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 /*

  * Copyright (c) 2005, 2010, 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

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "c1/c1_Instruction.hpp"

 #include "c1/c1_LinearScan.hpp"

 #include "utilities/bitMap.inline.hpp"

 //----------------------------------------------------------------------

 // Allocation of FPU stack slots (Intel x86 only)

 //----------------------------------------------------------------------

 void LinearScan::allocate_fpu_stack() {

   // First compute which FPU registers are live at the start of each basic block

   // (To minimize the amount of work we have to do if we have to merge FPU stacks)

   if (ComputeExactFPURegisterUsage) {

     Interval* intervals_in_register, *intervals_in_memory;

     create_unhandled_lists(&intervals_in_register, &intervals_in_memory, is_in_fpu_register, NULL);

     // ignore memory intervals by overwriting intervals_in_memory

     // the dummy interval is needed to enforce the walker to walk until the given id:

     // without it, the walker stops when the unhandled-list is empty -> live information

     // beyond this point would be incorrect.

     Interval* dummy_interval = new Interval(any_reg);

     dummy_interval->add_range(max_jint - 2, max_jint - 1);

     dummy_interval->set_next(Interval::end());

     intervals_in_memory = dummy_interval;

     IntervalWalker iw(this, intervals_in_register, intervals_in_memory);

     const int num_blocks = block_count();

     for (int i = 0; i < num_blocks; i++) {

       BlockBegin* b = block_at(i);

       // register usage is only needed for merging stacks -> compute only

       // when more than one predecessor.

       // the block must not have any spill moves at the beginning (checked by assertions)

       // spill moves would use intervals that are marked as handled and so the usage bit

       // would been set incorrectly

       // NOTE: the check for number_of_preds > 1 is necessary. A block with only one

       //       predecessor may have spill moves at the begin of the block.

       //       If an interval ends at the current instruction id, it is not possible

       //       to decide if the register is live or not at the block begin -> the

       //       register information would be incorrect.

       if (b->number_of_preds() > 1) {

         int id = b->first_lir_instruction_id();

         BitMap regs(FrameMap::nof_fpu_regs);

         regs.clear();

         iw.walk_to(id);   // walk after the first instruction (always a label) of the block

         assert(iw.current_position() == id, "did not walk completely to id");

         // Only consider FPU values in registers

         Interval* interval = iw.active_first(fixedKind);

         while (interval != Interval::end()) {

           int reg = interval->assigned_reg();

           assert(reg >= pd_first_fpu_reg && reg <= pd_last_fpu_reg, "no fpu register");

           assert(interval->assigned_regHi() == -1, "must not have hi register (doubles stored in one register)");

           assert(interval->from() <= id && id < interval->to(), "interval out of range");

 #ifndef PRODUCT

           if (TraceFPURegisterUsage) {

             tty->print("fpu reg %d is live because of ", reg - pd_first_fpu_reg); interval->print();

           }

 #endif

           regs.set_bit(reg - pd_first_fpu_reg);

           interval = interval->next();

         }

         b->set_fpu_register_usage(regs);

 #ifndef PRODUCT

         if (TraceFPURegisterUsage) {

           tty->print("FPU regs for block %d, LIR instr %d): ", b->block_id(), id); regs.print_on(tty); tty->print_cr("");

         }

 #endif

       }

     }

   }

   FpuStackAllocator alloc(ir()->compilation(), this);

   _fpu_stack_allocator = &alloc;

   alloc.allocate();

   _fpu_stack_allocator = NULL;

 }

 FpuStackAllocator::FpuStackAllocator(Compilation* compilation, LinearScan* allocator)

   : _compilation(compilation)

   , _lir(NULL)

   , _pos(-1)

   , _allocator(allocator)

   , _sim(compilation)

   , _temp_sim(compilation)

 {}

 void FpuStackAllocator::allocate() {

   int num_blocks = allocator()->block_count();

   for (int i = 0; i < num_blocks; i++) {

     // Set up to process block

     BlockBegin* block = allocator()->block_at(i);

     intArray* fpu_stack_state = block->fpu_stack_state();

 #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->cr();

       tty->print_cr("------- Begin of new Block %d -------", block->block_id());

     }

 #endif

     assert(fpu_stack_state != NULL ||

            block->end()->as_Base() != NULL ||

            block->is_set(BlockBegin::exception_entry_flag),

            "FPU stack state must be present due to linear-scan order for FPU stack allocation");

     // note: exception handler entries always start with an empty fpu stack

     //       because stack merging would be too complicated

     if (fpu_stack_state != NULL) {

       sim()->read_state(fpu_stack_state);

     } else {

       sim()->clear();

     }

 #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->print("Reading FPU state for block %d:", block->block_id());

       sim()->print();

       tty->cr();

     }

 #endif

     allocate_block(block);

     CHECK_BAILOUT();

   }

 }

 void FpuStackAllocator::allocate_block(BlockBegin* block) {

   bool processed_merge = false;

   LIR_OpList* insts = block->lir()->instructions_list();

   set_lir(block->lir());

   set_pos(0);

   // Note: insts->length() may change during loop

   while (pos() < insts->length()) {

     LIR_Op* op = insts->at(pos());

     _debug_information_computed = false;

