On Wed, 23 Feb 2022 05:43:10 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> Optimizes the divideUnsigned() and remainderUnsigned() methods in
>> java.lang.Integer and java.lang.Long classes using x86 intrinsics. This
>> change shows 3x improvement for Integer methods and upto 25% improvement for
>> Long. This change also implements the DivMod optimization which fuses
>> division and modulus operations if needed. The DivMod optimization shows 3x
>> improvement for Integer and ~65% improvement for Long.
>
> src/hotspot/cpu/x86/x86_64.ad line 8602:
>
>> 8600: __ jmp(done);
>> 8601: __ bind(neg_divisor_fastpath);
>> 8602: // Fastpath for divisor < 0:
>
> Move in macro assembly routine.
Sure, will move it to a macro assembly routine
> src/hotspot/cpu/x86/x86_64.ad line 8633:
>
>> 8631: __ jmp(done);
>> 8632: __ bind(neg_divisor_fastpath);
>> 8633: // Fastpath for divisor < 0:
>
> Move in macro assembly rountine.
Sure, will move it to a macro assembly routine
> src/hotspot/cpu/x86/x86_64.ad line 8902:
>
>> 8900: __ subl(tmp_rax, divisor);
>> 8901: __ andnl(tmp_rax, tmp_rax, rdx);
>> 8902: __ sarl(tmp_rax, 31);
>
> Please move this into a macro assembly routine.
Sure, will move it to a macro assembly routine
> src/hotspot/cpu/x86/x86_64.ad line 8932:
>
>> 8930: // Fastpath when divisor < 0:
>> 8931: // remainder = dividend - (((dividend & ~(dividend - divisor)) >>
>> (Long.SIZE - 1)) & divisor)
>> 8932: // See Hacker's Delight (2nd ed), section 9.3 which is implemented
>> in java.lang.Long.remainderUnsigned()
>
> Please move it into a macro assembly routine.
Sure, will move it to a macro assembly routine
> src/hotspot/share/opto/compile.cpp line 3499:
>
>> 3497: Node* d = n->find_similar(Op_UDivI);
>> 3498: if (d) {
>> 3499: // Replace them with a fused unsigned divmod if supported
>
> Can you explain a bit here, why can't this transformation be handled earlier ?
This is following the existing approach being used for signed DivMod
> test/micro/org/openjdk/bench/java/lang/LongDivMod.java line 75:
>
>> 73: }
>> 74: return quotients;
>> 75: }
>
> Do we need to return quotients, since it's a field being explicitly modified.
Will remove it.
> test/micro/org/openjdk/bench/java/lang/LongDivMod.java line 82:
>
>> 80: remainders[i] = Long.remainderUnsigned(dividends[i],
>> divisors[i]);
>> 81: }
>> 82: return remainders;
>
> Same as above
Will remove it.
-------------
PR: https://git.openjdk.java.net/jdk/pull/7572
