RFR: 8293833: Error mixing types with -XX:+UseCMoveUnconditionally -XX:+UseVectorCmov [v3]

[Christian Hagedorn]

On Thu, 13 Oct 2022 10:03:24 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> After JDK-8139340, JDK-8192846 and JDK-8289422, we can vectorize
>> the case below by enabling -XX:+UseCMoveUnconditionally and
>> -XX:+UseVectorCmov:
>> 
>> // double[] a, double[] b, double[] c;
>> for (int i = 0; i < a.length; i++) {
>>     c[i] = (a[i] > b[i]) ? a[i] : b[i];
>> }
>> 
>> 
>> But we don't support the case like:
>> 
>> // double[] a;
>> // int seed;
>> for (int i = 0; i < a.length; i++) {
>>     a[i] = (i % 2 == 0) ? seed + i : seed - i;
>> }
>> 
>> because the IR nodes for the CMoveD in the loop is:
>> 
>>   AddI  AndI     AddD   SubD
>>      \  /         /     /
>>      CmpI        /    /
>>        \        /   /
>>       Bool     /  /
>>           \   / /
>>           CMoveD
>> 
>> 
>> and it is not our target pattern, which requires that the inputs
>> of Cmp node must be the same as the inputs of CMove node
>> as commented in CMoveKit::make_cmovevd_pack(). Because
>> we can't vectorize the CMoveD pack, we shouldn't vectorize
>> its inputs, AddD and SubD. But the current function
>> CMoveKit::make_cmovevd_pack() doesn't clear the unqualified
>> CMoveD pack from the packset. In this way, superword wrongly
>> vectorizes AddD and SubD. Finally, we get a scalar CMoveD
>> node with two vector inputs, AddVD and SubVD, which has
>> wrong mixing types, then the assertion fails.
>> 
>> To fix it, we need to remove the unvectorized CMoveD pack
>> from the packset and clear related map info.
>
> Fei Gao has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Clean up the code style

Thanks for the update, looks good and testing passed!

-------------

Marked as reviewed by chagedorn (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10627