jdk

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/*
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 * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#include "code/codeBlob.hpp"
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#include "code/codeCache.hpp"
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#include "code/stubs.hpp"
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#include "memory/allocation.inline.hpp"
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#include "oops/oop.inline.hpp"
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#include "runtime/mutexLocker.hpp"
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#include "utilities/align.hpp"
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#include "utilities/checkedCast.hpp"
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// Implementation of StubQueue
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//
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// Standard wrap-around queue implementation; the queue dimensions
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// are specified by the _queue_begin & _queue_end indices. The queue
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// can be in two states (transparent to the outside):
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//
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// a) contiguous state: all queue entries in one block (or empty)
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//
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// Queue: |...|XXXXXXX|...............|
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//        ^0  ^begin  ^end            ^size = limit
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//            |_______|
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//            one block
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//
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// b) non-contiguous state: queue entries in two blocks
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//
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// Queue: |XXX|.......|XXXXXXX|.......|
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//        ^0  ^end    ^begin  ^limit  ^size
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//        |___|       |_______|
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//         1st block  2nd block
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//
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// In the non-contiguous state, the wrap-around point is
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// indicated via the _buffer_limit index since the last
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// queue entry may not fill up the queue completely in
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// which case we need to know where the 2nd block's end
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// is to do the proper wrap-around. When removing the
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// last entry of the 2nd block, _buffer_limit is reset
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// to _buffer_size.
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//
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// CAUTION: DO NOT MESS WITH THIS CODE IF YOU CANNOT PROVE
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// ITS CORRECTNESS! THIS CODE IS MORE SUBTLE THAN IT LOOKS!
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StubQueue::StubQueue(StubInterface* stub_interface, int buffer_size,
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                     Mutex* lock, const char* name) : _mutex(lock) {
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  intptr_t size = align_up(buffer_size, 2*BytesPerWord);
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  BufferBlob* blob = BufferBlob::create(name, checked_cast<int>(size));
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  if( blob == nullptr) {
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    vm_exit_out_of_memory(size, OOM_MALLOC_ERROR, "CodeCache: no room for %s", name);
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  }
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  _stub_interface  = stub_interface;
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  // The code blob alignment can be smaller than the requested stub alignment.
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  // Make sure we put the stubs at their requested alignment by aligning the buffer base and limits.
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  address aligned_start = align_up(blob->content_begin(), stub_alignment());
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  address aligned_end = align_down(blob->content_end(), stub_alignment());
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  int aligned_size = aligned_end - aligned_start;
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  _buffer_size     = aligned_size;
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  _buffer_limit    = aligned_size;
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  _stub_buffer     = aligned_start;
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  _queue_begin     = 0;
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  _queue_end       = 0;
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  _number_of_stubs = 0;
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}
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StubQueue::~StubQueue() {
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  // Note: Currently StubQueues are never destroyed so nothing needs to be done here.
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  //       If we want to implement the destructor, we need to release the BufferBlob
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  //       allocated in the constructor (i.e., we need to keep it around or look it
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  //       up via CodeCache::find_blob(...).
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  Unimplemented();
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}
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void StubQueue::deallocate_unused_tail() {
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  CodeBlob* blob = CodeCache::find_blob((void*)_stub_buffer);
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  CodeCache::free_unused_tail(blob, used_space());
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  // Update the limits to the new, trimmed CodeBlob size
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  address aligned_start = align_up(blob->content_begin(), stub_alignment());
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  address aligned_end = align_down(blob->content_end(), stub_alignment());
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  int aligned_size = aligned_end - aligned_start;
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  _buffer_size = aligned_size;
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  _buffer_limit = aligned_size;
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}
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Stub* StubQueue::stub_containing(address pc) const {
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  if (contains(pc)) {
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    for (Stub* s = first(); s != nullptr; s = next(s)) {
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      if (stub_contains(s, pc)) return s;
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    }
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  }
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  return nullptr;
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}
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Stub* StubQueue::request_committed(int code_size) {
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  Stub* s = request(code_size);
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  if (s != nullptr) commit(code_size);
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  return s;
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}
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int StubQueue::compute_stub_size(Stub* stub, int code_size) {
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  address stub_begin = (address) stub;
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  address code_begin = stub_code_begin(stub);
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  address code_end = align_up(code_begin + code_size, stub_alignment());
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  return (int)(code_end - stub_begin);
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}
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Stub* StubQueue::request(int requested_code_size) {
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  assert(requested_code_size > 0, "requested_code_size must be > 0");
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  if (_mutex != nullptr) _mutex->lock_without_safepoint_check();
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  Stub* s = current_stub();
