ORC: improvements (#17993)

* ORC: improvements
* ORC: fix .acyclic annotation for ref objects

(cherry picked from commit 39ad9a69a9)

compiler/ast.nim

@@ -807,7 +807,7 @@ type
 
   PInstantiation* = ref TInstantiation
 
-  TScope* = object
+  TScope* {.acyclic.} = object
     depthLevel*: int
     symbols*: TStrTable
     parent*: PScope

compiler/liftdestructors.nim

@@ -435,13 +435,17 @@ proc setLenSeqCall(c: var TLiftCtx; t: PType; x, y: PNode): PNode =
   result = newTree(nkCall, newSymNode(op, x.info), x, lenCall)
 
 proc forallElements(c: var TLiftCtx; t: PType; body, x, y: PNode) =
+  let counterIdx = body.len
   let i = declareCounter(c, body, toInt64(firstOrd(c.g.config, t)))
   let whileLoop = genWhileLoop(c, i, x)
   let elemType = t.lastSon
   let b = if c.kind == attachedTrace: y else: y.at(i, elemType)
   fillBody(c, elemType, whileLoop[1], x.at(i, elemType), b)
-  addIncStmt(c, whileLoop[1], i)
-  body.add whileLoop
+  if whileLoop[1].len > 0:
+    addIncStmt(c, whileLoop[1], i)
+    body.add whileLoop
+  else:
+    body.sons.setLen counterIdx
 
 proc fillSeqOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
   case c.kind
@@ -606,6 +610,7 @@ proc atomicRefOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
       else:
         # If the ref is polymorphic we have to account for this
         body.add callCodegenProc(c.g, "nimTraceRefDyn", c.info, genAddrOf(x), y)
+      #echo "can follow ", elemType, " static ", isFinal(elemType)
   of attachedDispose:
     # this is crucial! dispose is like =destroy but we don't follow refs
     # as that is dealt within the cycle collector.

compiler/modulegraphs.nim

@@ -31,7 +31,7 @@ import ast, intsets, tables, options, lineinfos, hashes, idents,
 type
   SigHash* = distinct MD5Digest
 
-  ModuleGraph* = ref object
+  ModuleGraph* {.acyclic.} = ref object
     modules*: seq[PSym]  ## indexed by int32 fileIdx
     packageSyms*: TStrTable
     deps*: IntSet # the dependency graph or potentially its transitive closure.

compiler/options.nim

@@ -19,7 +19,7 @@ const
   useEffectSystem* = true
   useWriteTracking* = false
   hasFFI* = defined(nimHasLibFFI)
-  copyrightYear* = "2020"
+  copyrightYear* = "2021"
 
 type                          # please make sure we have under 32 options
                               # (improves code efficiency a lot!)
@@ -230,7 +230,7 @@ type
   ProfileData* = ref object
     data*: TableRef[TLineInfo, ProfileInfo]
 
-  ConfigRef* = ref object ## every global configuration
+  ConfigRef* {.acyclic.} = ref object ## every global configuration
                           ## fields marked with '*' are subject to
                           ## the incremental compilation mechanisms
                           ## (+) means "part of the dependency"

compiler/semtypes.nim

@@ -841,7 +841,7 @@ proc addInheritedFields(c: PContext, check: var IntSet, pos: var int,
     addInheritedFields(c, check, pos, obj[0].skipGenericInvocation)
   addInheritedFieldsAux(c, check, pos, obj.n)
 
-proc semObjectNode(c: PContext, n: PNode, prev: PType; isInheritable: bool): PType =
+proc semObjectNode(c: PContext, n: PNode, prev: PType; flags: TTypeFlags): PType =
   if n.len == 0:
     return newConstraint(c, tyObject)
   var check = initIntSet()
@@ -877,8 +877,9 @@ proc semObjectNode(c: PContext, n: PNode, prev: PType; isInheritable: bool): PTy
   if n.kind != nkObjectTy: internalError(c.config, n.info, "semObjectNode")
   result = newOrPrevType(tyObject, prev, c)
   rawAddSon(result, realBase)
-  if realBase == nil and isInheritable:
+  if realBase == nil and tfInheritable in flags:
     result.flags.incl tfInheritable
+  if tfAcyclic in flags: result.flags.incl tfAcyclic
   if result.n.isNil:
     result.n = newNodeI(nkRecList, n.info)
   else:
@@ -903,8 +904,8 @@ proc semAnyRef(c: PContext; n: PNode; kind: TTypeKind; prev: PType): PType =
     let n = if n[0].kind == nkBracket: n[0] else: n
     checkMinSonsLen(n, 1, c.config)
     let body = n.lastSon
-    var t = if prev != nil and body.kind == nkObjectTy and tfInheritable in prev.flags:
-              semObjectNode(c, body, nil, isInheritable=true)
+    var t = if prev != nil and body.kind == nkObjectTy:
+              semObjectNode(c, body, nil, prev.flags)
             else:
               semTypeNode(c, body, nil)
     if t.kind == tyTypeDesc and tfUnresolved notin t.flags:
@@ -1916,7 +1917,7 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
           localError(c.config, n.info, "type expected, but got symbol '$1' of kind '$2'" %
             [s.name.s, substr($s.kind, 2)])
       result = newOrPrevType(tyError, prev, c)
-  of nkObjectTy: result = semObjectNode(c, n, prev, isInheritable=false)
+  of nkObjectTy: result = semObjectNode(c, n, prev, {})
   of nkTupleTy: result = semTuple(c, n, prev)
   of nkTupleClassTy: result = newConstraint(c, tyTuple)
   of nkTypeClassTy: result = semTypeClass(c, n, prev)

compiler/semtypinst.nim

@@ -67,7 +67,7 @@ proc cacheTypeInst*(inst: PType) =
   gt.sym.typeInstCache.add(inst)
 
 type
-  LayeredIdTable* = ref object
+  LayeredIdTable* {.acyclic.} = ref object
     topLayer*: TIdTable
     nextLayer*: LayeredIdTable