484 lines
15 KiB
C
484 lines
15 KiB
C
/* Target-dependent code for the TI TMS320C80 (MVP) for GDB, the GNU debugger.
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Copyright 1996, Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include "defs.h"
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#include "value.h"
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#include "frame.h"
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#include "inferior.h"
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#include "obstack.h"
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#include "target.h"
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#include "bfd.h"
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#include "gdb_string.h"
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#include "gdbcore.h"
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#include "symfile.h"
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/* Function: frame_find_saved_regs
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Return the frame_saved_regs structure for the frame.
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Doesn't really work for dummy frames, but it does pass back
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an empty frame_saved_regs, so I guess that's better than total failure */
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void
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tic80_frame_find_saved_regs (fi, regaddr)
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struct frame_info *fi;
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struct frame_saved_regs *regaddr;
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{
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memcpy (regaddr, &fi->fsr, sizeof (struct frame_saved_regs));
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}
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/* Function: skip_prologue
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Find end of function prologue. */
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CORE_ADDR
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tic80_skip_prologue (pc)
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CORE_ADDR pc;
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{
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CORE_ADDR func_addr, func_end;
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struct symtab_and_line sal;
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/* See what the symbol table says */
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if (find_pc_partial_function (pc, NULL, &func_addr, &func_end))
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{
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sal = find_pc_line (func_addr, 0);
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if (sal.line != 0 && sal.end < func_end)
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return sal.end;
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else
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/* Either there's no line info, or the line after the prologue is after
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the end of the function. In this case, there probably isn't a
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prologue. */
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return pc;
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}
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/* We can't find the start of this function, so there's nothing we can do. */
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return pc;
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}
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/* Function: tic80_scan_prologue
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This function decodes the target function prologue to determine:
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1) the size of the stack frame
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2) which registers are saved on it
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3) the offsets of saved regs
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4) the frame size
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This information is stored in the "extra" fields of the frame_info. */
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static void
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tic80_scan_prologue (fi)
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struct frame_info *fi;
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{
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struct symtab_and_line sal;
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CORE_ADDR prologue_start, prologue_end, current_pc;
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/* Assume there is no frame until proven otherwise. */
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fi->framereg = SP_REGNUM;
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fi->framesize = 0;
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fi->frameoffset = 0;
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/* this code essentially duplicates skip_prologue,
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but we need the start address below. */
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if (find_pc_partial_function (fi->pc, NULL, &prologue_start, &prologue_end))
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{
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sal = find_pc_line (prologue_start, 0);
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if (sal.line == 0) /* no line info, use current PC */
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if (prologue_start != entry_point_address ())
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prologue_end = fi->pc;
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else
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return; /* _start has no frame or prologue */
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else if (sal.end < prologue_end) /* next line begins after fn end */
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prologue_end = sal.end; /* (probably means no prologue) */
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}
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else
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/* FIXME */
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prologue_end = prologue_start + 40; /* We're in the boondocks: allow for */
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/* 16 pushes, an add, and "mv fp,sp" */
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prologue_end = min (prologue_end, fi->pc);
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/* Now search the prologue looking for instructions that set up the
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frame pointer, adjust the stack pointer, and save registers. */
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for (current_pc = prologue_start; current_pc < prologue_end; current_pc += 4)
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{
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unsigned int insn;
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int regno;
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int offset = 0;
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insn = read_memory_unsigned_integer (current_pc, 4);
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if ((insn & 0x301000) == 0x301000) /* Long immediate? */
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/* FIXME - set offset for long immediate instructions */
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current_pc += 4;
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else
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{
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offset = insn & 0x7fff; /* extract 15-bit offset */
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if (offset & 0x4000) /* if negative, sign-extend */
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offset = -(0x8000 - offset);
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}
