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hotspot/src/share/vm/code/location.hpp

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+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// A Location describes a concrete machine variable location
+// (such as integer or floating point register or a stack-held
+// variable). Used when generating debug-information for nmethods.
+//
+// Encoding:
+//
+// bits:
+//  Where:  [15]
+//  Type:   [14..12]
+//  Offset: [11..0]
+
+class Location VALUE_OBJ_CLASS_SPEC {
+  friend class VMStructs;
+ public:
+  enum Where {
+    on_stack,
+    in_register
+  };
+
+  enum Type {
+    normal,                     // Ints, floats, double halves
+    oop,                        // Oop (please GC me!)
+    int_in_long,                // Integer held in long register
+    lng,                        // Long held in one register
+    float_in_dbl,               // Float held in double register
+    dbl,                        // Double held in one register
+    addr,                       // JSR return address
+    invalid                     // Invalid location
+  };
+
+
+ private:
+  enum {
+    OFFSET_MASK  = (jchar) 0x0FFF,
+    OFFSET_SHIFT = 0,
+    TYPE_MASK    = (jchar) 0x7000,
+    TYPE_SHIFT   = 12,
+    WHERE_MASK   = (jchar) 0x8000,
+    WHERE_SHIFT  = 15
+  };
+
+  uint16_t _value;
+
+  // Create a bit-packed Location
+  Location(Where where_, Type type_, unsigned offset_) {
+    set(where_, type_, offset_);
+    assert( where () == where_ , "" );
+    assert( type  () == type_  , "" );
+    assert( offset() == offset_, "" );
+  }
+
+  inline void set(Where where_, Type type_, unsigned offset_) {
+    _value = (uint16_t) ((where_  << WHERE_SHIFT) |
+                         (type_   << TYPE_SHIFT)  |
+                         ((offset_ << OFFSET_SHIFT) & OFFSET_MASK));
+  }
+
+ public:
+
+  // Stack location Factory.  Offset is 4-byte aligned; remove low bits
+  static Location new_stk_loc( Type t, int offset ) { return Location(on_stack,t,offset>>LogBytesPerInt); }
+  // Register location Factory
+  static Location new_reg_loc( Type t, VMReg reg ) { return Location(in_register, t, reg->value()); }
+  // Default constructor
+  Location() { set(on_stack,invalid,(unsigned) -1); }
+
+  // Bit field accessors
+  Where where()  const { return (Where)       ((_value & WHERE_MASK)  >> WHERE_SHIFT);}
+  Type  type()   const { return (Type)        ((_value & TYPE_MASK)   >> TYPE_SHIFT); }
+  unsigned offset() const { return (unsigned) ((_value & OFFSET_MASK) >> OFFSET_SHIFT); }
+
+  // Accessors
+  bool is_register() const    { return where() == in_register; }
+  bool is_stack() const       { return where() == on_stack;    }
+
+  int stack_offset() const    { assert(where() == on_stack,    "wrong Where"); return offset()<<LogBytesPerInt; }
+  int register_number() const { assert(where() == in_register, "wrong Where"); return offset()   ; }
+
+  VMReg reg() const { assert(where() == in_register, "wrong Where"); return VMRegImpl::as_VMReg(offset())   ; }
+
+  // Printing
+  void print_on(outputStream* st) const;
+
+  // Serialization of debugging information
+  Location(DebugInfoReadStream* stream);
+  void write_on(DebugInfoWriteStream* stream);
+
+  // check
+  static bool legal_offset_in_bytes(int offset_in_bytes);
+};