fix nim-lang#16185

Clyybber · Jan 18, 2021 · c7db08d · c7db08d
1 parent 44ceefa
commit c7db08d
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Showing 2 changed files with 106 additions and 58 deletions.
diff --git a/compiler/injectdestructors.nim b/compiler/injectdestructors.nim
@@ -969,67 +969,68 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode): PNode =
       internalError(c.graph.config, n.info, "cannot inject destructors to node kind: " & $n.kind)
 
 proc moveOrCopy(dest, ri: PNode; c: var Con; s: var Scope, isDecl = false): PNode =
-  case ri.kind
-  of nkCallKinds:
-    result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
-  of nkBracketExpr:
-    if isUnpackedTuple(ri[0]):
-      # unpacking of tuple: take over the elements
+  if exprStructuralEquivalent(dest, ri, strictSymEquality = true):
+    # rule (self-assignment-removal):
+    result = newNodeI(nkEmpty, dest.info)
+  else:
+    case ri.kind
+    of nkCallKinds:
       result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
-    elif isAnalysableFieldAccess(ri, c.owner) and isLastRead(ri, c) and
-        not aliases(dest, ri):
-      # Rule 3: `=sink`(x, z); wasMoved(z)
-      var snk = c.genSink(dest, ri, isDecl)
-      result = newTree(nkStmtList, snk, c.genWasMoved(ri))
-    else:
-      result = c.genCopy(dest, ri)
-      result.add p(ri, c, s, consumed)
-      c.finishCopy(result, dest, isFromSink = false)
-  of nkBracket:
-    # array constructor
-    if ri.len > 0 and isDangerousSeq(ri.typ):
-      result = c.genCopy(dest, ri)
-      result.add p(ri, c, s, consumed)
-      c.finishCopy(result, dest, isFromSink = false)
-    else:
+    of nkBracketExpr:
+      if isUnpackedTuple(ri[0]):
+        # unpacking of tuple: take over the elements
+        result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
+      elif isAnalysableFieldAccess(ri, c.owner) and isLastRead(ri, c) and
+          not aliases(dest, ri):
+        # Rule 3: `=sink`(x, z); wasMoved(z)
+        var snk = c.genSink(dest, ri, isDecl)
+        result = newTree(nkStmtList, snk, c.genWasMoved(ri))
+      else:
+        result = c.genCopy(dest, ri)
+        result.add p(ri, c, s, consumed)
+        c.finishCopy(result, dest, isFromSink = false)
+    of nkBracket:
+      # array constructor
+      if ri.len > 0 and isDangerousSeq(ri.typ):
+        result = c.genCopy(dest, ri)
+        result.add p(ri, c, s, consumed)
+        c.finishCopy(result, dest, isFromSink = false)
+      else:
+        result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
+    of nkObjConstr, nkTupleConstr, nkClosure, nkCharLit..nkNilLit:
       result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
-  of nkObjConstr, nkTupleConstr, nkClosure, nkCharLit..nkNilLit:
-    result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
-  of nkSym:
-    if dest.kind == nkSym and dest.sym == ri.sym:
-      # rule (self-assignment-removal):
-      result = newNodeI(nkEmpty, dest.info)
-    elif isSinkParam(ri.sym) and isLastRead(ri, c):
-      # Rule 3: `=sink`(x, z); wasMoved(z)
-      let snk = c.genSink(dest, ri, isDecl)
-      result = newTree(nkStmtList, snk, c.genWasMoved(ri))
-    elif ri.sym.kind != skParam and ri.sym.owner == c.owner and
-        isLastRead(ri, c) and canBeMoved(c, dest.typ) and not isCursor(ri, c):
-      # Rule 3: `=sink`(x, z); wasMoved(z)
-      let snk = c.genSink(dest, ri, isDecl)
-      result = newTree(nkStmtList, snk, c.genWasMoved(ri))
-    else:
-      result = c.genCopy(dest, ri)
-      result.add p(ri, c, s, consumed)
-      c.finishCopy(result, dest, isFromSink = false)
-  of nkHiddenSubConv, nkHiddenStdConv, nkConv, nkObjDownConv, nkObjUpConv:
-    result = c.genSink(dest, p(ri, c, s, sinkArg), isDecl)
-  of nkStmtListExpr, nkBlockExpr, nkIfExpr, nkCaseStmt, nkTryStmt:
-    template process(child, s): untyped = moveOrCopy(dest, child, c, s, isDecl)
-    # We know the result will be a stmt so we use that fact to optimize
-    handleNestedTempl(ri, process, willProduceStmt = true)
-  of nkRaiseStmt:
-    result = pRaiseStmt(ri, c, s)
-  else:
-    if isAnalysableFieldAccess(ri, c.owner) and isLastRead(ri, c) and
-        canBeMoved(c, dest.typ):
-      # Rule 3: `=sink`(x, z); wasMoved(z)
-      let snk = c.genSink(dest, ri, isDecl)
-      result = newTree(nkStmtList, snk, c.genWasMoved(ri))
+    of nkSym:    
+      if isSinkParam(ri.sym) and isLastRead(ri, c):
+        # Rule 3: `=sink`(x, z); wasMoved(z)
+        let snk = c.genSink(dest, ri, isDecl)
+        result = newTree(nkStmtList, snk, c.genWasMoved(ri))
+      elif ri.sym.kind != skParam and ri.sym.owner == c.owner and
+          isLastRead(ri, c) and canBeMoved(c, dest.typ) and not isCursor(ri, c):
+        # Rule 3: `=sink`(x, z); wasMoved(z)
+        let snk = c.genSink(dest, ri, isDecl)
+        result = newTree(nkStmtList, snk, c.genWasMoved(ri))
+      else:
+        result = c.genCopy(dest, ri)
+        result.add p(ri, c, s, consumed)
+        c.finishCopy(result, dest, isFromSink = false)
+    of nkHiddenSubConv, nkHiddenStdConv, nkConv, nkObjDownConv, nkObjUpConv:
+      result = c.genSink(dest, p(ri, c, s, sinkArg), isDecl)
+    of nkStmtListExpr, nkBlockExpr, nkIfExpr, nkCaseStmt, nkTryStmt:
+      template process(child, s): untyped = moveOrCopy(dest, child, c, s, isDecl)
+      # We know the result will be a stmt so we use that fact to optimize
+      handleNestedTempl(ri, process, willProduceStmt = true)
+    of nkRaiseStmt:
+      result = pRaiseStmt(ri, c, s)
     else:
-      result = c.genCopy(dest, ri)
-      result.add p(ri, c, s, consumed)
-      c.finishCopy(result, dest, isFromSink = false)
+      if isAnalysableFieldAccess(ri, c.owner) and isLastRead(ri, c) and
+          canBeMoved(c, dest.typ):
+        # Rule 3: `=sink`(x, z); wasMoved(z)
+        let snk = c.genSink(dest, ri, isDecl)
+        result = newTree(nkStmtList, snk, c.genWasMoved(ri))
+      else:
+        result = c.genCopy(dest, ri)
+        result.add p(ri, c, s, consumed)
+        c.finishCopy(result, dest, isFromSink = false)
 