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if ((insn & 0x7fd0000) == 0x590000) /* st.{w,d} reg, xx(r1) */
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{
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regno = ((insn >> 27) & 0x1f);
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fi->fsr.regs[regno] = offset;
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if (insn & 0x8000) /* 64-bit store (st.d)? */
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fi->fsr.regs[regno + 1] = offset + 4;
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}
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else if ((insn & 0xffff8000) == 0x086c8000) /* addu xx, r1, r1 */
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fi->framesize = -offset;
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else if ((insn & 0xffff8000) == 0xf06c8000) /* addu xx, r1, r30 */
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{
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fi->framereg = FP_REGNUM; /* fp is now valid */
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fi->frameoffset = offset;
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break; /* end of stack adjustments */
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}
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else if (insn == 0xf03b2001) /* addu r1, r0, r30 */
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{
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fi->framereg = FP_REGNUM; /* fp is now valid */
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fi->frameoffset = 0;
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break; /* end of stack adjustments */
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}
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else
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/* FIXME - handle long immediate instructions */
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break; /* anything else isn't prologue */
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}
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}
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/* Function: init_extra_frame_info
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This function actually figures out the frame address for a given pc and
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sp. This is tricky on the c80 because we sometimes don't use an explicit
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frame pointer, and the previous stack pointer isn't necessarily recorded
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on the stack. The only reliable way to get this info is to
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examine the prologue. */
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void
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tic80_init_extra_frame_info (fi)
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struct frame_info *fi;
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{
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int reg;
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if (fi->next)
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fi->pc = FRAME_SAVED_PC (fi->next);
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/* Because zero is a valid register offset relative to SP, we initialize
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the offsets to -1 to indicate unused entries. */
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for (reg = 0; reg < NUM_REGS; reg++)
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fi->fsr.regs[reg] = -1;
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if (PC_IN_CALL_DUMMY (fi->pc, fi->frame, fi->frame))
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{
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/* We need to setup fi->frame here because run_stack_dummy gets it wrong
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by assuming it's always FP. */
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fi->frame = generic_read_register_dummy (fi->pc, fi->frame, SP_REGNUM);
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fi->framesize = 0;
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fi->frameoffset = 0;
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return;
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}
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else
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{
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tic80_scan_prologue (fi);
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if (!fi->next) /* this is the innermost frame? */
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fi->frame = read_register (fi->framereg);
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else
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/* not the innermost frame */
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/* If this function uses FP as the frame register, and the function
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it called saved the FP, get the saved FP. */ if (fi->framereg == FP_REGNUM &&
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fi->next->fsr.regs[FP_REGNUM] != (unsigned) -1)
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fi->frame = read_memory_integer (fi->next->fsr.regs[FP_REGNUM], 4);
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/* Convert SP-relative offsets of saved registers to real addresses. */
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for (reg = 0; reg < NUM_REGS; reg++)
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if (fi->fsr.regs[reg] == (unsigned) -1)
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fi->fsr.regs[reg] = 0; /* unused entry */
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else
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fi->fsr.regs[reg] += fi->frame - fi->frameoffset;
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}
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}
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/* Function: find_callers_reg
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Find REGNUM on the stack. Otherwise, it's in an active register. One thing
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we might want to do here is to check REGNUM against the clobber mask, and
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somehow flag it as invalid if it isn't saved on the stack somewhere. This
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would provide a graceful failure mode when trying to get the value of
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caller-saves registers for an inner frame. */
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CORE_ADDR
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tic80_find_callers_reg (fi, regnum)
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struct frame_info *fi;
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int regnum;
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{
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for (; fi; fi = fi->next)
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if (PC_IN_CALL_DUMMY (fi->pc, fi->frame, fi->frame))
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return generic_read_register_dummy (fi->pc, fi->frame, regnum);
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else if (fi->fsr.regs[regnum] != 0)
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return read_memory_integer (fi->fsr.regs[regnum],
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REGISTER_RAW_SIZE (regnum));
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return read_register (regnum);
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}
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/* Function: frame_chain
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Given a GDB frame, determine the address of the calling function's frame.
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This will be used to create a new GDB frame struct, and then
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INIT_EXTRA_FRAME_INFO and INIT_FRAME_PC will be called for the new frame.
