Luke Lau 1a58e88690 [RISCV] Move RISCVInsertVSETVLI to after phi elimination (#91440) ...

Split off from #70549, this patch moves RISCVInsertVSETVLI to after phi
elimination where we exit SSA and need to move to LiveVariables.

The motivation for splitting this off is to avoid the large scheduling
diffs from moving completely to after regalloc, and instead focus on
converting the pass to work on LiveIntervals.

The two main changes required are updating VSETVLIInfo to store VNInfos
instead of MachineInstrs, which allows us to still check for PHI defs in
needVSETVLIPHI, and fixing up the live intervals of any AVL operands
after inserting new instructions.

On O3 the pass is inserted after the register coalescer, otherwise we
end up with a bunch of COPYs around eliminated PHIs that trip up
needVSETVLIPHI.

Co-authored-by: Piyou Chen <piyou.chen@sifive.com>

2024-05-15 11:44:32 +08:00

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