From 20e2625d1199e3642b73188471e9804efa1ab763 Mon Sep 17 00:00:00 2001
From: Matthijs Kooijman <matthijs@stdin.nl>
Date: Tue, 6 Apr 2010 19:47:01 +0200
Subject: [PATCH] Split off selector case creation code into CoreTools.

---
 "c\316\273ash/CLasH/Normalize.hs"            |  7 ++----
 "c\316\273ash/CLasH/Utils/Core/CoreTools.hs" | 25 ++++++++++++++++++++
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git "a/c\316\273ash/CLasH/Normalize.hs" "b/c\316\273ash/CLasH/Normalize.hs"
index 620482f..8bc2ef0 100644
--- "a/c\316\273ash/CLasH/Normalize.hs"
+++ "b/c\316\273ash/CLasH/Normalize.hs"
@@ -569,12 +569,9 @@ casesimpl c expr@(Case scrut bndr ty alts) | not bndr_used = do
         -- inlinenonrep).
         if (not wild) && repr
           then do
-            -- Create on new binder that will actually capture a value in this
+            caseexpr <- Trans.lift $ mkSelCase scrut i
+            -- Create a new binder that will actually capture a value in this
             -- case statement, and return it.
-            let bty = (Id.idType b)
-            id <- Trans.lift $ mkInternalVar "sel" bty
-            let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
-            let caseexpr = Case scrut b bty [(con, binders, Var id)]
             return (wildbndrs!!i, Just (b, caseexpr))
           else 
             -- Just leave the original binder in place, and don't generate an
diff --git "a/c\316\273ash/CLasH/Utils/Core/CoreTools.hs" "b/c\316\273ash/CLasH/Utils/Core/CoreTools.hs"
index a4ea1ec..9b276d6 100644
--- "a/c\316\273ash/CLasH/Utils/Core/CoreTools.hs"
+++ "b/c\316\273ash/CLasH/Utils/Core/CoreTools.hs"
@@ -36,6 +36,7 @@ import qualified VarEnv
 -- Local imports
 import CLasH.Translator.TranslatorTypes
 import CLasH.Utils.GhcTools
+import CLasH.Utils.Core.BinderTools
 import CLasH.Utils.HsTools
 import CLasH.Utils.Pretty
 import CLasH.Utils
@@ -427,3 +428,27 @@ genUnique subst bndr = do
   -- binder.
   let subst' = VarEnv.extendVarEnv subst bndr bndr'
   return (subst', bndr')
+
+-- Create a "selector" case that selects the ith field from a datacon
+mkSelCase :: CoreSyn.CoreExpr -> Int -> TranslatorSession CoreSyn.CoreExpr
+mkSelCase scrut i = do
+  let scrut_ty = CoreUtils.exprType scrut
+  case Type.splitTyConApp_maybe scrut_ty of
+    -- The scrutinee should have a type constructor. We keep the type
+    -- arguments around so we can instantiate the field types below
+    Just (tycon, tyargs) -> case TyCon.tyConDataCons tycon of
+      -- The scrutinee type should have a single dataconstructor,
+      -- otherwise we can't construct a valid selector case.
+      [datacon] -> do
+        let field_tys = DataCon.dataConInstOrigArgTys datacon tyargs
+        -- Create a list of wild binders for the fields we don't want
+        let wildbndrs = map MkCore.mkWildBinder field_tys
+        -- Create a single binder for the field we want
+        sel_bndr <- mkInternalVar "sel" (field_tys!!i)
+        -- Create a wild binder for the scrutinee
+        let scrut_bndr = MkCore.mkWildBinder scrut_ty
+        -- Create the case expression
+        let binders = take i wildbndrs ++ [sel_bndr] ++ drop (i+1) wildbndrs
+        return $ CoreSyn.Case scrut scrut_bndr scrut_ty [(CoreSyn.DataAlt datacon, binders, CoreSyn.Var sel_bndr)]
+      dcs -> error $ "CoreTools.mkSelCase: Scrutinee type must have exactly one datacon. Extracting element " ++ (show i) ++ " from '" ++ pprString scrut ++ "' Datacons: " ++ (show dcs) ++ " Type: " ++ (pprString scrut_ty)
+    Nothing -> error $ "CoreTools.mkSelCase: Creating extractor case, but scrutinee has no tycon? Extracting element " ++ (show i) ++ " from '" ++ pprString scrut ++ "'"
-- 
2.30.2