void LoopInvariantCodeMotion::process_block(BlockBegin* block) {
TRACE_VALUE_NUMBERING(tty->print_cr("processing block B%d", block->block_id()));
Instruction* prev = block;
Instruction* cur = block->next();
while (cur != NULL) {
// determine if cur instruction is loop invariant
// only selected instruction types are processed here
bool cur_invariant = false;
if (cur->as_Constant() != NULL) {
cur_invariant = !cur->can_trap();
} else if (cur->as_ArithmeticOp() != NULL || cur->as_LogicOp() != NULL || cur->as_ShiftOp() != NULL) {
assert(cur->as_Op2() != NULL, "must be Op2");
Op2* op2 = (Op2*)cur;
cur_invariant = !op2->can_trap() && is_invariant(op2->x()) && is_invariant(op2->y());
} else if (cur->as_LoadField() != NULL) {
LoadField* lf = (LoadField*)cur;
// deoptimizes on NullPointerException
cur_invariant = !lf->needs_patching() && !lf->field()->is_volatile() && !_short_loop_optimizer->has_field_store(lf->field()->type()->basic_type()) && is_invariant(lf->obj()) && _insert_is_pred;
} else if (cur->as_ArrayLength() != NULL) {
ArrayLength *length = cur->as_ArrayLength();
cur_invariant = is_invariant(length->array());
} else if (cur->as_LoadIndexed() != NULL) {
LoadIndexed *li = (LoadIndexed *)cur->as_LoadIndexed();
cur_invariant = !_short_loop_optimizer->has_indexed_store(as_BasicType(cur->type())) && is_invariant(li->array()) && is_invariant(li->index()) && _insert_is_pred;
}
if (cur_invariant) {
// perform value numbering and mark instruction as loop-invariant
_gvn->substitute(cur);
if (cur->as_Constant() == NULL) {
// ensure that code for non-constant instructions is always generated
cur->pin();
}
// remove cur instruction from loop block and append it to block before loop
Instruction* next = cur->next();
Instruction* in = _insertion_point->next();
_insertion_point = _insertion_point->set_next(cur);
cur->set_next(in);
// Deoptimize on exception
cur->set_flag(Instruction::DeoptimizeOnException, true);
// Clear exception handlers
cur->set_exception_handlers(NULL);
TRACE_VALUE_NUMBERING(tty->print_cr("Instruction %c%d is loop invariant", cur->type()->tchar(), cur->id()));
if (cur->state_before() != NULL) {
cur->set_state_before(_state->copy());
}
if (cur->exception_state() != NULL) {
cur->set_exception_state(_state->copy());
}
cur = prev->set_next(next);
} else {
prev = cur;
cur = cur->next();
}
}
}