 #ifndef PRODUCT

     if (TraceFPUStack) {

       op->print();

     }

     check_invalid_lir_op(op);

 #endif

     LIR_OpBranch* branch = op->as_OpBranch();

     LIR_Op1* op1 = op->as_Op1();

     LIR_Op2* op2 = op->as_Op2();

     LIR_OpCall* opCall = op->as_OpCall();

     if (branch != NULL && branch->block() != NULL) {

       if (!processed_merge) {

         // propagate stack at first branch to a successor

         processed_merge = true;

         bool required_merge = merge_fpu_stack_with_successors(block);

         assert(!required_merge || branch->cond() == lir_cond_always, "splitting of critical edges should prevent FPU stack mismatches at cond branches");

       }

     } else if (op1 != NULL) {

       handle_op1(op1);

     } else if (op2 != NULL) {

       handle_op2(op2);

     } else if (opCall != NULL) {

       handle_opCall(opCall);

     }

     compute_debug_information(op);

     set_pos(1 + pos());

   }

   // Propagate stack when block does not end with branch

   if (!processed_merge) {

     merge_fpu_stack_with_successors(block);

   }

 }

 void FpuStackAllocator::compute_debug_information(LIR_Op* op) {

   if (!_debug_information_computed && op->id() != -1 && allocator()->has_info(op->id())) {

     visitor.visit(op);

     // exception handling

     if (allocator()->compilation()->has_exception_handlers()) {

       XHandlers* xhandlers = visitor.all_xhandler();

       int n = xhandlers->length();

       for (int k = 0; k < n; k++) {

         allocate_exception_handler(xhandlers->handler_at(k));

       }

     } else {

       assert(visitor.all_xhandler()->length() == 0, "missed exception handler");

     }

     // compute debug information

     int n = visitor.info_count();

     assert(n > 0, "should not visit operation otherwise");

     for (int j = 0; j < n; j++) {

       CodeEmitInfo* info = visitor.info_at(j);

       // Compute debug information

       allocator()->compute_debug_info(info, op->id());

     }

   }

   _debug_information_computed = true;

 }

 void FpuStackAllocator::allocate_exception_handler(XHandler* xhandler) {

   if (!sim()->is_empty()) {

     LIR_List* old_lir = lir();

     int old_pos = pos();

     intArray* old_state = sim()->write_state();

 #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->cr();

       tty->print_cr("------- begin of exception handler -------");

     }

 #endif

     if (xhandler->entry_code() == NULL) {

       // need entry code to clear FPU stack

       LIR_List* entry_code = new LIR_List(_compilation);

       entry_code->jump(xhandler->entry_block());

       xhandler->set_entry_code(entry_code);

     }

     LIR_OpList* insts = xhandler->entry_code()->instructions_list();

     set_lir(xhandler->entry_code());

     set_pos(0);

     // Note: insts->length() may change during loop

     while (pos() < insts->length()) {

       LIR_Op* op = insts->at(pos());

 #ifndef PRODUCT

       if (TraceFPUStack) {

         op->print();

       }

       check_invalid_lir_op(op);

 #endif

       switch (op->code()) {

         case lir_move:

           assert(op->as_Op1() != NULL, "must be LIR_Op1");

           assert(pos() != insts->length() - 1, "must not be last operation");

           handle_op1((LIR_Op1*)op);

           break;

         case lir_branch:

           assert(op->as_OpBranch()->cond() == lir_cond_always, "must be unconditional branch");

           assert(pos() == insts->length() - 1, "must be last operation");

           // remove all remaining dead registers from FPU stack

           clear_fpu_stack(LIR_OprFact::illegalOpr);

           break;

         default:

           // other operations not allowed in exception entry code

           ShouldNotReachHere();

       }

       set_pos(pos() + 1);

     }

 #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->cr();

       tty->print_cr("------- end of exception handler -------");

     }

 #endif

     set_lir(old_lir);

     set_pos(old_pos);

     sim()->read_state(old_state);

   }

 }

 int FpuStackAllocator::fpu_num(LIR_Opr opr) {

   assert(opr->is_fpu_register() && !opr->is_xmm_register(), "shouldn't call this otherwise");

   return opr->is_single_fpu() ? opr->fpu_regnr() : opr->fpu_regnrLo();

 }

 int FpuStackAllocator::tos_offset(LIR_Opr opr) {

   return sim()->offset_from_tos(fpu_num(opr));

 }

 LIR_Opr FpuStackAllocator::to_fpu_stack(LIR_Opr opr) {

   assert(opr->is_fpu_register() && !opr->is_xmm_register(), "shouldn't call this otherwise");

   int stack_offset = tos_offset(opr);

   if (opr->is_single_fpu()) {

     return LIR_OprFact::single_fpu(stack_offset)->make_fpu_stack_offset();

   } else {

     assert(opr->is_double_fpu(), "shouldn't call this otherwise");

     return LIR_OprFact::double_fpu(stack_offset)->make_fpu_stack_offset();

   }

 }

 LIR_Opr FpuStackAllocator::to_fpu_stack_top(LIR_Opr opr, bool dont_check_offset) {

   assert(opr->is_fpu_register() && !opr->is_xmm_register(), "shouldn't call this otherwise");

   assert(dont_check_offset || tos_offset(opr) == 0, "operand is not on stack top");

   int stack_offset = 0;

   if (opr->is_single_fpu()) {

     return LIR_OprFact::single_fpu(stack_offset)->make_fpu_stack_offset();

