[9] RFR(M): 8078554: Compiler: implement ranges (optionally constraints) for those flags that have them missing

Christian Thalinger christian.thalinger at oracle.com
Fri Oct 9 21:33:55 UTC 2015


After JEP 243 was integrated we fail one of the new tests with:

intx TypeProfileWidth=8 is outside the allowed range [ 0 ... 4 ]

The reason is that JVMCI can support more than 4 type profiles.  Currently the default is 8:

    if (UseJVMCICompiler) {
      if (FLAG_IS_DEFAULT(TypeProfileWidth)) {
        TypeProfileWidth = 8;
      }
    }

We should increase the range.  Not sure what a good number would be, though.  Maybe 100 just to be safe?

> On Oct 8, 2015, at 5:52 AM, Zoltán Majó <zoltan.majo at oracle.com> wrote:
> 
> Thank you, Tobias, for the review!
> 
> Best regards,
> 
> 
> Zoltán
> 
> On 10/08/2015 04:10 PM, Tobias Hartmann wrote:
>> Hi Zoltán,
>> 
>> On 08.10.2015 14:07, Zoltán Majó wrote:
>>> Hi Tobias,
>>> 
>>> 
>>> thank you for the feedback!
>>> 
>>> On 10/07/2015 03:38 PM, Tobias Hartmann wrote:
>>>> Hi Zoltan,
>>>> 
>>>> I had a look at your changes and just spotted some minor things:
>>>> 
>>>> globals_sparc.hpp:
>>>> - I think there is a '\' missing in line 119
>>> thank you for spotting that!
>>> 
>>>> globals_x86.hpp:
>>>> - Isn't this also a compiler flag we should add range checks for?
>>>>   136   product(uintx, RTMRetryCount, 5,
>>> JEP 245 considers it as a runtime flag and JDK-8078556 "Runtime: implement ranges..." [1] will take care of it. But you are right, that flag could be also considered a compiler flag.
>> Okay, thanks for pointing that out.
>> 
>>>> commandLineFlagConstraintsCompiler.cpp:
>>>> - I think there is a "rule" that the include statements should be in alphabetical order
>>> Yes, I think there is such a rule (or convention). I diverged from the rule because the include of code/relocInfo.hpp depends on 'os', 'vm_page_size', and 'Metadata'. Therefore, "oops/metadata.hpp" and "runtime/os.hpp" must be included before relocInfo.hpp (otherwise the Solaris compiler complains). The remaining includes are ordered alphabetically.
>> Okay, makes sense.
>> 
>>>> - the indentation is wrong here:
>>>>   179           return Flag::VIOLATES_CONSTRAINT;
>>> I updated the indentation.
>>> 
>>> Here is the updated webrev:
>>> http://cr.openjdk.java.net/~zmajo/8078554/webrev.02/
>>> 
>>> I re-tested the updated webrev with JPRT (testset hotspot), all tests pass.
>> Looks good to me (not a Reviewer).
>> 
>> Best,
>> Tobias
>> 
>> 
>>> Thank you and best regards,
>>> 
>>> 
>>> Zoltan
>>> 
>>> [1] https://bugs.openjdk.java.net/browse/JDK-8078556
>>>> Best,
>>>> Tobias
>>> 
>>>> On 06.10.2015 13:45, Zoltán Majó wrote:
>>>>> Hi Roland,
>>>>> 
>>>>> 
>>>>> thank you for the feedback!
>>>>> 
>>>>> On 10/02/2015 03:55 PM, Roland Westrelin wrote:
>>>>>> Hi Zoltan,
>>>>>> 
>>>>>>> Webrev:http://cr.openjdk.java.net/~zmajo/8078554/
>>>>>> c2_globals.hpp
>>>>>> 
>>>>>> That one is not correct:
>>>>>>    461   product(intx, MaxNodeLimit, 80000,                                        \
>>>>>>    462           "Maximum number of nodes")                                        \
>>>>>>    463           range(1000, 80000)                                                \
>>>>>> 
>>>>>> I think the upper bound should be max_juint
>>>>> You are right that the limit of 80'000 is too conservative. But max_j*u*int as an upper bound would cause an overflow when parsing the flag's value, because on 32-bit machines intx is a 32-bit signed integer.
>>>>> 
