Java example source code file (relocator.cpp)
The relocator.cpp Java example source code/*
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* This code is free software; you can redistribute it and/or modify it
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*
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* 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.
*
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#include "precompiled.hpp"
#include "classfile/stackMapTableFormat.hpp"
#include "interpreter/bytecodes.hpp"
#include "memory/metadataFactory.hpp"
#include "memory/oopFactory.hpp"
#include "memory/universe.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/relocator.hpp"
#define MAX_METHOD_LENGTH 65535
#define MAX_SHORT ((1 << 15) - 1)
#define MIN_SHORT (- (1 << 15))
// Encapsulates a code change request. There are 3 types.
// General instruction, jump instruction, and table/lookup switches
//
class ChangeItem : public ResourceObj {
int _bci;
public:
ChangeItem(int bci) { _bci = bci; }
virtual bool handle_code_change(Relocator *r) = 0;
// type info
virtual bool is_widen() { return false; }
virtual bool is_jump_widen() { return false; }
virtual bool is_switch_pad() { return false; }
// accessors
int bci() { return _bci; }
void relocate(int break_bci, int delta) { if (_bci > break_bci) { _bci += delta; } }
virtual bool adjust(int bci, int delta) { return false; }
// debug
virtual void print() = 0;
};
class ChangeWiden : public ChangeItem {
int _new_ilen; // New length of instruction at bci
u_char* _inst_buffer; // New bytecodes
public:
ChangeWiden(int bci, int new_ilen, u_char* inst_buffer) : ChangeItem(bci) {
_new_ilen = new_ilen;
_inst_buffer = inst_buffer;
}
// Callback to do instruction
bool handle_code_change(Relocator *r) { return r->handle_widen(bci(), _new_ilen, _inst_buffer); };
bool is_widen() { return true; }
void print() { tty->print_cr("ChangeWiden. bci: %d New_ilen: %d", bci(), _new_ilen); }
};
class ChangeJumpWiden : public ChangeItem {
int _delta; // New length of instruction at bci
public:
ChangeJumpWiden(int bci, int delta) : ChangeItem(bci) { _delta = delta; }
// Callback to do instruction
bool handle_code_change(Relocator *r) { return r->handle_jump_widen(bci(), _delta); };
bool is_jump_widen() { return true; }
// If the bci matches, adjust the delta in the change jump request.
bool adjust(int jump_bci, int delta) {
if (bci() == jump_bci) {
if (_delta > 0)
_delta += delta;
else
_delta -= delta;
return true;
}
return false;
}
void print() { tty->print_cr("ChangeJumpWiden. bci: %d Delta: %d", bci(), _delta); }
};
class ChangeSwitchPad : public ChangeItem {
int _padding;
bool _is_lookup_switch;
public:
ChangeSwitchPad(int bci, int padding, bool is_lookup_switch) : ChangeItem(bci) {
_padding = padding;
_is_lookup_switch = is_lookup_switch;
}
// Callback to do instruction
bool handle_code_change(Relocator *r) { return r->handle_switch_pad(bci(), _padding, _is_lookup_switch); };
bool is_switch_pad() { return true; }
int padding() { return _padding; }
bool is_lookup_switch() { return _is_lookup_switch; }
void print() { tty->print_cr("ChangeSwitchPad. bci: %d Padding: %d IsLookupSwitch: %d", bci(), _padding, _is_lookup_switch); }
};
//-----------------------------------------------------------------------------------------------------------
// Relocator code
Relocator::Relocator(methodHandle m, RelocatorListener* listener) {
set_method(m);
set_code_length(method()->code_size());
set_code_array(NULL);
// Allocate code array and copy bytecodes
if (!expand_code_array(0)) {
// Should have at least MAX_METHOD_LENGTH available or the verifier
// would have failed.
