Craig Topper 014390d937 [RISCV] Implement cross basic block VXRM write insertion. (#70382) ...

This adds a new pass to insert VXRM writes for vector instructions. With
the goal of avoiding redundant writes.

The pass does 2 dataflow algorithms. The first is a forward data flow to
calculate where a VXRM value is available. The second is a backwards
dataflow to determine where a VXRM value is anticipated.

Finally, we use the results of these two dataflows to insert VXRM writes
where a value is anticipated, but not available.

The pass does not split critical edges so we aren't always able to
eliminate all redundancy.

The pass will only insert vxrm writes on paths that always require it.

2023-11-02 14:09:27 -07:00

3.4 KiB

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