   } else {

     assert(opr->is_double_fpu(), "shouldn't call this otherwise");

     return LIR_OprFact::double_fpu(stack_offset)->make_fpu_stack_offset();

   }

 }

 void FpuStackAllocator::insert_op(LIR_Op* op) {

   lir()->insert_before(pos(), op);

   set_pos(1 + pos());

 }

 void FpuStackAllocator::insert_exchange(int offset) {

   if (offset > 0) {

     LIR_Op1* fxch_op = new LIR_Op1(lir_fxch, LIR_OprFact::intConst(offset), LIR_OprFact::illegalOpr);

     insert_op(fxch_op);

     sim()->swap(offset);

 #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->print("Exchanged register: %d         New state: ", sim()->get_slot(0)); sim()->print(); tty->cr();

     }

 #endif

   }

 }

 void FpuStackAllocator::insert_exchange(LIR_Opr opr) {

   insert_exchange(tos_offset(opr));

 }

 void FpuStackAllocator::insert_free(int offset) {

   // move stack slot to the top of stack and then pop it

   insert_exchange(offset);

   LIR_Op* fpop = new LIR_Op0(lir_fpop_raw);

   insert_op(fpop);

   sim()->pop();

 #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->print("Inserted pop                   New state: "); sim()->print(); tty->cr();

     }

 #endif

 }

 void FpuStackAllocator::insert_free_if_dead(LIR_Opr opr) {

   if (sim()->contains(fpu_num(opr))) {

     int res_slot = tos_offset(opr);

     insert_free(res_slot);

   }

 }

 void FpuStackAllocator::insert_free_if_dead(LIR_Opr opr, LIR_Opr ignore) {

   if (fpu_num(opr) != fpu_num(ignore) && sim()->contains(fpu_num(opr))) {

     int res_slot = tos_offset(opr);

     insert_free(res_slot);

   }

 }

 void FpuStackAllocator::insert_copy(LIR_Opr from, LIR_Opr to) {

   int offset = tos_offset(from);

   LIR_Op1* fld = new LIR_Op1(lir_fld, LIR_OprFact::intConst(offset), LIR_OprFact::illegalOpr);

   insert_op(fld);

   sim()->push(fpu_num(to));

 #ifndef PRODUCT

   if (TraceFPUStack) {

     tty->print("Inserted copy (%d -> %d)         New state: ", fpu_num(from), fpu_num(to)); sim()->print(); tty->cr();

   }

 #endif

 }

 void FpuStackAllocator::do_rename(LIR_Opr from, LIR_Opr to) {

   sim()->rename(fpu_num(from), fpu_num(to));

 }

 void FpuStackAllocator::do_push(LIR_Opr opr) {

   sim()->push(fpu_num(opr));

 }

 void FpuStackAllocator::pop_if_last_use(LIR_Op* op, LIR_Opr opr) {

   assert(op->fpu_pop_count() == 0, "fpu_pop_count alredy set");

   assert(tos_offset(opr) == 0, "can only pop stack top");

   if (opr->is_last_use()) {

     op->set_fpu_pop_count(1);

     sim()->pop();

   }

 }

 void FpuStackAllocator::pop_always(LIR_Op* op, LIR_Opr opr) {

   assert(op->fpu_pop_count() == 0, "fpu_pop_count alredy set");

   assert(tos_offset(opr) == 0, "can only pop stack top");

   op->set_fpu_pop_count(1);

   sim()->pop();

 }

 void FpuStackAllocator::clear_fpu_stack(LIR_Opr preserve) {

   int result_stack_size = (preserve->is_fpu_register() && !preserve->is_xmm_register() ? 1 : 0);

   while (sim()->stack_size() > result_stack_size) {

     assert(!sim()->slot_is_empty(0), "not allowed");

     if (result_stack_size == 0 || sim()->get_slot(0) != fpu_num(preserve)) {

       insert_free(0);

     } else {

       // move "preserve" to bottom of stack so that all other stack slots can be popped

       insert_exchange(sim()->stack_size() - 1);

     }

   }

 }

 void FpuStackAllocator::handle_op1(LIR_Op1* op1) {

   LIR_Opr in  = op1->in_opr();

   LIR_Opr res = op1->result_opr();

   LIR_Opr new_in  = in;  // new operands relative to the actual fpu stack top

   LIR_Opr new_res = res;

   // Note: this switch is processed for all LIR_Op1, regardless if they have FPU-arguments,

   //       so checks for is_float_kind() are necessary inside the cases

   switch (op1->code()) {

     case lir_return: {

       // FPU-Stack must only contain the (optional) fpu return value.

