Github user kiszk commented on a diff in the pull request:
https://github.com/apache/spark/pull/19222#discussion_r174361814
--- Diff:
common/unsafe/src/main/java/org/apache/spark/unsafe/array/LongArray.java ---
@@ -80,7 +76,7 @@ public void zeroOut() {
public void set(int index, long value) {
assert index >= 0 : "index (" + index + ") should >= 0";
assert index < length : "index (" + index + ") should < length (" +
length + ")";
- Platform.putLong(baseObj, baseOffset + index * WIDTH, value);
+ memory.putLong(memory.getBaseOffset() + index * WIDTH, value);
--- End diff --
@cloud-fan good point. We will want use `memory.putLong(index * WIDTH,
value).
I expect that JIT compiler could move loop invariants out of a loop or
could map the sequence to a scaled index instruction `move targetreg, [basereg
+ scalereg * constant + offsetreg]` well.
I will investigate what happens in the native code using the example that
you pointed out.
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