RFR: 8342382: Implementation of JEP G1: Improve Application Throughput with a More Efficient Write-Barrier [v5]

[Thomas Schatzl]

On Mon, 3 Mar 2025 14:47:00 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   * fix comment (trailing whitespace)
>>   * another assert when snapshotting at a safepoint.
>
> src/hotspot/share/gc/g1/g1CardTable.inline.hpp line 54:
> 
>> 52: // result = 0xBBAABBAA
>> 53: inline size_t blend(size_t a, size_t b, size_t mask) {
>> 54:   return a ^ ((a ^ b) & mask);
> 
> The example makes it much clearer; I wonder if `return (a & ~mask) | (b & mask);` is more readable.

... and hope that the optimizer knows this pattern? If you insist I can do that, brief examination of that code snippet by itself (not within this code) showed that it does.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23739#discussion_r1977739888