ShouldNotReachHere();
}
set_compressed_line_number_table(NULL);
set_compressed_line_number_table_size(0);
_listener = listener;
}
// size is the new size of the instruction at bci. Hence, if size is less than the current
// instruction sice, we will shrink the code.
methodHandle Relocator::insert_space_at(int bci, int size, u_char inst_buffer[], TRAPS) {
_changes = new GrowableArray<ChangeItem*> (10);
_changes->push(new ChangeWiden(bci, size, inst_buffer));
if (TraceRelocator) {
tty->print_cr("Space at: %d Size: %d", bci, size);
_method->print();
_method->print_codes();
tty->print_cr("-------------------------------------------------");
}
if (!handle_code_changes()) return methodHandle();
// Construct the new method
methodHandle new_method = Method::clone_with_new_data(method(),
code_array(), code_length(),
compressed_line_number_table(),
compressed_line_number_table_size(),
CHECK_(methodHandle()));
// Deallocate the old Method* from metadata
ClassLoaderData* loader_data = method()->method_holder()->class_loader_data();
loader_data->add_to_deallocate_list(method()());
set_method(new_method);
if (TraceRelocator) {
tty->print_cr("-------------------------------------------------");
tty->print_cr("new method");
_method->print_codes();
}
return new_method;
}
bool Relocator::handle_code_changes() {
assert(_changes != NULL, "changes vector must be initialized");
while (!_changes->is_empty()) {
// Inv: everything is aligned.
ChangeItem* ci = _changes->first();
if (TraceRelocator) {
ci->print();
}
// Execute operation
if (!ci->handle_code_change(this)) return false;
// Shuffel items up
for (int index = 1; index < _changes->length(); index++) {
_changes->at_put(index-1, _changes->at(index));
}
_changes->pop();
}
return true;
}
bool Relocator::is_opcode_lookupswitch(Bytecodes::Code bc) {
switch (bc) {
case Bytecodes::_tableswitch: return false;
case Bytecodes::_lookupswitch: // not rewritten on ia64
case Bytecodes::_fast_linearswitch: // rewritten _lookupswitch
case Bytecodes::_fast_binaryswitch: return true; // rewritten _lookupswitch
default: ShouldNotReachHere();
}
return true; // dummy
}
// We need a special instruction size method, since lookupswitches and tableswitches might not be
// properly alligned during relocation
int Relocator::rc_instr_len(int bci) {
Bytecodes::Code bc= code_at(bci);
switch (bc) {
// In the case of switch instructions, see if we have the original
// padding recorded.
case Bytecodes::_tableswitch:
case Bytecodes::_lookupswitch:
case Bytecodes::_fast_linearswitch:
case Bytecodes::_fast_binaryswitch:
{
int pad = get_orig_switch_pad(bci, is_opcode_lookupswitch(bc));
if (pad == -1) {
return instruction_length_at(bci);
}
// Otherwise, depends on the switch type.
switch (bc) {
case Bytecodes::_tableswitch: {
int lo = int_at(bci + 1 + pad + 4 * 1);
int hi = int_at(bci + 1 + pad + 4 * 2);
int n = hi - lo + 1;
return 1 + pad + 4*(3 + n);
}
case Bytecodes::_lookupswitch:
case Bytecodes::_fast_linearswitch:
case Bytecodes::_fast_binaryswitch: {
int npairs = int_at(bci + 1 + pad + 4 * 1);
return 1 + pad + 4*(2 + 2*npairs);
}
default:
ShouldNotReachHere();
}
}
}
return instruction_length_at(bci);
}
// If a change item is recorded for "pc", with type "ct", returns the
// associated padding, else -1.
int Relocator::get_orig_switch_pad(int bci, bool is_lookup_switch) {
for (int k = 0; k < _changes->length(); k++) {
ChangeItem* ci = _changes->at(k);
if (ci->is_switch_pad()) {
ChangeSwitchPad* csp = (ChangeSwitchPad*)ci;
if (csp->is_lookup_switch() == is_lookup_switch && csp->bci() == bci) {
return csp->padding();
}
}
}
return -1;
}
// Push a ChangeJumpWiden if it doesn't already exist on the work queue,
// otherwise adjust the item already there by delta. The calculation for
// new_delta is wrong for this because it uses the offset stored in the
// code stream itself which wasn't fixed when item was pushed on the work queue.
void Relocator::push_jump_widen(int bci, int delta, int new_delta) {
for (int j = 0; j < _changes->length(); j++) {
ChangeItem* ci = _changes->at(j);
if (ci->adjust(bci, delta)) return;
}
_changes->push(new ChangeJumpWiden(bci, new_delta));
}
// The current instruction of "c" is a jump; one of its offset starts
// at "offset" and is a short if "isShort" is "TRUE",
// and an integer otherwise. If the jump crosses "breakPC", change
// the span of the jump by "delta".
