improve wasMoved hooks; allow reset to use the overridden wasMoved hook (#21831)

* improve `wasMoved` hooks

* Because `wasMoved` is lifted

compiler/injectdestructors.nim

@@ -381,7 +381,7 @@ proc genWasMoved(c: var Con, n: PNode): PNode =
     result = genOp(c, op, n)
   else:
     result = newNodeI(nkCall, n.info)
-    result.add(newSymNode(createMagic(c.graph, c.idgen, "wasMoved", mWasMoved)))
+    result.add(newSymNode(createMagic(c.graph, c.idgen, "`=wasMoved`", mWasMoved)))
     result.add copyTree(n) #mWasMoved does not take the address
     #if n.kind != nkSym:
     #  message(c.graph.config, n.info, warnUser, "wasMoved(" & $n & ")")

compiler/liftdestructors.nim

@@ -89,7 +89,7 @@ proc defaultOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     call.typ = t
     body.add newAsgnStmt(x, call)
   elif c.kind == attachedWasMoved:
-    body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+    body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
 
 proc genAddr(c: var TLiftCtx; x: PNode): PNode =
   if x.kind == nkHiddenDeref:
@@ -143,7 +143,7 @@ proc destructorCall(c: var TLiftCtx; op: PSym; x: PNode): PNode =
   if sfNeverRaises notin op.flags:
     c.canRaise = true
   if c.addMemReset:
-    result = newTree(nkStmtList, destroy, genBuiltin(c, mWasMoved,  "wasMoved", x))
+    result = newTree(nkStmtList, destroy, genBuiltin(c, mWasMoved,  "`=wasMoved`", x))
   else:
     result = destroy
 
@@ -262,7 +262,7 @@ proc fillBodyObjT(c: var TLiftCtx; t: PType, body, x, y: PNode) =
     #body.add newAsgnStmt(blob, x)
 
     var wasMovedCall = newNodeI(nkCall, c.info)
-    wasMovedCall.add(newSymNode(createMagic(c.g, c.idgen, "wasMoved", mWasMoved)))
+    wasMovedCall.add(newSymNode(createMagic(c.g, c.idgen, "`=wasMoved`", mWasMoved)))
     wasMovedCall.add x # mWasMoved does not take the address
     body.add wasMovedCall
 
@@ -548,7 +548,7 @@ proc fillSeqOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     if canFormAcycle(c.g, t.elemType):
       # follow all elements:
       forallElements(c, t, body, x, y)
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -588,7 +588,7 @@ proc useSeqOrStrOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
       if op == nil:
         return # protect from recursion
       body.add newHookCall(c, op, x, y)
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -606,7 +606,7 @@ proc fillStrOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     body.add genBuiltin(c, mDestroy, "destroy", x)
   of attachedTrace:
     discard "strings are atomic and have no inner elements that are to trace"
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -707,7 +707,7 @@ proc atomicRefOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
         # If the ref is polymorphic we have to account for this
         body.add callCodegenProc(c.g, "nimTraceRefDyn", c.info, genAddrOf(x, c.idgen), y)
       #echo "can follow ", elemType, " static ", isFinal(elemType)
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -758,7 +758,7 @@ proc atomicClosureOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace:
     body.add callCodegenProc(c.g, "nimTraceRefDyn", c.info, genAddrOf(xenv, c.idgen), y)
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -785,7 +785,7 @@ proc weakrefOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
       body.sons.insert(des, 0)
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace: discard
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -813,7 +813,7 @@ proc ownedRefOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     body.add genIf(c, x, actions)
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace: discard
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -850,7 +850,7 @@ proc closureOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
         body.sons.insert(des, 0)
     of attachedDeepCopy: assert(false, "cannot happen")
     of attachedTrace: discard
-    of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+    of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
     of attachedDup:
       assert false, "cannot happen"
 
@@ -868,7 +868,7 @@ proc ownedClosureOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     body.add genIf(c, xx, actions)
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace: discard
-  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "wasMoved", x)
+  of attachedWasMoved: body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
   of attachedDup:
     assert false, "cannot happen"
 
