Tweak OpsADVal for slightly faster rewriting

src/HordeAd/Core/OpsADVal.hs

@@ -137,6 +137,7 @@ instance (ADReadyNoLet target, ShareTensor target)
   tunpair (D u u') = let (u1, u2) = tunpair u
                          (d1, d2) = unDeltaPair u'
                      in (dDnotShared u1 d1, dDnotShared u2 d2)
+  tfromSShare (D u u') = dDnotShared (tfromSShare u) (dFromS u')
 
 -- Note that these instances don't do vectorization. To enable it,
 -- use the Ast instance and only then interpret in ADVal.
@@ -545,7 +546,7 @@ instance (ADReadyNoLet target, ShareTensor target, ShareTensor (PrimalOf target)
   tlambda _ = id
   -- Bangs are for the proper order of sharing stamps.
   tcond !stk !b !u !v =
-    let uv = tfromVector (SNat @2) stk (V.fromList [u, v])
+    let uv = tfromVectorShare (SNat @2) stk (V.fromList [u, v])
     in tindexBuildShare (SNat @2) stk uv (ifF b 0 1)
   tprimalPart _stk (D u _) = u
   tdualPart _stk (D _ u') = u'