       // All remaining dead values are popped from the stack

       // If the input operand is a fpu-register, it is exchanged to the bottom of the stack

       clear_fpu_stack(in);

       if (in->is_fpu_register() && !in->is_xmm_register()) {

         new_in = to_fpu_stack_top(in);

       }

       break;

     }

     case lir_move: {

       if (in->is_fpu_register() && !in->is_xmm_register()) {

         if (res->is_xmm_register()) {

           // move from fpu register to xmm register (necessary for operations that

           // are not available in the SSE instruction set)

           insert_exchange(in);

           new_in = to_fpu_stack_top(in);

           pop_always(op1, in);

         } else if (res->is_fpu_register() && !res->is_xmm_register()) {

           // move from fpu-register to fpu-register:

           // * input and result register equal:

           //   nothing to do

           // * input register is last use:

           //   rename the input register to result register -> input register

           //   not present on fpu-stack afterwards

           // * input register not last use:

           //   duplicate input register to result register to preserve input

           //

           // Note: The LIR-Assembler does not produce any code for fpu register moves,

           //       so input and result stack index must be equal

           if (fpu_num(in) == fpu_num(res)) {

             // nothing to do

           } else if (in->is_last_use()) {

             insert_free_if_dead(res);//, in);

             do_rename(in, res);

           } else {

             insert_free_if_dead(res);

             insert_copy(in, res);

           }

           new_in = to_fpu_stack(res);

           new_res = new_in;

         } else {

           // move from fpu-register to memory

           // input operand must be on top of stack

           insert_exchange(in);

           // create debug information here because afterwards the register may have been popped

           compute_debug_information(op1);

           new_in = to_fpu_stack_top(in);

           pop_if_last_use(op1, in);

         }

       } else if (res->is_fpu_register() && !res->is_xmm_register()) {

         // move from memory/constant to fpu register

         // result is pushed on the stack

         insert_free_if_dead(res);

         // create debug information before register is pushed

         compute_debug_information(op1);

         do_push(res);

         new_res = to_fpu_stack_top(res);

       }

       break;

     }

     case lir_neg: {

       if (in->is_fpu_register() && !in->is_xmm_register()) {

         assert(res->is_fpu_register() && !res->is_xmm_register(), "must be");

         assert(in->is_last_use(), "old value gets destroyed");

         insert_free_if_dead(res, in);

         insert_exchange(in);

         new_in = to_fpu_stack_top(in);

         do_rename(in, res);

         new_res = to_fpu_stack_top(res);

       }

       break;

     }

     case lir_convert: {

       Bytecodes::Code bc = op1->as_OpConvert()->bytecode();

       switch (bc) {

         case Bytecodes::_d2f:

         case Bytecodes::_f2d:

           assert(res->is_fpu_register(), "must be");

           assert(in->is_fpu_register(), "must be");

           if (!in->is_xmm_register() && !res->is_xmm_register()) {

             // this is quite the same as a move from fpu-register to fpu-register

             // Note: input and result operands must have different types

             if (fpu_num(in) == fpu_num(res)) {

               // nothing to do

               new_in = to_fpu_stack(in);

             } else if (in->is_last_use()) {

               insert_free_if_dead(res);//, in);

               new_in = to_fpu_stack(in);

               do_rename(in, res);

             } else {

               insert_free_if_dead(res);

               insert_copy(in, res);

               new_in = to_fpu_stack_top(in, true);

             }

             new_res = to_fpu_stack(res);

           }

           break;

         case Bytecodes::_i2f:

         case Bytecodes::_l2f:

         case Bytecodes::_i2d:

         case Bytecodes::_l2d:

           assert(res->is_fpu_register(), "must be");

           if (!res->is_xmm_register()) {

             insert_free_if_dead(res);

             do_push(res);

             new_res = to_fpu_stack_top(res);

           }

           break;

         case Bytecodes::_f2i:

         case Bytecodes::_d2i:

           assert(in->is_fpu_register(), "must be");

           if (!in->is_xmm_register()) {

             insert_exchange(in);

             new_in = to_fpu_stack_top(in);

             // TODO: update registes of stub

           }

           break;

         case Bytecodes::_f2l:

         case Bytecodes::_d2l:

           assert(in->is_fpu_register(), "must be");

           if (!in->is_xmm_register()) {

             insert_exchange(in);

             new_in = to_fpu_stack_top(in);

             pop_always(op1, in);

           }

           break;

         case Bytecodes::_i2l:

         case Bytecodes::_l2i:

         case Bytecodes::_i2b:

         case Bytecodes::_i2c:

         case Bytecodes::_i2s:

           // no fpu operands

           break;

         default:

           ShouldNotReachHere();

       }

       break;

     }

     case lir_roundfp: {

       assert(in->is_fpu_register() && !in->is_xmm_register(), "input must be in register");

       assert(res->is_stack(), "result must be on stack");

       insert_exchange(in);

       new_in = to_fpu_stack_top(in);

       pop_if_last_use(op1, in);

       break;

     }

     default: {

       assert(!in->is_float_kind() && !res->is_float_kind(), "missed a fpu-operation");

     }

   }

   op1->set_in_opr(new_in);

   op1->set_result_opr(new_res);

 }

 void FpuStackAllocator::handle_op2(LIR_Op2* op2) {

   LIR_Opr left  = op2->in_opr1();

   if (!left->is_float_kind()) {

     return;

   }

   if (left->is_xmm_register()) {

     return;

   }

   LIR_Opr right = op2->in_opr2();

   LIR_Opr res   = op2->result_opr();

   LIR_Opr new_left  = left;  // new operands relative to the actual fpu stack top

   LIR_Opr new_right = right;

   LIR_Opr new_res   = res;

   assert(!left->is_xmm_register() && !right->is_xmm_register() && !res->is_xmm_register(), "not for xmm registers");

   switch (op2->code()) {

     case lir_cmp:

     case lir_cmp_fd2i:

     case lir_ucmp_fd2i: {

       assert(left->is_fpu_register(), "invalid LIR");

       assert(right->is_fpu_register(), "invalid LIR");

       // the left-hand side must be on top of stack.

