RFR: 8370196: C2: Improve (U)MulHiLNode::MulHiValue

[Andrew Haley]

On Sat, 1 Nov 2025 14:50:27 GMT, Zihao Lin <duke at openjdk.org> wrote:

> If nodes both are constant, support constant folding.

src/hotspot/share/opto/mulnode.cpp line 622:

> 620:   const TypeLong *longType1 = t1->is_long();
> 621:   const TypeLong *longType2 = t2->is_long();
> 622:   if(longType1 && longType2 && longType1->is_con() && longType2->is_con()){

Suggestion:

  if(longType1 != nullptr && longType2 != nullptr && longType1->is_con() && longType2->is_con()){

I know, it seems a bit fussy, but that's the way we do it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28097#discussion_r2509939997