8384507: Incorrect vector reassociation for signed saturating addition

[jatin-bhateja]

Reassociating vector broadcasts expects the vector operation to be associative, since we perform the following transformation:

VectorOp(ReplicateA, VectorOp(ReplicateB, Operand3))
  => VectorOp(Operand3, VectorOp(ReplicateA, ReplicateB))

Signed saturating addition is not an associative operation, i.e. sat_add(a, sat_add(b, c)) != sat_add(sat_add(a, b), c) because intermediate clamping can change the final result. This patch introduces is_associative_vector_operation() which skips the reassociation transformation for signed saturating addition while continuing to allow it for unsigned saturating addition (which is associative).

Please review and share your feedback.

Best Regards,
Jatin

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• JDK-8384507: Incorrect vector reassociation for signed saturating addition (Bug - P4)

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