUM <= reg && reg <= RL78_BANK3_RP3_REGNUM)
+    {
+      int raw_regnum = 2 * (reg - RL78_BANK0_RP0_REGNUM)
+                       + RL78_BANK0_R0_REGNUM;
+
+      regcache_raw_write (regcache, raw_regnum, buffer);
+      regcache_raw_write (regcache, raw_regnum + 1, buffer + 1);
+    }
+  else if (reg == RL78_SP_REGNUM)
+    {
+      regcache_raw_write (regcache, RL78_SPL_REGNUM, buffer);
+      regcache_raw_write (regcache, RL78_SPH_REGNUM, buffer + 1);
+    }
+  else if (RL78_X_REGNUM <= reg && reg <= RL78_H_REGNUM)
+    {
+      ULONGEST psw;
+      int bank;
+      int raw_regnum;
+
+      regcache_raw_read_unsigned (regcache, RL78_PSW_REGNUM, &psw);
+      bank = ((psw >> 3) & 1) | ((psw >> 4) & 1);
+      /* RSB0 is at bit 3; RSBS1 is at bit 5.  */
+      raw_regnum = RL78_BANK0_R0_REGNUM + bank * RL78_REGS_PER_BANK
+	           + (reg - RL78_X_REGNUM);
+      regcache_raw_write (regcache, raw_regnum, buffer);
+    }
+  else if (RL78_AX_REGNUM <= reg && reg <= RL78_HL_REGNUM)
+    {
+      ULONGEST psw;
+      int bank, raw_regnum;
+
+      regcache_raw_read_unsigned (regcache, RL78_PSW_REGNUM, &psw);
+      bank = ((psw >> 3) & 1) | ((psw >> 4) & 1);
+      /* RSB0 is at bit 3; RSBS1 is at bit 5.  */
+      raw_regnum = RL78_BANK0_R0_REGNUM + bank * RL78_REGS_PER_BANK
+		   + 2 * (reg - RL78_AX_REGNUM);
+      regcache_raw_write (regcache, raw_regnum, buffer);
+      regcache_raw_write (regcache, raw_regnum + 1, buffer + 1);
+    }
+  else
+    gdb_assert_not_reached ("invalid pseudo register number");
+}
+
+/* Implement the "breakpoint_from_pc" gdbarch method.  */
+
+const gdb_byte *
+rl78_breakpoint_from_pc (struct gdbarch *gdbarch, CORE_ADDR *pcptr,
+                         int *lenptr)
+{
+  /* The documented BRK instruction is actually a two byte sequence,
+     {0x61, 0xcc}, but instructions may be as short as one byte.
+     Correspondence with Renesas revealed that the one byte sequence
+     0xff is used when a one byte breakpoint instruction is required.  */
+  static gdb_byte breakpoint[] = { 0xff };
+
+  *lenptr = sizeof breakpoint;
+  return breakpoint;
+}
+
+/* Define a "handle" struct for fetching the next opcode.  */
+
+struct rl78_get_opcode_byte_handle
+{
+  CORE_ADDR pc;
+};
+
+/* Fetch a byte on behalf of the opcode decoder.  HANDLE contains
+   the memory address of the next byte to fetch.  If successful,
+   the address in the handle is updated and the byte fetched is
+   returned as the value of the function.  If not successful, -1
+   is returned.  */
+
+static int
+rl78_get_opcode_byte (void *handle)
+{
+  struct rl78_get_opcode_byte_handle *opcdata = handle;
+  int status;
+  gdb_byte byte;
+
+  status = target_read_memory (opcdata->pc, &byte, 1);
+  if (status == 0)
+    {
+      opcdata->pc += 1;
+      return byte;
+    }
+  else
+    return -1;
+}
+
+/* Function for finding saved registers in a 'struct pv_area'; this
+   function is passed to pv_area_scan.
