Cleaned up CallbackSystem::run method

[vultix]

Just some small cleanup to make CallbackSystem::run have fewer branches and IMO simplify it a bit.

ASM before (160 lines):

bevy_eventlistener_core::callbacks::CallbackSystem::run:
 sub     sp, sp, #128
 stp     x29, x30, [sp, #112]
 add     x29, sp, #112
 str     x0, [sp, #8]
 str     x1, [sp, #16]
 sturb   wzr, [x29, #-17]
 sturb   wzr, [x29, #-18]
 bl      __ZN23bevy_eventlistener_core9callbacks14CallbackSystem14is_initialized17hde01dbcc5bb54d25E
 tbz     w0, #0, LBB22_2
 b       LBB22_1
LBB22_1:
 ldr     x8, [sp, #8]
 ldr     x8, [x8]
 subs    x8, x8, #2
 cset    w8, eq
 tbnz    w8, #0, LBB22_24
 b       LBB22_25
LBB22_2:
 ldr     x0, [sp, #8]
 mov     w8, #1
 sturb   w8, [x29, #-18]
 add     x1, sp, #24
 str     xzr, [sp, #24]
 bl      __ZN4core3mem4swap17h9768ad68f6db01b6E
 b       LBB22_5
LBB22_3:
 ldr     x8, [sp, #24]
 subs    x8, x8, #1
 cset    w8, eq
 tbnz    w8, #0, LBB22_16
 b       LBB22_17
LBB22_4:
 stur    x0, [x29, #-16]
 mov     x8, x1
 stur    w8, [x29, #-8]
 b       LBB22_3
LBB22_5:
 ldr     x8, [sp, #24]
 subs    x8, x8, #1
 cset    w8, ne
 tbnz    w8, #0, LBB22_7
 b       LBB22_6
LBB22_6:
 ldr     x1, [sp, #16]
 sturb   wzr, [x29, #-18]
 mov     w8, #1
 sturb   w8, [x29, #-17]
 ldr     x9, [sp, #32]
 ldr     x8, [sp, #40]
 str     x9, [sp, #48]
 str     x8, [sp, #56]
 ldr     x0, [sp, #48]
 ldr     x8, [sp, #56]
 ldr     x8, [x8, #104]
 blr     x8
 b       LBB22_10
LBB22_7:
 ldr     x8, [sp, #24]
 subs    x8, x8, #1
 cset    w8, eq
 tbnz    w8, #0, LBB22_20
 b       LBB22_21
LBB22_8:
 ldurb   w8, [x29, #-17]
 tbnz    w8, #0, LBB22_14
 b       LBB22_3
LBB22_9:
 stur    x0, [x29, #-16]
 mov     x8, x1
 stur    w8, [x29, #-8]
 b       LBB22_8
LBB22_10:
 ldr     x0, [sp, #8]
 sturb   wzr, [x29, #-17]
 ldr     x9, [sp, #48]
 ldr     x8, [sp, #56]
 stur    x9, [x29, #-40]
 stur    x8, [x29, #-32]
 mov     w8, #2
 stur    x8, [x29, #-48]
 bl      __ZN4core3ptr71drop_in_place$LT$bevy_eventlistener_core..callbacks..CallbackSystem$GT$17h72d559a889af9b7cE
 b       LBB22_13
LBB22_11:
 ldr     x9, [sp, #8]
 ldur    q0, [x29, #-48]
