On Thu, 19 Mar 2026 16:48:03 GMT, Tobias Hartmann <[email protected]> wrote:
>> To do `acmp`, if the pointer comparison fails, we check nullity of operands,
>> whether operands have the same class, and if this class is a value class.
>> And if everything works, we call `isSubstitutable`.
>>
>> Currently, when we have profiling information, we use it to speculate that
>> operands are null or of an identity class (in which case, pointer comparison
>> is all we should do). This patch proposes to take advantage of the profiling
>> when it hints that operands are value objects. By speculating that at least
>> one operand is of a given value class, the call to `isSubstitutable` can be
>> intrinsified later, and thus, spare the Java call.
>>
>> Speculating on one operand is enough since we will check that operands are
>> of the same type.
>>
>>
>> Some relevant microbenchmark in `valhalla.acmp.array.Value032` (in ns/op
>> (lower is better)):
>>
>> | | branch_obj_equals000 | branch_val_equals000 |
>> branch_obj_equals025 | branch_val_equals025 |
>> |---------------|----------------------|----------------------|----------------------|----------------------|
>> | Before | 4.361 ± 0.153 ns/op | 0.907 ± 0.015 ns/op | 3.332 ±
>> 0.040 ns/op | 0.845 ± 0.032 ns/op |
>> | With this fix | 0.911 ± 0.019 ns/op | 0.899 ± 0.021 ns/op | 0.838 ±
>> 0.023 ns/op | 0.806 ± 0.012 ns/op |
>>
>>
>>
>> <details>
>> <summary>Full results of
>> <tt>micro:valhalla.acmp.array.Value032</tt></summary>
>> In more details, before:
>>
>>
>> Benchmark Mode Cnt Score Error
>> Units
>> Value032.branch_obj_equals000 avgt 15 4.087 ± 0.122
>> ns/op
>> Value032.branch_obj_equals025 avgt 15 3.117 ± 0.067
>> ns/op
>> Value032.branch_obj_equals050 avgt 15 2.235 ± 0.083
>> ns/op
>> Value032.branch_obj_equals075 avgt 15 1.292 ± 0.077
>> ns/op
>> Value032.branch_obj_equals100 avgt 15 0.316 ± 0.004
>> ns/op
>> Value032.branch_val_equals000 avgt 15 0.891 ± 0.024
>> ns/op
>> Value032.branch_val_equals025 avgt 15 0.839 ± 0.033
>> ns/op
>> Value032.branch_val_equals050 avgt 15 0.869 ± 0.087
>> ns/op
>> Value032.branch_val_equals075 avgt 15 0.816 ± 0.023
>> ns/op
>> Value032.branch_val_equals100 avgt 15 0.906 ± 0.032
>> ns/op
>> Value032.result_obj_equals000 avgt 15 4.115 ± 0.185
>> ns/op
>> Value032.result_obj_equals025 avgt 15 3.326 ± 0.346
>> ns/op
>> Value...
>
> test/hotspot/jtreg/compiler/valhalla/inlinetypes/TestLWorldProfiling.java
> line 1250:
>
>> 1248: @Test
>> 1249: @IR(applyIfOr = {"UseACmpProfile", "true", "TypeProfileLevel", "=
>> 222"},
>> 1250: failOn = {STATIC_CALL_OF_METHOD, "isSubstitutable.*"},
>
> Indentation seems a bit off here, same below.
Urgh. Intellij has weird opinion on how these things should be indented. When I
try to fight it to make it consistent with the rest, it ends up looking like
that.
-------------
PR Review Comment:
https://git.openjdk.org/valhalla/pull/2237#discussion_r2964369765
