#1520

- First working tail recursion testcase
  - Limited to the last statement being an assignment to a recursive call; but adding if-statements, if-expressions and match-expressions should be a minor addition


git-svn-id: https://openmodelica.org/svn/OpenModelica/trunk@9451 f25d12d1-65f4-0310-ae8a-bbce733d8d8e

Compiler/FrontEnd/Expression.mo

@@ -7019,5 +7019,15 @@ algorithm
   DAE.CREF(componentRef=DAE.CREF_IDENT(ident=name,subscriptLst={})) := exp; 
 end simpleCrefName;
 
+public function isTailCall
+  input DAE.Exp exp;
+  output Boolean isTail;
+algorithm
+  isTail := match exp
+    case DAE.CALL(attr=DAE.CALL_ATTR(tailCall=DAE.TAIL(vars=_))) then true;
+    else false;
+  end match;
+end isTailCall;
+
 end Expression;
 

Compiler/FrontEnd/Inst.mo

@@ -16469,12 +16469,14 @@ algorithm
       equation
         name = Expression.simpleCrefName(lhs);
         rhs = optimizeStatementTail2(path,rhs,{name},invars,outvars,source);
-      then fail();
+        stmt = Util.if_(Expression.isTailCall(rhs),DAE.STMT_NORETCALL(rhs,source),DAE.STMT_ASSIGN(tp,lhs,rhs,source));
+      then stmt;
     case (path,DAE.STMT_TUPLE_ASSIGN(tp,lhsLst,rhs,source),invars,outvars)
       equation
         lhsNames = Util.listMap(lhsLst,Expression.simpleCrefName);
         rhs = optimizeStatementTail2(path,rhs,lhsNames,invars,outvars,source);
-      then fail();
+        stmt = Util.if_(Expression.isTailCall(rhs),DAE.STMT_NORETCALL(rhs,source),DAE.STMT_TUPLE_ASSIGN(tp,lhsLst,rhs,source));
+      then stmt;
     else stmt;
   end matchcontinue;
 end optimizeStatementTail;
@@ -16503,12 +16505,16 @@ algorithm
     local
       Absyn.Path path1,path2;
       String str;
-    case (path1,DAE.CALL(path=path2),vars,source)
+      DAE.InlineType i;
+      Boolean b1,b2;
+      DAE.ExpType tp;
+      list<DAE.Exp> es;
+    case (path1,DAE.CALL(path=path2,expLst=es,attr=DAE.CALL_ATTR(tp,b1,b2,i,DAE.NO_TAIL())),vars,source)
       equation
-        // str = "Tail recursion of: " +& ExpressionDump.printExpStr(rhs) +& " with input vars: " +& Util.stringDelimitList(vars,",");
-        // Error.addSourceMessage(Error.COMPILER_NOTIFICATION,{str},DAEUtil.getElementSourceFileInfo(source));
-        // TODO: Embed input variable names to the function call or whatever...
-      then fail();
+        true = Absyn.pathEqual(path1,path2);
+        str = "Tail recursion of: " +& ExpressionDump.printExpStr(rhs) +& " with input vars: " +& Util.stringDelimitList(vars,",");
+        Error.addSourceMessage(Error.COMPILER_NOTIFICATION,{str},DAEUtil.getElementSourceFileInfo(source));
+      then DAE.CALL(path2,es,DAE.CALL_ATTR(tp,b1,b2,i,DAE.TAIL(vars)));
   end match;
 end optimizeStatementTail3;
 

Compiler/susan_codegen/SimCode/SimCodeC.tpl

@@ -2768,6 +2768,7 @@ case FUNCTION(__) then
     <%funArgs%>
     /* functionBodyRegularFunction: locals */
     <%varDecls%>
+    _tailrecursive:
     /* functionBodyRegularFunction: out inits */
     <%outVarInits%>
     
@@ -5171,6 +5172,15 @@ template daeExpCall(Exp call, Context context, Text &preExp /*BUFP*/,
     let argStr = daeExp(s1, context, &preExp, &varDecls)
     unboxRecord(argStr, ty, &preExp, &varDecls)
 
+  case exp as CALL(attr=attr as CALL_ATTR(tailCall=tail as TAIL(__))) then
+    let res = <<
+    /* Tail recursive call <%printExpStr(exp)%> */
+    <%daeExpTailCall(expLst,tail.vars,context,&preExp,&varDecls)%>goto _tailrecursive;
+    /* TODO: Make sure any eventual dead code below is never generated */
+    >>
+    let &preExp += res
+    ""
+
   case exp as CALL(attr=attr as CALL_ATTR(__)) then
     let argStr = (expLst |> exp => '<%daeExp(exp, context, &preExp /*BUFC*/, &varDecls /*BUFD*/)%>' ;separator=", ")
     let funName = '<%underscorePath(path)%>'
@@ -5202,6 +5212,15 @@ template daeExpCall(Exp call, Context context, Text &preExp /*BUFP*/,
         '<%retVar%>'
 end daeExpCall;
 
+template daeExpTailCall(list<DAE.Exp> es, list<String> vs, Context context, Text &preExp, Text &varDecls)
+::=
+  match es
+  case e::erest then
+    match vs
+    case v::vrest then
+      let exp = daeExp(e,context,&preExp,&varDecls)
+      '_<%v%> = <%exp%>;<%\n%><%daeExpTailCall(erest, vrest, context, &preExp, &varDecls)%>'
+end daeExpTailCall;
 
 template daeExpCallBuiltinPrefix(Boolean builtin)
  "Helper to daeExpCall."

Compiler/susan_codegen/SimCode/SimCodeTV.mo

@@ -1310,6 +1310,14 @@ package DAE
       Exp after;
     end OP_DERIVE;
   end SymbolicOperation;
+
+  uniontype TailCall
+    record NO_TAIL
+    end NO_TAIL;
+    record TAIL
+      list<String> vars;
+    end TAIL;
+  end TailCall;
 end DAE;
 
 
@@ -1892,6 +1900,14 @@ package Util
     replaceable type Type_a subtypeof Any;
   end listUnion;
 
+  function listThreadTuple
+    replaceable type Type_b subtypeof Any;
+    input list<Type_a> inTypeALst;
+    input list<Type_b> inTypeBLst;
+    output list<tuple<Type_a, Type_b>> outTplTypeATypeBLst;
+    replaceable type Type_a subtypeof Any;
+  end listThreadTuple;
+
 end Util;