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For c80, we save the frame size when we initialize the frame_info. */
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CORE_ADDR
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tic80_frame_chain (fi)
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struct frame_info *fi;
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{
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CORE_ADDR fn_start, callers_pc, fp;
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/* is this a dummy frame? */
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if (PC_IN_CALL_DUMMY (fi->pc, fi->frame, fi->frame))
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return fi->frame; /* dummy frame same as caller's frame */
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/* is caller-of-this a dummy frame? */
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callers_pc = FRAME_SAVED_PC (fi); /* find out who called us: */
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fp = tic80_find_callers_reg (fi, FP_REGNUM);
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if (PC_IN_CALL_DUMMY (callers_pc, fp, fp))
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return fp; /* dummy frame's frame may bear no relation to ours */
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if (find_pc_partial_function (fi->pc, 0, &fn_start, 0))
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if (fn_start == entry_point_address ())
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return 0; /* in _start fn, don't chain further */
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if (fi->framereg == FP_REGNUM)
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return tic80_find_callers_reg (fi, FP_REGNUM);
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else
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return fi->frame + fi->framesize;
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}
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/* Function: pop_frame
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Discard from the stack the innermost frame,
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restoring all saved registers. */
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struct frame_info *
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tic80_pop_frame (frame)
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struct frame_info *frame;
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{
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int regnum;
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if (PC_IN_CALL_DUMMY (frame->pc, frame->frame, frame->frame))
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generic_pop_dummy_frame ();
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else
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{
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for (regnum = 0; regnum < NUM_REGS; regnum++)
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if (frame->fsr.regs[regnum] != 0)
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write_register (regnum,
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read_memory_integer (frame->fsr.regs[regnum], 4));
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write_register (PC_REGNUM, FRAME_SAVED_PC (frame));
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write_register (SP_REGNUM, read_register (FP_REGNUM));
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#if 0
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if (read_register (PSW_REGNUM) & 0x80)
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write_register (SPU_REGNUM, read_register (SP_REGNUM));
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else
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write_register (SPI_REGNUM, read_register (SP_REGNUM));
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#endif
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}
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flush_cached_frames ();
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return NULL;
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}
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/* Function: frame_saved_pc
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Find the caller of this frame. We do this by seeing if LR_REGNUM is saved
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in the stack anywhere, otherwise we get it from the registers. */
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CORE_ADDR
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tic80_frame_saved_pc (fi)
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struct frame_info *fi;
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{
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if (PC_IN_CALL_DUMMY (fi->pc, fi->frame, fi->frame))
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return generic_read_register_dummy (fi->pc, fi->frame, PC_REGNUM);
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else
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return tic80_find_callers_reg (fi, LR_REGNUM);
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}
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/* Function: tic80_push_return_address (pc, sp)
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Set up the return address for the inferior function call.
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Necessary for targets that don't actually execute a JSR/BSR instruction
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(ie. when using an empty CALL_DUMMY) */
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CORE_ADDR
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tic80_push_return_address (pc, sp)
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CORE_ADDR pc;
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CORE_ADDR sp;
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{
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write_register (LR_REGNUM, CALL_DUMMY_ADDRESS ());
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return sp;
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}
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/* Function: push_arguments
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Setup the function arguments for calling a function in the inferior.
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On the TI C80 architecture, there are six register pairs (R2/R3 to R12/13)
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which are dedicated for passing function arguments. Up to the first six
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arguments (depending on size) may go into these registers.
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The rest go on the stack.
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Arguments that are smaller than 4 bytes will still take up a whole
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register or a whole 32-bit word on the stack, and will be
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right-justified in the register or the stack word. This includes
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chars, shorts, and small aggregate types.
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Arguments that are four bytes or less in size are placed in the
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even-numbered register of a register pair, and the odd-numbered
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register is not used.
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Arguments of 8 bytes size (such as floating point doubles) are placed
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in a register pair. The least significant 32-bit word is placed in
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the even-numbered register, and the most significant word in the
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odd-numbered register.
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Aggregate types with sizes between 4 and 8 bytes are passed
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entirely on the stack, and are left-justified within the
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double-word (as opposed to aggregates smaller than 4 bytes
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which are right-justified).
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Aggregates of greater than 8 bytes are first copied onto the stack,
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and then a pointer to the copy is passed in the place of the normal
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argument (either in a register if available, or on the stack).
