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 /*

  * Copyright (c) 2006, 2011, 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 "ci/ciMethodBlocks.hpp"

 #include "ci/ciStreams.hpp"

 #include "interpreter/bytecode.hpp"

 #include "utilities/copy.hpp"

 // ciMethodBlocks

 ciBlock *ciMethodBlocks::block_containing(int bci) {

   ciBlock *blk = _bci_to_block[bci];

   return blk;

 }

 bool ciMethodBlocks::is_block_start(int bci) {

   assert(bci >=0 && bci < _code_size, "valid bytecode range");

   ciBlock *b = _bci_to_block[bci];

   assert(b != NULL, "must have block for bytecode");

   return b->start_bci() == bci;

 }

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

 // ciMethodBlocks::split_block_at

 //

 // Split the block spanning bci into two separate ranges.  The former

 // block becomes the second half and a new range is created for the

 // first half.  Returns the range beginning at bci.

 ciBlock *ciMethodBlocks::split_block_at(int bci) {

   ciBlock *former_block = block_containing(bci);

   ciBlock *new_block = new(_arena) ciBlock(_method, _num_blocks++, former_block->start_bci());

   _blocks->append(new_block);

   assert(former_block != NULL, "must not be NULL");

   new_block->set_limit_bci(bci);

   former_block->set_start_bci(bci);

   for (int pos=bci-1; pos >= 0; pos--) {

     ciBlock *current_block = block_containing(pos);

     if (current_block == former_block) {

       // Replace it.

       _bci_to_block[pos] = new_block;

     } else if (current_block == NULL) {

       // Non-bytecode start.  Skip.

       continue;

     } else {

       // We are done with our backwards walk

       break;

     }

   }

   // Move an exception handler information if needed.

   if (former_block->is_handler()) {

     int ex_start = former_block->ex_start_bci();

     int ex_end = former_block->ex_limit_bci();

     new_block->set_exception_range(ex_start, ex_end);

     // Clear information in former_block.

     former_block->clear_exception_handler();

   }

   return former_block;

 }

 ciBlock *ciMethodBlocks::make_block_at(int bci) {

   ciBlock *cb = block_containing(bci);

   if (cb == NULL ) {

     // This is our first time visiting this bytecode.  Create

     // a fresh block and assign it this starting point.

     ciBlock *nb = new(_arena) ciBlock(_method, _num_blocks++, bci);

     _blocks->append(nb);

      _bci_to_block[bci] = nb;

     return nb;

   } else if (cb->start_bci() == bci) {

     // The block begins at bci.  Simply return it.

     return cb;

   } else {

     // We have already created a block containing bci but

     // not starting at bci.  This existing block needs to

     // be split into two.

     return split_block_at(bci);

   }

 }

 ciBlock *ciMethodBlocks::make_dummy_block() {

   ciBlock *dum = new(_arena) ciBlock(_method, -1, 0);

   return dum;

 }

 void ciMethodBlocks::do_analysis() {

   ciBytecodeStream s(_method);

   ciBlock *cur_block = block_containing(0);

   int limit_bci = _method->code_size();

   while (s.next() != ciBytecodeStream::EOBC()) {

     int bci = s.cur_bci();

     // Determine if a new block has been made at the current bci.  If

     // this block differs from our current range, switch to the new

     // one and end the old one.

     assert(cur_block != NULL, "must always have a current block");

     ciBlock *new_block = block_containing(bci);

     if (new_block == NULL || new_block == cur_block) {

       // We have not marked this bci as the start of a new block.

       // Keep interpreting the current_range.

       _bci_to_block[bci] = cur_block;

     } else {

       cur_block->set_limit_bci(bci);

       cur_block = new_block;

     }

     switch (s.cur_bc()) {

       case Bytecodes::_ifeq        :

       case Bytecodes::_ifne        :

       case Bytecodes::_iflt        :

       case Bytecodes::_ifge        :

       case Bytecodes::_ifgt        :

       case Bytecodes::_ifle        :

       case Bytecodes::_if_icmpeq   :

       case Bytecodes::_if_icmpne   :

       case Bytecodes::_if_icmplt   :

       case Bytecodes::_if_icmpge   :

       case Bytecodes::_if_icmpgt   :

       case Bytecodes::_if_icmple   :

       case Bytecodes::_if_acmpeq   :

       case Bytecodes::_if_acmpne   :

       case Bytecodes::_ifnull      :

       case Bytecodes::_ifnonnull   :

