RFR: JDK-8238851: Shenandoah: C1: Resolve into registers of correct type

Roman Kennke rkennke at redhat.com
Wed Feb 12 14:21:12 UTC 2020


>>>> In ShBSC1::ensure_in_register() we are blindly creating registers of
>>>> type T_OBJECT, even though in some cases we actually need T_ADDRESS.
>>>> This blows up when we verify oop registers: when the argument is of type
>>>> T_OBJECT we perform extra checks that fail when the value in register is
>>>> not actually an object.
>>>>
>>>> Bug:
>>>> https://bugs.openjdk.java.net/browse/JDK-8238851
>>>> Webrev:
>>>> http://cr.openjdk.java.net/~rkennke/JDK-8238851/webrev.01/
>>>> Testing: the provided testcase passes now. hotspot_gc_shenandoah
>>>
>>> This path probably needs adjustment too:
>>>
>>>  167 #ifdef AARCH64
>>>  168       // AArch64 expects double-size register.
>>>  169       obj_reg = gen->new_pointer_register();
>>>  170 #else
>>
>> The provided test passes on aarch64 without any additional changes.
>>
>> I tried removing the block, hoping that the suggested change does
>> perhaps make it unnecessary, but no. It's still needed.
> 
> Gaawh. The non-AARCH64 path still looks good, so we can push it in current form. We really need to
> figure out AARCH64 thingie, please file the follow-up RFR?

Turns out that we can fix this rather easily. It is the non-aarch64 path
that is wrong though:

Differential:
http://cr.openjdk.java.net/~rkennke/JDK-8238851/webrev.01.diff/
Full:
http://cr.openjdk.java.net/~rkennke/JDK-8238851/webrev.01/

This is also consistent with the implementations of LIRAssembler::leal()
both x86 and aarch64.

Testing: passes hotspot_gc_shenandoah both aarch64 and x86

Good?

Roman



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