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Functions that must return an aggregate type can return it in the
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normal return value registers (R2 and R3) if its size is 8 bytes or
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less. For larger return values, the caller must allocate space for
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the callee to copy the return value to. A pointer to this space is
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passed as an implicit first argument, always in R0. */
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CORE_ADDR
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tic80_push_arguments (nargs, args, sp, struct_return, struct_addr)
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int nargs;
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value_ptr *args;
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CORE_ADDR sp;
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unsigned char struct_return;
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CORE_ADDR struct_addr;
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{
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int stack_offset, stack_alloc;
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int argreg;
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int argnum;
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struct type *type;
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CORE_ADDR regval;
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char *val;
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char valbuf[4];
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int len;
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int odd_sized_struct;
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int is_struct;
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/* first force sp to a 4-byte alignment */
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sp = sp & ~3;
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argreg = ARG0_REGNUM;
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/* The "struct return pointer" pseudo-argument goes in R0 */
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if (struct_return)
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write_register (argreg++, struct_addr);
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/* Now make sure there's space on the stack */
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for (argnum = 0, stack_alloc = 0;
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argnum < nargs; argnum++)
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stack_alloc += ((TYPE_LENGTH (VALUE_TYPE (args[argnum])) + 3) & ~3);
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sp -= stack_alloc; /* make room on stack for args */
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/* Now load as many as possible of the first arguments into
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registers, and push the rest onto the stack. There are 16 bytes
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in four registers available. Loop thru args from first to last. */
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argreg = ARG0_REGNUM;
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for (argnum = 0, stack_offset = 0; argnum < nargs; argnum++)
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{
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type = VALUE_TYPE (args[argnum]);
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len = TYPE_LENGTH (type);
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memset (valbuf, 0, sizeof (valbuf));
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val = (char *) VALUE_CONTENTS (args[argnum]);
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/* FIXME -- tic80 can take doubleword arguments in register pairs */
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is_struct = (type->code == TYPE_CODE_STRUCT);
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odd_sized_struct = 0;
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if (!is_struct)
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{
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if (len < 4)
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{ /* value gets right-justified in the register or stack word */
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memcpy (valbuf + (4 - len), val, len);
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val = valbuf;
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}
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if (len > 4 && (len & 3) != 0)
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odd_sized_struct = 1; /* such structs go entirely on stack */
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}
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else
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{
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/* Structs are always passed by reference. */
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write_register (argreg, sp + stack_offset);
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argreg++;
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}
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while (len > 0)
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{
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if (is_struct || argreg > ARGLAST_REGNUM || odd_sized_struct)
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{ /* must go on the stack */
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write_memory (sp + stack_offset, val, 4);
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stack_offset += 4;
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}
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/* NOTE WELL!!!!! This is not an "else if" clause!!!
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That's because some things get passed on the stack
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AND in the registers! */
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if (!is_struct && argreg <= ARGLAST_REGNUM)
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{ /* there's room in a register */
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regval = extract_address (val, REGISTER_RAW_SIZE (argreg));
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write_register (argreg, regval);
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argreg += 2; /* FIXME -- what about doubleword args? */
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}
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/* Store the value 4 bytes at a time. This means that things
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larger than 4 bytes may go partly in registers and partly
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on the stack. */
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len -= REGISTER_RAW_SIZE (argreg);
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val += REGISTER_RAW_SIZE (argreg);
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}
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}
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return sp;
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}
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/* Function: tic80_write_sp
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Because SP is really a read-only register that mirrors either SPU or SPI,
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we must actually write one of those two as well, depending on PSW. */
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void
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tic80_write_sp (val)
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CORE_ADDR val;
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{
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#if 0
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unsigned long psw = read_register (PSW_REGNUM);
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if (psw & 0x80) /* stack mode: user or interrupt */
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write_register (SPU_REGNUM, val);
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else
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write_register (SPI_REGNUM, val);
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#endif
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write_register (SP_REGNUM, val);
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}
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void
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_initialize_tic80_tdep ()
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{
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tm_print_insn = print_insn_tic80;
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}
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