diff --git a/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC32.hs b/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC32.hs
index 25a5542e..10c1f444 100644
--- a/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC32.hs
+++ b/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC32.hs
@@ -21,4 +21,11 @@ import           Data.Macaw.PPC.PPCReg ( locToRegTH )
 import           Data.Macaw.PPC.Semantics.TH ( ppcAppEvaluator, ppcNonceAppEval )
 
 execInstruction :: MC.Value PPC ids (MT.BVType 32) -> Instruction -> Maybe (Generator PPC ids s ())
-execInstruction = $(genExecInstruction (Proxy @PPC) (locToRegTH (Proxy @PPC)) ppcNonceAppEval ppcAppEvaluator 'ppcInstructionMatcher allSemantics allOpcodeInfo)
+execInstruction = $(genExecInstruction (Proxy @PPC) (locToRegTH (Proxy @PPC))
+                    ppcNonceAppEval
+                    ppcAppEvaluator
+                    'ppcInstructionMatcher
+                    allSemantics allOpcodeInfo
+                    ([t| Dismantle.PPC.Operand |], [t| PPC |])
+                   )
+
diff --git a/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC64.hs b/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC64.hs
index f2d86704..280d88df 100644
--- a/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC64.hs
+++ b/macaw-ppc/src/Data/Macaw/PPC/Semantics/PPC64.hs
@@ -21,4 +21,5 @@ import           Data.Macaw.PPC.PPCReg ( locToRegTH )
 import           Data.Macaw.PPC.Semantics.TH ( ppcAppEvaluator, ppcNonceAppEval )
 
 execInstruction :: MC.Value PPC ids (MT.BVType 64) -> Instruction -> Maybe (Generator PPC ids s ())
-execInstruction = $(genExecInstruction (Proxy @PPC) (locToRegTH (Proxy @PPC)) ppcNonceAppEval ppcAppEvaluator 'ppcInstructionMatcher allSemantics allOpcodeInfo)
+execInstruction = $(genExecInstruction (Proxy @PPC) (locToRegTH (Proxy @PPC)) ppcNonceAppEval ppcAppEvaluator 'ppcInstructionMatcher allSemantics allOpcodeInfo
+                    ([t| Dismantle.PPC.Operand |], [t| PPC |]))
diff --git a/macaw-semmc/src/Data/Macaw/SemMC/TH.hs b/macaw-semmc/src/Data/Macaw/SemMC/TH.hs
index d8ac1686..9459f257 100644
--- a/macaw-semmc/src/Data/Macaw/SemMC/TH.hs
+++ b/macaw-semmc/src/Data/Macaw/SemMC/TH.hs
@@ -37,6 +37,7 @@ import qualified Control.Concurrent.Async as Async
 import qualified Data.Functor.Const as C
 import           Data.Proxy ( Proxy(..) )
 import qualified Data.List as L
+import           Data.Semigroup
 import qualified Data.Text as T
 import           Language.Haskell.TH
 import           Language.Haskell.TH.Syntax
@@ -102,25 +103,54 @@ instructionMatcher :: (OrdF a, LF.LiftF a, A.Architecture arch)
                    -- ^ The name of the architecture-specific instruction
                    -- matcher to run before falling back to the generic one
                    -> Map.MapF a (PairF (ParameterizedFormula (Sym t) arch) (DT.CaptureInfo a))
+                   -> (Q Type, Q Type)
                    -> Q Exp
-instructionMatcher ltr ena ae archSpecificMatcher formulas = do
+instructionMatcher ltr ena ae archSpecificMatcher formulas operandResultType = do
   ipVarName <- newName "ipVal"
   opcodeVar <- newName "opcode"
   operandListVar <- newName "operands"
-  let normalCases = map (mkSemanticsCase ltr ena ae ipVarName operandListVar) (Map.toList formulas)
-  let fallthroughCase = match wildP (normalB [| error ("Unimplemented instruction: " ++ show $(varE opcodeVar)) |]) []
-  let allCases = concat [ normalCases
+  (normalCases, bodyDefs) <- unzip <$> mapM (mkSemanticsCase ltr ena ae ipVarName operandListVar operandResultType) (Map.toList formulas)
+  (fallthruNm, unimp) <- unimplementedInstruction
+  fallthroughCase <- match wildP (normalB (appE (varE fallthruNm) (varE opcodeVar))) []
+  let allCases :: [Match]
+      allCases = concat [ normalCases
                         , [fallthroughCase]
                         ]
-  [| \ $(varP ipVarName) i@(D.Instruction $(varP opcodeVar) $(varP operandListVar)) ->
-        case $(varE archSpecificMatcher) i of
-          Just action -> Just action
-          Nothing -> $(caseE (varE opcodeVar) allCases)
-   |]
+  instrVar <- newName "i"
+  instrArg <- asP instrVar [p| D.Instruction $(varP opcodeVar) $(varP operandListVar) |]
+  matcherRes <- appE (varE archSpecificMatcher) (varE instrVar)
+  actionVar <- newName "action"
+  let instrCase = LetE (unimp : fullDefs) $ CaseE (VarE opcodeVar) allCases
+      fullDefs = concatMap (\(t,i) -> [t,i]) bodyDefs
+  return $ LamE [(VarP ipVarName), instrArg] $
+         CaseE matcherRes
+                   [ Match (ConP 'Just [VarP actionVar])
+                               (NormalB $ AppE (ConE 'Just) (VarE actionVar)) []
+                   , Match (ConP 'Nothing [])
+                               (NormalB instrCase) []
+                   ]
+
+
+unimplementedInstruction :: Q (Name, Dec)
+unimplementedInstruction = do
+    fname <- newName "noMatch"
+    arg1Nm <- newName "unknownOpcode"
+    fdecl <- funD fname
+             [clause [varP arg1Nm]
+                         (normalB [| error ("Unimplemented instruction: " ++ show $(varE arg1Nm)) |])
+                         []]
+    return (fname, fdecl)
+
 
