X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FdeSugar%2FDsGRHSs.lhs;h=4daab975ecbe28d85fdd5aae5a748a3c1a7de604;hb=d3d2b45d5b07064f73d76b33ce571e3f10cc3f42;hp=146771d5ddceba23f3e9bbd2cfdf726ccb5094f8;hpb=7fc749a43b4b6b85d234fa95d4928648259584f4;p=ghc-hetmet.git

diff --git a/compiler/deSugar/DsGRHSs.lhs b/compiler/deSugar/DsGRHSs.lhs
index 146771d..4daab97 100644
--- a/compiler/deSugar/DsGRHSs.lhs
+++ b/compiler/deSugar/DsGRHSs.lhs
@@ -105,12 +105,10 @@ matchGuards [] ctx rhs rhs_ty
 	-- NB:	The success of this clause depends on the typechecker not
 	-- 	wrapping the 'otherwise' in empty HsTyApp or HsWrap constructors
 	--	If it does, you'll get bogus overlap warnings
-matchGuards (ExprStmt (L _ (HsVar v)) _ _ : stmts) ctx rhs rhs_ty
-  |  v `hasKey` otherwiseIdKey
-  || v `hasKey` getUnique trueDataConId	
-	-- trueDataConId doesn't have the same unique as trueDataCon
-  = matchGuards stmts ctx rhs rhs_ty
-
+matchGuards (ExprStmt e _ _ : stmts) ctx rhs rhs_ty
+  | Just addTicks <- isTrueLHsExpr e
+  = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
+    returnDs (adjustMatchResultDs addTicks match_result)
 matchGuards (ExprStmt expr _ _ : stmts) ctx rhs rhs_ty
   = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
     dsLExpr expr			`thenDs` \ pred_expr ->
@@ -128,6 +126,31 @@ matchGuards (BindStmt pat bind_rhs _ _ : stmts) ctx rhs rhs_ty
   = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
     dsLExpr bind_rhs			`thenDs` \ core_rhs ->
     matchSinglePat core_rhs ctx pat rhs_ty match_result
+
+isTrueLHsExpr :: LHsExpr Id -> Maybe (CoreExpr -> DsM CoreExpr)
+
+-- Returns Just {..} if we're sure that the expression is True
+-- I.e.   * 'True' datacon
+--	  * 'otherwise' Id
+--	  * Trivial wappings of these
+-- The arguments to Just are any HsTicks that we have found,
+-- because we still want to tick then, even it they are aways evaluted.
+isTrueLHsExpr (L _ (HsVar v)) |  v `hasKey` otherwiseIdKey
+			      || v `hasKey` getUnique trueDataConId	
+                                      = Just returnDs
+	-- trueDataConId doesn't have the same unique as trueDataCon
+isTrueLHsExpr (L loc (HsTick    ix frees e)) 
+    | Just ticks <- isTrueLHsExpr e   = Just (\ e1 -> 
+			     ticks e1 `thenDs` \ e2 -> 
+			     mkTickBox ix frees e2)
+   -- This encodes that the result is constant True for Hpc tick purposes;
+   -- which is specifically what isTrueLHsExpr is trying to find out.
+isTrueLHsExpr (L loc (HsBinTick ixT _ e))
+    | Just ticks <- isTrueLHsExpr e   = Just (\ e1 -> 
+			     ticks e1 `thenDs` \ e2 -> 
+			     mkTickBox ixT [] e2)
+isTrueLHsExpr (L _ (HsPar e))         = isTrueLHsExpr e
+isTrueLHsExpr other = Nothing
 \end{code}
 
 Should {\em fail} if @e@ returns @D@