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 /*

  * 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

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  */

 #include "precompiled.hpp"

 #include "asm/macroAssembler.hpp"

 #include "asm/macroAssembler.inline.hpp"

 #include "asm/codeBuffer.hpp"

 #include "runtime/atomic.hpp"

 #include "runtime/atomic.inline.hpp"

 #include "runtime/icache.hpp"

 #include "runtime/os.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, err_msg("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::a_byte(int x) {

   emit_byte(x);

 }

 void AbstractAssembler::a_long(jint x) {

   emit_long(x);

 }

 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 StackBangPages.  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 = StackShadowPages*page_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) {

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

   if (_patch_index < PatchCacheSize) {

     _patches[_patch_index] = branch_loc;

   } 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;

     if (_patch_index >= PatchCacheSize) {

       branch_loc = _patch_overflow->pop();

     } else {

       branch_loc = _patches[_patch_index];

     }

     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);

   }

 }

 struct DelayedConstant {

   typedef void (*value_fn_t)();

   BasicType type;

   intptr_t value;

   value_fn_t value_fn;

   // This limit of 20 is generous for initial uses.

   // The limit needs to be large enough to store the field offsets

   // into classes which do not have statically fixed layouts.

   // (Initial use is for method handle object offsets.)

   // Look for uses of "delayed_value" in the source code

   // and make sure this number is generous enough to handle all of them.

   enum { DC_LIMIT = 20 };

   static DelayedConstant delayed_constants[DC_LIMIT];

   static DelayedConstant* add(BasicType type, value_fn_t value_fn);

   bool match(BasicType t, value_fn_t cfn) {

     return type == t && value_fn == cfn;

   }

   static void update_all();

 };

 DelayedConstant DelayedConstant::delayed_constants[DC_LIMIT];

 // Default C structure initialization rules have the following effect here:

 // = { { (BasicType)0, (intptr_t)NULL }, ... };

 DelayedConstant* DelayedConstant::add(BasicType type,

                                       DelayedConstant::value_fn_t cfn) {

   for (int i = 0; i < DC_LIMIT; i++) {

     DelayedConstant* dcon = &delayed_constants[i];

     if (dcon->match(type, cfn))

       return dcon;

     if (dcon->value_fn == NULL) {

       // (cmpxchg not because this is multi-threaded but because I'm paranoid)

       if (Atomic::cmpxchg_ptr(CAST_FROM_FN_PTR(void*, cfn), &dcon->value_fn, NULL) == NULL) {

         dcon->type = type;

         return dcon;

       }

     }

   }

   // If this assert is hit (in pre-integration testing!) then re-evaluate

   // the comment on the definition of DC_LIMIT.

   guarantee(false, "too many delayed constants");

   return NULL;

 }

 void DelayedConstant::update_all() {

   for (int i = 0; i < DC_LIMIT; i++) {

     DelayedConstant* dcon = &delayed_constants[i];

     if (dcon->value_fn != NULL && dcon->value == 0) {

       typedef int     (*int_fn_t)();

       typedef address (*address_fn_t)();

       switch (dcon->type) {

       case T_INT:     dcon->value = (intptr_t) ((int_fn_t)    dcon->value_fn)(); break;

       case T_ADDRESS: dcon->value = (intptr_t) ((address_fn_t)dcon->value_fn)(); break;

       }

     }

   }

 }

 RegisterOrConstant AbstractAssembler::delayed_value(int(*value_fn)(), Register tmp, int offset) {

   intptr_t val = (intptr_t) (*value_fn)();

   if (val != 0)  return val + offset;

   return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);

 }

 RegisterOrConstant AbstractAssembler::delayed_value(address(*value_fn)(), Register tmp, int offset) {

   intptr_t val = (intptr_t) (*value_fn)();

   if (val != 0)  return val + offset;

   return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);

 }

 intptr_t* AbstractAssembler::delayed_value_addr(int(*value_fn)()) {

   DelayedConstant* dcon = DelayedConstant::add(T_INT, (DelayedConstant::value_fn_t) value_fn);

   return &dcon->value;

 }

 intptr_t* AbstractAssembler::delayed_value_addr(address(*value_fn)()) {

   DelayedConstant* dcon = DelayedConstant::add(T_ADDRESS, (DelayedConstant::value_fn_t) value_fn);

   return &dcon->value;

 }

 void AbstractAssembler::update_delayed_values() {

   DelayedConstant::update_all();

 }

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

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

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

   }

 }

 bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {

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

   // only when this method returns false.

 #ifdef _LP64

   if (UseCompressedOops && Universe::narrow_oop_base() != NULL) {

     assert (Universe::heap() != NULL, "java heap should be initialized");

     // The first page after heap_base is unmapped and

     // the 'offset' is equal to [heap_base + offset] for

     // narrow oop implicit null checks.

     uintptr_t base = (uintptr_t)Universe::narrow_oop_base();

     if ((uintptr_t)offset >= base) {

       // Normalize offset for the next check.

       offset = (intptr_t)(pointer_delta((void*)offset, (void*)base, 1));

     }

   }

 #endif

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

 }