+
+   If VALUE is a saved register, ADDR says it was saved at a constant
+   offset from the frame base, and SIZE indicates that the whole
+   register was saved, record its offset.  */
+
+static void
+check_for_saved (void *result_untyped, pv_t addr, CORE_ADDR size,
+                 pv_t value)
+{
+  struct rl78_prologue *result = (struct rl78_prologue *) result_untyped;
+
+  if (value.kind == pvk_register
+      && value.k == 0
+      && pv_is_register (addr, RL78_SP_REGNUM)
+      && size == register_size (target_gdbarch, value.reg))
+    result->reg_offset[value.reg] = addr.k;
+}
+
+/* Analyze a prologue starting at START_PC, going no further than
+   LIMIT_PC.  Fill in RESULT as appropriate.  */
+
+static void
+rl78_analyze_prologue (CORE_ADDR start_pc,
+		       CORE_ADDR limit_pc, struct rl78_prologue *result)
+{
+  CORE_ADDR pc, next_pc;
+  int rn;
+  pv_t reg[RL78_NUM_TOTAL_REGS];
+  struct pv_area *stack;
+  struct cleanup *back_to;
+  CORE_ADDR after_last_frame_setup_insn = start_pc;
+  int bank = 0;
+
+  memset (result, 0, sizeof (*result));
+
+  for (rn = 0; rn < RL78_NUM_TOTAL_REGS; rn++)
+    {
+      reg[rn] = pv_register (rn, 0);
+      result->reg_offset[rn] = 1;
+    }
+
+  stack = make_pv_area (RL78_SP_REGNUM, gdbarch_addr_bit (target_gdbarch));
+  back_to = make_cleanup_free_pv_area (stack);
+
+  /* The call instruction has saved the return address on the stack.  */
+  reg[RL78_SP_REGNUM] = pv_add_constant (reg[RL78_SP_REGNUM], -4);
+  pv_area_store (stack, reg[RL78_SP_REGNUM], 4, reg[RL78_PC_REGNUM]);
+
+  pc = start_pc;
+  while (pc < limit_pc)
+    {
+      int bytes_read;
+      struct rl78_get_opcode_byte_handle opcode_handle;
+      RL78_Opcode_Decoded opc;
+
+      opcode_handle.pc = pc;
+      bytes_read = rl78_decode_opcode (pc, &opc, rl78_get_opcode_byte,
+				     &opcode_handle);
+      next_pc = pc + bytes_read;
+
+      if (opc.id == RLO_sel)
+	{
+	  bank = opc.op[1].addend;
+	}
+      else if (opc.id == RLO_mov
+               && opc.op[0].type == RL78_Operand_PreDec
+               && opc.op[0].reg == RL78_Reg_SP
+	       && opc.op[1].type == RL78_Operand_Register)
+	{
+	  int rsrc = (bank * RL78_REGS_PER_BANK) 
+	           + 2 * (opc.op[1].reg - RL78_Reg_AX);
+
+	  reg[RL78_SP_REGNUM] = pv_add_constant (reg[RL78_SP_REGNUM], -1);
+	  pv_area_store (stack, reg[RL78_SP_REGNUM], 1, reg[rsrc]);
+	  reg[RL78_SP_REGNUM] = pv_add_constant (reg[RL78_SP_REGNUM], -1);
+	  pv_area_store (stack, reg[RL78_SP_REGNUM], 1, reg[rsrc + 1]);
+	  after_last_frame_setup_insn = next_pc;
+	}
+      else if (opc.id == RLO_sub
+               && opc.op[0].type == RL78_Operand_Register
+	       && opc.op[0].reg == RL78_Reg_SP
+	       && opc.op[1].type == RL78_Operand_Immediate)
+	{
+	  int addend = opc.op[1].addend;
+
+	  reg[RL78_SP_REGNUM] = pv_add_constant (reg[RL78_SP_REGNUM],
+	                                         -addend);
+	  after_last_frame_setup_insn = next_pc;
+	}
+      else
+	{
+	  /* Terminate the prologue scan.  */
+	  break;
+	}
+
+      pc = next_pc;
+    }
+
+  /* Is the frame size (offset, really) a known constant?  */
+  if (pv_is_register (reg[RL78_SP_REGNUM], RL78_SP_REGNUM))
+    result->frame_size = reg[RL78_SP_REGNUM].k;
+
+  /* Record where all the registers were saved.  */
+  pv_area_scan (stack, check_for_saved, (void *) result);
+
+  result->prologue_end = after_last_frame_setup_insn;
+
+  do_cleanups (back_to);
+}
+
+/* Implement the "addr_bits_remove" gdbarch method.  */
