Optimize lent in JS [backport:1.6] (#19393)

* Optimize lent in JS [backport:1.6]

* addr on lent doesn't work anymore, don't use it

* use unsafeAddr  in test again for older versions

compiler/jsgen.nim

@@ -178,7 +178,7 @@ const
 proc mapType(typ: PType): TJSTypeKind =
   let t = skipTypes(typ, abstractInst)
   case t.kind
-  of tyVar, tyRef, tyPtr, tyLent:
+  of tyVar, tyRef, tyPtr:
     if skipTypes(t.lastSon, abstractInst).kind in MappedToObject:
       result = etyObject
     else:
@@ -186,7 +186,8 @@ proc mapType(typ: PType): TJSTypeKind =
   of tyPointer:
     # treat a tyPointer like a typed pointer to an array of bytes
     result = etyBaseIndex
-  of tyRange, tyDistinct, tyOrdinal, tyProxy:
+  of tyRange, tyDistinct, tyOrdinal, tyProxy, tyLent:
+    # tyLent is no-op as JS has pass-by-reference semantics
     result = mapType(t[0])
   of tyInt..tyInt64, tyUInt..tyUInt64, tyEnum, tyChar: result = etyInt
   of tyBool: result = etyBool
@@ -1060,14 +1061,14 @@ proc genAsgnAux(p: PProc, x, y: PNode, noCopyNeeded: bool) =
     xtyp = etySeq
   case xtyp
   of etySeq:
-    if (needsNoCopy(p, y) and needsNoCopy(p, x)) or noCopyNeeded:
+    if x.typ.kind in {tyVar, tyLent} or (needsNoCopy(p, y) and needsNoCopy(p, x)) or noCopyNeeded:
       lineF(p, "$1 = $2;$n", [a.rdLoc, b.rdLoc])
     else:
       useMagic(p, "nimCopy")
       lineF(p, "$1 = nimCopy(null, $2, $3);$n",
                [a.rdLoc, b.res, genTypeInfo(p, y.typ)])
   of etyObject:
-    if x.typ.kind in {tyVar} or (needsNoCopy(p, y) and needsNoCopy(p, x)) or noCopyNeeded:
+    if x.typ.kind in {tyVar, tyLent} or (needsNoCopy(p, y) and needsNoCopy(p, x)) or noCopyNeeded:
       lineF(p, "$1 = $2;$n", [a.rdLoc, b.rdLoc])
     else:
       useMagic(p, "nimCopy")
@@ -1092,10 +1093,18 @@ proc genAsgnAux(p: PProc, x, y: PNode, noCopyNeeded: bool) =
         lineF(p, "$# = [$#, $#];$n", [a.res, b.address, b.res])
         lineF(p, "$1 = $2;$n", [a.address, b.res])
         lineF(p, "$1 = $2;$n", [a.rdLoc, b.rdLoc])
+      elif a.typ == etyBaseIndex:
+        # array indexing may not map to var type
+        if b.address != nil:
+          lineF(p, "$1 = $2; $3 = $4;$n", [a.address, b.address, a.res, b.res])
+        else:
+          lineF(p, "$1 = $2;$n", [a.address, b.res])
       else:
         internalError(p.config, x.info, $("genAsgn", b.typ, a.typ))
-    else:
+    elif b.address != nil:
       lineF(p, "$1 = $2; $3 = $4;$n", [a.address, b.address, a.res, b.res])
+    else:
+      lineF(p, "$1 = $2;$n", [a.address, b.res])
   else:
     lineF(p, "$1 = $2;$n", [a.rdLoc, b.rdLoc])
 
@@ -1288,7 +1297,7 @@ template isIndirect(x: PSym): bool =
     v.kind notin {skProc, skFunc, skConverter, skMethod, skIterator,
                   skConst, skTemp, skLet})
 