 str     q0, [x9]
 ldur    x8, [x29, #-32]
 str     x8, [x9, #16]
 b       LBB22_8
LBB22_12:
 stur    x0, [x29, #-16]
 mov     x8, x1
 stur    w8, [x29, #-8]
 b       LBB22_11
LBB22_13:
 ldr     x9, [sp, #8]
 ldur    q0, [x29, #-48]
 str     q0, [x9]
 ldur    x8, [x29, #-32]
 str     x8, [x9, #16]
 sturb   wzr, [x29, #-17]
 b       LBB22_7
LBB22_14:
 add     x0, sp, #48
 bl      __ZN4core3ptr147drop_in_place$LT$alloc..boxed..Box$LT$dyn$u20$bevy_ecs..system..system..System$u2b$Out$u20$$u3d$$u20$$LP$$RP$$u2b$In$u20$$u3d$$u20$$LP$$RP$$GT$$GT$17hbc1ade13abce4d42E
 b       LBB22_3
LBB22_15:
 bl      __ZN4core9panicking19panic_cannot_unwind17h911ff5cd61f62d63E
LBB22_16:
 ldurb   w8, [x29, #-18]
 tbnz    w8, #0, LBB22_19
 b       LBB22_18
LBB22_17:
 add     x0, sp, #24
 bl      __ZN4core3ptr71drop_in_place$LT$bevy_eventlistener_core..callbacks..CallbackSystem$GT$17h72d559a889af9b7cE
 b       LBB22_18
LBB22_18:
 ldur    x0, [x29, #-16]
 bl      __Unwind_Resume
LBB22_19:
 add     x8, sp, #24
 add     x0, x8, #8
 bl      __ZN4core3ptr147drop_in_place$LT$alloc..boxed..Box$LT$dyn$u20$bevy_ecs..system..system..System$u2b$Out$u20$$u3d$$u20$$LP$$RP$$u2b$In$u20$$u3d$$u20$$LP$$RP$$GT$$GT$17hbc1ade13abce4d42E
 b       LBB22_18
LBB22_20:
 ldurb   w8, [x29, #-18]
 tbnz    w8, #0, LBB22_23
 b       LBB22_22
LBB22_21:
 add     x0, sp, #24
 bl      __ZN4core3ptr71drop_in_place$LT$bevy_eventlistener_core..callbacks..CallbackSystem$GT$17h72d559a889af9b7cE
 b       LBB22_22
LBB22_22:
 sturb   wzr, [x29, #-18]
 b       LBB22_1
LBB22_23:
 add     x8, sp, #24
 add     x0, x8, #8
 bl      __ZN4core3ptr147drop_in_place$LT$alloc..boxed..Box$LT$dyn$u20$bevy_ecs..system..system..System$u2b$Out$u20$$u3d$$u20$$LP$$RP$$u2b$In$u20$$u3d$$u20$$LP$$RP$$GT$$GT$17hbc1ade13abce4d42E
 b       LBB22_22
LBB22_24:
 ldr     x1, [sp, #16]
 ldr     x8, [sp, #8]
 ldr     x0, [x8, #8]
 ldr     x8, [x8, #16]
 ldr     x8, [x8, #88]
 blr     x8
 ldr     x8, [sp, #8]
 ldr     x1, [sp, #16]
 ldr     x0, [x8, #8]
 ldr     x8, [x8, #16]
 ldr     x8, [x8, #96]
 blr     x8
 b       LBB22_25
LBB22_25:
 ldp     x29, x30, [sp, #112]
 add     sp, sp, #128
 ret

