[LRE] Adjust order of cases in eliminateDeadDefs (#162108) If we have a rematerializable instruction without live virtual register uses (that we didn't heuristically decide to shrink), but with a physreg use, we were creating a kill to keep the physreg operand liveness unchanged. This meant we *weren't* keeping around the remat instruction, and thus inhibiting future remat within the original live interval. If we keep the remat instruction, that *also* keeps the physreg use, and thus we can achieve both objectives at once. Noticed this via inspection, and we don't currently seem to have any rematerializable instructions which could observe the difference. This could in theory happen for both trivial and non-trivial remat, but requires the rematerialization of an instruction with a physreg use.
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