/*

 * Copyright (c) 1997, 2017, 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 "asm/codeBuffer.hpp"

#include "asm/macroAssembler.hpp"

#include "asm/macroAssembler.inline.hpp"

#include "gc/shared/collectedHeap.hpp"

#include "memory/universe.hpp"

#include "oops/compressedOops.hpp"

#include "runtime/atomic.hpp"

#include "runtime/icache.hpp"

#include "runtime/os.hpp"

#include "runtime/thread.hpp"

// Implementation of AbstractAssembler

//

// The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,

// the assembler keeps a copy of the code buffers boundaries & modifies them when

// emitting bytes rather than using the code buffers accessor functions all the time.

// The code buffer is updated via set_code_end(...) after emitting a whole instruction.

AbstractAssembler::AbstractAssembler(CodeBuffer* code) {

  if (code == NULL)  return;

  CodeSection* cs = code->insts();

  cs->clear_mark();   // new assembler kills old mark

  if (cs->start() == NULL)  {

    vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "CodeCache: no room for %s", code->name());

  }

  _code_section = cs;

  _oop_recorder= code->oop_recorder();

  DEBUG_ONLY( _short_branch_delta = 0; )

}

void AbstractAssembler::set_code_section(CodeSection* cs) {

  assert(cs->outer() == code_section()->outer(), "sanity");

  assert(cs->is_allocated(), "need to pre-allocate this section");

  cs->clear_mark();  // new assembly into this section kills old mark

  _code_section = cs;

}

// Inform CodeBuffer that incoming code and relocation will be for stubs

address AbstractAssembler::start_a_stub(int required_space) {

  CodeBuffer*  cb = code();

  CodeSection* cs = cb->stubs();

  assert(_code_section == cb->insts(), "not in insts?");

  if (cs->maybe_expand_to_ensure_remaining(required_space)

      && cb->blob() == NULL) {

    return NULL;

  }

  set_code_section(cs);

  return pc();

}

// Inform CodeBuffer that incoming code and relocation will be code

// Should not be called if start_a_stub() returned NULL

void AbstractAssembler::end_a_stub() {

  assert(_code_section == code()->stubs(), "not in stubs?");

  set_code_section(code()->insts());

}

// Inform CodeBuffer that incoming code and relocation will be for stubs

address AbstractAssembler::start_a_const(int required_space, int required_align) {

  CodeBuffer*  cb = code();

  CodeSection* cs = cb->consts();

  assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?");

  address end = cs->end();

  int pad = -(intptr_t)end & (required_align-1);

  if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {

    if (cb->blob() == NULL)  return NULL;

    end = cs->end();  // refresh pointer

  }

  if (pad > 0) {

    while (--pad >= 0) { *end++ = 0; }

    cs->set_end(end);

  }

  set_code_section(cs);

  return end;

}

// Inform CodeBuffer that incoming code and relocation will be code

// in section cs (insts or stubs).

void AbstractAssembler::end_a_const(CodeSection* cs) {

  assert(_code_section == code()->consts(), "not in consts?");

  set_code_section(cs);

}

void AbstractAssembler::flush() {

  ICache::invalidate_range(addr_at(0), offset());

}

void AbstractAssembler::bind(Label& L) {

  if (L.is_bound()) {

    // Assembler can bind a label more than once to the same place.

    guarantee(L.loc() == locator(), "attempt to redefine label");

    return;

  }

  L.bind_loc(locator());

  L.patch_instructions((MacroAssembler*)this);

}

void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) {

  if (UseStackBanging) {

    // Each code entry causes one stack bang n pages down the stack where n

    // is configurable by StackShadowPages.  The setting depends on the maximum

    // depth of VM call stack or native before going back into java code,

    // since only java code can raise a stack overflow exception using the

    // stack banging mechanism.  The VM and native code does not detect stack

    // overflow.

    // The code in JavaCalls::call() checks that there is at least n pages

    // available, so all entry code needs to do is bang once for the end of

    // this shadow zone.