       // the right-hand side is never popped, even if is_last_use is set

       insert_exchange(left);

       new_left = to_fpu_stack_top(left);

       new_right = to_fpu_stack(right);

       pop_if_last_use(op2, left);

       break;

     }

     case lir_mul_strictfp:

     case lir_div_strictfp: {

       assert(op2->tmp1_opr()->is_fpu_register(), "strict operations need temporary fpu stack slot");

       insert_free_if_dead(op2->tmp1_opr());

       assert(sim()->stack_size() <= 7, "at least one stack slot must be free");

       // fall-through: continue with the normal handling of lir_mul and lir_div

     }

     case lir_add:

     case lir_sub:

     case lir_mul:

     case lir_div: {

       assert(left->is_fpu_register(), "must be");

       assert(res->is_fpu_register(), "must be");

       assert(left->is_equal(res), "must be");

       // either the left-hand or the right-hand side must be on top of stack

       // (if right is not a register, left must be on top)

       if (!right->is_fpu_register()) {

         insert_exchange(left);

         new_left = to_fpu_stack_top(left);

       } else {

         // no exchange necessary if right is alredy on top of stack

         if (tos_offset(right) == 0) {

           new_left = to_fpu_stack(left);

           new_right = to_fpu_stack_top(right);

         } else {

           insert_exchange(left);

           new_left = to_fpu_stack_top(left);

           new_right = to_fpu_stack(right);

         }

         if (right->is_last_use()) {

           op2->set_fpu_pop_count(1);

           if (tos_offset(right) == 0) {

             sim()->pop();

           } else {

             // if left is on top of stack, the result is placed in the stack

             // slot of right, so a renaming from right to res is necessary

             assert(tos_offset(left) == 0, "must be");

             sim()->pop();

             do_rename(right, res);

           }

         }

       }

       new_res = to_fpu_stack(res);

       break;

     }

     case lir_rem: {

       assert(left->is_fpu_register(), "must be");

       assert(right->is_fpu_register(), "must be");

       assert(res->is_fpu_register(), "must be");

       assert(left->is_equal(res), "must be");

       // Must bring both operands to top of stack with following operand ordering:

       // * fpu stack before rem: ... right left

       // * fpu stack after rem:  ... left

       if (tos_offset(right) != 1) {

         insert_exchange(right);

         insert_exchange(1);

       }

       insert_exchange(left);

       assert(tos_offset(right) == 1, "check");

       assert(tos_offset(left) == 0, "check");

       new_left = to_fpu_stack_top(left);

       new_right = to_fpu_stack(right);

       op2->set_fpu_pop_count(1);

       sim()->pop();

       do_rename(right, res);

       new_res = to_fpu_stack_top(res);

       break;

     }

     case lir_abs:

     case lir_sqrt: {

       // Right argument appears to be unused

       assert(right->is_illegal(), "must be");

       assert(left->is_fpu_register(), "must be");

       assert(res->is_fpu_register(), "must be");

       assert(left->is_last_use(), "old value gets destroyed");

       insert_free_if_dead(res, left);

       insert_exchange(left);

       do_rename(left, res);

       new_left = to_fpu_stack_top(res);

       new_res = new_left;

       op2->set_fpu_stack_size(sim()->stack_size());

       break;

     }

     case lir_log:

     case lir_log10: {

       // log and log10 need one temporary fpu stack slot, so

       // there is one temporary registers stored in temp of the

       // operation. the stack allocator must guarantee that the stack

       // slots are really free, otherwise there might be a stack

       // overflow.

       assert(right->is_illegal(), "must be");

       assert(left->is_fpu_register(), "must be");

       assert(res->is_fpu_register(), "must be");

       assert(op2->tmp1_opr()->is_fpu_register(), "must be");

       insert_free_if_dead(op2->tmp1_opr());

       insert_free_if_dead(res, left);

       insert_exchange(left);

       do_rename(left, res);

       new_left = to_fpu_stack_top(res);

       new_res = new_left;

       op2->set_fpu_stack_size(sim()->stack_size());

       assert(sim()->stack_size() <= 7, "at least one stack slot must be free");

       break;

     }

     case lir_tan:

     case lir_sin:

     case lir_cos:

     case lir_exp: {

       // sin, cos and exp need two temporary fpu stack slots, so there are two temporary

       // registers (stored in right and temp of the operation).

