Subversion Repositories openrisc_2011-10-31

/* ========================================================================== */

/* Local macros                                                               */

/* Construct a l.movhi instruction for the given reg and value */

#define OR32_MOVHI(rd, k)                                               \

  ((0x6 << 26) | ((rd) << 21) | (k))

/* Construct a l.ori instruction for the given two regs and value */

#define OR32_ORI(rd, ra, k)                                             \

  ((0x2a << 26) | ((rd) << 21) | ((ra) << 16) | (k))

/* Construct a l.lwz instruction for the given two registers and offset */

#define OR32_LWZ(rd, ra, i)                                             \

  ((0x21 << 26) | ((rd) << 21) | ((ra) << 16) | (i))

/* Construct a l.jr instruction for the given register */

#define OR32_JR(rb)                                                     \

  ((0x11 << 26) | ((rb) << 11))

/* -------------------------------------------------------------------------- */

/*!Emit a move from SRC to DEST.

   Assume that the move expanders can handle all moves if !can_create_pseudo_p

   ().  The distinction is important because, unlike emit_move_insn, the move

   expanders know how to force Pmode objects into the constant pool even when

   the constant pool address is not itself legitimate.

   @param[in] dest  Destination of the move.

   @param[in] src   Source for the move.

   @return  RTX for the move.                                                 */

/* -------------------------------------------------------------------------- */

rtx

or32_emit_move (rtx dest, rtx src)

{

  return (can_create_pseudo_p ()

          ? emit_move_insn (dest, src)

          : emit_move_insn_1 (dest, src));

}       /* or32_emit_move () */

/* -------------------------------------------------------------------------- */

/*!Emit an instruction of the form (set TARGET (CODE OP0 OP1)).

   @param[in] code    The code for the operation.

   @param[in] target  Destination for the set operation.

   @param[in] op0     First operand.

   @param[in] op1     Second operand.                                         */

/* -------------------------------------------------------------------------- */

static void

or32_emit_binary (enum rtx_code  code,

                  rtx            target,

                  rtx            op0,

                  rtx            op1)

{

  emit_insn (gen_rtx_SET (VOIDmode, target,

                          gen_rtx_fmt_ee (code, GET_MODE (target), op0, op1)));

}       /* or32_emit_binary () */

/* -------------------------------------------------------------------------- */

/*!Compute the result of an operation into a new register.

   Compute ("code" "op0" "op1") and store the result in a new register of mode

   "mode".

   @param[in] mode  Mode of the result

   @parma[in] code  RTX for the operation to perform

   @param[in] op0   RTX for the first operand

   @param[in] op1   RTX for the second operand

   @return  The RTX for the new register.                                     */

/* -------------------------------------------------------------------------- */

static rtx

or32_force_binary (enum machine_mode  mode,

                   enum rtx_code      code,

                   rtx                op0,

                   rtx                op1)

{

  rtx  reg;

  reg = gen_reg_rtx (mode);

  or32_emit_binary (code, reg, op0, op1);

  return reg;

}       /* or32_force_binary () */

/* ========================================================================== */

/* Global support functions                                                   */

/* -------------------------------------------------------------------------- */

/* Return the size in bytes of the trampoline code.

   Padded to TRAMPOLINE_ALIGNMENT bits. The code sequence is documented in

   or32_trampoline_init ().

   This is just the code size. the static chain pointer and target function

   address immediately follow.

   @return  The size of the trampoline code in bytes.                         */

/* -------------------------------------------------------------------------- */

int

or32_trampoline_code_size (void)

{

  const int  TRAMP_BYTE_ALIGN = TRAMPOLINE_ALIGNMENT / 8;

  /* Five 32-bit code words are needed */

  return (5 * 4 + TRAMP_BYTE_ALIGN - 1) / TRAMP_BYTE_ALIGN * TRAMP_BYTE_ALIGN;

}       /* or32_trampoline_code_size () */

/*!Initialize a trampoline for nested functions.

   A nested function is defined by *two* pieces of information, the address of

   the function (like any other function) and a pointer to the frame of the

   enclosing function. The latter is required to allow the nested function to

   access local variables in the enclosing function's frame.

   This represents a problem, since a function in C is represented as an

   address that can be held in a single variable as a pointer. Requiring two

   pointers will not fit.

   The solution is documented in "Lexical Closures for C++" by Thomas

   M. Breuel (USENIX C++ Conference Proceedings, October 17-21, 1988). The

   nested function is represented by a small block of code and data on the

   enclosing function's stack frame, which sets up a pointer to the enclosing

   function's stack frame (the static chain pointer) in a register defined by

   the ABI, and then jumps to the code of the function proper.

   The function can be represented as a single pointer to this block of code,

   known as a trampoline, which when called generates both pointers

   needed. The nested function (which knows it is a nested function at compile

   time) can then generate code to access the enclosing frame via the static

   chain register.

   There is a catch that the trampoline is set up as data, but executed as

   instructions. The former will be via the data cache, the latter via the

   instruction cache. There is a risk that a later trampoline will not be seen

   by the instruction cache, so the wrong code will be executed. So the

   instruction cache should be flushed for the trampoline address range.

   This hook is called to initialize a trampoline. "m_tramp" is an RTX for the

   memory block for the trampoline; "fndecl" is the FUNCTION_DECL for the

   nested function; "static_chain" is an RTX for the static chain value that

   should be passed to the function when it is called.