void Relocator::change_jump(int bci, int offset, bool is_short, int break_bci, int delta) {
int bci_delta = (is_short) ? short_at(offset) : int_at(offset);
int targ = bci + bci_delta;
if ((bci <= break_bci && targ > break_bci) ||
(bci > break_bci && targ <= break_bci)) {
int new_delta;
if (bci_delta > 0)
new_delta = bci_delta + delta;
else
new_delta = bci_delta - delta;
if (is_short && ((new_delta > MAX_SHORT) || new_delta < MIN_SHORT)) {
push_jump_widen(bci, delta, new_delta);
} else if (is_short) {
short_at_put(offset, new_delta);
} else {
int_at_put(offset, new_delta);
}
}
}
// Changes all jumps crossing "break_bci" by "delta". May enqueue things
// on "rc->changes"
void Relocator::change_jumps(int break_bci, int delta) {
int bci = 0;
Bytecodes::Code bc;
// Now, adjust any affected instructions.
while (bci < code_length()) {
switch (bc= code_at(bci)) {
case Bytecodes::_ifeq:
case Bytecodes::_ifne:
case Bytecodes::_iflt:
case Bytecodes::_ifge:
case Bytecodes::_ifgt:
case Bytecodes::_ifle:
case Bytecodes::_if_icmpeq:
case Bytecodes::_if_icmpne:
case Bytecodes::_if_icmplt:
case Bytecodes::_if_icmpge:
case Bytecodes::_if_icmpgt:
case Bytecodes::_if_icmple:
case Bytecodes::_if_acmpeq:
case Bytecodes::_if_acmpne:
case Bytecodes::_ifnull:
case Bytecodes::_ifnonnull:
case Bytecodes::_goto:
case Bytecodes::_jsr:
change_jump(bci, bci+1, true, break_bci, delta);
break;
case Bytecodes::_goto_w:
case Bytecodes::_jsr_w:
change_jump(bci, bci+1, false, break_bci, delta);
break;
case Bytecodes::_tableswitch:
case Bytecodes::_lookupswitch:
case Bytecodes::_fast_linearswitch:
case Bytecodes::_fast_binaryswitch: {
int recPad = get_orig_switch_pad(bci, (bc != Bytecodes::_tableswitch));
int oldPad = (recPad != -1) ? recPad : align(bci+1) - (bci+1);
if (bci > break_bci) {
int new_bci = bci + delta;
int newPad = align(new_bci+1) - (new_bci+1);
// Do we need to check the padding?
if (newPad != oldPad) {
if (recPad == -1) {
_changes->push(new ChangeSwitchPad(bci, oldPad, (bc != Bytecodes::_tableswitch)));
}
}
}
// Then the rest, which depend on the kind of switch.
switch (bc) {
case Bytecodes::_tableswitch: {
change_jump(bci, bci +1 + oldPad, false, break_bci, delta);
// We cannot use the Bytecode_tableswitch abstraction, since the padding might not be correct.
int lo = int_at(bci + 1 + oldPad + 4 * 1);
int hi = int_at(bci + 1 + oldPad + 4 * 2);
int n = hi - lo + 1;
for (int k = 0; k < n; k++) {
change_jump(bci, bci +1 + oldPad + 4*(k+3), false, break_bci, delta);
}
// Special next-bci calculation here...
bci += 1 + oldPad + (n+3)*4;
continue;
}
case Bytecodes::_lookupswitch:
case Bytecodes::_fast_linearswitch:
case Bytecodes::_fast_binaryswitch: {
change_jump(bci, bci +1 + oldPad, false, break_bci, delta);
// We cannot use the Bytecode_lookupswitch abstraction, since the padding might not be correct.
int npairs = int_at(bci + 1 + oldPad + 4 * 1);
for (int k = 0; k < npairs; k++) {
change_jump(bci, bci + 1 + oldPad + 4*(2 + 2*k + 1), false, break_bci, delta);
}
/* Special next-bci calculation here... */
bci += 1 + oldPad + (2 + (npairs*2))*4;
continue;
}
default:
ShouldNotReachHere();
}
}
default:
break;
}
bci += rc_instr_len(bci);
}
}
// The width of instruction at "pc" is changing by "delta". Adjust the
// exception table, if any, of "rc->mb".