-proc genSymAddr(p: PProc, n: PNode, typ: PType, r: var TCompRes) = 
+proc genSymAddr(p: PProc, n: PNode, typ: PType, r: var TCompRes) =
   let s = n.sym
   if s.loc.r == nil: internalError(p.config, n.info, "genAddr: 3")
   case s.kind
@@ -1456,13 +1465,17 @@ proc genSym(p: PProc, n: PNode, r: var TCompRes) =
   else:
     if s.loc.r == nil:
       internalError(p.config, n.info, "symbol has no generated name: " & s.name.s)
-    r.res = s.loc.r
+    if mapType(p, s.typ) == etyBaseIndex:
+      r.address = s.loc.r
+      r.res = s.loc.r & "_Idx"
+    else:
+      r.res = s.loc.r
   r.kind = resVal
 
 proc genDeref(p: PProc, n: PNode, r: var TCompRes) =
   let it = n[0]
   let t = mapType(p, it.typ)
-  if t == etyObject:
+  if t == etyObject or it.typ.kind == tyLent:
     gen(p, it, r)
   else:
     var a: TCompRes
@@ -1703,7 +1716,7 @@ proc createVar(p: PProc, typ: PType, indirect: bool): Rope =
       result = putToSeq("0", indirect)
   of tyFloat..tyFloat128:
     result = putToSeq("0.0", indirect)
-  of tyRange, tyGenericInst, tyAlias, tySink, tyOwned:
+  of tyRange, tyGenericInst, tyAlias, tySink, tyOwned, tyLent:
     result = createVar(p, lastSon(typ), indirect)
   of tySet:
     result = putToSeq("{}", indirect)
@@ -1745,7 +1758,7 @@ proc createVar(p: PProc, typ: PType, indirect: bool): Rope =
     createObjInitList(p, t, initIntSet(), initList)
     result = ("({$1})") % [initList]
     if indirect: result = "[$1]" % [result]
-  of tyVar, tyPtr, tyLent, tyRef, tyPointer:
+  of tyVar, tyPtr, tyRef, tyPointer:
     if mapType(p, t) == etyBaseIndex:
       result = putToSeq("[null, 0]", indirect)
     else:
@@ -2394,16 +2407,17 @@ proc genProc(oldProc: PProc, prc: PSym): Rope =
   if prc.typ[0] != nil and sfPure notin prc.flags:
     resultSym = prc.ast[resultPos].sym
     let mname = mangleName(p.module, resultSym)
-    if not isIndirect(resultSym) and
+    let returnAddress = not isIndirect(resultSym) and
       resultSym.typ.kind in {tyVar, tyPtr, tyLent, tyRef, tyOwned} and
-        mapType(p, resultSym.typ) == etyBaseIndex:
+        mapType(p, resultSym.typ) == etyBaseIndex
+    if returnAddress:
       resultAsgn = p.indentLine(("var $# = null;$n") % [mname])
       resultAsgn.add p.indentLine("var $#_Idx = 0;$n" % [mname])
     else:
       let resVar = createVar(p, resultSym.typ, isIndirect(resultSym))
       resultAsgn = p.indentLine(("var $# = $#;$n") % [mname, resVar])
     gen(p, prc.ast[resultPos], a)
-    if mapType(p, resultSym.typ) == etyBaseIndex:
+    if returnAddress:
       returnStmt = "return [$#, $#];$n" % [a.address, a.res]
     else:
       returnStmt = "return $#;$n" % [a.res]
@@ -2579,8 +2593,15 @@ proc gen(p: PProc, n: PNode, r: var TCompRes) =
   of nkObjConstr: genObjConstr(p, n, r)
   of nkHiddenStdConv, nkHiddenSubConv, nkConv: genConv(p, n, r)
   of nkAddr, nkHiddenAddr:
-    genAddr(p, n, r)
-  of nkDerefExpr, nkHiddenDeref: genDeref(p, n, r)
+    if n.typ.kind in {tyLent}:
+      gen(p, n[0], r)
+    else:
+      genAddr(p, n, r)
+  of nkDerefExpr, nkHiddenDeref:
+    if n.typ.kind in {tyLent}:
+      gen(p, n[0], r)
+    else:
+      genDeref(p, n, r)
   of nkBracketExpr: genArrayAccess(p, n, r)
   of nkDotExpr: genFieldAccess(p, n, r)
   of nkCheckedFieldExpr: genCheckedFieldOp(p, n, nil, r)