RFR: 8279607: Existing optimization "~x+1" -> "-x" can be generalized to "~x+c" -> "(c-1)-x". [v4]

[Tobias Hartmann]

On Sat, 15 Jan 2022 21:44:55 GMT, Zhiqiang Zang <duke at openjdk.java.net> wrote:

>> Hi all,
>> 
>> Existing optimization `~x+1 -> -x` can be generalized to `~x+c -> (c-1)-x`. I included both microbenchmark and jtreg tests.
>> 
>> 
>> // Convert (~x+c) into (c-1)-x. Note there isn't a bitwise not
>> // bytecode, "~x" would typically represented as "x^(-1)", so (~x+c)
>> // will be (x^(-1))+c.
>> if (op1 == Op_Xor(bt) &&
>>     (in2->Opcode() == Op_ConI || in2->Opcode() == Op_ConL) &&
>>     phase->type(in1->in(2)) == TypeInteger::minus_1(bt)) {
>>   Node* c_minus_one = phase->makecon(add_ring(phase->type(in(2)), TypeInteger::minus_1(bt)));
>>   return SubNode::make(c_minus_one, in1->in(1), bt);
>> }
>> 
>> 
>> Thank you for reviewing.
>
> Zhiqiang Zang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   cast to jlong instead of long.

That looks good to me and all testing passed.

You need a second review.

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Marked as reviewed by thartmann (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6858