void Relocator::adjust_exception_table(int bci, int delta) {
ExceptionTable table(_method());
for (int index = 0; index < table.length(); index ++) {
if (table.start_pc(index) > bci) {
table.set_start_pc(index, table.start_pc(index) + delta);
table.set_end_pc(index, table.end_pc(index) + delta);
} else if (bci < table.end_pc(index)) {
table.set_end_pc(index, table.end_pc(index) + delta);
}
if (table.handler_pc(index) > bci)
table.set_handler_pc(index, table.handler_pc(index) + delta);
}
}
// The width of instruction at "bci" is changing by "delta". Adjust the line number table.
void Relocator::adjust_line_no_table(int bci, int delta) {
if (method()->has_linenumber_table()) {
CompressedLineNumberReadStream reader(method()->compressed_linenumber_table());
CompressedLineNumberWriteStream writer(64); // plenty big for most line number tables
while (reader.read_pair()) {
int adjustment = (reader.bci() > bci) ? delta : 0;
writer.write_pair(reader.bci() + adjustment, reader.line());
}
writer.write_terminator();
set_compressed_line_number_table(writer.buffer());
set_compressed_line_number_table_size(writer.position());
}
}
// The width of instruction at "bci" is changing by "delta". Adjust the local variable table.
void Relocator::adjust_local_var_table(int bci, int delta) {
int localvariable_table_length = method()->localvariable_table_length();
if (localvariable_table_length > 0) {
LocalVariableTableElement* table = method()->localvariable_table_start();
for (int i = 0; i < localvariable_table_length; i++) {
u2 current_bci = table[i].start_bci;
if (current_bci > bci) {
table[i].start_bci = current_bci + delta;
} else {
u2 current_length = table[i].length;
if (current_bci + current_length > bci) {
table[i].length = current_length + delta;
}
}
}
}
}
// Create a new array, copying the src array but adding a hole at
// the specified location
static Array<u1>* insert_hole_at(ClassLoaderData* loader_data,
size_t where, int hole_sz, Array<u1>* src) {
Thread* THREAD = Thread::current();
Array<u1>* dst =
MetadataFactory::new_array<u1>(loader_data, src->length() + hole_sz, 0, CHECK_NULL);
address src_addr = (address)src->adr_at(0);
address dst_addr = (address)dst->adr_at(0);
memcpy(dst_addr, src_addr, where);
memcpy(dst_addr + where + hole_sz,
src_addr + where, src->length() - where);
return dst;
}
// The width of instruction at "bci" is changing by "delta". Adjust the stack
// map frames.
void Relocator::adjust_stack_map_table(int bci, int delta) {
if (method()->has_stackmap_table()) {
Array<u1>* data = method()->stackmap_data();
// The data in the array is a classfile representation of the stackmap table
stack_map_table* sm_table =
stack_map_table::at((address)data->adr_at(0));
int count = sm_table->number_of_entries();
stack_map_frame* frame = sm_table->entries();
int bci_iter = -1;
bool offset_adjusted = false; // only need to adjust one offset
for (int i = 0; i < count; ++i) {
int offset_delta = frame->offset_delta();
bci_iter += offset_delta;
if (!offset_adjusted && bci_iter > bci) {
int new_offset_delta = offset_delta + delta;
if (frame->is_valid_offset(new_offset_delta)) {
frame->set_offset_delta(new_offset_delta);
} else {
assert(frame->is_same_frame() ||
frame->is_same_locals_1_stack_item_frame(),
"Frame must be one of the compressed forms");
// The new delta exceeds the capacity of the 'same_frame' or
// 'same_frame_1_stack_item_frame' frame types. We need to
// convert these frames to the extended versions, but the extended
// version is bigger and requires more room. So we allocate a
// new array and copy the data, being sure to leave u2-sized hole
// right after the 'frame_type' for the new offset field.
//
// We can safely ignore the reverse situation as a small delta
// can still be used in an extended version of the frame.
size_t frame_offset = (address)frame - (address)data->adr_at(0);
ClassLoaderData* loader_data = method()->method_holder()->class_loader_data();
Array<u1>* new_data = insert_hole_at(loader_data, frame_offset + 1, 2, data);
if (new_data == NULL) {
return; // out-of-memory?
