CmmSink: Use a UniqSet instead of a listwip/cmmsink

Vanilla:

  39,547,770,160 bytes allocated in the heap
   3,923,879,584 bytes copied during GC
     113,403,744 bytes maximum residency (39 sample(s))
         778,848 bytes maximum slop
             303 MB total memory in use (0 MB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0      2595 colls,     0 par   10.290s  10.495s     0.0040s    0.3172s
  Gen  1        39 colls,     0 par    0.023s   0.024s     0.0006s    0.0030s

  TASKS: 4 (1 bound, 3 peak workers (3 total), using -N1)

  SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)

  INIT    time    0.000s  (  0.003s elapsed)
  MUT     time   52.526s  ( 54.734s elapsed)
  GC      time   10.314s  ( 10.519s elapsed)
  EXIT    time    0.017s  (  0.051s elapsed)
  Total   time   62.857s  ( 65.308s elapsed)

  Alloc rate    752,919,176 bytes per MUT second

  Productivity  83.6% of total user, 83.9% of total elapsed

gc_alloc_block_sync: 0
whitehole_spin: 0
gen[0].sync: 0
gen[1].sync: 0

`skipped` as UniqSet:

  41,426,419,720 bytes allocated in the heap
   3,953,425,208 bytes copied during GC
     116,264,392 bytes maximum residency (39 sample(s))
         664,480 bytes maximum slop
             314 MB total memory in use (0 MB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0      3244 colls,     0 par   10.307s  10.504s     0.0032s    0.3317s
  Gen  1        39 colls,     0 par    0.024s   0.025s     0.0006s    0.0030s

  TASKS: 4 (1 bound, 3 peak workers (3 total), using -N1)

  SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)

  INIT    time    0.000s  (  0.003s elapsed)
  MUT     time   37.890s  ( 40.121s elapsed)
  GC      time   10.331s  ( 10.529s elapsed)
  EXIT    time    0.019s  (  0.063s elapsed)
  Total   time   48.241s  ( 50.715s elapsed)

  Alloc rate    1,093,320,118 bytes per MUT second

  Productivity  78.6% of total user, 79.2% of total elapsed

gc_alloc_block_sync: 0
whitehole_spin: 0
gen[0].sync: 0
gen[1].sync: 0

1 files changed, 8 insertions, 7 deletions

diff --git a/compiler/cmm/CmmSink.hs b/compiler/cmm/CmmSink.hs
index a674e54a54..1892e28fed 100644
--- a/compiler/cmm/CmmSink.hs
+++ b/compiler/cmm/CmmSink.hs
@@ -18,6 +18,7 @@ import Platform (isARM, platformArch)
 
 import DynFlags
 import UniqFM
+import UniqSet
 import PprCmm ()
 
 import Data.List (partition)
@@ -399,7 +400,7 @@ tryToInline
       , Assignments             -- Remaining assignments
       )
 
-tryToInline dflags live node assigs = go usages node [] assigs
+tryToInline dflags live node assigs = go usages node emptyUniqSet assigs
  where
   usages :: UniqFM Int -- Maps each LocalReg to a count of how often it is used
   usages = foldLocalRegsUsed dflags addUsage emptyUFM node
@@ -422,7 +423,7 @@ tryToInline dflags live node assigs = go usages node [] assigs
         inline_and_keep    = keep inl_node -- inline the assignment, keep it
 
         keep node' = (final_node, a : rest')
-          where (final_node, rest') = go usages' node' (l:skipped) rest
+          where (final_node, rest') = go usages' node' (addOneToUniqSet skipped l) rest
                 usages' = foldLocalRegsUsed dflags (\m r -> addToUFM m r 2)
                                             usages rhs
                 -- we must not inline anything that is mentioned in the RHS
@@ -430,7 +431,7 @@ tryToInline dflags live node assigs = go usages node [] assigs
                 -- usages of the regs on the RHS to 2.
 
         cannot_inline = skipped `regsUsedIn` rhs -- Note [dependent assignments]
-                        || l `elem` skipped
+                        || l `elementOfUniqSet` skipped
                         || not (okToInline dflags rhs node)
 
         l_usages = lookupUFM usages l
@@ -521,11 +522,11 @@ And we do that right here in tryToInline, just as we do cmmMachOpFold.
 addUsage :: UniqFM Int -> LocalReg -> UniqFM Int
 addUsage m r = addToUFM_C (+) m r 1
 
-regsUsedIn :: [LocalReg] -> CmmExpr -> Bool
-regsUsedIn [] _ = False
+regsUsedIn :: UniqSet LocalReg -> CmmExpr -> Bool
+regsUsedIn ls _ | isEmptyUniqSet ls = False
 regsUsedIn ls e = wrapRecExpf f e False
-  where f (CmmReg (CmmLocal l))      _ | l `elem` ls = True
-        f (CmmRegOff (CmmLocal l) _) _ | l `elem` ls = True
+  where f (CmmReg (CmmLocal l))      _ | l `elementOfUniqSet` ls = True
+        f (CmmRegOff (CmmLocal l) _) _ | l `elementOfUniqSet` ls = True
         f _ z = z
 
 -- we don't inline into CmmUnsafeForeignCall if the expression refers