Setting inferred volatile on symbol affected by address-of main::pscreen = &main::screen

CONTROL FLOW GRAPH SSA

void main()
main: scope:[main]  from __start
  main::screen = (byte*)$400
  sub::ch#0 = 'a'
  sub::dst#0 = main::pscreen
  call sub 
  to:main::@1
main::@1: scope:[main]  from main
  sub::ch#1 = 'b'
  sub::dst#1 = main::pscreen
  call sub 
  to:main::@2
main::@2: scope:[main]  from main::@1
  to:main::@return
main::@return: scope:[main]  from main::@2
  return 
  to:@return

void sub(byte sub::ch , byte** sub::dst)
sub: scope:[sub]  from main main::@1
  sub::dst#2 = phi( main/sub::dst#0, main::@1/sub::dst#1 )
  sub::ch#2 = phi( main/sub::ch#0, main::@1/sub::ch#1 )
  *(*sub::dst#2) = sub::ch#2
  *sub::dst#2 = ++ *sub::dst#2
  to:sub::@return
sub::@return: scope:[sub]  from sub
  return 
  to:@return

void __start()
__start: scope:[__start]  from
  call main 
  to:__start::@1
__start::@1: scope:[__start]  from __start
  to:__start::@return
__start::@return: scope:[__start]  from __start::@1
  return 
  to:@return

SYMBOL TABLE SSA
void __start()
void main()
const byte** main::pscreen = &main::screen
volatile byte* main::screen loadstore
void sub(byte sub::ch , byte** sub::dst)
byte sub::ch
byte sub::ch#0
byte sub::ch#1
byte sub::ch#2
byte** sub::dst
byte** sub::dst#0
byte** sub::dst#1
byte** sub::dst#2

Simplifying constant pointer cast (byte*) 1024
Successful SSA optimization PassNCastSimplification
Constant sub::ch#0 = 'a'
Constant sub::dst#0 = main::pscreen
Constant sub::ch#1 = 'b'
Constant sub::dst#1 = main::pscreen
Successful SSA optimization Pass2ConstantIdentification
Removing unused procedure __start
Removing unused procedure block __start
Removing unused procedure block __start::@1
Removing unused procedure block __start::@return
Successful SSA optimization PassNEliminateEmptyStart
Inlining constant with var siblings sub::ch#0
Inlining constant with var siblings sub::dst#0
Inlining constant with var siblings sub::ch#1
Inlining constant with var siblings sub::dst#1
Constant inlined sub::ch#1 = 'b'
Constant inlined sub::ch#0 = 'a'
Constant inlined sub::dst#1 = main::pscreen
Constant inlined sub::dst#0 = main::pscreen
Successful SSA optimization Pass2ConstantInlining
Identical Phi Values sub::dst#2 main::pscreen
Successful SSA optimization Pass2IdenticalPhiElimination
Adding NOP phi() at start of main::@1
Adding NOP phi() at start of main::@2
CALL GRAPH
Calls in [main] to sub:1 sub:3 

Created 1 initial phi equivalence classes
Coalesced down to 1 phi equivalence classes
Culled Empty Block label main::@2
Adding NOP phi() at start of main::@1

FINAL CONTROL FLOW GRAPH

void main()
main: scope:[main]  from
  [0] main::screen = (byte*) 1024
  [1] call sub 
  to:main::@1
main::@1: scope:[main]  from main
  [2] phi()
  [3] call sub 
  to:main::@return
main::@return: scope:[main]  from main::@1
  [4] return 
  to:@return

void sub(byte sub::ch , byte** sub::dst)
sub: scope:[sub]  from main main::@1
  [5] sub::ch#2 = phi( main/'a', main::@1/'b' )
  [6] *(*main::pscreen) = sub::ch#2
  [7] *main::pscreen = ++ *main::pscreen
  to:sub::@return
sub::@return: scope:[sub]  from sub
  [8] return 
  to:@return


VARIABLE REGISTER WEIGHTS
void main()
volatile byte* main::screen loadstore 20.0
void sub(byte sub::ch , byte** sub::dst)
byte sub::ch
byte sub::ch#2 11.0
byte** sub::dst

Initial phi equivalence classes
[ sub::ch#2 ]
Added variable main::screen to live range equivalence class [ main::screen ]
Complete equivalence classes
[ sub::ch#2 ]
[ main::screen ]
Allocated zp[1]:2 [ sub::ch#2 ]
Allocated zp[2]:3 [ main::screen ]
REGISTER UPLIFT POTENTIAL REGISTERS
Statement [0] main::screen = (byte*) 1024 [ ] (  [ ] { }  ) always clobbers reg byte a 
Statement [6] *(*main::pscreen) = sub::ch#2 [ ] ( sub:1 [ ] { }  sub:3 [ ] { }  ) always clobbers reg byte y 
Potential registers zp[1]:2 [ sub::ch#2 ] : zp[1]:2 , reg byte a , reg byte x , reg byte y , 
Potential registers zp[2]:3 [ main::screen ] : zp[2]:3 , 

REGISTER UPLIFT SCOPES
Uplift Scope [main] 20: zp[2]:3 [ main::screen ] 
Uplift Scope [sub] 11: zp[1]:2 [ sub::ch#2 ] 
Uplift Scope [] 

Uplifting [main] best 88 combination zp[2]:3 [ main::screen ] 
Uplifting [sub] best 79 combination reg byte a [ sub::ch#2 ] 
Uplifting [] best 79 combination 
Allocated (was zp[2]:3) zp[2]:2 [ main::screen ]

