$b4147902 optional-chain-base-identifier.js:1:1
  Registers: 9
  Blocks:    3
  Constants:
    [0] = Int32(44)
    [1] = Undefined

block0:
  [   0] NewObject dst:reg5
  [  10] NewObject dst:reg6
  [  20] InitObjectLiteralProperty object:reg6, `b`, src:Int32(44), shape_cache_index:1, property_slot:0
  [  38] CacheObjectShape object:reg6
  [  48] InitObjectLiteralProperty object:reg5, `a`, src:reg6, shape_cache_index:0, property_slot:0
  [  60] CacheObjectShape object:reg5
  [  70] SetGlobal `obj`, src:reg5
  [  80] Mov dst:reg5, src:Undefined
  [  90] GetGlobal dst:reg7, `obj`
  [  a0] GetById dst:reg8, base:reg7, `a` (obj.a)
  [  b8] Mov2 dst1:reg5, src1:reg7, dst2:reg6, src2:reg8
  [  d0] JumpNullish condition:reg6, true_target:block1, false_target:block2

block1:
  [  e0] Mov dst:reg6, src:Undefined
  [  f0] End value:reg6

block2:
  [  f8] Mov dst:reg5, src:reg6
  [ 108] GetById dst:reg6, base:reg6, `b`
  [ 120] End value:reg6