>>>>> Using max_jint instead of max_j*u*int as an upper bound would not cause an overflow at parse time. However, in Parse::do_call() the maximum node limit is increased by 3 times for jsr292 users
>>>>> 
>>>>> C->set_max_node_limit(3*MaxNodeLimit);
>>>>> 
>>>>> If MaxNodeLimit == max_jint, this expression will overflow, I think.
>>>>> 
>>>>> So I set the limit to (max_jint / 3) in the updated webrev.
>>>>> 
>>>>> If we would set MaxNodeLimit to max_j*u*int / 3 (instead of max_jint / 3), the expression 3 * MaxNodeLimit would overflow as well. Changing the type of the flag from intx to uintx could let use use max_j*u*int / 3 as an upper bound, but that is most likely not worth the effort.
>>>>> 
>>>>>>    699   product(intx, LiveNodeCountInliningCutoff, 40000,                         \
>>>>>>    700           "max number of live nodes in a method")                           \
>>>>>>    701           range(0, max_juint / 8)                                           \
>>>>>> 
>>>>>> Out of curiosity why max_juint / 8 (not that it makes much of a difference)?
>>>>> In Compile::inline_incrementally, the 80% of LiveNodeCountInliningCutoff is computed the following way:
>>>>> 
>>>>> if (low_live_nodes < (uint)LiveNodeCountInliningCutoff * 8 / 10) {
>>>>> 
>>>>> If LiveNodeCountInliningCutoff == max_juint, we'd have an overflow because of the multiplication by 8.
>>>>> 
>>>>>> arguments.cpp
>>>>>> 
>>>>>> 1099       Tier3InvokeNotifyFreqLog = 0;
>>>>>> 1100       Tier4InvocationThreshold = 0;
>>>>>> 
>>>>>> Why that change?
>>>>> I proposed that change because I misread the code. I reverted that change and also changed the range of all Tier*FreqLog flags from range(1, 30) to range(0, 30).
>>>>> 
>>>>>> globals.hp
>>>>>> 
>>>>>> 2870   product_pd(uintx, TypeProfileLevel,                                       \
>>>>>> 2871           "=XYZ, with Z: Type profiling of arguments at call; "             \
>>>>>> 2872                      "Y: Type profiling of return value at call; "          \
>>>>>> 2873                      "X: Type profiling of parameters to methods; "         \
>>>>>> 2874           "X, Y and Z in 0=off ; 1=jsr292 only; 2=all methods")             \
>>>>>> 2875           range(0, 222)
>>>>>> 
>>>>>> Legal values are 0, 1, 2, 10, 11, 12, 100, 101, 102, 110, 111, 112 etc.
>>>>>> 
>>>>>> 70 is not for instance. So range(0, 222) is incorrect.
>>>>> I agree. I removed the range check and implemented a constraint function instead (TypeProfileLevelConstraintFunc).
>>>>> 
>>>>>> 2877   product(intx, TypeProfileArgsLimit,     2,                                \
>>>>>> 2878           "max number of call arguments to consider for type profiling")    \
>>>>>> 2879           range(0, 16)                                                      \
>>>>>> 
>>>>>> 2880                                                                             \
>>>>>> 2881   product(intx, TypeProfileParmsLimit,    2,                                \
>>>>>> 2882           "max number of incoming parameters to consider for type profiling"\
>>>>>> 2883           ", -1 for all")                                                   \
>>>>>> 2884           range(-1, 64)
>>>>>> 
>>>>>> Why 16 and 64?
>>>>> These are the largest values that work on all platforms we support.
>>>>> 
>>>>> Here is the updated webrev: http://cr.openjdk.java.net/~zmajo/8078554/webrev.01/
>>>>> 
>>>>> I repeated the testing with JPRT. I also executed the currently disabled TestOptionsWithRanges.java test on all platforms we support. All tests pass.
>>>>> 
>>>>> Thank you and best regards,
>>>>> 
>>>>> 
>>>>> Zoltan
>>>>> 
>>>>>> Roland.
> 

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