这里一会lower16，一会upper16是在做什么？
__text:336BD7AE MOVW R1, #(:lower16:(selRef_alloc - 0x336BD7C4))
__text:336BD7B2 MOV R4, R0
__text:336BD7B4 MOVT.W R1, #(:upper16:(selRef_alloc - 0x336BD7C4))
__text:336BD7AC ; void __cdecl -[StoreSettingsController _showAccountSheetWithStyle:](struct StoreSettingsController *self, SEL, int)
__text:336BD7AC StoreSettingsController__showAccountSheetWithStyle
__text:336BD7AC ; DATA XREF: __objc_const:39DD4700o
__text:336BD7AC PUSH {R4-R7,LR}
__text:336BD7AE MOVW R1, #(:lower16:(selRef_alloc - 0x336BD7C4))
__text:336BD7B2 MOV R4, R0
__text:336BD7B4 MOVT.W R1, #(:upper16:(selRef_alloc - 0x336BD7C4))
__text:336BD7B8 MOV R0, #(classRef_SUAccountViewController - 0x336BD7C6)
__text:336BD7C0 ADD R1, PC ; selRef_alloc
__text:336BD7C2 ADD R0, PC ; classRef_SUAccountViewController
__text:336BD7C4 ADD R7, SP, #0xC
__text:336BD7C6 LDR R1, [R1] ; “alloc”
__text:336BD7C8 MOV R5, R2
__text:336BD7CA LDR R0, [R0] ; OBJC_CLASS$_SUAccountViewController
__text:336BD7CC BLX _objc_msgSend
__text:336BD7D0 MOV R1, #(selRef_init - 0x336BD7DC)
__text:336BD7D8 ADD R1, PC ; selRef_init
__text:336BD7DA LDR R1, [R1] ; “init”
__text:336BD7DC BLX _objc_msgSend
__text:336BD7E0 MOVW R1, #(:lower16:(selRef_sharedClient - 0x336BD7F6))
__text:336BD7E4 MOV R6, R0
__text:336BD7E6 MOVT.W R1, #(:upper16:(selRef_sharedClient - 0x336BD7F6))
__text:336BD7EA MOV R0, #(classRef_SUClient - 0x336BD7F8)
__text:336BD7F2 ADD R1, PC ; selRef_sharedClient
__text:336BD7F4 ADD R0, PC ; classRef_SUClient
__text:336BD7F6 LDR R1, [R1] ; “sharedClient”
__text:336BD7F8 LDR R0, [R0] ; OBJC_CLASS$_SUClient
__text:336BD7FA BLX _objc_msgSend
__text:336BD7FE MOV R1, #(selRef_clientInterface - 0x336BD80A)
__text:336BD806 ADD R1, PC ; selRef_clientInterface
__text:336BD808 LDR R1, [R1] ; “clientInterface”
__text:336BD80A BLX _objc_msgSend
__text:336BD80E MOV R2, R0
_text:336BD810 MOV R0, #(selRef_setClientInterface - 0x336BD81C)
_text:336BD818 ADD R0, PC ; selRef_setClientInterface
__text:336BD81A LDR R1, [R0] ; “setClientInterface:”
__text:336BD81C MOV R0, R6
__text:336BD81E BLX _objc_msgSend
_text:336BD822 MOVW R0, #(:lower16:(selRef_setStyle - 0x336BD830))
__text:336BD826 MOV R2, R5
_text:336BD828 MOVT.W R0, #(:upper16:(selRef_setStyle - 0x336BD830))
_text:336BD82C ADD R0, PC ; selRef_setStyle
__text:336BD82E LDR R1, [R0] ; “setStyle:”
__text:336BD830 MOV R0, R6
__text:336BD832 BLX _objc_msgSend
_text:336BD836 MOVW R0, #(:lower16:(selRef__showAccountSheetWithViewController_animated - 0x336BD846))
__text:336BD83A MOV R2, R6
_text:336BD83C MOVT.W R0, #(:upper16:(selRef__showAccountSheetWithViewController_animated - 0x336BD846))
__text:336BD840 MOVS R3, #1
_text:336BD842 ADD R0, PC ; selRef__showAccountSheetWithViewController_animated
__text:336BD844 LDR R1, [R0] ; “_showAccountSheetWithViewController:ani”…
__text:336BD846 MOV R0, R4
__text:336BD848 BLX _objc_msgSend
__text:336BD84C MOV R0, #(selRef_release - 0x336BD858)
__text:336BD854 ADD R0, PC ; selRef_release
__text:336BD856 LDR R1, [R0] ; “release”
__text:336BD858 MOV R0, R6
__text:336BD85A POP.W {R4-R7,LR}
__text:336BD85E B.W j__objc_msgSend
__text:336BD85E ; End of function -[StoreSettingsController _showAccountSheetWithStyle:]