       // the stack allocator must guarantee that the stack slots are really free,

       // otherwise there might be a stack overflow.

       assert(left->is_fpu_register(), "must be");

       assert(res->is_fpu_register(), "must be");

       // assert(left->is_last_use(), "old value gets destroyed");

       assert(right->is_fpu_register(), "right is used as the first temporary register");

       assert(op2->tmp1_opr()->is_fpu_register(), "temp is used as the second temporary register");

       assert(fpu_num(left) != fpu_num(right) && fpu_num(right) != fpu_num(op2->tmp1_opr()) && fpu_num(op2->tmp1_opr()) != fpu_num(res), "need distinct temp registers");

       insert_free_if_dead(right);

       insert_free_if_dead(op2->tmp1_opr());

       insert_free_if_dead(res, left);

       insert_exchange(left);

       do_rename(left, res);

       new_left = to_fpu_stack_top(res);

       new_res = new_left;

       op2->set_fpu_stack_size(sim()->stack_size());

       assert(sim()->stack_size() <= 6, "at least two stack slots must be free");

       break;

     }

     case lir_pow: {

       // pow needs two temporary fpu stack slots, so there are two temporary

       // registers (stored in tmp1 and tmp2 of the operation).

       // the stack allocator must guarantee that the stack slots are really free,

       // otherwise there might be a stack overflow.

       assert(left->is_fpu_register(), "must be");

       assert(right->is_fpu_register(), "must be");

       assert(res->is_fpu_register(), "must be");

       assert(op2->tmp1_opr()->is_fpu_register(), "tmp1 is the first temporary register");

       assert(op2->tmp2_opr()->is_fpu_register(), "tmp2 is the second temporary register");

       assert(fpu_num(left) != fpu_num(right) && fpu_num(left) != fpu_num(op2->tmp1_opr()) && fpu_num(left) != fpu_num(op2->tmp2_opr()) && fpu_num(left) != fpu_num(res), "need distinct temp registers");

       assert(fpu_num(right) != fpu_num(op2->tmp1_opr()) && fpu_num(right) != fpu_num(op2->tmp2_opr()) && fpu_num(right) != fpu_num(res), "need distinct temp registers");

       assert(fpu_num(op2->tmp1_opr()) != fpu_num(op2->tmp2_opr()) && fpu_num(op2->tmp1_opr()) != fpu_num(res), "need distinct temp registers");

       assert(fpu_num(op2->tmp2_opr()) != fpu_num(res), "need distinct temp registers");

       insert_free_if_dead(op2->tmp1_opr());

       insert_free_if_dead(op2->tmp2_opr());

       // Must bring both operands to top of stack with following operand ordering:

       // * fpu stack before pow: ... right left

       // * fpu stack after pow:  ... left

       insert_free_if_dead(res, right);

       if (tos_offset(right) != 1) {

         insert_exchange(right);

         insert_exchange(1);

       }

       insert_exchange(left);

       assert(tos_offset(right) == 1, "check");

       assert(tos_offset(left) == 0, "check");

       new_left = to_fpu_stack_top(left);

       new_right = to_fpu_stack(right);

       op2->set_fpu_stack_size(sim()->stack_size());

       assert(sim()->stack_size() <= 6, "at least two stack slots must be free");

       sim()->pop();

       do_rename(right, res);

       new_res = to_fpu_stack_top(res);

       break;

     }

     default: {

       assert(false, "missed a fpu-operation");

     }

   }

   op2->set_in_opr1(new_left);

   op2->set_in_opr2(new_right);

   op2->set_result_opr(new_res);

 }

 void FpuStackAllocator::handle_opCall(LIR_OpCall* opCall) {

   LIR_Opr res = opCall->result_opr();

   // clear fpu-stack before call

   // it may contain dead values that could not have been remved by previous operations

   clear_fpu_stack(LIR_OprFact::illegalOpr);

   assert(sim()->is_empty(), "fpu stack must be empty now");

   // compute debug information before (possible) fpu result is pushed

   compute_debug_information(opCall);

   if (res->is_fpu_register() && !res->is_xmm_register()) {

     do_push(res);

     opCall->set_result_opr(to_fpu_stack_top(res));

   }

 }

 #ifndef PRODUCT

 void FpuStackAllocator::check_invalid_lir_op(LIR_Op* op) {

   switch (op->code()) {

     case lir_24bit_FPU:

     case lir_reset_FPU:

     case lir_ffree:

       assert(false, "operations not allowed in lir. If one of these operations is needed, check if they have fpu operands");

       break;

     case lir_fpop_raw:

     case lir_fxch:

     case lir_fld:

       assert(false, "operations only inserted by FpuStackAllocator");

       break;

   }

 }

 #endif

 void FpuStackAllocator::merge_insert_add(LIR_List* instrs, FpuStackSim* cur_sim, int reg) {

   LIR_Op1* move = new LIR_Op1(lir_move, LIR_OprFact::doubleConst(0), LIR_OprFact::double_fpu(reg)->make_fpu_stack_offset());

   instrs->instructions_list()->push(move);

   cur_sim->push(reg);

   move->set_result_opr(to_fpu_stack(move->result_opr()));

   #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->print("Added new register: %d         New state: ", reg); cur_sim->print(); tty->cr();

     }

   #endif

 }

 void FpuStackAllocator::merge_insert_xchg(LIR_List* instrs, FpuStackSim* cur_sim, int slot) {

   assert(slot > 0, "no exchange necessary");

   LIR_Op1* fxch = new LIR_Op1(lir_fxch, LIR_OprFact::intConst(slot));

   instrs->instructions_list()->push(fxch);

   cur_sim->swap(slot);

   #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->print("Exchanged register: %d         New state: ", cur_sim->get_slot(slot)); cur_sim->print(); tty->cr();

