1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  24 
  25 #ifndef SHARE_CODE_EXCEPTIONHANDLERTABLE_HPP
  26 #define SHARE_CODE_EXCEPTIONHANDLERTABLE_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "oops/method.hpp"
  30 #include "utilities/align.hpp"
  31 
  32 // A HandlerTableEntry describes an individual entry of a subtable
  33 // of ExceptionHandlerTable. An entry consists of a pair(bci, pco),
  34 // where bci is the exception handler bci, and pco is the pc offset
  35 // relative to the nmethod code start for the compiled exception
  36 // handler corresponding to the (interpreted) exception handler
  37 // starting at bci.
  38 //
  39 // The first HandlerTableEntry of each subtable holds the length
  40 // and catch_pco for the subtable (the length is the number of
  41 // subtable entries w/o header).
  42 
  43 class HandlerTableEntry {
  44  private:
  45   int _bci;
  46   int _pco;
  47   int _scope_depth;
  48 
  49  public:
  50   HandlerTableEntry(int bci, int pco, int scope_depth) {
  51     assert( 0 <= pco, "pco must be positive");
  52     assert( 0 <= scope_depth, "scope_depth must be positive");
  53     _bci = bci;
  54     _pco = pco;
  55     _scope_depth = scope_depth;
  56   }
  57 
  58   int len() const { return _bci; } // for entry at subtable begin
  59   int bci() const { return _bci; }
  60   int pco() const { return _pco; }
  61   int scope_depth() const { return _scope_depth; }
  62 };
  63 
  64 
  65 // An ExceptionHandlerTable is an abstraction over a list of subtables
  66 // of exception handlers for CatchNodes. Each subtable has a one-entry
  67 // header holding length and catch_pco of the subtable, followed
  68 // by 'length' entries for each exception handler that can be reached
  69 // from the corresponding CatchNode. The catch_pco is the pc offset of
  70 // the CatchNode in the corresponding nmethod. Empty subtables are dis-
  71 // carded.
  72 //
  73 // Structure of the table:
  74 //
  75 // table    = { subtable }.
  76 // subtable = header entry { entry }.
  77 // header   = a pair (number of subtable entries, catch pc offset, [unused])
  78 // entry    = a pair (handler bci, handler pc offset, scope depth)
  79 //
  80 // An ExceptionHandlerTable can be created from scratch, in which case
  81 // it is possible to add subtables. It can also be created from an
  82 // nmethod (for lookup purposes) in which case the table cannot be
  83 // modified.
  84 
  85 class nmethod;
  86 class ExceptionHandlerTable {
  87  private:
  88   HandlerTableEntry* _table;    // the table
  89   int                _length;   // the current length of the table
  90   int                _size;     // the number of allocated entries
  91   ReallocMark        _nesting;  // assertion check for reallocations
  92 
  93  public:
  94   // add the entry & grow the table if needed
  95   void add_entry(HandlerTableEntry entry);
  96   HandlerTableEntry* subtable_for(int catch_pco) const;
  97 
  98   // (compile-time) construction within compiler
  99   ExceptionHandlerTable(int initial_size = 8);
 100 
 101   // (run-time) construction from nmethod
 102   ExceptionHandlerTable(const CompiledMethod* nm);
 103 
 104   // (compile-time) add entries
 105   void add_subtable(
 106     int                 catch_pco, // the pc offset for the CatchNode
 107     GrowableArray<intptr_t>* handler_bcis, // the exception handler entry point bcis
 108     GrowableArray<intptr_t>* scope_depths_from_top_scope,
 109                                            // if representing exception handlers in multiple
 110                                            // inlined scopes, indicates which scope relative to
 111                                            // the youngest/innermost one in which we are performing
 112                                            // the lookup; zero (or null GrowableArray) indicates
 113                                            // innermost scope
 114     GrowableArray<intptr_t>* handler_pcos  // pc offsets for the compiled handlers
 115   );
 116 
 117   // nmethod support
 118   int  size_in_bytes() const { return align_up(_length * (int)sizeof(HandlerTableEntry), oopSize); }
 119   void copy_to(CompiledMethod* nm);
 120   void copy_bytes_to(address addr);
 121 
 122   // lookup
 123   HandlerTableEntry* entry_for(int catch_pco, int handler_bci, int scope_depth) const;
 124 
 125   // debugging
 126   void print_subtable(HandlerTableEntry* t) const;
 127   void print() const;
 128   void print_subtable_for(int catch_pco) const;
 129 };
 130 
 131 
 132 // ----------------------------------------------------------------------------
 133 // Implicit null exception tables.  Maps an exception PC offset to a
 134 // continuation PC offset.  During construction it's a variable sized
 135 // array with a max size and current length.  When stored inside an
 136 // nmethod a zero length table takes no space.  This is detected by
 137 // nul_chk_table_size() == 0.  Otherwise the table has a length word
 138 // followed by pairs of <excp-offset, const-offset>.
 139 
 140 // Use 32-bit representation for offsets
 141 typedef  uint              implicit_null_entry;
 142 
 143 class ImplicitExceptionTable {
 144   uint _size;
 145   uint _len;
 146   implicit_null_entry *_data;
 147   implicit_null_entry *adr( uint idx ) const { return &_data[2*idx]; }
 148   ReallocMark          _nesting;  // assertion check for reallocations
 149 
 150 public:
 151   ImplicitExceptionTable( ) :  _size(0), _len(0), _data(0) { }
 152   // (run-time) construction from nmethod
 153   ImplicitExceptionTable( const CompiledMethod *nm );
 154 
 155   void set_size( uint size );
 156   void append( uint exec_off, uint cont_off );
 157 
 158 #if INCLUDE_JVMCI
 159   void add_deoptimize(uint exec_off) {
 160     // Use the same offset as a marker value for deoptimization
 161     append(exec_off, exec_off);
 162   }
 163 #endif
 164 
 165   // Returns the offset to continue execution at.  If the returned
 166   // value equals exec_off then the dispatch is expected to be a
 167   // deoptimization instead.
 168   uint continuation_offset( uint exec_off ) const;
 169 
 170   uint len() const { return _len; }
 171 
 172   uint get_exec_offset(uint i) { assert(i < _len, "oob"); return *adr(i); }
 173   uint get_cont_offset(uint i) { assert(i < _len, "oob"); return *(adr(i) + 1); }
 174 
 175   int size_in_bytes() const { return len() == 0 ? 0 : ((2 * len() + 1) * sizeof(implicit_null_entry)); }
 176 
 177   void copy_to(nmethod* nm);
 178   void copy_bytes_to(address addr, int size);
 179   void print(address base) const;
 180   void verify(nmethod *nm) const;
 181 };
 182 
 183 #endif // SHARE_CODE_EXCEPTIONHANDLERTABLE_HPP