 -- | Generate a single case for one opcode of the case expression.
+-- Generates two parts: the case match, which calls a function to
+-- handle the match, and the function definition for handling the
+-- match (inlining the function body would create a more complicated
+-- case expression which makes GHC much slower).
 --
--- > ADD4 -> ${BODY}
+-- > ADD4 -> bodyfun operands
+-- >
+-- > bodyfun operands = ${BODY}
 --
 -- where the ${BODY} is generated by 'mkOperandListCase'
 mkSemanticsCase :: (LF.LiftF a, A.Architecture arch)
@@ -129,10 +159,26 @@ mkSemanticsCase :: (LF.LiftF a, A.Architecture arch)
                 -> (forall tp . BoundVarInterpretations arch t -> S.App (S.Elt t) tp -> Maybe (MacawQ arch t Exp))
                 -> Name
                 -> Name
+                -> (Q Type, Q Type)
                 -> Map.Pair a (PairF (ParameterizedFormula (Sym t) arch) (DT.CaptureInfo a))
-                -> MatchQ
-mkSemanticsCase ltr ena ae ipVarName operandListVar (Map.Pair opc (PairF semantics capInfo)) =
-  match (conP (DT.capturedOpcodeName capInfo) []) (normalB (mkOperandListCase ltr ena ae ipVarName operandListVar opc semantics capInfo)) []
+                -> Q (Match, (Dec, Dec))
+mkSemanticsCase ltr ena ae ipVarName operandListVar operandResultType (Map.Pair opc (PairF semantics capInfo)) =
+    do arg1Nm <- newName "operands"
+       ofname <- newName $ "opc_" <> (filter ((/=) '"') $ nameBase $ DT.capturedOpcodeName capInfo)
+       lTypeVar <- newName "l"
+       idsTypeVar <- newName "ids"
+       sTypeVar <- newName "s"
+       ofsig <- sigD ofname [t| SL.List $(fst operandResultType) $(varT lTypeVar)
+                                  -> Maybe (G.Generator $(snd operandResultType)
+                                                        $(varT idsTypeVar)
+                                                        $(varT sTypeVar) ()) |]
+       ofdef <- funD ofname
+                 [clause [varP arg1Nm]
+                  (normalB (mkOperandListCase ltr ena ae ipVarName arg1Nm opc semantics capInfo))
+                  []]
+       mtch <- match (conP (DT.capturedOpcodeName capInfo) []) (normalB (appE (varE ofname) (varE operandListVar))) []
+       return (mtch, (ofsig, ofdef))
+
 
