NRVO does not occur with init procedures

[Astavie]

I've read that using result guarantees NRVO to take place, so I was hoping that in the example initX and initXInPlace would be equivalent, resulting in no copying of type X resulting in innerAddress and outerAddress staying the same
However it seems that doesn't happen, because test "NRVO1" fails while "NRVO2" succeeds

I added the filler field just to check if the object needed to be of a sufficient size, but no luck there either

Example

import unittest

type
  X = object
    filler: array[2048, int]
    innerAddress: uint

proc initX(): X =
  result.innerAddress = cast[uint](result.addr)

proc initXInPlace(x: var X) =
  x.innerAddress = cast[uint](x.addr)

test "NRVO1":
  var x = initX()
  let innerAddress = x.innerAddress
  let outerAddress = cast[uint](x.addr)
  check(innerAddress == outerAddress) # [FAILED]

test "NRVO2":
  var x: X
  initXInPlace(x)
  let innerAddress = x.innerAddress
  let outerAddress = cast[uint](x.addr)
  check(innerAddress == outerAddress) # [OK]

Current Output

innerAddress was 140730050675008
outerAddress was 94589955355680
[FAILED] NRVO1
[OK] NRVO2

Expected Output

[OK] NRVO1
[OK] NRVO2

Possible Solution

Additional Information

Tested on the latest stable and development releases. Also tested on version 1.2.0 and 1.4.0 of the compiler, which also have the same issue.

$ nim -v
Nim Compiler Version 1.7.1 [Linux: amd64]
Compiled at 2021-11-01
Copyright (c) 2006-2021 by Andreas Rumpf

git hash: 2f730afe9e7eb981258aea257deba0240f488dd1
active boot switches: -d:release

[arnetheduck]

type
  SomeType = object
    a, b, c, d: seq[byte]


proc xxxxxx(): SomeType =
  var res = SomeType(a: @[])
  res

debugEcho xxxxxx()

Simplified example I just ran into - this generates the following code which is .. quite bad (nim 1.2.14):

N_LIB_PRIVATE N_NIMCALL(void, xxxxxx__eBuu7pI70biYLIU048cjuw)(tyObject_SomeType__t9b4CnNFTxaAmAeIEYM69azg* Result) {
        tyObject_SomeType__t9b4CnNFTxaAmAeIEYM69azg res;
        nimfr_("xxxxxx", "/home/arnetheduck/status/nimbus-eth2/beacon_chain/testit.nim");
        nimln_(7, "/home/arnetheduck/status/nimbus-eth2/beacon_chain/testit.nim");
        nimZeroMem((void*)(&res), sizeof(tyObject_SomeType__t9b4CnNFTxaAmAeIEYM69azg));
        chckNil((void*)(&res));
        nimZeroMem((void*)(&res), sizeof(tyObject_SomeType__t9b4CnNFTxaAmAeIEYM69azg));
        res.a = NIM_NIL;
        genericSeqAssign((&(*Result).a), res.a, (&NTI__6H5Oh5UUvVCLiakt9aTwtUQ_));
        genericSeqAssign((&(*Result).b), res.b, (&NTI__6H5Oh5UUvVCLiakt9aTwtUQ_));
        genericSeqAssign((&(*Result).c), res.c, (&NTI__6H5Oh5UUvVCLiakt9aTwtUQ_));
        genericSeqAssign((&(*Result).d), res.d, (&NTI__6H5Oh5UUvVCLiakt9aTwtUQ_));
        popFrame();
}