       {

         cur_block->set_control_bci(bci);

         ciBlock *fall_through = make_block_at(s.next_bci());

         int dest_bci = s.get_dest();

         ciBlock *dest = make_block_at(dest_bci);

         break;

       }

       case Bytecodes::_goto        :

       {

         cur_block->set_control_bci(bci);

         if (s.next_bci() < limit_bci) {

           (void) make_block_at(s.next_bci());

         }

         int dest_bci = s.get_dest();

         ciBlock *dest = make_block_at(dest_bci);

         break;

       }

       case Bytecodes::_jsr         :

       {

         cur_block->set_control_bci(bci);

         ciBlock *ret = make_block_at(s.next_bci());

         int dest_bci = s.get_dest();

         ciBlock *dest = make_block_at(dest_bci);

         break;

       }

       case Bytecodes::_tableswitch :

         {

           cur_block->set_control_bci(bci);

           Bytecode_tableswitch sw(&s);

           int len = sw.length();

           ciBlock *dest;

           int dest_bci;

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

             dest_bci = s.cur_bci() + sw.dest_offset_at(i);

             dest = make_block_at(dest_bci);

           }

           dest_bci = s.cur_bci() + sw.default_offset();

           make_block_at(dest_bci);

           if (s.next_bci() < limit_bci) {

             dest = make_block_at(s.next_bci());

           }

         }

         break;

       case Bytecodes::_lookupswitch:

         {

           cur_block->set_control_bci(bci);

           Bytecode_lookupswitch sw(&s);

           int len = sw.number_of_pairs();

           ciBlock *dest;

           int dest_bci;

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

             dest_bci = s.cur_bci() + sw.pair_at(i).offset();

             dest = make_block_at(dest_bci);

           }

           dest_bci = s.cur_bci() + sw.default_offset();

           dest = make_block_at(dest_bci);

           if (s.next_bci() < limit_bci) {

             dest = make_block_at(s.next_bci());

           }

         }

         break;

       case Bytecodes::_goto_w      :

       {

         cur_block->set_control_bci(bci);

         if (s.next_bci() < limit_bci) {

           (void) make_block_at(s.next_bci());

         }

         int dest_bci = s.get_far_dest();

         ciBlock *dest = make_block_at(dest_bci);

         break;

       }

       case Bytecodes::_jsr_w       :

       {

         cur_block->set_control_bci(bci);

         ciBlock *ret = make_block_at(s.next_bci());

         int dest_bci = s.get_far_dest();

         ciBlock *dest = make_block_at(dest_bci);

         break;

       }

       case Bytecodes::_athrow      :

         cur_block->set_may_throw();

         // fall-through

       case Bytecodes::_ret         :

       case Bytecodes::_ireturn     :

       case Bytecodes::_lreturn     :

       case Bytecodes::_freturn     :

       case Bytecodes::_dreturn     :

       case Bytecodes::_areturn     :

       case Bytecodes::_return      :

         cur_block->set_control_bci(bci);

         if (s.next_bci() < limit_bci) {

           (void) make_block_at(s.next_bci());

         }

         break;

     }

   }

   //  End the last block

   cur_block->set_limit_bci(limit_bci);

 }

 ciMethodBlocks::ciMethodBlocks(Arena *arena, ciMethod *meth): _method(meth),

                           _arena(arena), _num_blocks(0), _code_size(meth->code_size()) {

   int block_estimate = _code_size / 8;

   _blocks =  new(_arena) GrowableArray<ciBlock *>(_arena, block_estimate, 0, NULL);

   int b2bsize = _code_size * sizeof(ciBlock **);

   _bci_to_block = (ciBlock **) arena->Amalloc(b2bsize);

   Copy::zero_to_words((HeapWord*) _bci_to_block, b2bsize / sizeof(HeapWord));

   // create initial block covering the entire method

   ciBlock *b = new(arena) ciBlock(_method, _num_blocks++, 0);

   _blocks->append(b);

   _bci_to_block[0] = b;

   // create blocks for exception handlers

   if (meth->has_exception_handlers()) {

     for(ciExceptionHandlerStream str(meth); !str.is_done(); str.next()) {

       ciExceptionHandler* handler = str.handler();

       ciBlock *eb = make_block_at(handler->handler_bci());

       //

       // Several exception handlers can have the same handler_bci:

       //

       //  try {

       //    if (a.foo(b) < 0) {

       //      return a.error();

       //    }

       //    return CoderResult.UNDERFLOW;

       //  } finally {

       //      a.position(b);

       //  }

       //

       //  The try block above is divided into 2 exception blocks

       //  separated by 'areturn' bci.