ASM after (130 lines):

bevy_eventlistener_core::callbacks::CallbackSystem::run:
 sub     sp, sp, #144
 stp     x29, x30, [sp, #128]
 add     x29, sp, #128
 str     x0, [sp]
 str     x1, [sp, #8]
 sturb   wzr, [x29, #-17]
 add     x8, sp, #40
 bl      __ZN4core3mem4take17hd9ecf489a6ec01b4E
 ldr     x8, [sp, #40]
 str     x8, [sp, #16]
 subs    x8, x8, #0
 cset    w8, eq
 tbnz    w8, #0, LBB19_4
 b       LBB19_1
LBB19_1:
 ldr     x8, [sp, #16]
 subs    x8, x8, #1
 cset    w8, eq
 tbnz    w8, #0, LBB19_5
 b       LBB19_2
LBB19_2:
 b       LBB19_6
LBB19_4:
 sturb   wzr, [x29, #-17]
 b       LBB19_21
LBB19_5:
 ldr     x1, [sp, #8]
 ldr     x9, [sp, #48]
 ldr     x8, [sp, #56]
 str     x9, [sp, #64]
 str     x8, [sp, #72]
 ldr     x0, [sp, #64]
 ldr     x8, [sp, #72]
 ldr     x8, [x8, #104]
 blr     x8
 b       LBB19_10
LBB19_6:
 ldr     x9, [sp, #48]
 ldr     x8, [sp, #56]
 mov     w10, #1
 sturb   w10, [x29, #-17]
 str     x9, [sp, #24]
 str     x8, [sp, #32]
 b       LBB19_7
LBB19_7:
 ldr     x1, [sp, #8]
 ldr     x0, [sp, #24]
 ldr     x8, [sp, #32]
 ldr     x8, [x8, #88]
 blr     x8
 b       LBB19_15
LBB19_8:
 add     x0, sp, #64
 bl      __ZN4core3ptr147drop_in_place$LT$alloc..boxed..Box$LT$dyn$u20$bevy_ecs..system..system..System$u2b$Out$u20$$u3d$$u20$$LP$$RP$$u2b$In$u20$$u3d$$u20$$LP$$RP$$GT$$GT$17hbc1ade13abce4d42E
 b       LBB19_12
LBB19_9:
 stur    x0, [x29, #-16]
 mov     x8, x1
 stur    w8, [x29, #-8]
 b       LBB19_8
LBB19_10:
 mov     w8, #1
 sturb   w8, [x29, #-17]
 ldr     x9, [sp, #64]
 ldr     x8, [sp, #72]
 str     x9, [sp, #24]
 str     x8, [sp, #32]
 b       LBB19_7
LBB19_11:
 bl      __ZN4core9panicking19panic_cannot_unwind17h911ff5cd61f62d63E
LBB19_12:
 ldur    x0, [x29, #-16]
 bl      __Unwind_Resume
LBB19_13:
 ldurb   w8, [x29, #-17]
 tbnz    w8, #0, LBB19_20
 b       LBB19_12
LBB19_14:
 stur    x0, [x29, #-16]
 mov     x8, x1
 stur    w8, [x29, #-8]
 b       LBB19_13
LBB19_15:
 ldr     x1, [sp, #8]
 ldr     x0, [sp, #24]
 ldr     x8, [sp, #32]
 ldr     x8, [x8, #96]
 blr     x8
 b       LBB19_16
LBB19_16:
 ldr     x0, [sp]
 sturb   wzr, [x29, #-17]
 ldr     x9, [sp, #24]
 ldr     x8, [sp, #32]
 stur    x9, [x29, #-40]
 stur    x8, [x29, #-32]
 mov     w8, #2
 stur    x8, [x29, #-48]
 bl      __ZN4core3ptr71drop_in_place$LT$bevy_eventlistener_core..callbacks..CallbackSystem$GT$17h72d559a889af9b7cE
 b       LBB19_19
LBB19_17:
 ldr     x9, [sp]
 ldur    q0, [x29, #-48]
 str     q0, [x9]
 ldur    x8, [x29, #-32]
 str     x8, [x9, #16]
 b       LBB19_13
LBB19_18:
 stur    x0, [x29, #-16]
 mov     x8, x1
 stur    w8, [x29, #-8]
 b       LBB19_17
LBB19_19:
 ldr     x9, [sp]
 ldur    q0, [x29, #-48]
 str     q0, [x9]
 ldur    x8, [x29, #-32]
 str     x8, [x9, #16]
 sturb   wzr, [x29, #-17]
 b       LBB19_21
LBB19_20:
 add     x0, sp, #24
 bl      __ZN4core3ptr147drop_in_place$LT$alloc..boxed..Box$LT$dyn$u20$bevy_ecs..system..system..System$u2b$Out$u20$$u3d$$u20$$LP$$RP$$u2b$In$u20$$u3d$$u20$$LP$$RP$$GT$$GT$17hbc1ade13abce4d42E
 b       LBB19_12
LBB19_21:
 ldp     x29, x30, [sp, #128]
 add     sp, sp, #144
 ret

[aevyrie]

Thanks!