/*

 * Copyright (c) 2006, 2007, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

//------------------------------OptoReg----------------------------------------

// We eventually need Registers for the Real World.  Registers are essentially

// non-SSA names.  A Register is represented as a number.  Non-regular values

// (e.g., Control, Memory, I/O) use the Special register.  The actual machine

// registers (as described in the ADL file for a machine) start at zero.

// Stack-slots (spill locations) start at the nest Chunk past the last machine

// register.

//

// Note that stack spill-slots are treated as a very large register set.

// They have all the correct properties for a Register: not aliased (unique

// named).  There is some simple mapping from a stack-slot register number

// to the actual location on the stack; this mapping depends on the calling

// conventions and is described in the ADL.

//

// Note that Name is not enum. C++ standard defines that the range of enum

// is the range of smallest bit-field that can represent all enumerators

// declared in the enum. The result of assigning a value to enum is undefined

// if the value is outside the enumeration's valid range. OptoReg::Name is

// typedef'ed as int, because it needs to be able to represent spill-slots.

//

class OptoReg VALUE_OBJ_CLASS_SPEC {

 friend class C2Compiler;

 public:

  typedef int Name;

  enum {

    // Chunk 0

    Physical = AdlcVMDeps::Physical, // Start of physical regs

    // A few oddballs at the edge of the world

    Special = -2,               // All special (not allocated) values

    Bad = -1                    // Not a register

  };

 private:

 static const VMReg opto2vm[REG_COUNT];

 static Name vm2opto[ConcreteRegisterImpl::number_of_registers];

 public:

  // Stack pointer register

  static OptoReg::Name c_frame_pointer;

  // Increment a register number.  As in:

  //    "for ( OptoReg::Name i; i=Control; i = add(i,1) ) ..."

  static Name add( Name x, int y ) { return Name(x+y); }

  // (We would like to have an operator+ for RegName, but it is not

  // a class, so this would be illegal in C++.)

  static void dump( int );

  // Get the stack slot number of an OptoReg::Name

  static unsigned int reg2stack( OptoReg::Name r) {

    assert( r >= stack0(), " must be");

    return r - stack0();

  }

  // convert a stack slot number into an OptoReg::Name

  static OptoReg::Name stack2reg( int idx) {

    return Name(stack0() + idx);

  }

  static bool is_stack(Name n) {

    return n >= stack0();

  }

  static bool is_valid(Name n) {

    return (n != Bad);

  }

  static bool is_reg(Name n) {

    return  is_valid(n) && !is_stack(n);

  }

  static VMReg as_VMReg(OptoReg::Name n) {

    if (is_reg(n)) {

      // Must use table, it'd be nice if Bad was indexable...

      return opto2vm[n];

    } else {

      assert(!is_stack(n), "must un warp");

      return VMRegImpl::Bad();

    }

  }

  // Can un-warp a stack slot or convert a register or Bad

  static VMReg as_VMReg(OptoReg::Name n, int frame_size, int arg_count) {

    if (is_reg(n)) {

      // Must use table, it'd be nice if Bad was indexable...

      return opto2vm[n];

    } else if (is_stack(n)) {

      int stack_slot = reg2stack(n);

      if (stack_slot < arg_count) {

        return VMRegImpl::stack2reg(stack_slot + frame_size);

      }

      return VMRegImpl::stack2reg(stack_slot - arg_count);

      // return return VMRegImpl::stack2reg(reg2stack(OptoReg::add(n, -arg_count)));

    } else {

      return VMRegImpl::Bad();

    }

  }

  static OptoReg::Name as_OptoReg(VMReg r) {

    if (r->is_stack()) {

      assert(false, "must warp");

      return stack2reg(r->reg2stack());

    } else if (r->is_valid()) {

      // Must use table, it'd be nice if Bad was indexable...

      return vm2opto[r->value()];

    } else {

      return Bad;

    }

  }

  static OptoReg::Name stack0() {

    return VMRegImpl::stack0->value();

  }

  static const char* regname(OptoReg::Name n) {

    return as_VMReg(n)->name();

  }

};

//---------------------------OptoRegPair-------------------------------------------

// Pairs of 32-bit registers for the allocator.

// This is a very similar class to VMRegPair. C2 only interfaces with VMRegPair

// via the calling convention code which is shared between the compilers.

// Since C2 uses OptoRegs for register allocation it is more efficient to use

// VMRegPair internally for nodes that can contain a pair of OptoRegs rather

// than use VMRegPair and continually be converting back and forth. So normally

// C2 will take in a VMRegPair from the calling convention code and immediately

// convert them to an OptoRegPair and stay in the OptoReg world. The only over

// conversion between OptoRegs and VMRegs is for debug info and oopMaps. This

// is not a high bandwidth spot and so it is not an issue.

// Note that onde other consequence of staying in the OptoReg world with OptoRegPairs

// is that there are "physical" OptoRegs that are not representable in the VMReg

// world, notably flags. [ But by design there is "space" in the VMReg world

// for such registers they just may not be concrete ]. So if we were to use VMRegPair

// then the VMReg world would have to have a representation for these registers

// so that a OptoReg->VMReg->OptoReg would reproduce ther original OptoReg. As it

// stands if you convert a flag (condition code) to a VMReg you will get VMRegImpl::Bad

// and converting that will return OptoReg::Bad losing the identity of the OptoReg.

class OptoRegPair {

private:

  short _second;

  short _first;

public:

  void set_bad (                   ) { _second = OptoReg::Bad; _first = OptoReg::Bad; }

  void set1    ( OptoReg::Name n  ) { _second = OptoReg::Bad; _first = n; }

  void set2    ( OptoReg::Name n  ) { _second = n + 1;       _first = n; }

  void set_pair( OptoReg::Name second, OptoReg::Name first    ) { _second= second;    _first= first; }

  void set_ptr ( OptoReg::Name ptr ) {

#ifdef _LP64

    _second = ptr+1;

#else

    _second = OptoReg::Bad;

#endif

    _first = ptr;

  }

  OptoReg::Name second() const { return _second; }

  OptoReg::Name first() const { return _first; }

  OptoRegPair(OptoReg::Name second, OptoReg::Name first) {  _second = second; _first = first; }

  OptoRegPair(OptoReg::Name f) { _second = OptoReg::Bad; _first = f; }

  OptoRegPair() { _second = OptoReg::Bad; _first = OptoReg::Bad; }

};