       //

       int ex_start = handler->start();

       int ex_end = handler->limit();

       // ensure a block at the start of exception range and start of following code

       (void) make_block_at(ex_start);

       if (ex_end < _code_size)

         (void) make_block_at(ex_end);

       if (eb->is_handler()) {

         // Extend old handler exception range to cover additional range.

         int old_ex_start = eb->ex_start_bci();

         int old_ex_end   = eb->ex_limit_bci();

         if (ex_start > old_ex_start)

           ex_start = old_ex_start;

         if (ex_end < old_ex_end)

           ex_end = old_ex_end;

         eb->clear_exception_handler(); // Reset exception information

       }

       eb->set_exception_range(ex_start, ex_end);

     }

   }

   // scan the bytecodes and identify blocks

   do_analysis();

   // mark blocks that have exception handlers

   if (meth->has_exception_handlers()) {

     for(ciExceptionHandlerStream str(meth); !str.is_done(); str.next()) {

       ciExceptionHandler* handler = str.handler();

       int ex_start = handler->start();

       int ex_end = handler->limit();

       int bci = ex_start;

       while (bci < ex_end) {

         ciBlock *b = block_containing(bci);

         b->set_has_handler();

         bci = b->limit_bci();

       }

     }

   }

 }

 void ciMethodBlocks::clear_processed() {

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

     _blocks->at(i)->clear_processed();

 }

 #ifndef PRODUCT

 void ciMethodBlocks::dump() {

   tty->print("---- blocks for method: ");

   _method->print();

   tty->cr();

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

     tty->print("  B%d: ", i); _blocks->at(i)->dump();

   }

 }

 #endif

 ciBlock::ciBlock(ciMethod *method, int index, int start_bci) :

 #ifndef PRODUCT

                          _method(method),

 #endif

                          _idx(index), _flags(0), _start_bci(start_bci), _limit_bci(-1), _control_bci(fall_through_bci),

                          _ex_start_bci(-1), _ex_limit_bci(-1) {

 }

 void ciBlock::set_exception_range(int start_bci, int limit_bci)  {

    assert(limit_bci >= start_bci, "valid range");

    assert(!is_handler() && _ex_start_bci == -1 && _ex_limit_bci == -1, "must not be handler");

    _ex_start_bci = start_bci;

    _ex_limit_bci = limit_bci;

    set_handler();

 }

 #ifndef PRODUCT

 static const char *flagnames[] = {

   "Processed",

   "Handler",

   "MayThrow",

   "Jsr",

   "Ret",

   "RetTarget",

   "HasHandler",

 };

 void ciBlock::dump() {

   tty->print(" [%d .. %d), {", _start_bci, _limit_bci);

   for (int i = 0; i < 8; i++) {

     if ((_flags & (1 << i)) != 0) {

       tty->print(" %s", flagnames[i]);

     }

   }

   tty->print(" ]");

   if (is_handler())

     tty->print(" handles(%d..%d)", _ex_start_bci, _ex_limit_bci);

   tty->cr();

 }

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

 // ciBlock::print_on

 void ciBlock::print_on(outputStream* st) const {

   st->print_cr("--------------------------------------------------------");

   st->print   ("ciBlock [%d - %d) control : ", start_bci(), limit_bci());

   if (control_bci() == fall_through_bci) {

     st->print_cr("%d:fall through", limit_bci());

   } else {

     st->print_cr("%d:%s", control_bci(),

         Bytecodes::name(method()->java_code_at_bci(control_bci())));

   }

   if (Verbose || WizardMode) {

     method()->print_codes_on(start_bci(), limit_bci(), st);

   }

 }

 #endif