5fdab3c81b
Like what has been done in AArch64 (D125335). We enable this under `-O2` to show the codegen diffs here but we may only do this under `-O3` like AArch64. There are two cases that we may produce these eliminable copies: 1. ISel of `FrameIndex`. Like `rvv/fixed-vectors-calling-conv.ll`. 2. Tail duplication. Like `select-optimize-multiple.ll`. Reviewed By: craig.topper Differential Revision: https://reviews.llvm.org/D144535