RFR (L): 7173584: Implement arraycopy as a macro node

[Vladimir Kozlov]

Thank you for the case. I did go through the code and this change looks fine.

Thanks,
Vladimir

Roland Westrelin wrote:
> Vladimir,
> 
> Thanks for taking a look at this.
> 
>> I am not comfortable with this predicate change. The check come from generate_limit_guard() :
>>
>> if (a.length u< offset+copy_length) uncommon_trap; else arraycopy;
>>
>> which is reversed by igvn to
>>
>> if (offset+copy_length u< a.length) arraycopy; else uncommon_trap;
>>
>> So it should not be IfFalse projection. Can you explain the case which you hit?
> 
> 
> This is the java code that triggers this:
> 
>        for (int i=0; i<a1.length; i++) {
>  
>             a2 = new …[a3.length+a1.length-i-1];
> 
>             System.arraycopy(a3, 0, a2, 0, a3.length);
>             System.arraycopy(a1, i+1, a2, a3.length, a1.length-i-1);
>         }
> 
> For the first arraycopy, one of the check is:
> 
> if (a2.length < a3.length) uncommon_trap; else arraycopy;
> 
> if (a3.length + a1.length-i-1 < a3.length) uncommon_trap; else arraycopy;
> 
> a1.length is 5
> 
> if (a3.length + 4 - i < a3.length) uncommon_trap; else arraycopy;
> 
> a3.length is a loop invariant.
> 
> 
>> Also instead of duplicating gen_subtype_check() in macroArrayCopy.cpp can you modify the original one to work for you (by passing additional flag)?
> 
> Ok I'll do that.
> 
> Roland.