
CONTROL FLOW GRAPH SSA

void main()
main: scope:[main]  from __start
  get::ptr#0 = main::SCREEN
  call get
  get::return#0 = get::return#4
  to:main::@1
main::@1: scope:[main]  from main
  get::return#5 = phi( main/get::return#0 )
  main::$0 = get::return#5
  main::SCREEN[1] = main::$0
  get::ptr#1 = 0
  call get
  get::return#1 = get::return#4
  to:main::@2
main::@2: scope:[main]  from main::@1
  get::return#6 = phi( main::@1/get::return#1 )
  main::$1 = get::return#6
  main::SCREEN[0] = main::$1
  to:main::@return
main::@return: scope:[main]  from main::@2
  return 
  to:@return

char get(char *ptr)
get: scope:[get]  from main main::@1
  get::ptr#2 = phi( main/get::ptr#0, main::@1/get::ptr#1 )
  get::$0 = 0 == get::ptr#2
  get::$1 = ! get::$0
  if(get::$1) goto get::@1
  to:get::@2
get::@1: scope:[get]  from get
  get::ptr#3 = phi( get/get::ptr#2 )
  get::return#2 = *get::ptr#3
  to:get::@return
get::@2: scope:[get]  from get
  get::return#3 = 0
  to:get::@return
get::@return: scope:[get]  from get::@1 get::@2
  get::return#7 = phi( get::@1/get::return#2, get::@2/get::return#3 )
  get::return#4 = get::return#7
  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()
char get(char *ptr)
bool get::$0
bool get::$1
char *get::ptr
char *get::ptr#0
char *get::ptr#1
char *get::ptr#2
char *get::ptr#3
char get::return
char get::return#0
char get::return#1
char get::return#2
char get::return#3
char get::return#4
char get::return#5
char get::return#6
char get::return#7
void main()
char main::$0
char main::$1
__constant char *main::SCREEN = (char *)$400

Adding number conversion cast (unumber) 1 in main::SCREEN[1] = main::$0
Adding number conversion cast (unumber) 0 in get::ptr#1 = 0
Adding number conversion cast (unumber) 0 in main::SCREEN[0] = main::$1
Adding number conversion cast (unumber) 0 in get::$0 = 0 == get::ptr#2
Adding number conversion cast (unumber) 0 in get::return#3 = 0
Successful SSA optimization PassNAddNumberTypeConversions
Inlining cast get::ptr#1 = (unumber)0
Inlining cast get::return#3 = (unumber)0
Successful SSA optimization Pass2InlineCast
Simplifying constant pointer cast (char *) 1024
Simplifying constant integer cast 1
Simplifying constant integer cast 0
Simplifying constant integer cast 0
Simplifying constant integer cast 0
Simplifying constant integer cast 0
Successful SSA optimization PassNCastSimplification
Finalized unsigned number type (char) 1
Finalized unsigned number type (char) 0
Finalized unsigned number type (char) 0
Finalized unsigned number type (char) 0
Finalized unsigned number type (char) 0
Successful SSA optimization PassNFinalizeNumberTypeConversions
Inversing boolean not [15] get::$1 = 0 != get::ptr#2 from [14] get::$0 = 0 == get::ptr#2
Successful SSA optimization Pass2UnaryNotSimplification
Alias get::return#0 = get::return#5 
Alias get::return#1 = get::return#6 
Alias get::ptr#2 = get::ptr#3 
Alias get::return#4 = get::return#7 
Successful SSA optimization Pass2AliasElimination
Simple Condition get::$1 [13] if(0!=get::ptr#2) goto get::@1
Successful SSA optimization Pass2ConditionalJumpSimplification
Constant get::ptr#0 = main::SCREEN
Constant get::ptr#1 = 0
Constant get::return#3 = 0
Successful SSA optimization Pass2ConstantIdentification
Simplifying expression containing zero main::SCREEN in [9] main::SCREEN[0] = main::$1
Successful SSA optimization PassNSimplifyExpressionWithZero
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 get::ptr#0
Inlining constant with var siblings get::ptr#1
Inlining constant with var siblings get::return#3
Constant inlined get::ptr#1 = 0
Constant inlined get::return#3 = 0
Constant inlined get::ptr#0 = main::SCREEN
Successful SSA optimization Pass2ConstantInlining
Consolidated array index constant in *(main::SCREEN+1)
Successful SSA optimization Pass2ConstantAdditionElimination
Adding NOP phi() at start of main
Adding NOP phi() at start of get::@2
CALL GRAPH
Calls in [main] to get:1 get:5 

