This patch adds a peephole optimization SETCC(FREEZE(x),const) => FREEZE(SETCC(x,const))
if the SETCC is only used by BRCOND.
Combined with BRCOND(FREEZE(X)) => BRCOND(X), this leads to a nice improvement in the generated assembly when x is a masked loaded value.
Maybe worth calling out the one-use constraint in this comment?