Currently, aarch64 port does not make use of load/store pair instructions in the call_stub code to save space (or maybe improve performance):
StubRoutines::call_stub [0x0000007f7407a540, 0x0000007f7407a6b0[ (368 bytes)
  0x0000007f7407a540: stp	x29, x30, [sp,#-16]!
  0x0000007f7407a544: mov	x29, sp
  0x0000007f7407a548: sub	sp, x29, #0xd0
  0x0000007f7407a54c: str	x7, [x29,#-8]
  0x0000007f7407a550: str	w6, [x29,#-16]
  0x0000007f7407a554: str	x5, [x29,#-24]
  0x0000007f7407a558: str	x4, [x29,#-32]
  0x0000007f7407a55c: str	x3, [x29,#-40]
  0x0000007f7407a560: str	x2, [x29,#-48]
  0x0000007f7407a564: str	x1, [x29,#-56]
  0x0000007f7407a568: str	x0, [x29,#-64]
  0x0000007f7407a56c: str	x19, [x29,#-72]
  0x0000007f7407a570: str	x20, [x29,#-80]
  0x0000007f7407a574: str	x21, [x29,#-88]
  0x0000007f7407a578: str	x22, [x29,#-96]
  0x0000007f7407a57c: str	x23, [x29,#-104]
  0x0000007f7407a580: str	x24, [x29,#-112]
  0x0000007f7407a584: str	x25, [x29,#-120]
  0x0000007f7407a588: str	x26, [x29,#-128]
  0x0000007f7407a58c: str	x27, [x29,#-136]
  0x0000007f7407a590: str	x28, [x29,#-144]
  0x0000007f7407a594: str	d8, [x29,#-152]
  0x0000007f7407a598: str	d9, [x29,#-160]
  0x0000007f7407a59c: str	d10, [x29,#-168]
  0x0000007f7407a5a0: str	d11, [x29,#-176]
  0x0000007f7407a5a4: str	d12, [x29,#-184]
  0x0000007f7407a5a8: str	d13, [x29,#-192]
  0x0000007f7407a5ac: str	d14, [x29,#-200]
  0x0000007f7407a5b0: str	d15, [x29,#-208]
  ......
  0x0000007f7407a624: ldr	d15, [x29,#-208]
  0x0000007f7407a628: ldr	d14, [x29,#-200]
  0x0000007f7407a62c: ldr	d13, [x29,#-192]
  0x0000007f7407a630: ldr	d12, [x29,#-184]
  0x0000007f7407a634: ldr	d11, [x29,#-176]
  0x0000007f7407a638: ldr	d10, [x29,#-168]
  0x0000007f7407a63c: ldr	d9, [x29,#-160]
  0x0000007f7407a640: ldr	d8, [x29,#-152]
  0x0000007f7407a644: ldr	x28, [x29,#-144]
  0x0000007f7407a648: ldr	x27, [x29,#-136]
  0x0000007f7407a64c: ldr	x26, [x29,#-128]
  0x0000007f7407a650: ldr	x25, [x29,#-120]
  0x0000007f7407a654: ldr	x24, [x29,#-112]
  0x0000007f7407a658: ldr	x23, [x29,#-104]
  0x0000007f7407a65c: ldr	x22, [x29,#-96]
  0x0000007f7407a660: ldr	x21, [x29,#-88]
  0x0000007f7407a664: ldr	x20, [x29,#-80]
  0x0000007f7407a668: ldr	x19, [x29,#-72]
  0x0000007f7407a66c: ldr	x0, [x29,#-64]
  0x0000007f7407a670: ldr	x1, [x29,#-56]
  0x0000007f7407a674: ldr	w2, [x29,#-48]
  0x0000007f7407a678: ldr	x3, [x29,#-40]
  0x0000007f7407a67c: ldr	x4, [x29,#-32]
  0x0000007f7407a680: ldr	x5, [x29,#-24]
  0x0000007f7407a684: ldr	x6, [x29,#-16]
  0x0000007f7407a688: ldr	x7, [x29,#-8]


The above code stub can be optimized into the following code sequence saving 24 instructions:

StubRoutines::call_stub [0x0000007f8c07a540, 0x0000007f8c07a650[ (272 bytes)
  0x0000007f8c07a540: stp	x29, x30, [sp,#-16]!
  0x0000007f8c07a544: mov	x29, sp
  0x0000007f8c07a548: sub	sp, x29, #0xd0
  0x0000007f8c07a54c: str	x7, [x29,#-8]
  0x0000007f8c07a550: str	w6, [x29,#-16]
  0x0000007f8c07a554: stp	x4, x5, [x29,#-32]
  0x0000007f8c07a558: stp	x2, x3, [x29,#-48]
  0x0000007f8c07a55c: stp	x0, x1, [x29,#-64]
  0x0000007f8c07a560: stp	x20, x19, [x29,#-80]
  0x0000007f8c07a564: stp	x22, x21, [x29,#-96]
  0x0000007f8c07a568: stp	x24, x23, [x29,#-112]
  0x0000007f8c07a56c: stp	x26, x25, [x29,#-128]
  0x0000007f8c07a570: stp	x28, x27, [x29,#-144]
  0x0000007f8c07a574: stp	d9, d8, [x29,#-160]
  0x0000007f8c07a578: stp	d11, d10, [x29,#-176]
  0x0000007f8c07a57c: stp	d13, d12, [x29,#-192]
  0x0000007f8c07a580: stp	d15, d14, [x29,#-208]
  ......
  0x0000007f8c07a5f4: ldp	d15, d14, [x29,#-208]
  0x0000007f8c07a5f8: ldp	d13, d12, [x29,#-192]
  0x0000007f8c07a5fc: ldp	d11, d10, [x29,#-176]
  0x0000007f8c07a600: ldp	d9, d8, [x29,#-160]
  0x0000007f8c07a604: ldp	x28, x27, [x29,#-144]
  0x0000007f8c07a608: ldp	x26, x25, [x29,#-128]
  0x0000007f8c07a60c: ldp	x24, x23, [x29,#-112]
  0x0000007f8c07a610: ldp	x22, x21, [x29,#-96]
  0x0000007f8c07a614: ldp	x20, x19, [x29,#-80]
  0x0000007f8c07a618: ldp	x0, x1, [x29,#-64]
  0x0000007f8c07a61c: ldr	w2, [x29,#-48]
  0x0000007f8c07a620: ldr	x3, [x29,#-40]
  0x0000007f8c07a624: ldp	x4, x5, [x29,#-32]
  0x0000007f8c07a628: ldp	x6, x7, [x29,#-16]