void LinearScan::allocate_fpu_stack() {
// First compute which FPU registers are live at the start of each basic block
// (To minimize the amount of work we have to do if we have to merge FPU stacks)
if (ComputeExactFPURegisterUsage) {
Interval* intervals_in_register, *intervals_in_memory;
create_unhandled_lists(&intervals_in_register, &intervals_in_memory, is_in_fpu_register, NULL);
// ignore memory intervals by overwriting intervals_in_memory
// the dummy interval is needed to enforce the walker to walk until the given id:
// without it, the walker stops when the unhandled-list is empty -> live information
// beyond this point would be incorrect.
Interval* dummy_interval = new Interval(any_reg);
dummy_interval->add_range(max_jint - 2, max_jint - 1);
dummy_interval->set_next(Interval::end());
intervals_in_memory = dummy_interval;
IntervalWalker iw(this, intervals_in_register, intervals_in_memory);
const int num_blocks = block_count();
for (int i = 0; i < num_blocks; i++) {
BlockBegin* b = block_at(i);
// register usage is only needed for merging stacks -> compute only
// when more than one predecessor.
// the block must not have any spill moves at the beginning (checked by assertions)
// spill moves would use intervals that are marked as handled and so the usage bit
// would been set incorrectly
// NOTE: the check for number_of_preds > 1 is necessary. A block with only one
// predecessor may have spill moves at the begin of the block.
// If an interval ends at the current instruction id, it is not possible
// to decide if the register is live or not at the block begin -> the
// register information would be incorrect.
if (b->number_of_preds() > 1) {
int id = b->first_lir_instruction_id();
ResourceBitMap regs(FrameMap::nof_fpu_regs);
iw.walk_to(id); // walk after the first instruction (always a label) of the block
assert(iw.current_position() == id, "did not walk completely to id");
// Only consider FPU values in registers
Interval* interval = iw.active_first(fixedKind);
while (interval != Interval::end()) {
int reg = interval->assigned_reg();
assert(reg >= pd_first_fpu_reg && reg <= pd_last_fpu_reg, "no fpu register");
assert(interval->assigned_regHi() == -1, "must not have hi register (doubles stored in one register)");
assert(interval->from() <= id && id < interval->to(), "interval out of range");
#ifndef PRODUCT
if (TraceFPURegisterUsage) {
tty->print("fpu reg %d is live because of ", reg - pd_first_fpu_reg); interval->print();
}
#endif
regs.set_bit(reg - pd_first_fpu_reg);
interval = interval->next();
}
b->set_fpu_register_usage(regs);
#ifndef PRODUCT
if (TraceFPURegisterUsage) {
tty->print("FPU regs for block %d, LIR instr %d): ", b->block_id(), id); regs.print_on(tty); tty->cr();
}
#endif
}
}
}
FpuStackAllocator alloc(ir()->compilation(), this);
_fpu_stack_allocator = &alloc;
alloc.allocate();
_fpu_stack_allocator = NULL;
}
