RFR: 8373396: Min and Max Ideal missing AddNode::Ideal optimisations

[Emanuel Peter]

On Fri, 12 Dec 2025 06:54:18 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

>> `MaxI` and `MinI` are missing `AddNode::Ideal` optimizations. These optimizations include commutation, flattening, pushing constants...etc. The PR changes `MaxINode::Ideal` and `MinINode::Ideal` to call `AddNode::Ideal`. Long versions already call `AddNode::Ideal` so nothing to change there.
>> 
>> The PR also includes a template framework generated test (cc @eme64) that verifies that all of `AddNode::Ideal` optimizations now apply correctly for min/max for longs and ints. Long tests have been added to validate that both ints and longs produce the same results.
>> 
>> Fixing this issue indirectly fixes `compiler/codegen/TestBooleanVect.java` when run with `-XX:VerifyIterativeGVN=1110`, which was failing due to `min` not having one of those optimisations. However, this PR does not make changes to `PhaseIterGVN::verify_Identity_for` because there are additional failures observed with min/max for integers in JDK-8373134. Therefore, changes there will in the PR for JDK-8373134 instead.
>> 
>> If you look at `PhaseIterGVN::verify_Ideal_for`, it contains. This looks like it could be removed in this PR as it looks like they were quite likely disabled due to the issue here. However, it's unclear what test was failing here (@eme64 ?):
>> 
>> 
>>     // MinINode::Ideal
>>     // Did not investigate, but there are some patterns that might
>>     // need more notification.
>>     case Op_MinI:
>>     case Op_MaxI: // preemptively removed it as well.
>>       return false;
>> 
>> 
>> I've run tier1-3 tests on linux/x64 and they passed.
>
> src/hotspot/share/opto/addnode.cpp line 1459:
> 
>> 1457: // Ideal transformations for MaxINode
>> 1458: Node* MaxINode::Ideal(PhaseGVN* phase, bool can_reshape) {
>> 1459:   Node* n = AddNode::Ideal(phase, can_reshape);
> 
> Why not move this into `MaxNode::IdealI`?

Yes, the call below `return IdealI(phase, can_reshape);` already looks like it wants to handle all the superclass optimiazations. So it should go in there.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28770#discussion_r2613871712