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*/
// A HandlerTableEntry describes an individual entry of a subtable // of ExceptionHandlerTable. An entry consists of a pair(bci, pco), // where bci is the exception handler bci, and pco is the pc offset // relative to the nmethod code start for the compiled exception // handler corresponding to the (interpreted) exception handler // starting at bci. // // The first HandlerTableEntry of each subtable holds the length // and catch_pco for the subtable (the length is the number of // subtable entries w/o header).
class HandlerTableEntry { private: int _bci; int _pco; int _scope_depth;
public:
HandlerTableEntry(int bci, int pco, int scope_depth) {
assert( 0 <= pco, "pco must be positive");
assert( 0 <= scope_depth, "scope_depth must be positive");
_bci = bci;
_pco = pco;
_scope_depth = scope_depth;
}
int len() const { return _bci; } // for entry at subtable begin int bci() const { return _bci; } int pco() const { return _pco; } int scope_depth() const { return _scope_depth; }
};
// An ExceptionHandlerTable is an abstraction over a list of subtables // of exception handlers for CatchNodes. Each subtable has a one-entry // header holding length and catch_pco of the subtable, followed // by 'length' entries for each exception handler that can be reached // from the corresponding CatchNode. The catch_pco is the pc offset of // the CatchNode in the corresponding nmethod. Empty subtables are dis- // carded. // // Structure of the table: // // table = { subtable }. // subtable = header entry { entry }. // header = a pair (number of subtable entries, catch pc offset, [unused]) // entry = a pair (handler bci, handler pc offset, scope depth) // // An ExceptionHandlerTable can be created from scratch, in which case // it is possible to add subtables. It can also be created from an // nmethod (for lookup purposes) in which case the table cannot be // modified.
class nmethod; class ExceptionHandlerTable { private:
HandlerTableEntry* _table; // the table int _length; // the current length of the table int _size; // the number of allocated entries
ReallocMark _nesting; // assertion check for reallocations
public: // add the entry & grow the table if needed void add_entry(HandlerTableEntry entry);
HandlerTableEntry* subtable_for(int catch_pco) const;
// (compile-time) construction within compiler
ExceptionHandlerTable(int initial_size = 8);
// (run-time) construction from nmethod
ExceptionHandlerTable(const CompiledMethod* nm);
// (compile-time) add entries void add_subtable( int catch_pco, // the pc offset for the CatchNode
GrowableArray<intptr_t>* handler_bcis, // the exception handler entry point bcis
GrowableArray<intptr_t>* scope_depths_from_top_scope, // if representing exception handlers in multiple // inlined scopes, indicates which scope relative to // the youngest/innermost one in which we are performing // the lookup; zero (or null GrowableArray) indicates // innermost scope
GrowableArray<intptr_t>* handler_pcos // pc offsets for the compiled handlers
);
// nmethod support int size_in_bytes() const { return align_up(_length * (int)sizeof(HandlerTableEntry), oopSize); } void copy_to(CompiledMethod* nm); void copy_bytes_to(address addr);
// lookup
HandlerTableEntry* entry_for(int catch_pco, int handler_bci, int scope_depth) const;
// ---------------------------------------------------------------------------- // Implicit null exception tables. Maps an exception PC offset to a // continuation PC offset. During construction it's a variable sized // array with a max size and current length. When stored inside an // nmethod a zero length table takes no space. This is detected by // nul_chk_table_size() == 0. Otherwise the table has a length word // followed by pairs of <excp-offset, const-offset>.
// Use 32-bit representation for offsets typedef uint implicit_null_entry;
#if INCLUDE_JVMCI void add_deoptimize(uint exec_off) { // Use the same offset as a marker value for deoptimization
append(exec_off, exec_off);
} #endif
// Returns the offset to continue execution at. If the returned // value equals exec_off then the dispatch is expected to be a // deoptimization instead.
uint continuation_offset( uint exec_off ) const;
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