Created 2 initial phi equivalence classes
Coalesced [16] get::return#8 = get::return#2
Coalesced down to 2 phi equivalence classes
Culled Empty Block label get::@2
Adding NOP phi() at start of main

FINAL CONTROL FLOW GRAPH

void main()
main: scope:[main]  from
  [0] phi()
  [1] call get
  [2] get::return#0 = get::return#4
  to:main::@1
main::@1: scope:[main]  from main
  [3] main::$0 = get::return#0
  [4] *(main::SCREEN+1) = main::$0
  [5] call get
  [6] get::return#1 = get::return#4
  to:main::@2
main::@2: scope:[main]  from main::@1
  [7] main::$1 = get::return#1
  [8] *main::SCREEN = main::$1
  to:main::@return
main::@return: scope:[main]  from main::@2
  [9] return 
  to:@return

char get(char *ptr)
get: scope:[get]  from main main::@1
  [10] get::ptr#2 = phi( main/main::SCREEN, main::@1/0 )
  [11] if(0!=get::ptr#2) goto get::@1
  to:get::@return
get::@1: scope:[get]  from get
  [12] get::return#2 = *get::ptr#2
  to:get::@return
get::@return: scope:[get]  from get get::@1
  [13] get::return#4 = phi( get::@1/get::return#2, get/0 )
  [14] return 
  to:@return


VARIABLE REGISTER WEIGHTS
char get(char *ptr)
char *get::ptr
char *get::ptr#2 // 11.0
char get::return
char get::return#0 // 4.0
char get::return#1 // 4.0
char get::return#2 // 22.0
char get::return#4 // 3.75
void main()
char main::$0 // 4.0
char main::$1 // 4.0

Initial phi equivalence classes
[ get::ptr#2 ]
[ get::return#4 get::return#2 ]
Added variable get::return#0 to live range equivalence class [ get::return#0 ]
Added variable main::$0 to live range equivalence class [ main::$0 ]
Added variable get::return#1 to live range equivalence class [ get::return#1 ]
Added variable main::$1 to live range equivalence class [ main::$1 ]
Complete equivalence classes
[ get::ptr#2 ]
[ get::return#4 get::return#2 ]
[ get::return#0 ]
[ main::$0 ]
[ get::return#1 ]
[ main::$1 ]
Allocated zp[1]:2 [ get::return#4 get::return#2 ]
Allocated zp[2]:3 [ get::ptr#2 ]
Allocated zp[1]:5 [ get::return#0 ]
Allocated zp[1]:6 [ main::$0 ]
Allocated zp[1]:7 [ get::return#1 ]
Allocated zp[1]:8 [ main::$1 ]
REGISTER UPLIFT POTENTIAL REGISTERS
Statement [11] if(0!=get::ptr#2) goto get::@1 [ get::ptr#2 ] ( get:1 [ get::ptr#2 ] { { get::return#0 = get::return#4 } }  get:5 [ get::ptr#2 ] { { get::return#1 = get::return#4 } }  ) always clobbers reg byte a 
Statement [12] get::return#2 = *get::ptr#2 [ get::return#2 ] ( get:1 [ get::return#2 ] { { get::return#0 = get::return#4 } }  get:5 [ get::return#2 ] { { get::return#1 = get::return#4 } }  ) always clobbers reg byte a reg byte y 
Potential registers zp[2]:3 [ get::ptr#2 ] : zp[2]:3 , 
Potential registers zp[1]:2 [ get::return#4 get::return#2 ] : zp[1]:2 , reg byte a , reg byte x , reg byte y , 
Potential registers zp[1]:5 [ get::return#0 ] : zp[1]:5 , reg byte a , reg byte x , reg byte y , 
Potential registers zp[1]:6 [ main::$0 ] : zp[1]:6 , reg byte a , reg byte x , reg byte y , 
Potential registers zp[1]:7 [ get::return#1 ] : zp[1]:7 , reg byte a , reg byte x , reg byte y , 
Potential registers zp[1]:8 [ main::$1 ] : zp[1]:8 , reg byte a , reg byte x , reg byte y , 