 proc computeUninit(c: var Con) =
   if not c.uninitComputed:

diff --git a/tests/arc/t14383.nim b/tests/arc/t14383.nim
@@ -168,3 +168,50 @@ proc testRefs() =
 testRefs()
 
 doAssert(dDestroyed == 2)
+
+
+#------------------------------------------------------------------------------
+# Issue #16185, complex self-assingment elimination
+#------------------------------------------------------------------------------
+
+type
+  CpuStorage*[T] = ref CpuStorageObj[T]
+  CpuStorageObj[T] = object
+    size*: int
+    raw_buffer*: ptr UncheckedArray[T]
+  Tensor[T] = object
+    buf*: CpuStorage[T]
+  TestObject = object
+    x: Tensor[float]
+
+proc `=destroy`[T](s: var CpuStorageObj[T]) =
+  if s.raw_buffer != nil:
+    s.raw_buffer.deallocShared()
+    s.size = 0
+    s.raw_buffer = nil
+
+proc `=`[T](a: var CpuStorageObj[T]; b: CpuStorageObj[T]) {.error.}
+
+proc allocCpuStorage[T](s: var CpuStorage[T], size: int) =
+  new(s)
+  s.raw_buffer = cast[ptr UncheckedArray[T]](allocShared0(sizeof(T) * size))
+  s.size = size
+
+proc newTensor[T](size: int): Tensor[T] =
+  allocCpuStorage(result.buf, size)
+
+proc `[]`[T](t: Tensor[T], idx: int): T = t.buf.raw_buffer[idx]
+proc `[]=`[T](t: Tensor[T], idx: int, val: T) = t.buf.raw_buffer[idx] = val
+
+proc toTensor[T](s: seq[T]): Tensor[T] =
+  result = newTensor[T](s.len)
+  for i, x in s:
+    result[i] = x
+
+proc main() =
+  var t: TestObject
+  t.x = toTensor(@[1.0, 2, 3, 4])
+  t.x = t.x  
+  doAssert(t.x.buf != nil) # self-assignment above should be eliminated
+
+main()