+
+static CORE_ADDR
+rl78_addr_bits_remove (struct gdbarch *gdbarch, CORE_ADDR addr)
+{
+  return addr & 0xffffff;
+}
+
+/* Implement the "address_to_pointer" gdbarch method.  */
+
+static void
+rl78_address_to_pointer (struct gdbarch *gdbarch,
+			 struct type *type, gdb_byte *buf, CORE_ADDR addr)
+{
+  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+
+  store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order,
+                          addr & 0xffffff);
+}
+
+/* Implement the "pointer_to_address" gdbarch method.  */
+
+static CORE_ADDR
+rl78_pointer_to_address (struct gdbarch *gdbarch,
+                         struct type *type, const gdb_byte *buf)
+{
+  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  CORE_ADDR addr
+    = extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order);
+
+  /* Is it a code address?  */
+  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
+      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
+      || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type))
+      || TYPE_LENGTH (type) == 4)
+    return rl78_make_instruction_address (addr);
+  else
+    return rl78_make_data_address (addr);
+}
+
+/* Implement the "skip_prologue" gdbarch method.  */
+
+static CORE_ADDR
+rl78_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
+{
+  char *name;
+  CORE_ADDR func_addr, func_end;
+  struct rl78_prologue p;
+
+  /* Try to find the extent of the function that contains PC.  */
+  if (!find_pc_partial_function (pc, &name, &func_addr, &func_end))
+    return pc;
+
+  rl78_analyze_prologue (pc, func_end, &p);
+  return p.prologue_end;
+}
+
+/* Implement the "unwind_pc" gdbarch method.  */
+
+static CORE_ADDR
+rl78_unwind_pc (struct gdbarch *arch, struct frame_info *next_frame)
+{
+  return rl78_addr_bits_remove
+           (arch, frame_unwind_register_unsigned (next_frame,
+	                                          RL78_PC_REGNUM));
+}
+
+/* Implement the "unwind_sp" gdbarch method.  */
+
+static CORE_ADDR
+rl78_unwind_sp (struct gdbarch *arch, struct frame_info *next_frame)
+{
+  return frame_unwind_register_unsigned (next_frame, RL78_SP_REGNUM);
+}
+
+/* Given a frame described by THIS_FRAME, decode the prologue of its
+   associated function if there is not cache entry as specified by
+   THIS_PROLOGUE_CACHE.  Save the decoded prologue in the cache and
+   return that struct as the value of this function.  */
+
+static struct rl78_prologue *
+rl78_analyze_frame_prologue (struct frame_info *this_frame,
+			   void **this_prologue_cache)
+{
+  if (!*this_prologue_cache)
+    {
+      CORE_ADDR func_start, stop_addr;
+
+      *this_prologue_cache = FRAME_OBSTACK_ZALLOC (struct rl78_prologue);
+
+      func_start = get_frame_func (this_frame);
+      stop_addr = get_frame_pc (this_frame);
+
+      /* If we couldn't find any function containing the PC, then
+         just initialize the prologue cache, but don't do anything.  */
+      if (!func_start)
+	stop_addr = func_start;
+
+      rl78_analyze_prologue (func_start, stop_addr, *this_prologue_cache);
+    }
+
+  return *this_prologue_cache;
+}
+
+/* Given a frame and a prologue cache, return this frame's base.  */
+
+static CORE_ADDR
+rl78_frame_base (struct frame_info *this_frame, void **this_prologue_cache)
+{
+  struct rl78_prologue *p
+    = rl78_analyze_frame_prologue (this_frame, this_prologue_cache);
+  CORE_ADDR sp = get_frame_register_unsigned (this_frame, RL78_SP_REGNUM);
+