   If the target defines TARGET_ASM_TRAMPOLINE_TEMPLATE, then the first thing

   this hook should do is emit a block move into "m_tramp" from the memory

   block returned by assemble_trampoline_template. Note that the block move

   need only cover the constant parts of the trampoline. If the target

   isolates the variable parts of the trampoline to the end, not all

   TRAMPOLINE_SIZE bytes need be copied.

   If the target requires any other actions, such as flushing caches or

   enabling stack execution, these actions should be performed after

   initializing the trampoline proper.

   For the OR32, no static chain register is used. We choose to use the return

   value (rv) register. The rvh register is used as a temporary. The code is

   based on that for MIPS. The trampoline code is:

              l.movhi r12,hi(end_addr)

              l.ori   r12,lo(end_addr)

              l.lwz   r13,4(r12)

              l.jr    r13

              l.lwz   r11,0(r12)

      end_addr:

              .word   <static chain>

              .word   <nested_function>

   @note For the OR32 we need to flush the instruction cache, which is a

         privileged operation. Needs fixing.

   @param[in] m_tramp      The lowest address of the trampoline on the stack.

   @param[in] fndecl       Declaration of the enclosing function.

   @param[in] chain_value  Static chain pointer to pass to the nested

                           function.                                          */

/* -------------------------------------------------------------------------- */

static void

or32_trampoline_init (rtx   m_tramp,

                      tree  fndecl,

                      rtx   chain_value)

{

  rtx  addr;                            /* Start address of the trampoline */

  rtx  end_addr;                        /* End address of the code block */

  rtx  high;                            /* RTX for the high part of end_addr */

  rtx  low;                             /* RTX for the low part of end_addr */

  rtx  opcode;                          /* RTX for generated opcodes */

  rtx  mem;                             /* RTX for trampoline memory */

  rtx trampoline[5];                    /* The trampoline code */

  unsigned int  i;                      /* Index into trampoline */

  unsigned int  j;                      /* General counter */

  HOST_WIDE_INT  end_addr_offset;         /* Offset to end of code */

  HOST_WIDE_INT  static_chain_offset;     /* Offset to stack chain word */

  HOST_WIDE_INT  target_function_offset;  /* Offset to func address word */

  /* Work out the offsets of the pointers from the start of the trampoline

     code.  */

  end_addr_offset        = or32_trampoline_code_size ();

  static_chain_offset    = end_addr_offset;

  target_function_offset = static_chain_offset + GET_MODE_SIZE (ptr_mode);

  /* Get pointers in registers to the beginning and end of the code block.  */

  addr     = force_reg (Pmode, XEXP (m_tramp, 0));

  end_addr = or32_force_binary (Pmode, PLUS, addr, GEN_INT (end_addr_offset));

  /* Build up the code in TRAMPOLINE.

              l.movhi r12,hi(end_addr)

              l.ori   r12,lo(end_addr)

              l.lwz   r13,4(r12)

              l.jr    r13

              l.lwz   r11,0(r12)

       end_addr:

  */

  i = 0;

  /* Break out the high and low parts of the end_addr */

  high = expand_simple_binop (SImode, LSHIFTRT, end_addr, GEN_INT (16),

                              NULL, false, OPTAB_WIDEN);

  low  = convert_to_mode (SImode, gen_lowpart (HImode, end_addr), true);

  /* Emit the l.movhi, adding an operation to OR in the high bits from the

     RTX. */

  opcode = gen_int_mode (OR32_MOVHI (12, 0), SImode);

  trampoline[i++] = expand_simple_binop (SImode, IOR, opcode, high, NULL,

                                         false, OPTAB_WIDEN);

  /* Emit the l.ori, adding an operations to OR in the low bits from the

     RTX. */

  opcode = gen_int_mode (OR32_ORI (12, 12, 0), SImode);

  trampoline[i++] = expand_simple_binop (SImode, IOR, opcode, low, NULL,

                                         false, OPTAB_WIDEN);

  /* Emit the l.lwz of the function address. No bits to OR in here, so we can

     do the opcode directly. */

  trampoline[i++] =

    gen_int_mode (OR32_LWZ (13, 12, target_function_offset - end_addr_offset),

                  SImode);

  /* Emit the l.jr of the function. No bits to OR in here, so we can do the

     opcode directly. */

  trampoline[i++] = gen_int_mode (OR32_JR (13), SImode);

  /* Emit the l.lwz of the static chain. No bits to OR in here, so we can

     do the opcode directly. */

  trampoline[i++] =

    gen_int_mode (OR32_LWZ (STATIC_CHAIN_REGNUM, 12,

                            static_chain_offset - end_addr_offset), SImode);

  /* Copy the trampoline code.  Leave any padding uninitialized.  */

  for (j = 0; j < i; j++)

    {

      mem = adjust_address (m_tramp, SImode, j * GET_MODE_SIZE (SImode));

      or32_emit_move (mem, trampoline[j]);

    }

  /* Set up the static chain pointer field.  */

  mem = adjust_address (m_tramp, ptr_mode, static_chain_offset);

  or32_emit_move (mem, chain_value);

  /* Set up the target function field.  */

  mem = adjust_address (m_tramp, ptr_mode, target_function_offset);

  or32_emit_move (mem, XEXP (DECL_RTL (fndecl), 0));

  /* Flushing the trampoline from the instruction cache needs to be done

     here. */

}       /* or32_trampoline_init () */

/* -------------------------------------------------------------------------- */

#undef  TARGET_TRAMPOLINE_INIT

#define TARGET_TRAMPOLINE_INIT  or32_trampoline_init