RFR: 8333840: C2 SuperWord: wrong result for MulAddS2I when inputs permuted [v3]

[Emanuel Peter]

On Wed, 12 Jun 2024 15:37:24 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   more refactoring
>
> src/hotspot/share/opto/superword.cpp line 2815:
> 
>> 2813:   if (VectorNode::is_muladds2i(use)) {
>> 2814:     assert(1 <= u_idx && u_idx <= 4, "expected range for the 4 inputs");
>> 2815:     return _packset.is_muladds2i_pack_with_pack_inputs(u_pk);
> 
> Do we really need this assert? `is_muladds2i()` checks that use is MulAddS2I which by definition has 4 data inputs + control.

I can remove it.

> src/hotspot/share/opto/superword.cpp line 2846:
> 
>> 2844: //   v = MulAddS2I(a, b) = a0 * b0 + b1 + a1     (case 2)
>> 2845: //   v = MulAddS2I(a, b) = a1 * b1 + a0 + b0     (case 3)
>> 2846: //   v = MulAddS2I(a, b) = a1 * b1 + b0 + a0     (case 4)
> 
> The same typo for second pair.

Will fix that, thanks for spotting it!

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

PR Review Comment: https://git.openjdk.org/jdk/pull/19619#discussion_r1637617781
PR Review Comment: https://git.openjdk.org/jdk/pull/19619#discussion_r1637618061