+  return rl78_make_data_address (sp - p->frame_size);
+}
+
+/* Implement the "frame_this_id" method for unwinding frames.  */
+
+static void
+rl78_this_id (struct frame_info *this_frame,
+	      void **this_prologue_cache, struct frame_id *this_id)
+{
+  *this_id = frame_id_build (rl78_frame_base (this_frame,
+                                              this_prologue_cache),
+			     get_frame_func (this_frame));
+}
+
+/* Implement the "frame_prev_register" method for unwinding frames.  */
+
+static struct value *
+rl78_prev_register (struct frame_info *this_frame,
+                    void **this_prologue_cache, int regnum)
+{
+  struct rl78_prologue *p
+    = rl78_analyze_frame_prologue (this_frame, this_prologue_cache);
+  CORE_ADDR frame_base = rl78_frame_base (this_frame, this_prologue_cache);
+
+  if (regnum == RL78_SP_REGNUM)
+    return frame_unwind_got_constant (this_frame, regnum, frame_base);
+
+  else if (regnum == RL78_SPL_REGNUM)
+    return frame_unwind_got_constant (this_frame, regnum,
+                                      (frame_base & 0xff));
+
+  else if (regnum == RL78_SPH_REGNUM)
+    return frame_unwind_got_constant (this_frame, regnum,
+                                      ((frame_base >> 8) & 0xff));
+
+  /* If prologue analysis says we saved this register somewhere,
+     return a description of the stack slot holding it.  */
+  else if (p->reg_offset[regnum] != 1)
+    {
+      struct value *rv =
+        frame_unwind_got_memory (this_frame, regnum,
+				 frame_base + p->reg_offset[regnum]);
+
+      if (regnum == RL78_PC_REGNUM)
+	{
+	  ULONGEST pc = rl78_make_instruction_address (value_as_long (rv));
+
+	  return frame_unwind_got_constant (this_frame, regnum, pc);
+	}
+      return rv;
+    }
+
+  /* Otherwise, presume we haven't changed the value of this
+     register, and get it from the next frame.  */
+  else
+    return frame_unwind_got_register (this_frame, regnum, regnum);
+}
+
+static const struct frame_unwind rl78_unwind =
+{
+  NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
+  rl78_this_id,
+  rl78_prev_register,
+  NULL,
+  default_frame_sniffer
+};
+
+/* Implement the "dwarf_reg_to_regnum" gdbarch method.  */
+
+static int
+rl78_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int reg)
+{
+  if (0 <= reg && reg <= 31)
+    {
+      if ((reg & 1) == 0)
+        /* Map even registers to their 16-bit counterparts.  This
+	   is usually what is required from the DWARF info.  */
+	return (reg >> 1) + RL78_BANK0_RP0_REGNUM;
+      else
+	return reg;
+    }
+  else if (reg == 32)
+    return RL78_SP_REGNUM;
+  else if (reg == 33)
+    return RL78_PC_REGNUM;
+  else
+    internal_error (__FILE__, __LINE__,
+                    _("Undefined dwarf2 register mapping of reg %d"),
+		    reg);
+}
+
+/* Implement the "return_value" gdbarch method.  */
+
+static enum return_value_convention
+rl78_return_value (struct gdbarch *gdbarch,
+		   struct type *func_type,
+		   struct type *valtype,
+		   struct regcache *regcache,
+		   gdb_byte *readbuf, const gdb_byte *writebuf)
+{
+  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  ULONGEST valtype_len = TYPE_LENGTH (valtype);
+
+  if (valtype_len > 8)
+    return RETURN_VALUE_STRUCT_CONVENTION;
+
+  if (readbuf)
+    {
+      ULONGEST u;
+      int argreg = RL78_BANK1_R0_REGNUM;
+      int offset = 0;
+
+      while (valtype_len > 0)
+	{
+	  regcache_cooked_read_unsigned (regcache, argreg, &u);
+	  store_unsigned_integer (readbuf + offset, 1, byte_order, u);