 -- | For each opcode case, we have a sub-case expression to destructure the
 -- operand list into names that we can reference.  This generates an expression
@@ -274,10 +320,11 @@ genExecInstruction :: forall arch (a :: [Symbol] -> *) (proxy :: * -> *)
                    -- ^ Extra information for each opcode to let us generate
                    -- some TH to match them.  This comes from the semantics
                    -- definitions in semmc.
+                   -> (Q Type, Q Type)
                    -> Q Exp
-genExecInstruction _ ltr ena ae archInsnMatcher semantics captureInfo = do
+genExecInstruction _ ltr ena ae archInsnMatcher semantics captureInfo operandResultType = do
   logCfg <- runIO $ U.mkNonLogCfg
-  r <- genExecInstructionLogging (Proxy @arch) ltr ena ae archInsnMatcher semantics captureInfo logCfg
+  r <- genExecInstructionLogging (Proxy @arch) ltr ena ae archInsnMatcher semantics captureInfo operandResultType logCfg
   runIO $ U.logEndWith logCfg
   return r
 
@@ -317,11 +364,12 @@ genExecInstructionLogStdErr :: forall arch (a :: [Symbol] -> *) (proxy :: * -> *
                    -- ^ Extra information for each opcode to let us generate
                    -- some TH to match them.  This comes from the semantics
                    -- definitions in semmc.
+                   -> (Q Type, Q Type)
                    -> Q Exp
-genExecInstructionLogStdErr _ ltr ena ae archInsnMatcher semantics captureInfo = do
+genExecInstructionLogStdErr _ ltr ena ae archInsnMatcher semantics captureInfo operandResultType = do
   logCfg <- runIO $ U.mkLogCfg "genExecInstruction"
   logThread <- runIO $ U.asyncLinked (U.stdErrLogEventConsumer (const True) logCfg)
-  r <- genExecInstructionLogging (Proxy @arch) ltr ena ae archInsnMatcher semantics captureInfo logCfg
+  r <- genExecInstructionLogging (Proxy @arch) ltr ena ae archInsnMatcher semantics captureInfo operandResultType logCfg
   runIO $ U.logEndWith logCfg
   runIO $ Async.wait logThread
   return r
@@ -368,19 +416,20 @@ genExecInstructionLogging :: forall arch (a :: [Symbol] -> *) (proxy :: * -> *)
                    -- ^ Extra information for each opcode to let us generate
                    -- some TH to match them.  This comes from the semantics
                    -- definitions in semmc.
+                   -> (Q Type, Q Type)
                    -> U.LogCfg
                    -- ^ Logging configuration (explicit rather than
                    -- the typical implicit expression because I don't
                    -- know how to pass implicits to TH splices
                    -- invocations.
                    -> Q Exp
-genExecInstructionLogging _ ltr ena ae archInsnMatcher semantics captureInfo logcfg =
+genExecInstructionLogging _ ltr ena ae archInsnMatcher semantics captureInfo operandResultType logcfg =
     U.withLogCfg logcfg $ do
       Some ng <- runIO PN.newIONonceGenerator
       sym <- runIO (S.newSimpleBackend ng)
       formulas <- runIO (loadFormulas sym semantics)
       let formulasWithInfo = foldr (attachInfo formulas) Map.empty captureInfo
-      instructionMatcher ltr ena ae archInsnMatcher formulasWithInfo
+      instructionMatcher ltr ena ae archInsnMatcher formulasWithInfo operandResultType
         where
           attachInfo m0 (Some ci) m =
               let co = DT.capturedOpcode ci