ASSEMBLER BEFORE OPTIMIZATION
  // File Comments
// Tests optimization of constant pointers to pointers
  // Upstart
  // Commodore 64 PRG executable file
.file [name="ptrptr-optimize-1.prg", type="prg", segments="Program"]
.segmentdef Program [segments="Basic, Code, Data"]
.segmentdef Basic [start=$0801]
.segmentdef Code [start=$80d]
.segmentdef Data [startAfter="Code"]
.segment Basic
:BasicUpstart(main)
  // Global Constants & labels
.segment Code
  // main
main: {
    .label pscreen = screen
    .label screen = 2
    // [0] main::screen = (byte*) 1024 -- pbuz1=pbuc1 
    lda #<$400
    sta.z screen
    lda #>$400
    sta.z screen+1
    // [1] call sub 
    // [5] phi from main to sub [phi:main->sub]
  sub_from_main:
    // [5] phi sub::ch#2 = 'a' [phi:main->sub#0] -- vbuaa=vbuc1 
    lda #'a'
    jsr sub
    // [2] phi from main to main::@1 [phi:main->main::@1]
  __b1_from_main:
    jmp __b1
    // main::@1
  __b1:
    // [3] call sub 
    // [5] phi from main::@1 to sub [phi:main::@1->sub]
  sub_from___b1:
    // [5] phi sub::ch#2 = 'b' [phi:main::@1->sub#0] -- vbuaa=vbuc1 
    lda #'b'
    jsr sub
    jmp __breturn
    // main::@return
  __breturn:
    // [4] return 
    rts
}
  // sub
// sub(byte register(A) ch)
sub: {
    // [6] *(*main::pscreen) = sub::ch#2 -- _deref_(_deref_qbuc1)=vbuaa 
    ldy.z main.pscreen
    sty.z $fe
    ldy.z main.pscreen+1
    sty.z $ff
    ldy #0
    sta ($fe),y
    // [7] *main::pscreen = ++ *main::pscreen -- _deref_qbuc1=_inc__deref_qbuc1 
    inc.z main.pscreen
    bne !+
    inc.z main.pscreen+1
  !:
    jmp __breturn
    // sub::@return
  __breturn:
    // [8] return 
    rts
}
  // File Data

ASSEMBLER OPTIMIZATIONS
Removing instruction jmp __b1
Removing instruction jmp __breturn
Removing instruction jmp __breturn
Succesful ASM optimization Pass5NextJumpElimination
Removing instruction __b1_from_main:
Removing instruction sub_from___b1:
Succesful ASM optimization Pass5RedundantLabelElimination
Removing instruction sub_from_main:
Removing instruction __b1:
Removing instruction __breturn:
Removing instruction __breturn:
Succesful ASM optimization Pass5UnusedLabelElimination

FINAL SYMBOL TABLE
void main()
const byte** main::pscreen = &main::screen
volatile byte* main::screen loadstore zp[2]:2 20.0
void sub(byte sub::ch , byte** sub::dst)
byte sub::ch
byte sub::ch#2 reg byte a 11.0
byte** sub::dst

reg byte a [ sub::ch#2 ]
zp[2]:2 [ main::screen ]


FINAL ASSEMBLER
Score: 70

  // File Comments
// Tests optimization of constant pointers to pointers
  // Upstart
  // Commodore 64 PRG executable file
.file [name="ptrptr-optimize-1.prg", type="prg", segments="Program"]
.segmentdef Program [segments="Basic, Code, Data"]
.segmentdef Basic [start=$0801]
.segmentdef Code [start=$80d]
.segmentdef Data [startAfter="Code"]
.segment Basic
:BasicUpstart(main)
  // Global Constants & labels
.segment Code
  // main
main: {
    .label pscreen = screen
    .label screen = 2
    // screen = 0x400
    // [0] main::screen = (byte*) 1024 -- pbuz1=pbuc1 
    lda #<$400
    sta.z screen
    lda #>$400
    sta.z screen+1
    // sub('a',pscreen)
    // [1] call sub 
    // [5] phi from main to sub [phi:main->sub]
    // [5] phi sub::ch#2 = 'a' [phi:main->sub#0] -- vbuaa=vbuc1 
    lda #'a'
    jsr sub
    // [2] phi from main to main::@1 [phi:main->main::@1]
    // main::@1
    // sub('b',pscreen)
    // [3] call sub 
    // [5] phi from main::@1 to sub [phi:main::@1->sub]
    // [5] phi sub::ch#2 = 'b' [phi:main::@1->sub#0] -- vbuaa=vbuc1 
    lda #'b'
    jsr sub
    // main::@return
    // }
    // [4] return 
    rts
}
  // sub
// sub(byte register(A) ch)
sub: {
    // *(*dst)++ = ch
    // [6] *(*main::pscreen) = sub::ch#2 -- _deref_(_deref_qbuc1)=vbuaa 
    ldy.z main.pscreen
    sty.z $fe
    ldy.z main.pscreen+1
    sty.z $ff
    ldy #0
    sta ($fe),y
    // *(*dst)++ = ch;
    // [7] *main::pscreen = ++ *main::pscreen -- _deref_qbuc1=_inc__deref_qbuc1 
    inc.z main.pscreen
    bne !+
    inc.z main.pscreen+1
  !:
    // sub::@return
    // }
    // [8] return 
    rts
}
  // File Data