RFR: 8347645: C2: XOR bounded value handling blocks constant folding [v26]

[Quan Anh Mai]

On Sat, 1 Feb 2025 19:27:01 GMT, Johannes Graham <duke at openjdk.org> wrote:

>> C2 does not eliminate XOR nodes with constant arguments. This has a noticeable effect on `Long.expand` with a constant mask, on architectures that don't have instructions equivalent  to `PDEP` to be used in an intrinsic.
>> 
>> This patch demonstrates a potential fix to the problem, but there might well be better ways to do it.
>
> Johannes Graham has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add IR tests for long, simplify tests for int

Otherwise LGTM, very nice tests, thanks very much!

src/hotspot/share/opto/addnode.cpp line 1028:

> 1026:   if (r0->is_con() && r1->is_con()) {
> 1027:     // Constant fold: (c1 ^ c2) -> c3
> 1028:     return TypeInt::make( r0->get_con() ^ r1->get_con() );

Format

src/hotspot/share/opto/addnode.cpp line 1056:

> 1054:   if (r0->is_con() && r1->is_con()) {
> 1055:     // Constant fold: (c1 ^ c2) -> c3
> 1056:     return TypeLong::make( r0->get_con() ^ r1->get_con() );

Format here, too.

test/hotspot/jtreg/compiler/c2/irTests/XorINodeIdealizationTests.java line 313:

> 311:     }
> 312: 
> 313: /*

Please remove these commented out code

-------------

Marked as reviewed by qamai (Committer).

PR Review: https://git.openjdk.org/jdk/pull/23089#pullrequestreview-2611597506
PR Review Comment: https://git.openjdk.org/jdk/pull/23089#discussion_r1952453683
PR Review Comment: https://git.openjdk.org/jdk/pull/23089#discussion_r1952453982
PR Review Comment: https://git.openjdk.org/jdk/pull/23089#discussion_r1952456217