}
// Deallocate old data
MetadataFactory::free_array<u1>(loader_data, data);
data = new_data;
address frame_addr = (address)(data->adr_at(0) + frame_offset);
frame = stack_map_frame::at(frame_addr);
// Now convert the frames in place
if (frame->is_same_frame()) {
same_frame_extended::create_at(frame_addr, new_offset_delta);
} else {
same_locals_1_stack_item_extended::create_at(
frame_addr, new_offset_delta, NULL);
// the verification_info_type should already be at the right spot
}
}
offset_adjusted = true; // needs to be done only once, since subsequent
// values are offsets from the current
}
// The stack map frame may contain verification types, if so we need to
// check and update any Uninitialized type's bci (no matter where it is).
int number_of_types = frame->number_of_types();
verification_type_info* types = frame->types();
for (int i = 0; i < number_of_types; ++i) {
if (types->is_uninitialized() && types->bci() > bci) {
types->set_bci(types->bci() + delta);
}
types = types->next();
}
// Full frame has stack values too
full_frame* ff = frame->as_full_frame();
if (ff != NULL) {
address eol = (address)types;
number_of_types = ff->stack_slots(eol);
types = ff->stack(eol);
for (int i = 0; i < number_of_types; ++i) {
if (types->is_uninitialized() && types->bci() > bci) {
types->set_bci(types->bci() + delta);
}
types = types->next();
}
}
frame = frame->next();
}
method()->set_stackmap_data(data); // in case it has changed
}
}
bool Relocator::expand_code_array(int delta) {
int length = MAX2(code_length() + delta, code_length() * (100+code_slop_pct()) / 100);
if (length > MAX_METHOD_LENGTH) {
if (delta == 0 && code_length() <= MAX_METHOD_LENGTH) {
length = MAX_METHOD_LENGTH;
} else {
return false;
}
}
unsigned char* new_code_array = NEW_RESOURCE_ARRAY(unsigned char, length);
if (!new_code_array) return false;
// Expanding current array
if (code_array() != NULL) {
memcpy(new_code_array, code_array(), code_length());
} else {
// Initial copy. Copy directly from Method*
memcpy(new_code_array, method()->code_base(), code_length());
}
set_code_array(new_code_array);
set_code_array_length(length);
return true;
}
// The instruction at "bci", whose size is "ilen", is changing size by
// "delta". Reallocate, move code, recalculate jumps, and enqueue
// change items as necessary.
bool Relocator::relocate_code(int bci, int ilen, int delta) {
int next_bci = bci + ilen;
if (delta > 0 && code_length() + delta > code_array_length()) {
// Expand allocated code space, if necessary.
if (!expand_code_array(delta)) {
return false;
}
}
// We require 4-byte alignment of code arrays.
assert(((intptr_t)code_array() & 3) == 0, "check code alignment");
// Change jumps before doing the copying; this routine requires aligned switches.
change_jumps(bci, delta);
// In case we have shrunken a tableswitch/lookupswitch statement, we store the last
// bytes that get overwritten. We have to copy the bytes after the change_jumps method
// has been called, since it is likly to update last offset in a tableswitch/lookupswitch
if (delta < 0) {
assert(delta>=-3, "we cannot overwrite more than 3 bytes");
memcpy(_overwrite, addr_at(bci + ilen + delta), -delta);
}
memmove(addr_at(next_bci + delta), addr_at(next_bci), code_length() - next_bci);
set_code_length(code_length() + delta);
// Also adjust exception tables...
adjust_exception_table(bci, delta);
// Line number tables...
adjust_line_no_table(bci, delta);
// And local variable table...
adjust_local_var_table(bci, delta);
// Adjust stack maps
adjust_stack_map_table(bci, delta);
// Relocate the pending change stack...
