RFR: 8310929: Optimization for Integer.toString [v12]

[温绍锦]

On Tue, 18 Jul 2023 01:38:47 GMT, Chen Liang <liach at openjdk.org> wrote:

>> The value range of the r variable is 0-99, and the length of PACKED_DIGITS is 100, There is no need to check the array boundary here.
>
> I think he means to check the `charPos` to ensure it is not out of bounds.

Oh, I see, charPos needs to do bound checks,  I added assert with reference to the implementation of StringUTF16#putChar, is this safe enough?

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PR Review Comment: https://git.openjdk.org/jdk/pull/14699#discussion_r1266090826