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Java example source code file (stackValue.cpp)

This example Java source code file (stackValue.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

basiclock, const64, constantlongvalue, handle, holds, location\:\:float_in_dbl, location\:\:int_in_long, registermap, shouldnotreachhere, sparc, stackvalue, wrap

The stackValue.cpp Java example source code

/*
 * Copyright (c) 1997, 2012, 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 "code/debugInfo.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/frame.inline.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/stackValue.hpp"

StackValue* StackValue::create_stack_value(const frame* fr, const RegisterMap* reg_map, ScopeValue* sv) {
  if (sv->is_location()) {
    // Stack or register value
    Location loc = ((LocationValue *)sv)->location();

#ifdef SPARC
    // %%%%% Callee-save floats will NOT be working on a Sparc until we
    // handle the case of a 2 floats in a single double register.
    assert( !(loc.is_register() && loc.type() == Location::float_in_dbl), "Sparc does not handle callee-save floats yet" );
#endif // SPARC

    // First find address of value

    address value_addr = loc.is_register()
      // Value was in a callee-save register
      ? reg_map->location(VMRegImpl::as_VMReg(loc.register_number()))
      // Else value was directly saved on the stack. The frame's original stack pointer,
      // before any extension by its callee (due to Compiler1 linkage on SPARC), must be used.
      : ((address)fr->unextended_sp()) + loc.stack_offset();

    // Then package it right depending on type
    // Note: the transfer of the data is thru a union that contains
    // an intptr_t. This is because an interpreter stack slot is
    // really an intptr_t. The use of a union containing an intptr_t
    // ensures that on a 64 bit platform we have proper alignment
    // and that we store the value where the interpreter will expect
    // to find it (i.e. proper endian). Similarly on a 32bit platform
    // using the intptr_t ensures that when a value is larger than
    // a stack slot (jlong/jdouble) that we capture the proper part
    // of the value for the stack slot in question.
    //
    switch( loc.type() ) {
    case Location::float_in_dbl: { // Holds a float in a double register?
      // The callee has no clue whether the register holds a float,
      // double or is unused.  He always saves a double.  Here we know
      // a double was saved, but we only want a float back.  Narrow the
      // saved double to the float that the JVM wants.
      assert( loc.is_register(), "floats always saved to stack in 1 word" );
      union { intptr_t p; jfloat jf; } value;
      value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
      value.jf = (jfloat) *(jdouble*) value_addr;
      return new StackValue(value.p); // 64-bit high half is stack junk
    }
    case Location::int_in_long: { // Holds an int in a long register?
      // The callee has no clue whether the register holds an int,
      // long or is unused.  He always saves a long.  Here we know
      // a long was saved, but we only want an int back.  Narrow the
      // saved long to the int that the JVM wants.
      assert( loc.is_register(), "ints always saved to stack in 1 word" );
      union { intptr_t p; jint ji;} value;
      value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
      value.ji = (jint) *(jlong*) value_addr;
      return new StackValue(value.p); // 64-bit high half is stack junk
    }
#ifdef _LP64
    case Location::dbl:
      // Double value in an aligned adjacent pair
      return new StackValue(*(intptr_t*)value_addr);
    case Location::lng:
      // Long   value in an aligned adjacent pair
      return new StackValue(*(intptr_t*)value_addr);
    case Location::narrowoop: {
      union { intptr_t p; narrowOop noop;} value;
      value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
      if (loc.is_register()) {
        // The callee has no clue whether the register holds an int,
        // long or is unused.  He always saves a long.  Here we know
        // a long was saved, but we only want an int back.  Narrow the
        // saved long to the int that the JVM wants.
        value.noop =  (narrowOop) *(julong*) value_addr;
      } else {
        value.noop = *(narrowOop*) value_addr;
      }
      // Decode narrowoop and wrap a handle around the oop
      Handle h(oopDesc::decode_heap_oop(value.noop));
      return new StackValue(h);
    }
#endif
    case Location::oop: {
      oop val = *(oop *)value_addr;
#ifdef _LP64
      if (Universe::is_narrow_oop_base(val)) {
         // Compiled code may produce decoded oop = narrow_oop_base
         // when a narrow oop implicit null check is used.
         // The narrow_oop_base could be NULL or be the address
         // of the page below heap. Use NULL value for both cases.
         val = (oop)NULL;
      }
#endif
      Handle h(val); // Wrap a handle around the oop
      return new StackValue(h);
    }
    case Location::addr: {
      ShouldNotReachHere(); // both C1 and C2 now inline jsrs
    }
    case Location::normal: {
      // Just copy all other bits straight through
      union { intptr_t p; jint ji;} value;
      value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
      value.ji = *(jint*)value_addr;
      return new StackValue(value.p);
    }
    case Location::invalid:
      return new StackValue();
    default:
      ShouldNotReachHere();
    }

  } else if (sv->is_constant_int()) {
    // Constant int: treat same as register int.
    union { intptr_t p; jint ji;} value;
    value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
    value.ji = (jint)((ConstantIntValue*)sv)->value();
    return new StackValue(value.p);
  } else if (sv->is_constant_oop()) {
    // constant oop
    return new StackValue(sv->as_ConstantOopReadValue()->value());
#ifdef _LP64
  } else if (sv->is_constant_double()) {
    // Constant double in a single stack slot
    union { intptr_t p; double d; } value;
    value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
    value.d = ((ConstantDoubleValue *)sv)->value();
    return new StackValue(value.p);
  } else if (sv->is_constant_long()) {
    // Constant long in a single stack slot
    union { intptr_t p; jlong jl; } value;
    value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
    value.jl = ((ConstantLongValue *)sv)->value();
    return new StackValue(value.p);
#endif
  } else if (sv->is_object()) { // Scalar replaced object in compiled frame
    Handle ov = ((ObjectValue *)sv)->value();
    return new StackValue(ov, (ov.is_null()) ? 1 : 0);
  }

  // Unknown ScopeValue type
  ShouldNotReachHere();
  return new StackValue((intptr_t) 0);   // dummy
}


BasicLock* StackValue::resolve_monitor_lock(const frame* fr, Location location) {
  assert(location.is_stack(), "for now we only look at the stack");
  int word_offset = location.stack_offset() / wordSize;
  // (stack picture)
  // high: [     ]  word_offset + 1
  // low   [     ]  word_offset
  //
  // sp->  [     ]  0
  // the word_offset is the distance from the stack pointer to the lowest address
  // The frame's original stack pointer, before any extension by its callee
  // (due to Compiler1 linkage on SPARC), must be used.
  return (BasicLock*) (fr->unextended_sp() + word_offset);
}


#ifndef PRODUCT

void StackValue::print_on(outputStream* st) const {
  switch(_type) {
    case T_INT:
      st->print("%d (int) %f (float) %x (hex)",  *(int *)&_i, *(float *)&_i,  *(int *)&_i);
      break;

    case T_OBJECT:
     _o()->print_value_on(st);
      st->print(" <" INTPTR_FORMAT ">", (address)_o());
     break;

    case T_CONFLICT:
     st->print("conflict");
     break;

    default:
     ShouldNotReachHere();
  }
}

#endif

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