for (int j = 0; j < _changes->length(); j++) {
ChangeItem* ci = _changes->at(j);
ci->relocate(bci, delta);
}
// Notify any listeners about code relocation
notify(bci, delta, code_length());
return true;
}
// relocate a general instruction. Called by ChangeWiden class
bool Relocator::handle_widen(int bci, int new_ilen, u_char inst_buffer[]) {
int ilen = rc_instr_len(bci);
if (!relocate_code(bci, ilen, new_ilen - ilen))
return false;
// Insert new bytecode(s)
for(int k = 0; k < new_ilen; k++) {
code_at_put(bci + k, (Bytecodes::Code)inst_buffer[k]);
}
return true;
}
// handle jump_widen instruction. Called be ChangeJumpWiden class
bool Relocator::handle_jump_widen(int bci, int delta) {
int ilen = rc_instr_len(bci);
Bytecodes::Code bc = code_at(bci);
switch (bc) {
case Bytecodes::_ifeq:
case Bytecodes::_ifne:
case Bytecodes::_iflt:
case Bytecodes::_ifge:
case Bytecodes::_ifgt:
case Bytecodes::_ifle:
case Bytecodes::_if_icmpeq:
case Bytecodes::_if_icmpne:
case Bytecodes::_if_icmplt:
case Bytecodes::_if_icmpge:
case Bytecodes::_if_icmpgt:
case Bytecodes::_if_icmple:
case Bytecodes::_if_acmpeq:
case Bytecodes::_if_acmpne:
case Bytecodes::_ifnull:
case Bytecodes::_ifnonnull: {
const int goto_length = Bytecodes::length_for(Bytecodes::_goto);
// If 'if' points to the next bytecode after goto, it's already handled.
// it shouldn't be.
assert (short_at(bci+1) != ilen+goto_length, "if relocation already handled");
assert(ilen == 3, "check length");
// Convert to 0 if <cond> goto 6
// 3 _goto 11
// 6 _goto_w <wide delta offset>
// 11 <else code>
const int goto_w_length = Bytecodes::length_for(Bytecodes::_goto_w);
const int add_bci = goto_length + goto_w_length;
if (!relocate_code(bci, 3, /*delta*/add_bci)) return false;
// if bytecode points to goto_w instruction
short_at_put(bci + 1, ilen + goto_length);
int cbci = bci + ilen;
// goto around
code_at_put(cbci, Bytecodes::_goto);
short_at_put(cbci + 1, add_bci);
// goto_w <wide delta>
cbci = cbci + goto_length;
code_at_put(cbci, Bytecodes::_goto_w);
if (delta > 0) {
delta += 2; // goto_w is 2 bytes more than "if" code
} else {
delta -= ilen+goto_length; // branch starts at goto_w offset
}
int_at_put(cbci + 1, delta);
break;
}
case Bytecodes::_goto:
case Bytecodes::_jsr:
assert(ilen == 3, "check length");
if (!relocate_code(bci, 3, 2)) return false;
if (bc == Bytecodes::_goto)
code_at_put(bci, Bytecodes::_goto_w);
else
code_at_put(bci, Bytecodes::_jsr_w);
// If it's a forward jump, add 2 for the widening.
if (delta > 0) delta += 2;
int_at_put(bci + 1, delta);
break;
default: ShouldNotReachHere();
}
return true;
}
// handle lookup/table switch instructions. Called be ChangeSwitchPad class
bool Relocator::handle_switch_pad(int bci, int old_pad, bool is_lookup_switch) {
int ilen = rc_instr_len(bci);
int new_pad = align(bci+1) - (bci+1);
int pad_delta = new_pad - old_pad;
if (pad_delta != 0) {
int len;
if (!is_lookup_switch) {
int low = int_at(bci+1+old_pad+4);
int high = int_at(bci+1+old_pad+8);
len = high-low+1 + 3; // 3 for default, hi, lo.
} else {
int npairs = int_at(bci+1+old_pad+4);
len = npairs*2 + 2; // 2 for default, npairs.
}
// Because "relocateCode" does a "changeJumps" loop,
// which parses instructions to determine their length,
// we need to call that before messing with the current
// instruction. Since it may also overwrite the current
// instruction when moving down, remember the possibly
// overwritten part.
// Move the code following the instruction...
if (!relocate_code(bci, ilen, pad_delta)) return false;
if (pad_delta < 0) {
// Move the shrunken instruction down.
memmove(addr_at(bci + 1 + new_pad),
addr_at(bci + 1 + old_pad),
len * 4 + pad_delta);
memmove(addr_at(bci + 1 + new_pad + len*4 + pad_delta),
_overwrite, -pad_delta);
} else {
assert(pad_delta > 0, "check");
// Move the expanded instruction up.
memmove(addr_at(bci +1 + new_pad),
addr_at(bci +1 + old_pad),
len * 4);
memset(addr_at(bci + 1), 0, new_pad); // pad must be 0
}
}
return true;
}
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