1 /*
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  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  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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  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 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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 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   friend class SCCache;
 88   friend class SCCReader;
 89 
 90  private:
 91   HandlerTableEntry* _table;    // the table
 92   int                _length;   // the current length of the table
 93   int                _size;     // the number of allocated entries
 94   ReallocMark        _nesting;  // assertion check for reallocations
 95 
 96   int length() const { return _length; }
 97   void set_length(int length) { _length = length; }
 98  public:
 99   // add the entry & grow the table if needed
100   void add_entry(HandlerTableEntry entry);
101   HandlerTableEntry* subtable_for(int catch_pco) const;
102 
103   // (compile-time) construction within compiler
104   ExceptionHandlerTable(int initial_size = 8);
105 
106   // (run-time) construction from nmethod
107   ExceptionHandlerTable(const CompiledMethod* nm);
108 
109   // (compile-time) add entries
110   void add_subtable(
111     int                 catch_pco, // the pc offset for the CatchNode
112     GrowableArray<intptr_t>* handler_bcis, // the exception handler entry point bcis
113     GrowableArray<intptr_t>* scope_depths_from_top_scope,
114                                            // if representing exception handlers in multiple
115                                            // inlined scopes, indicates which scope relative to
116                                            // the youngest/innermost one in which we are performing
117                                            // the lookup; zero (or null GrowableArray) indicates
118                                            // innermost scope
119     GrowableArray<intptr_t>* handler_pcos  // pc offsets for the compiled handlers
120   );
121 
122   HandlerTableEntry* table() const { return _table; }
123   // nmethod support
124   int  size_in_bytes() const { return align_up(_length * (int)sizeof(HandlerTableEntry), oopSize); }
125   void copy_to(CompiledMethod* nm);
126   void copy_bytes_to(address addr);
127 
128   // lookup
129   HandlerTableEntry* entry_for(int catch_pco, int handler_bci, int scope_depth) const;
130 
131   // debugging
132   void print_subtable(HandlerTableEntry* t, address base = nullptr) const;
133   void print(address base = nullptr) const;
134   void print_subtable_for(int catch_pco) const;
135 };
136 
137 
138 // ----------------------------------------------------------------------------
139 // Implicit null exception tables.  Maps an exception PC offset to a
140 // continuation PC offset.  During construction it's a variable sized
141 // array with a max size and current length.  When stored inside an
142 // nmethod a zero length table takes no space.  This is detected by
143 // nul_chk_table_size() == 0.  Otherwise the table has a length word
144 // followed by pairs of <excp-offset, const-offset>.
145 
146 // Use 32-bit representation for offsets
147 typedef  uint              implicit_null_entry;
148 
149 class ImplicitExceptionTable {
150   friend class SCCache;
151   friend class SCCReader;
152  private:
153   uint _size;
154   uint _len;
155   implicit_null_entry *_data;
156   implicit_null_entry *adr( uint idx ) const { return &_data[2*idx]; }
157   ReallocMark          _nesting;  // assertion check for reallocations
158 
159   void set_len(int length) { _len = length; }
160 
161 public:
162   ImplicitExceptionTable( ) :  _size(0), _len(0), _data(0) { }
163   // (run-time) construction from nmethod
164   ImplicitExceptionTable( const CompiledMethod *nm );
165 
166   void set_size( uint size );
167   void append( uint exec_off, uint cont_off );
168 
169 #if INCLUDE_JVMCI
170   void add_deoptimize(uint exec_off) {
171     // Use the same offset as a marker value for deoptimization
172     append(exec_off, exec_off);
173   }
174 #endif
175 
176   // Returns the offset to continue execution at.  If the returned
177   // value equals exec_off then the dispatch is expected to be a
178   // deoptimization instead.
179   uint continuation_offset( uint exec_off ) const;
180 
181   uint len() const { return _len; }
182   
183   implicit_null_entry* data() const { return _data; }
184 
185   uint get_exec_offset(uint i) { assert(i < _len, "oob"); return *adr(i); }
186   uint get_cont_offset(uint i) { assert(i < _len, "oob"); return *(adr(i) + 1); }
187 
188   int size_in_bytes() const { return len() == 0 ? 0 : ((2 * len() + 1) * (int)sizeof(implicit_null_entry)); }
189 
190   void copy_to(nmethod* nm);
191   void copy_bytes_to(address addr, int size);
192   void print(address base) const;
193   void verify(nmethod *nm) const;
194 };
195 
196 #endif // SHARE_CODE_EXCEPTIONHANDLERTABLE_HPP