SLLI and ADD are more compressible than SLLIW and ADDW. SLLI/ADD both have a 5-bit register encoding. SLLIW/ADDW have a 3-bit register encoding. They both require the dest to also be one of the sources.
We aggressively form ADDW/SLLIW as it helps hasAllWBitUsers in RISCVISelDAGToDAG to not require recursion. So we need a pass to remove excessive -w suffixes.
Differential Revision: https://reviews.llvm.org/D139948
The default implementation of findCommutedOpIndices picks the
first two source operands. That's exactly what we want for the
scalar FMA instructions.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D124463
