CONTROL FLOW GRAPH SSA
@begin: scope:[]  from
  to:@1

(void()) main()
main: scope:[main]  from @1
  (byte) main::a#0 ← (byte) $80
  (byte) main::b#0 ← (byte) 2
  to:main::@1
main::@1: scope:[main]  from main main::@4 main::@5
  (byte) main::b#2 ← phi( main/(byte) main::b#0 main::@4/(byte) main::b#4 main::@5/(byte) main::b#1 )
  (byte) main::a#2 ← phi( main/(byte) main::a#0 main::@4/(byte) main::a#1 main::@5/(byte) main::a#6 )
  (bool~) main::$0 ← (byte) main::a#2 != (byte) main::b#2
  if((bool~) main::$0) goto main::@2
  to:main::@3
main::@2: scope:[main]  from main::@1
  (byte) main::b#3 ← phi( main::@1/(byte) main::b#2 )
  (byte) main::a#3 ← phi( main::@1/(byte) main::a#2 )
  (bool~) main::$1 ← (byte) main::a#3 > (byte) main::b#3
  if((bool~) main::$1) goto main::@4
  to:main::@5
main::@3: scope:[main]  from main::@1
  (byte) main::a#4 ← phi( main::@1/(byte) main::a#2 )
  *((const byte*) SCREEN) ← (byte) main::a#4
  to:main::@return
main::@4: scope:[main]  from main::@2
  (byte) main::b#4 ← phi( main::@2/(byte) main::b#3 )
  (byte) main::a#5 ← phi( main::@2/(byte) main::a#3 )
  (byte~) main::$3 ← (byte) main::a#5 - (byte) main::b#4
  (byte) main::a#1 ← (byte~) main::$3
  to:main::@1
main::@5: scope:[main]  from main::@2
  (byte) main::a#6 ← phi( main::@2/(byte) main::a#3 )
  (byte) main::b#5 ← phi( main::@2/(byte) main::b#3 )
  (byte~) main::$2 ← (byte) main::b#5 - (byte) main::a#6
  (byte) main::b#1 ← (byte~) main::$2
  to:main::@1
main::@return: scope:[main]  from main::@3
  return 
  to:@return
@1: scope:[]  from @begin
  call main 
  to:@2
@2: scope:[]  from @1
  to:@end
@end: scope:[]  from @2

SYMBOL TABLE SSA
(label) @1
(label) @2
(label) @begin
(label) @end
(const byte*) SCREEN = (byte*)(number) $400
(void()) main()
(bool~) main::$0
(bool~) main::$1
(byte~) main::$2
(byte~) main::$3
(label) main::@1
(label) main::@2
(label) main::@3
(label) main::@4
(label) main::@5
(label) main::@return
(byte) main::a
(byte) main::a#0
(byte) main::a#1
(byte) main::a#2
(byte) main::a#3
(byte) main::a#4
(byte) main::a#5
(byte) main::a#6
(byte) main::b
(byte) main::b#0
(byte) main::b#1
(byte) main::b#2
(byte) main::b#3
(byte) main::b#4
(byte) main::b#5

Simplifying constant pointer cast (byte*) 1024
Successful SSA optimization PassNCastSimplification
Alias main::a#2 = main::a#3 main::a#4 main::a#5 main::a#6 
Alias main::b#2 = main::b#3 main::b#4 main::b#5 
Alias main::a#1 = main::$3 
Alias main::b#1 = main::$2 
Successful SSA optimization Pass2AliasElimination
Simple Condition (bool~) main::$0 [4] if((byte) main::a#2!=(byte) main::b#2) goto main::@2
Simple Condition (bool~) main::$1 [6] if((byte) main::a#2>(byte) main::b#2) goto main::@4
Successful SSA optimization Pass2ConditionalJumpSimplification
Constant (const byte) main::a#0 = $80
Constant (const byte) main::b#0 = 2
Successful SSA optimization Pass2ConstantIdentification
Inlining constant with var siblings (const byte) main::a#0
Inlining constant with var siblings (const byte) main::b#0
Constant inlined main::a#0 = (byte) $80
Constant inlined main::b#0 = (byte) 2
Successful SSA optimization Pass2ConstantInlining
Adding NOP phi() at start of @begin
Adding NOP phi() at start of @1
Adding NOP phi() at start of @2
Adding NOP phi() at start of @end
Adding NOP phi() at start of main
CALL GRAPH
Calls in [] to main:2 

Created 2 initial phi equivalence classes
Coalesced (already) [12] main::a#8 ← main::a#2
Coalesced [13] main::b#7 ← main::b#1
Coalesced [15] main::a#7 ← main::a#1
Coalesced (already) [16] main::b#6 ← main::b#2
Coalesced down to 2 phi equivalence classes
Culled Empty Block (label) @2
Adding NOP phi() at start of @begin
Adding NOP phi() at start of @1
Adding NOP phi() at start of @end
Adding NOP phi() at start of main

FINAL CONTROL FLOW GRAPH
@begin: scope:[]  from
  [0] phi()
  to:@1
@1: scope:[]  from @begin
  [1] phi()
  [2] call main 
  to:@end
@end: scope:[]  from @1
  [3] phi()