@@ -934,8 +934,14 @@ proc fillBody(c: var TLiftCtx; t: PType; body, x, y: PNode) =
       defaultOp(c, t, body, x, y)
   of tyObject:
     if not considerUserDefinedOp(c, t, body, x, y):
-      if c.kind in {attachedAsgn, attachedSink} and t.sym != nil and sfImportc in t.sym.flags:
-        body.add newAsgnStmt(x, y)
+      if t.sym != nil and sfImportc in t.sym.flags:
+        case c.kind
+        of {attachedAsgn, attachedSink}:
+          body.add newAsgnStmt(x, y)
+        of attachedWasMoved:
+          body.add genBuiltin(c, mWasMoved, "`=wasMoved`", x)
+        else:
+          fillBodyObjT(c, t, body, x, y)
       else:
         fillBodyObjT(c, t, body, x, y)
   of tyDistinct:
@@ -1004,6 +1010,9 @@ proc symPrototype(g: ModuleGraph; typ: PType; owner: PSym; kind: TTypeAttachedOp
   result.ast = n
   incl result.flags, sfFromGeneric
   incl result.flags, sfGeneratedOp
+  if kind == attachedWasMoved:
+    incl result.flags, sfNoSideEffect
+    incl result.typ.flags, tfNoSideEffect
 
 proc genTypeFieldCopy(c: var TLiftCtx; t: PType; body, x, y: PNode) =
   let xx = genBuiltin(c, mAccessTypeField, "accessTypeField", x)

compiler/optimizer.nim

@@ -113,7 +113,7 @@ proc analyse(c: var Con; b: var BasicBlock; n: PNode) =
     if n[0].kind == nkSym:
       let s = n[0].sym
       let name = s.name.s.normalize
-      if s.magic == mWasMoved or name == "=wasmoved":
+      if name == "=wasmoved":
         b.wasMovedLocs.add n
         special = true
       elif name == "=destroy":

compiler/semmagic.nim

@@ -613,6 +613,15 @@ proc magicsAfterOverloadResolution(c: PContext, n: PNode,
     let op = getAttachedOp(c.graph, t, attachedTrace)
     if op != nil:
       result[0] = newSymNode(op)
+  of mWasMoved:
+    result = n
+    let t = n[1].typ.skipTypes(abstractVar)
+    let op = getAttachedOp(c.graph, t, attachedWasMoved)
+    if op != nil:
+      result[0] = newSymNode(op)
+      let addrExp = newNodeIT(nkHiddenAddr, result[1].info, makePtrType(c, t))
+      addrExp.add result[1]
+      result[1] = addrExp
   of mUnown:
     result = semUnown(c, n)
   of mExists, mForall:

lib/system.nim

@@ -137,15 +137,20 @@ proc new*[T](a: var ref T, finalizer: proc (x: ref T) {.nimcall.}) {.
   ## **Note**: The `finalizer` refers to the type `T`, not to the object!
   ## This means that for each object of type `T` the finalizer will be called!
 
-proc wasMoved*[T](obj: var T) {.magic: "WasMoved", noSideEffect.} =
+proc `=wasMoved`[T](obj: var T) {.magic: "WasMoved", noSideEffect.} =
+  ## Generic `wasMoved`:idx: implementation that can be overridden.
+
+proc wasMoved*[T](obj: var T) {.inline, noSideEffect.} =
   ## Resets an object `obj` to its initial (binary zero) value to signify
   ## it was "moved" and to signify its destructor should do nothing and
   ## ideally be optimized away.
-  discard
+  {.cast(raises: []), cast(tags: []).}:
+    `=wasMoved`(obj)
 
 proc move*[T](x: var T): T {.magic: "Move", noSideEffect.} =
   result = x
-  wasMoved(x)
+  {.cast(raises: []), cast(tags: []).}:
+    `=wasMoved`(x)
 
 type
   range*[T]{.magic: "Range".}         ## Generic type to construct range types.
@@ -912,7 +917,7 @@ proc reset*[T](obj: var T) {.noSideEffect.} =
     when defined(gcDestructors):
       {.cast(noSideEffect), cast(raises: []), cast(tags: []).}:
         `=destroy`(obj)
-        wasMoved(obj)
+        `=wasMoved`(obj)
     else:
       obj = default(typeof(obj))