    // The entry code may need to bang additional pages if the framesize

    // is greater than a page.

    const int page_size = os::vm_page_size();

    int bang_end = (int)JavaThread::stack_shadow_zone_size();

    // This is how far the previous frame's stack banging extended.

    const int bang_end_safe = bang_end;

    if (frame_size_in_bytes > page_size) {

      bang_end += frame_size_in_bytes;

    }

    int bang_offset = bang_end_safe;

    while (bang_offset <= bang_end) {

      // Need at least one stack bang at end of shadow zone.

      bang_stack_with_offset(bang_offset);

      bang_offset += page_size;

    }

  } // end (UseStackBanging)

}

void Label::add_patch_at(CodeBuffer* cb, int branch_loc, const char* file, int line) {

  assert(_loc == -1, "Label is unbound");

  // Don't add patch locations during scratch emit.

  if (cb->insts()->scratch_emit()) { return; }

  if (_patch_index < PatchCacheSize) {

    _patches[_patch_index] = branch_loc;

#ifdef ASSERT

    _lines[_patch_index] = line;

    _files[_patch_index] = file;

#endif

  } else {

    if (_patch_overflow == NULL) {

      _patch_overflow = cb->create_patch_overflow();

    }

    _patch_overflow->push(branch_loc);

  }

  ++_patch_index;

}

void Label::patch_instructions(MacroAssembler* masm) {

  assert(is_bound(), "Label is bound");

  CodeBuffer* cb = masm->code();

  int target_sect = CodeBuffer::locator_sect(loc());

  address target = cb->locator_address(loc());

  while (_patch_index > 0) {

    --_patch_index;

    int branch_loc;

    int line = 0;

    const char* file = NULL;

    if (_patch_index >= PatchCacheSize) {

      branch_loc = _patch_overflow->pop();

    } else {

      branch_loc = _patches[_patch_index];

#ifdef ASSERT

      line = _lines[_patch_index];

      file = _files[_patch_index];

#endif

    }

    int branch_sect = CodeBuffer::locator_sect(branch_loc);

    address branch = cb->locator_address(branch_loc);

    if (branch_sect == CodeBuffer::SECT_CONSTS) {

      // The thing to patch is a constant word.

      *(address*)branch = target;

      continue;

    }

#ifdef ASSERT

    // Cross-section branches only work if the

    // intermediate section boundaries are frozen.

    if (target_sect != branch_sect) {

      for (int n = MIN2(target_sect, branch_sect),

               nlimit = (target_sect + branch_sect) - n;

           n < nlimit; n++) {

        CodeSection* cs = cb->code_section(n);

        assert(cs->is_frozen(), "cross-section branch needs stable offsets");

      }

    }

#endif //ASSERT

    // Push the target offset into the branch instruction.

    masm->pd_patch_instruction(branch, target, file, line);

  }

}

void AbstractAssembler::block_comment(const char* comment) {

  if (sect() == CodeBuffer::SECT_INSTS) {

    code_section()->outer()->block_comment(offset(), comment);

  }

}

const char* AbstractAssembler::code_string(const char* str) {

  if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) {

    return code_section()->outer()->code_string(str);

  }

  return NULL;

}

bool MacroAssembler::uses_implicit_null_check(void* address) {

  // Exception handler checks the nmethod's implicit null checks table

  // only when this method returns false.

  uintptr_t addr = reinterpret_cast<uintptr_t>(address);

  uintptr_t page_size = (uintptr_t)os::vm_page_size();

#ifdef _LP64

  if (UseCompressedOops && CompressedOops::base() != NULL) {

    // A SEGV can legitimately happen in C2 code at address

    // (heap_base + offset) if  Matcher::narrow_oop_use_complex_address

    // is configured to allow narrow oops field loads to be implicitly

    // null checked

    uintptr_t start = (uintptr_t)CompressedOops::base();

    uintptr_t end = start + page_size;

    if (addr >= start && addr < end) {

      return true;

    }

  }

#endif

  return addr < page_size;

}

bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {

  // The offset -1 is used (hardcoded) in a number of places in C1 and MacroAssembler

  // to indicate an unknown offset. For example, TemplateTable::pop_and_check_object(Register r)

  // calls MacroAssembler::null_check(Register reg, int offset = -1) which gets here

  // with -1. Another example is GraphBuilder::access_field(...) which uses -1 as placeholder

  // for offsets to be patched in later. The -1 there means the offset is not yet known

  // and may lie outside of the zero-trapping page, and thus we need to ensure we're forcing

  // an explicit null check for -1.

  // Check if offset is outside of [0, os::vm_page_size()]

  return offset < 0 || offset >= os::vm_page_size();

}