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8304460: Improve array usages

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Reviewed-by: iveresov, rhalade, chagedorn
This commit is contained in:
Tobias Hartmann 2023-03-21 15:39:50 +00:00 committed by Henry Jen
parent 5e47b8e5e6
commit 34dbb22505
1 changed files with 7 additions and 8 deletions

15
src/hotspot/share/c1/c1_RangeCheckElimination.cpp

@ -228,24 +228,23 @@ void RangeCheckEliminator::Visitor::do_ArithmeticOp(ArithmeticOp *ao) {
Bound* y_bound = _rce->get_bound(y);
if (x_bound->lower() >= 0 && x_bound->lower_instr() == nullptr && y->as_ArrayLength() != nullptr) {
_bound = new Bound(0, nullptr, -1, y);
} else if (y->type()->as_IntConstant() && y->type()->as_IntConstant()->value() != 0) {
} else if (x_bound->has_lower() && x_bound->lower() >= 0 && y->type()->as_IntConstant() &&
y->type()->as_IntConstant()->value() != 0 && y->type()->as_IntConstant()->value() != min_jint) {
// The binary % operator is said to yield the remainder of its operands from an implied division; the
// left-hand operand is the dividend and the right-hand operand is the divisor.
//
// % operator follows from this rule that the result of the remainder operation can be negative only
// It follows from this rule that the result of the remainder operation can be negative only
// if the dividend is negative, and can be positive only if the dividend is positive. Moreover, the
// magnitude of the result is always less than the magnitude of the divisor(See JLS 15.17.3).
// magnitude of the result is always less than the magnitude of the divisor (see JLS 15.17.3).
//
// So if y is a constant integer and not equal to 0, then we can deduce the bound of remainder operation:
// x % -y ==> [0, y - 1] Apply RCE
// x % y ==> [0, y - 1] Apply RCE
// -x % y ==> [-y + 1, 0]
// -x % -y ==> [-y + 1, 0]
if (x_bound->has_lower() && x_bound->lower() >= 0) {
_bound = new Bound(0, nullptr, y->type()->as_IntConstant()->value() - 1, nullptr);
} else {
_bound = new Bound();
}
//
// Use the absolute value of y as an upper bound. Skip min_jint because abs(min_jint) is undefined.
_bound = new Bound(0, nullptr, abs(y->type()->as_IntConstant()->value()) - 1, nullptr);
} else {
_bound = new Bound();
}