anySrc p CmmNop = False
anySrc p other = True -- Conservative
-regUsedIn :: CmmReg -> CmmExpr -> Bool
-reg `regUsedIn` CmmLit _ = False
-reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
-reg `regUsedIn` CmmReg reg' = reg == reg'
-reg `regUsedIn` CmmRegOff reg' _ = reg == reg'
-reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
-
locUsedIn :: CmmExpr -> CmmType -> CmmExpr -> Bool
-- (locUsedIn a r e) checks whether writing to r[a] could affect the value of
-- 'e'. Returns True if it's not sure.