REGISTER UPLIFT SCOPES
Uplift Scope [get] 25.75: zp[1]:2 [ get::return#4 get::return#2 ] 11: zp[2]:3 [ get::ptr#2 ] 4: zp[1]:5 [ get::return#0 ] 4: zp[1]:7 [ get::return#1 ] 
Uplift Scope [main] 4: zp[1]:6 [ main::$0 ] 4: zp[1]:8 [ main::$1 ] 
Uplift Scope [] 

Uplifting [get] best 96 combination reg byte a [ get::return#4 get::return#2 ] zp[2]:3 [ get::ptr#2 ] reg byte a [ get::return#0 ] reg byte a [ get::return#1 ] 
Uplifting [main] best 84 combination reg byte a [ main::$0 ] reg byte a [ main::$1 ] 
Uplifting [] best 84 combination 
Allocated (was zp[2]:3) zp[2]:2 [ get::ptr#2 ]

ASSEMBLER BEFORE OPTIMIZATION
  // File Comments
// Test the NULL pointer
  // Upstart
  // Commodore 64 PRG executable file
.file [name="null-constant-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 SCREEN = $400
    // [1] call get
    // [10] phi from main to get [phi:main->get]
  get_from_main:
    // [10] phi get::ptr#2 = main::SCREEN [phi:main->get#0] -- pbuz1=pbuc1 
    lda #<SCREEN
    sta.z get.ptr
    lda #>SCREEN
    sta.z get.ptr+1
    jsr get
    // [2] get::return#0 = get::return#4
    jmp __b1
    // main::@1
  __b1:
    // [3] main::$0 = get::return#0
    // [4] *(main::SCREEN+1) = main::$0 -- _deref_pbuc1=vbuaa 
    sta SCREEN+1
    // [5] call get
    // [10] phi from main::@1 to get [phi:main::@1->get]
  get_from___b1:
    // [10] phi get::ptr#2 = 0 [phi:main::@1->get#0] -- pbuz1=vwuc1 
    lda #<0
    sta.z get.ptr
    lda #>0
    sta.z get.ptr+1
    jsr get
    // [6] get::return#1 = get::return#4
    jmp __b2
    // main::@2
  __b2:
    // [7] main::$1 = get::return#1
    // [8] *main::SCREEN = main::$1 -- _deref_pbuc1=vbuaa 
    sta SCREEN
    jmp __breturn
    // main::@return
  __breturn:
    // [9] return 
    rts
}
  // get
// __register(A) char get(__zp(2) char *ptr)
get: {
    .label ptr = 2
    // [11] if(0!=get::ptr#2) goto get::@1 -- 0_neq_pbuz1_then_la1 
    lda.z ptr
    ora.z ptr+1
    bne __b1
    // [13] phi from get to get::@return [phi:get->get::@return]
  __breturn_from_get:
    // [13] phi get::return#4 = 0 [phi:get->get::@return#0] -- vbuaa=vbuc1 
    lda #0
    jmp __breturn
    // get::@1
  __b1:
    // [12] get::return#2 = *get::ptr#2 -- vbuaa=_deref_pbuz1 
    ldy #0
    lda (ptr),y
    // [13] phi from get::@1 to get::@return [phi:get::@1->get::@return]
  __breturn_from___b1:
    // [13] phi get::return#4 = get::return#2 [phi:get::@1->get::@return#0] -- register_copy 
    jmp __breturn
    // get::@return
  __breturn:
    // [14] return 
    rts
}
  // File Data

