JDK-8303113 : [SuperWord] investigate if enabling _do_vector_loop by default creates speedup
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 21
  • Priority: P4
  • Status: In Progress
  • Resolution: Unresolved
  • Submitted: 2023-02-23
  • Updated: 2023-05-16
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tbdUnresolved
Related Reports
Relates :  
JDK-8298935 - fix independence bug in create_pack logic in SuperWord::find_adjacent_refs
Relates :  
JDK-8260943 - C2 SuperWord: Remove dead vectorization optimization added by 8076284
Sub Tasks
JDK-8308606 :  
C2 SuperWord: remove alignment checks when not required - Resolved
Description
See discussion in PR:
https://github.com/openjdk/jdk/pull/12350

Also see
https://github.com/openjdk/jdk/pull/12350#issuecomment-1469539789

Check if these cases can be vectorized with it. Add IR tests for TestPickLastMemoryState.java.

Consider splitting packs, when we have conversion, and one type has more elements per vector than the other.
Comments
New insights and plan: _do_vector_loop currently has 2 effects: 1. disables the alignment requirement on memops. This we can hopefully easily disable. 2. takes info from CloneMap to only allow unroll-clone nodes of the same single-iteration node to be packed. Sometimes this is helpful, sometimes not. We may have to eventually try once with and once without this, and compare the results. I will first try to attack step 1, and then separately address 2 later.
16-05-2023
I will first remove the dead code from JDK-8260943, and then tackle this here.
11-05-2023
Tests in TestPickLastMemoryState.java are complex - use a lot of arrays and expressions. What about simpler misaligned case - store constants: for () { iArr[i1] += C1; iArr[i1 + 2] -= C2; }
15-03-2023