Rewrite stores of register on the stack

Tests failing:
   ghc-api          CmmCopyPropagationTest [bad stdout] (normal)
   ghc-api/T7478    T7478 [bad exit code] (normal)
   ghci/linking     ghcilink002 [bad exit code] (normal)
   ghci/linking     ghcilink005 [bad exit code] (normal)
   ghci/scripts     ghci024 [bad stdout] (normal)
   perf/compiler    T1969 [stat not good enough] (normal)
   perf/compiler    T3064 [stat not good enough] (normal)
   perf/compiler    T3294 [stat not good enough] (normal)
   perf/compiler    T4801 [stat not good enough] (normal)
   perf/compiler    T5030 [stat not good enough] (normal)
   perf/compiler    T5321FD [stat not good enough] (normal)
   perf/compiler    T5321Fun [stat not good enough] (normal)
   perf/compiler    T5631 [stat not good enough] (normal)
   perf/compiler    T5642 [stat not good enough] (normal)
   perf/compiler    T5837 [stat not good enough] (normal)
   perf/compiler    T783 [stat not good enough] (normal)
   perf/compiler    parsing001 [stat not good enough] (normal)
   perf/should_run  T7797 [stat too good] (normal)
   perf/should_run  T7850 [stat too good] (normal)
   perf/should_run  lazy-bs-alloc [stat too good] (normal)
   rts              T7919 [exit code non-0] (normal)

CmmCopyPropagationTest fails because I didn't prepare stdout file
for it yet. ghci024 fails because I'm using additinal flag which
the test does not expect. Other tests also fail on HEAD.