RFR: 8364766: C2: Improve Value() of DivI and DivL for non-constant inputs [v6]

[Manuel Hässig]

On Mon, 25 Aug 2025 09:08:33 GMT, Benoît Maillard <bmaillard at openjdk.org> wrote:

>> Tobias Hotz has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove too strict assert from old code path
>
> src/hotspot/share/opto/divnode.cpp line 543:
> 
>> 541:   NativeType i2_hi = i2->_hi == 0 ? -1 : i2->_hi;
>> 542:   NativeType min_val = std::numeric_limits<NativeType>::min();
>> 543:   assert(min_val == min_jint || min_val == min_jlong, "min has to be either min_jint or min_jlong");
> 
> I find this assert a little confusing, as its outcome is completely independent from the inputs of the function. I would remove it

It depends on the template type. I would rather keep it to sanity check that the minimum value of `NativeType` is as we expect. If that does not hold, the optimization below is potentially wrong and has UB.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26143#discussion_r2297570098