     }

   #endif

 }

 void FpuStackAllocator::merge_insert_pop(LIR_List* instrs, FpuStackSim* cur_sim) {

   int reg = cur_sim->get_slot(0);

   LIR_Op* fpop = new LIR_Op0(lir_fpop_raw);

   instrs->instructions_list()->push(fpop);

   cur_sim->pop(reg);

   #ifndef PRODUCT

     if (TraceFPUStack) {

       tty->print("Removed register: %d           New state: ", reg); cur_sim->print(); tty->cr();

     }

   #endif

 }

 bool FpuStackAllocator::merge_rename(FpuStackSim* cur_sim, FpuStackSim* sux_sim, int start_slot, int change_slot) {

   int reg = cur_sim->get_slot(change_slot);

   for (int slot = start_slot; slot >= 0; slot--) {

     int new_reg = sux_sim->get_slot(slot);

     if (!cur_sim->contains(new_reg)) {

       cur_sim->set_slot(change_slot, new_reg);

       #ifndef PRODUCT

         if (TraceFPUStack) {

           tty->print("Renamed register %d to %d       New state: ", reg, new_reg); cur_sim->print(); tty->cr();

         }

       #endif

       return true;

     }

   }

   return false;

 }

 void FpuStackAllocator::merge_fpu_stack(LIR_List* instrs, FpuStackSim* cur_sim, FpuStackSim* sux_sim) {

 #ifndef PRODUCT

   if (TraceFPUStack) {

     tty->cr();

     tty->print("before merging: pred: "); cur_sim->print(); tty->cr();

     tty->print("                 sux: "); sux_sim->print(); tty->cr();

   }

   int slot;

   for (slot = 0; slot < cur_sim->stack_size(); slot++) {

     assert(!cur_sim->slot_is_empty(slot), "not handled by algorithm");

   }

   for (slot = 0; slot < sux_sim->stack_size(); slot++) {

     assert(!sux_sim->slot_is_empty(slot), "not handled by algorithm");

   }

 #endif

   // size difference between cur and sux that must be resolved by adding or removing values form the stack

   int size_diff = cur_sim->stack_size() - sux_sim->stack_size();

   if (!ComputeExactFPURegisterUsage) {

     // add slots that are currently free, but used in successor

     // When the exact FPU register usage is computed, the stack does

     // not contain dead values at merging -> no values must be added

     int sux_slot = sux_sim->stack_size() - 1;

     while (size_diff < 0) {

       assert(sux_slot >= 0, "slot out of bounds -> error in algorithm");

       int reg = sux_sim->get_slot(sux_slot);

       if (!cur_sim->contains(reg)) {

         merge_insert_add(instrs, cur_sim, reg);

         size_diff++;

         if (sux_slot + size_diff != 0) {

           merge_insert_xchg(instrs, cur_sim, sux_slot + size_diff);

         }

       }

      sux_slot--;

     }

   }

   assert(cur_sim->stack_size() >= sux_sim->stack_size(), "stack size must be equal or greater now");

   assert(size_diff == cur_sim->stack_size() - sux_sim->stack_size(), "must be");

   // stack merge algorithm:

   // 1) as long as the current stack top is not in the right location (that meens

   //    it should not be on the stack top), exchange it into the right location

   // 2) if the stack top is right, but the remaining stack is not ordered correctly,

   //    the stack top is exchanged away to get another value on top ->

   //    now step 1) can be continued

   // the stack can also contain unused items -> these items are removed from stack

   int finished_slot = sux_sim->stack_size() - 1;

   while (finished_slot >= 0 || size_diff > 0) {

     while (size_diff > 0 || (cur_sim->stack_size() > 0 && cur_sim->get_slot(0) != sux_sim->get_slot(0))) {

       int reg = cur_sim->get_slot(0);

       if (sux_sim->contains(reg)) {

         int sux_slot = sux_sim->offset_from_tos(reg);

         merge_insert_xchg(instrs, cur_sim, sux_slot + size_diff);

       } else if (!merge_rename(cur_sim, sux_sim, finished_slot, 0)) {

         assert(size_diff > 0, "must be");

         merge_insert_pop(instrs, cur_sim);

         size_diff--;

       }

       assert(cur_sim->stack_size() == 0 || cur_sim->get_slot(0) != reg, "register must have been changed");

     }

     while (finished_slot >= 0 && cur_sim->get_slot(finished_slot) == sux_sim->get_slot(finished_slot)) {

       finished_slot--;

     }

     if (finished_slot >= 0) {

       int reg = cur_sim->get_slot(finished_slot);

       if (sux_sim->contains(reg) || !merge_rename(cur_sim, sux_sim, finished_slot, finished_slot)) {

         assert(sux_sim->contains(reg) || size_diff > 0, "must be");

         merge_insert_xchg(instrs, cur_sim, finished_slot);

       }

       assert(cur_sim->get_slot(finished_slot) != reg, "register must have been changed");

     }

   }

 #ifndef PRODUCT

   if (TraceFPUStack) {

     tty->print("after merging:  pred: "); cur_sim->print(); tty->cr();

     tty->print("                 sux: "); sux_sim->print(); tty->cr();

     tty->cr();

   }

 #endif

   assert(cur_sim->stack_size() == sux_sim->stack_size(), "stack size must be equal now");