+	  valtype_len -= 1;
+	  offset += 1;
+	  argreg++;
+	}
+    }
+
+  if (writebuf)
+    {
+      ULONGEST u;
+      int argreg = RL78_BANK1_R0_REGNUM;
+      int offset = 0;
+
+      while (valtype_len > 0)
+	{
+	  u = extract_unsigned_integer (writebuf + offset, 1, byte_order);
+	  regcache_cooked_write_unsigned (regcache, argreg, u);
+	  valtype_len -= 1;
+	  offset += 1;
+	  argreg++;
+	}
+    }
+
+  return RETURN_VALUE_REGISTER_CONVENTION;
+}
+
+
+/* Implement the "frame_align" gdbarch method.  */
+
+static CORE_ADDR
+rl78_frame_align (struct gdbarch *gdbarch, CORE_ADDR sp)
+{
+  return rl78_make_data_address (align_down (sp, 2));
+}
+
+
+/* Implement the "dummy_id" gdbarch method.  */
+
+static struct frame_id
+rl78_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame)
+{
+  return
+    frame_id_build (rl78_make_data_address
+                      (get_frame_register_unsigned
+		        (this_frame, RL78_SP_REGNUM)),
+		    get_frame_pc (this_frame));
+}
+
+
+/* Implement the "push_dummy_call" gdbarch method.  */
+
+static CORE_ADDR
+rl78_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
+		      struct regcache *regcache, CORE_ADDR bp_addr,
+		      int nargs, struct value **args, CORE_ADDR sp,
+		      int struct_return, CORE_ADDR struct_addr)
+{
+  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  gdb_byte buf[4];
+  int i;
+
+  /* Push arguments in reverse order.  */
+  for (i = nargs - 1; i >= 0; i--)
+    {
+      struct type *value_type = value_enclosing_type (args[i]);
+      int len = TYPE_LENGTH (value_type);
+      int container_len = (len + 1) & ~1;
+      int offset;
+
+      sp -= container_len;
+      write_memory (rl78_make_data_address (sp),
+                    value_contents_all (args[i]), len);
+    }
+
+  /* Store struct value address.  */
+  if (struct_return)
+    {
+      store_unsigned_integer (buf, 2, byte_order, struct_addr);
+      sp -= 2;
+      write_memory (rl78_make_data_address (sp), buf, 2);
+    }
+
+  /* Store return address.  */
+  sp -= 4;
+  store_unsigned_integer (buf, 4, byte_order, bp_addr);
+  write_memory (rl78_make_data_address (sp), buf, 4);
+
+  /* Finally, update the stack pointer...  */
+  regcache_cooked_write_unsigned (regcache, RL78_SP_REGNUM, sp);
+
+  /* DWARF2/GCC uses the stack address *before* the function call as a
+     frame's CFA.  */
+  return rl78_make_data_address (sp + 4);
+}
+
+/* Allocate and initialize a gdbarch object.  */
+
+static struct gdbarch *
+rl78_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
+{
+  struct gdbarch *gdbarch;
+  struct gdbarch_tdep *tdep;
+  int elf_flags;
+
+  /* Extract the elf_flags if available.  */
+  if (info.abfd != NULL
+      && bfd_get_flavour (info.abfd) == bfd_target_elf_flavour)
+    elf_flags = elf_elfheader (info.abfd)->e_flags;
+  else
+    elf_flags = 0;
+
+
+  /* Try to find the architecture in the list of already defined
+     architectures.  */
+  for (arches = gdbarch_list_lookup_by_info (arches, &info);
+       arches != NULL;
+       arches = gdbarch_list_lookup_by_info (arches->next, &info))
+    {
+      if (gdbarch_tdep (arches->gdbarch)->elf_flags != elf_flags)
+	continue;
+
+      return arches->gdbarch;
+    }
+
+  /* None found, create a new architecture from the information
+     provided.  */
+  tdep = (struct gdbarch_tdep *) xmalloc (sizeof (struct gdbarch_tdep));
+  gdbarch = gdbarch_alloc (&info, tdep);
+  tdep->elf_flags = elf_flags;
+
+  /* Initialize types.  */