ASSEMBLER OPTIMIZATIONS
Removing instruction jmp __b1
Removing instruction jmp __b2
Removing instruction jmp __breturn
Removing instruction jmp __breturn
Succesful ASM optimization Pass5NextJumpElimination
Removing instruction lda #>0
Succesful ASM optimization Pass5UnnecesaryLoadElimination
Removing instruction __breturn_from___b1:
Succesful ASM optimization Pass5RedundantLabelElimination
Removing instruction get_from_main:
Removing instruction __b1:
Removing instruction get_from___b1:
Removing instruction __b2:
Removing instruction __breturn:
Removing instruction __breturn_from_get:
Succesful ASM optimization Pass5UnusedLabelElimination
Replacing jump to rts with rts in jmp __breturn
Succesful ASM optimization Pass5DoubleJumpElimination
Removing instruction __breturn:
Succesful ASM optimization Pass5UnusedLabelElimination

FINAL SYMBOL TABLE
char get(char *ptr)
char *get::ptr
char *get::ptr#2 // ptr zp[2]:2 11.0
char get::return
char get::return#0 // reg byte a 4.0
char get::return#1 // reg byte a 4.0
char get::return#2 // reg byte a 22.0
char get::return#4 // reg byte a 3.75
void main()
char main::$0 // reg byte a 4.0
char main::$1 // reg byte a 4.0
__constant char *main::SCREEN = (char *) 1024

zp[2]:2 [ get::ptr#2 ]
reg byte a [ get::return#4 get::return#2 ]
reg byte a [ get::return#0 ]
reg byte a [ main::$0 ]
reg byte a [ get::return#1 ]
reg byte a [ main::$1 ]


FINAL ASSEMBLER
Score: 73

  // File Comments
// Test the NULL pointer
  // Upstart
  // Commodore 64 PRG executable file
.file [name="null-constant-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 SCREEN = $400
    // get(SCREEN)
    // [1] call get
    // [10] phi from main to get [phi:main->get]
    // [10] phi get::ptr#2 = main::SCREEN [phi:main->get#0] -- pbuz1=pbuc1 
    lda #<SCREEN
    sta.z get.ptr
    lda #>SCREEN
    sta.z get.ptr+1
    jsr get
    // get(SCREEN)
    // [2] get::return#0 = get::return#4
    // main::@1
    // [3] main::$0 = get::return#0
    // SCREEN[1] = get(SCREEN)
    // [4] *(main::SCREEN+1) = main::$0 -- _deref_pbuc1=vbuaa 
    sta SCREEN+1
    // get(NULL)
    // [5] call get
    // [10] phi from main::@1 to get [phi:main::@1->get]
    // [10] phi get::ptr#2 = 0 [phi:main::@1->get#0] -- pbuz1=vwuc1 
    lda #<0
    sta.z get.ptr
    sta.z get.ptr+1
    jsr get
    // get(NULL)
    // [6] get::return#1 = get::return#4
    // main::@2
    // [7] main::$1 = get::return#1
    // SCREEN[0] = get(NULL)
    // [8] *main::SCREEN = main::$1 -- _deref_pbuc1=vbuaa 
    sta SCREEN
    // main::@return
    // }
    // [9] return 
    rts
}
  // get
// __register(A) char get(__zp(2) char *ptr)
get: {
    .label ptr = 2
    // if(NULL==ptr)
    // [11] if(0!=get::ptr#2) goto get::@1 -- 0_neq_pbuz1_then_la1 
    lda.z ptr
    ora.z ptr+1
    bne __b1
    // [13] phi from get to get::@return [phi:get->get::@return]
    // [13] phi get::return#4 = 0 [phi:get->get::@return#0] -- vbuaa=vbuc1 
    lda #0
    rts
    // get::@1
  __b1:
    // return *ptr;
    // [12] get::return#2 = *get::ptr#2 -- vbuaa=_deref_pbuz1 
    ldy #0
    lda (ptr),y
    // [13] phi from get::@1 to get::@return [phi:get::@1->get::@return]
    // [13] phi get::return#4 = get::return#2 [phi:get::@1->get::@return#0] -- register_copy 
    // get::@return
    // }
    // [14] return 
    rts
}
  // File Data