 }

 void FpuStackAllocator::merge_cleanup_fpu_stack(LIR_List* instrs, FpuStackSim* cur_sim, BitMap& live_fpu_regs) {

 #ifndef PRODUCT

   if (TraceFPUStack) {

     tty->cr();

     tty->print("before cleanup: state: "); cur_sim->print(); tty->cr();

     tty->print("                live:  "); live_fpu_regs.print_on(tty); tty->cr();

   }

 #endif

   int slot = 0;

   while (slot < cur_sim->stack_size()) {

     int reg = cur_sim->get_slot(slot);

     if (!live_fpu_regs.at(reg)) {

       if (slot != 0) {

         merge_insert_xchg(instrs, cur_sim, slot);

       }

       merge_insert_pop(instrs, cur_sim);

     } else {

       slot++;

     }

   }

 #ifndef PRODUCT

   if (TraceFPUStack) {

     tty->print("after cleanup:  state: "); cur_sim->print(); tty->cr();

     tty->print("                live:  "); live_fpu_regs.print_on(tty); tty->cr();

     tty->cr();

   }

   // check if fpu stack only contains live registers

   for (unsigned int i = 0; i < live_fpu_regs.size(); i++) {

     if (live_fpu_regs.at(i) != cur_sim->contains(i)) {

       tty->print_cr("mismatch between required and actual stack content");

       break;

     }

   }

 #endif

 }

 bool FpuStackAllocator::merge_fpu_stack_with_successors(BlockBegin* block) {

 #ifndef PRODUCT

   if (TraceFPUStack) {

     tty->print_cr("Propagating FPU stack state for B%d at LIR_Op position %d to successors:",

                   block->block_id(), pos());

     sim()->print();

     tty->cr();

   }

 #endif

   bool changed = false;

   int number_of_sux = block->number_of_sux();

   if (number_of_sux == 1 && block->sux_at(0)->number_of_preds() > 1) {

     // The successor has at least two incoming edges, so a stack merge will be necessary

     // If this block is the first predecessor, cleanup the current stack and propagate it

     // If this block is not the first predecessor, a stack merge will be necessary

     BlockBegin* sux = block->sux_at(0);

     intArray* state = sux->fpu_stack_state();

     LIR_List* instrs = new LIR_List(_compilation);

     if (state != NULL) {

       // Merge with a successors that already has a FPU stack state

       // the block must only have one successor because critical edges must been split

       FpuStackSim* cur_sim = sim();

       FpuStackSim* sux_sim = temp_sim();

       sux_sim->read_state(state);

       merge_fpu_stack(instrs, cur_sim, sux_sim);

     } else {

       // propagate current FPU stack state to successor without state

       // clean up stack first so that there are no dead values on the stack

       if (ComputeExactFPURegisterUsage) {

         FpuStackSim* cur_sim = sim();

         BitMap live_fpu_regs = block->sux_at(0)->fpu_register_usage();

         assert(live_fpu_regs.size() == FrameMap::nof_fpu_regs, "missing register usage");

         merge_cleanup_fpu_stack(instrs, cur_sim, live_fpu_regs);

       }

       intArray* state = sim()->write_state();

       if (TraceFPUStack) {

         tty->print_cr("Setting FPU stack state of B%d (merge path)", sux->block_id());

         sim()->print(); tty->cr();

       }

       sux->set_fpu_stack_state(state);

     }

     if (instrs->instructions_list()->length() > 0) {

       lir()->insert_before(pos(), instrs);

       set_pos(instrs->instructions_list()->length() + pos());

       changed = true;

     }

   } else {

     // Propagate unmodified Stack to successors where a stack merge is not necessary

     intArray* state = sim()->write_state();

     for (int i = 0; i < number_of_sux; i++) {

       BlockBegin* sux = block->sux_at(i);

 #ifdef ASSERT

       for (int j = 0; j < sux->number_of_preds(); j++) {

         assert(block == sux->pred_at(j), "all critical edges must be broken");

       }

       // check if new state is same

       if (sux->fpu_stack_state() != NULL) {

         intArray* sux_state = sux->fpu_stack_state();

         assert(state->length() == sux_state->length(), "overwriting existing stack state");

         for (int j = 0; j < state->length(); j++) {

           assert(state->at(j) == sux_state->at(j), "overwriting existing stack state");

         }

       }

 #endif

 #ifndef PRODUCT

       if (TraceFPUStack) {

         tty->print_cr("Setting FPU stack state of B%d", sux->block_id());

         sim()->print(); tty->cr();

       }

 #endif

       sux->set_fpu_stack_state(state);

     }

   }

 #ifndef PRODUCT

   // assertions that FPU stack state conforms to all successors' states

   intArray* cur_state = sim()->write_state();

   for (int i = 0; i < number_of_sux; i++) {

     BlockBegin* sux = block->sux_at(i);

     intArray* sux_state = sux->fpu_stack_state();

     assert(sux_state != NULL, "no fpu state");

     assert(cur_state->length() == sux_state->length(), "incorrect length");

     for (int i = 0; i < cur_state->length(); i++) {

       assert(cur_state->at(i) == sux_state->at(i), "element not equal");

     }

   }

 #endif

   return changed;

 }