+  tdep->rl78_void = arch_type (gdbarch, TYPE_CODE_VOID, 1, "void");
+  tdep->rl78_uint8 = arch_integer_type (gdbarch, 8, 1, "uint8_t");
+  tdep->rl78_int8 = arch_integer_type (gdbarch, 8, 0, "int8_t");
+  tdep->rl78_uint16 = arch_integer_type (gdbarch, 16, 1, "uint16_t");
+  tdep->rl78_int16 = arch_integer_type (gdbarch, 16, 0, "int16_t");
+  tdep->rl78_uint32 = arch_integer_type (gdbarch, 32, 1, "uint32_t");
+  tdep->rl78_int32 = arch_integer_type (gdbarch, 32, 0, "int32_t");
+
+  tdep->rl78_data_pointer
+    = arch_type (gdbarch, TYPE_CODE_PTR, 16 / TARGET_CHAR_BIT,
+                 xstrdup ("rl78_data_addr_t"));
+  TYPE_TARGET_TYPE (tdep->rl78_data_pointer) = tdep->rl78_void;
+  TYPE_UNSIGNED (tdep->rl78_data_pointer) = 1;
+
+  tdep->rl78_code_pointer
+    = arch_type (gdbarch, TYPE_CODE_PTR, 32 / TARGET_CHAR_BIT,
+                 xstrdup ("rl78_code_addr_t"));
+  TYPE_TARGET_TYPE (tdep->rl78_code_pointer) = tdep->rl78_void;
+  TYPE_UNSIGNED (tdep->rl78_code_pointer) = 1;
+
+  /* Registers.  */
+  set_gdbarch_num_regs (gdbarch, RL78_NUM_REGS);
+  set_gdbarch_num_pseudo_regs (gdbarch, RL78_NUM_PSEUDO_REGS);
+  set_gdbarch_register_name (gdbarch, rl78_register_name);
+  set_gdbarch_register_type (gdbarch, rl78_register_type);
+  set_gdbarch_pc_regnum (gdbarch, RL78_PC_REGNUM);
+  set_gdbarch_sp_regnum (gdbarch, RL78_SP_REGNUM);
+  set_gdbarch_pseudo_register_read (gdbarch, rl78_pseudo_register_read);
+  set_gdbarch_pseudo_register_write (gdbarch, rl78_pseudo_register_write);
+  set_gdbarch_dwarf2_reg_to_regnum (gdbarch, rl78_dwarf_reg_to_regnum);
+
+  /* Data types.  */
+  set_gdbarch_char_signed (gdbarch, 0);
+  set_gdbarch_short_bit (gdbarch, 16);
+  set_gdbarch_int_bit (gdbarch, 16);
+  set_gdbarch_long_bit (gdbarch, 32);
+  set_gdbarch_long_long_bit (gdbarch, 64);
+  set_gdbarch_ptr_bit (gdbarch, 16);
+  set_gdbarch_addr_bit (gdbarch, 32);
+  set_gdbarch_float_bit (gdbarch, 32);
+  set_gdbarch_float_format (gdbarch, floatformats_ieee_single);
+  set_gdbarch_double_bit (gdbarch, 32);
+  set_gdbarch_long_double_bit (gdbarch, 64);
+  set_gdbarch_double_format (gdbarch, floatformats_ieee_single);
+  set_gdbarch_long_double_format (gdbarch, floatformats_ieee_double);
+  set_gdbarch_pointer_to_address (gdbarch, rl78_pointer_to_address);
+  set_gdbarch_address_to_pointer (gdbarch, rl78_address_to_pointer);
+  set_gdbarch_addr_bits_remove (gdbarch, rl78_addr_bits_remove);
+
+  /* Breakpoints.  */
+  set_gdbarch_breakpoint_from_pc (gdbarch, rl78_breakpoint_from_pc);
+  set_gdbarch_decr_pc_after_break (gdbarch, 1);
+
+  /* Disassembly.  */
+  set_gdbarch_print_insn (gdbarch, print_insn_rl78);
+
+  /* Frames, prologues, etc.  */
+  set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
+  set_gdbarch_skip_prologue (gdbarch, rl78_skip_prologue);
+  set_gdbarch_unwind_pc (gdbarch, rl78_unwind_pc);
+  set_gdbarch_unwind_sp (gdbarch, rl78_unwind_sp);
+  set_gdbarch_frame_align (gdbarch, rl78_frame_align);
+  frame_unwind_append_unwinder (gdbarch, &rl78_unwind);
+
+  /* Dummy frames, return values.  */
+  set_gdbarch_dummy_id (gdbarch, rl78_dummy_id);
+  set_gdbarch_push_dummy_call (gdbarch, rl78_push_dummy_call);
+  set_gdbarch_return_value (gdbarch, rl78_return_value);
+
+  /* Virtual tables.  */
+  set_gdbarch_vbit_in_delta (gdbarch, 1);
+
+  return gdbarch;
+}
+
+/* Register the above initialization routine.  */
+
+void
+_initialize_rl78_tdep (void)
+{
+  register_gdbarch_init (bfd_arch_rl78, rl78_gdbarch_init);
+}