revert #12217 since the root problem seems to have been fixed; fix #1…

…5974;fix #12551; fix #19464

compiler/vmgen.nim

@@ -1382,9 +1382,6 @@ proc unneededIndirection(n: PNode): bool =
   n.typ.skipTypes(abstractInstOwned-{tyTypeDesc}).kind == tyRef
 
 proc canElimAddr(n: PNode): PNode =
-  if n[0].typ.skipTypes(abstractInst).kind in {tyObject, tyTuple, tyArray}:
-    # objects are reference types in the VM
-    return n[0]
   case n[0].kind
   of nkObjUpConv, nkObjDownConv, nkChckRange, nkChckRangeF, nkChckRange64:
     var m = n[0][0]

tests/vm/tmisc_vm.nim

@@ -17,6 +17,15 @@ foo4
 (a: 0, b: 0)
 (a: 0, b: 0)
 (a: 0, b: 0)
+z1 m: (lo: 12)
+z2 a: (lo: 3)
+x1 a: (lo: 3)
+x2 a: (lo: 6)
+x3 a: (lo: 0)
+z3 a: (lo: 3)
+x1 a: (lo: 3)
+x2 a: (lo: 6)
+x3 a: (lo: 0)
 '''
 """
 import std/sets
@@ -249,3 +258,114 @@ static:
   echo x2[]
   let x3 = new(ref MyObject) # cannot generate VM code for ref MyObject
   echo x3[]
+
+# bug #19464
+type
+  Wrapper = object
+    inner: int
+
+proc assign(r: var Wrapper, a: Wrapper) =
+  r = a
+
+proc myEcho(a: Wrapper) =
+  var tmp = a
+  assign(tmp, Wrapper(inner: 0)) # this shouldn't modify `a`
+  doAssert a.inner == 1
+
+static:
+  var result: Wrapper
+  assign(result, Wrapper(inner: 1))
+  myEcho(result)
+
+when true:
+  # bug #15974
+  type Foo = object
+    f0: int
+
+  proc fn(a: var Foo) =
+    var s: Foo
+    a = Foo(f0: 2)
+    s = a
+    doAssert s.f0 == 2
+    a = Foo(f0: 3)
+    doAssert s.f0 == 2
+
+  proc test2()=
+    var a = Foo(f0: 1)
+    fn(a)
+
+  static: test2()
+  test2()
+
+# bug #12551
+type
+  StUint = object
+    lo: uint64
+
+func `+=`(x: var Stuint, y: Stuint) =
+  x.lo += y.lo
+
+func `-`(x, y: Stuint): Stuint =
+  result.lo = x.lo - y.lo
+
+func `+`(x, y: Stuint): Stuint =
+  result.lo = x.lo + y.lo
+
+func `-=`(x: var Stuint, y: Stuint) =
+  x = x - y
+
+func `<`(x, y: Stuint): bool=
+  x.lo < y.lo
+
+func `==`(x, y: Stuint): bool =
+  x.lo == y.lo
+
+func `<=`(x, y: Stuint): bool =
+  x.lo <= y.lo
+
+proc div3n2n(r: var Stuint, b: Stuint) =
+  var d: Stuint
+  r = d
+  r += b
+
+func div2n1n(r: var Stuint, b: Stuint) =
+  div3n2n(r, b)
+
+func divmodBZ(x, y: Stuint, r: var Stuint)=
+  div2n1n(r, y)
+  r.lo = 3
+
+func `mod`(x, y: Stuint): Stuint =
+  divmodBZ(x, y, result)
+
+func doublemod_internal(a, m: Stuint): Stuint =
+  result = a
+  if a >= m - a:
+    result -= m
+  result += a
+
+func mulmod_internal(a, b, m: Stuint): Stuint =
+  var (a, b) = (a, b)
+  swap(a, b)
+  debugEcho "x1 a: ", a
+  a = doublemod_internal(a, m)
+  debugEcho "x2 a: ", a
+  a = doublemod_internal(a, m)
+  debugEcho "x3 a: ", a
+
+func powmod_internal(a, m: Stuint): Stuint =
+  var a = a
+  debugEcho "z1 m: ", m
+  debugEcho "z2 a: ", a
+  result = mulmod_internal(result, a, m)
+  debugEcho "z3 a: ", a
+  a = mulmod_internal(a, a, m)
+
+func powmod*(a, m: Stuint) =
+  discard powmod_internal(a mod m, m)
+
+static:
+  var x = Stuint(lo: high(uint64))
+  var y = Stuint(lo: 12)
+
+  powmod(x, y)