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  int requested_size = compute_stub_size(s, requested_code_size);
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  if (requested_size <= available_space()) {
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    if (is_contiguous()) {
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      // Queue: |...|XXXXXXX|.............|
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      //        ^0  ^begin  ^end          ^size = limit
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      assert(_buffer_limit == _buffer_size, "buffer must be fully usable");
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      if (_queue_end + requested_size <= _buffer_size) {
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        // code fits in at the end => nothing to do
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        stub_initialize(s, requested_size);
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        return s;
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      } else {
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        // stub doesn't fit in at the queue end
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        // => reduce buffer limit & wrap around
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        assert(!is_empty(), "just checkin'");
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        _buffer_limit = _queue_end;
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        _queue_end = 0;
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      }
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    }
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  }
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  if (requested_size <= available_space()) {
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    assert(!is_contiguous(), "just checkin'");
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    assert(_buffer_limit <= _buffer_size, "queue invariant broken");
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    // Queue: |XXX|.......|XXXXXXX|.......|
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    //        ^0  ^end    ^begin  ^limit  ^size
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    s = current_stub();
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    stub_initialize(s, requested_size);
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    return s;
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  }
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  // Not enough space left
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  if (_mutex != nullptr) _mutex->unlock();
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  return nullptr;
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}
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void StubQueue::commit(int committed_code_size) {
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  assert(committed_code_size > 0, "committed_code_size must be > 0");
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  Stub* s = current_stub();
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  int committed_size = compute_stub_size(s, committed_code_size);
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  assert(committed_size <= stub_size(s), "committed size must not exceed requested size");
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  stub_initialize(s, committed_size);
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  _queue_end += committed_size;
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  _number_of_stubs++;
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  if (_mutex != nullptr) _mutex->unlock();
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  debug_only(stub_verify(s);)
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}
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void StubQueue::remove_first() {
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  if (number_of_stubs() == 0) return;
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  Stub* s = first();
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  debug_only(stub_verify(s);)
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  stub_finalize(s);
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  _queue_begin += stub_size(s);
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  assert(_queue_begin <= _buffer_limit, "sanity check");
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  if (_queue_begin == _queue_end) {
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    // buffer empty
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    // => reset queue indices
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    _queue_begin  = 0;
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    _queue_end    = 0;
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    _buffer_limit = _buffer_size;
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  } else if (_queue_begin == _buffer_limit) {
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    // buffer limit reached
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    // => reset buffer limit & wrap around
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    _buffer_limit = _buffer_size;
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    _queue_begin = 0;
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  }
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  _number_of_stubs--;
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}
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void StubQueue::remove_first(int n) {
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  int i = MIN2(n, number_of_stubs());
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  while (i-- > 0) remove_first();
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}
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void StubQueue::remove_all(){
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  debug_only(verify();)
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  remove_first(number_of_stubs());
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  assert(number_of_stubs() == 0, "sanity check");
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}
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void StubQueue::verify() {
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  // verify only if initialized
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  if (_stub_buffer == nullptr) return;
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  MutexLocker lock(_mutex, Mutex::_no_safepoint_check_flag);
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  // verify index boundaries
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  guarantee(0 <= _buffer_size, "buffer size must be positive");
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  guarantee(0 <= _buffer_limit && _buffer_limit <= _buffer_size , "_buffer_limit out of bounds");
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  guarantee(0 <= _queue_begin  && _queue_begin  <  _buffer_limit, "_queue_begin out of bounds");
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  guarantee(0 <= _queue_end    && _queue_end    <= _buffer_limit, "_queue_end   out of bounds");
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  // verify alignment
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  guarantee(_queue_begin  % stub_alignment() == 0, "_queue_begin  not aligned");
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  guarantee(_queue_end    % stub_alignment() == 0, "_queue_end    not aligned");
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  // verify buffer limit/size relationship
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  if (is_contiguous()) {
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    guarantee(_buffer_limit == _buffer_size, "_buffer_limit must equal _buffer_size");
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  }
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  // verify contents
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  int n = 0;
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  for (Stub* s = first(); s != nullptr; s = next(s)) {
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    stub_verify(s);
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    n++;
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  }
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  guarantee(n == number_of_stubs(), "number of stubs inconsistent");
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  guarantee(_queue_begin != _queue_end || n == 0, "buffer indices must be the same");
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}
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void StubQueue::print() {
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  ConditionalMutexLocker lock(_mutex, _mutex != nullptr, Mutex::_no_safepoint_check_flag);
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  for (Stub* s = first(); s != nullptr; s = next(s)) {
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    stub_print(s);
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  }
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}
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