On Wed, 7 May 2025 17:14:19 GMT, fabioromano1 <[email protected]> wrote:
>> src/java.base/share/classes/java/math/BigInteger.java line 2643:
>>
>>> 2641: : new BigInteger(result,
>>> newSign).shiftLeft(bitsToShift);
>>> 2642: } else {
>>> 2643: if ((bitLength() - 1L) * exponent >= (long)
>>> MAX_MAG_LENGTH << 5) {
>>
>> Suggestion:
>>
>> if ((bitLength() - 1L) * exponent >= 32L * MAX_MAG_LENGTH) {
>>
>> or
>> Suggestion:
>>
>> if ((bitLength() - 1L) * exponent >= (long) Integer.SIZE *
>> MAX_MAG_LENGTH) {
>>
>>
>> Both variant are easier to read, more honest, and exactly as efficient as
>> with the shift. The right-hand sides are compile-time constants, so they
>> have no impact on runtime performance.
>>
>> More generally, the runtime compilers are perfectly capable to optimize
>> multiplications by constant powers of 2 and replace them with shifts, even
>> if the other operand is not a constant.
>
> @rgiulietti What about `(bitLength() - 1L) * exponent >= Integer.MAX_VALUE`?
Ah right, but you probably want
Suggestion:
if ((bitLength() - 1L) * exponent > Integer.MAX_VALUE) {
I mean `>` rather than `>=`
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PR Review Comment: https://git.openjdk.org/jdk/pull/24690#discussion_r2078138621