(void()) main()
main: scope:[main]  from @1
  [4] phi()
  to:main::@1
main::@1: scope:[main]  from main main::@4 main::@5
  [5] (byte) main::b#2 ← phi( main/(byte) 2 main::@4/(byte) main::b#2 main::@5/(byte) main::b#1 )
  [5] (byte) main::a#2 ← phi( main/(byte) $80 main::@4/(byte) main::a#1 main::@5/(byte) main::a#2 )
  [6] if((byte) main::a#2!=(byte) main::b#2) goto main::@2
  to:main::@3
main::@3: scope:[main]  from main::@1
  [7] *((const byte*) SCREEN) ← (byte) main::a#2
  to:main::@return
main::@return: scope:[main]  from main::@3
  [8] return 
  to:@return
main::@2: scope:[main]  from main::@1
  [9] if((byte) main::a#2>(byte) main::b#2) goto main::@4
  to:main::@5
main::@5: scope:[main]  from main::@2
  [10] (byte) main::b#1 ← (byte) main::b#2 - (byte) main::a#2
  to:main::@1
main::@4: scope:[main]  from main::@2
  [11] (byte) main::a#1 ← (byte) main::a#2 - (byte) main::b#2
  to:main::@1


VARIABLE REGISTER WEIGHTS
(void()) main()
(byte) main::a
(byte) main::a#1 202.0
(byte) main::a#2 179.5
(byte) main::b
(byte) main::b#1 202.0
(byte) main::b#2 176.75

Initial phi equivalence classes
[ main::a#2 main::a#1 ]
[ main::b#2 main::b#1 ]
Complete equivalence classes
[ main::a#2 main::a#1 ]
[ main::b#2 main::b#1 ]
Allocated zp[1]:2 [ main::a#2 main::a#1 ]
Allocated zp[1]:3 [ main::b#2 main::b#1 ]

INITIAL ASM
Target platform is c64basic / MOS6502X
  // File Comments
// Demonstrates a problem where wrong alive ranges result in clobbering an alive variable
// The compiler does not realize that A is alive in the statement b=b-a - and thus can clobber it.
  // Upstart
.pc = $801 "Basic"
:BasicUpstart(main)
.pc = $80d "Program"
  // Global Constants & labels
  .label SCREEN = $400
  // @begin
__bbegin:
  // [1] phi from @begin to @1 [phi:@begin->@1]
__b1_from___bbegin:
  jmp __b1
  // @1
__b1:
  // [2] call main 
  // [4] phi from @1 to main [phi:@1->main]
main_from___b1:
  jsr main
  // [3] phi from @1 to @end [phi:@1->@end]
__bend_from___b1:
  jmp __bend
  // @end
__bend:
  // main
main: {
    .label a = 2
    .label b = 3
    // [5] phi from main to main::@1 [phi:main->main::@1]
  __b1_from_main:
    // [5] phi (byte) main::b#2 = (byte) 2 [phi:main->main::@1#0] -- vbuz1=vbuc1 
    lda #2
    sta.z b
    // [5] phi (byte) main::a#2 = (byte) $80 [phi:main->main::@1#1] -- vbuz1=vbuc1 
    lda #$80
    sta.z a
    jmp __b1
    // main::@1
  __b1:
    // [6] if((byte) main::a#2!=(byte) main::b#2) goto main::@2 -- vbuz1_neq_vbuz2_then_la1 
    lda.z a
    cmp.z b
    bne __b2
    jmp __b3
    // main::@3
  __b3:
    // [7] *((const byte*) SCREEN) ← (byte) main::a#2 -- _deref_pbuc1=vbuz1 
    lda.z a
    sta SCREEN
    jmp __breturn
    // main::@return
  __breturn:
    // [8] return 
    rts
    // main::@2
  __b2:
    // [9] if((byte) main::a#2>(byte) main::b#2) goto main::@4 -- vbuz1_gt_vbuz2_then_la1 
    lda.z b
    cmp.z a
    bcc __b4
    jmp __b5
    // main::@5
  __b5:
    // [10] (byte) main::b#1 ← (byte) main::b#2 - (byte) main::a#2 -- vbuz1=vbuz1_minus_vbuz2 
    lda.z b
    sec
    sbc.z a
    sta.z b
    // [5] phi from main::@4 main::@5 to main::@1 [phi:main::@4/main::@5->main::@1]
  __b1_from___b4:
  __b1_from___b5:
    // [5] phi (byte) main::b#2 = (byte) main::b#2 [phi:main::@4/main::@5->main::@1#0] -- register_copy 
    // [5] phi (byte) main::a#2 = (byte) main::a#1 [phi:main::@4/main::@5->main::@1#1] -- register_copy 
    jmp __b1
    // main::@4
  __b4:
    // [11] (byte) main::a#1 ← (byte) main::a#2 - (byte) main::b#2 -- vbuz1=vbuz1_minus_vbuz2 
    lda.z a
    sec
    sbc.z b
    sta.z a
    jmp __b1_from___b4
}
  // File Data

REGISTER UPLIFT POTENTIAL REGISTERS
Statement [10] (byte) main::b#1 ← (byte) main::b#2 - (byte) main::a#2 [ main::a#2 main::b#1 ] ( main:2 [ main::a#2 main::b#1 ] { }  ) always clobbers reg byte a 
Removing always clobbered register reg byte a as potential for zp[1]:2 [ main::a#2 main::a#1 ]
Statement [11] (byte) main::a#1 ← (byte) main::a#2 - (byte) main::b#2 [ main::b#2 main::a#1 ] ( main:2 [ main::b#2 main::a#1 ] { }  ) always clobbers reg byte a 
Removing always clobbered register reg byte a as potential for zp[1]:3 [ main::b#2 main::b#1 ]
Statement [10] (byte) main::b#1 ← (byte) main::b#2 - (byte) main::a#2 [ main::a#2 main::b#1 ] ( main:2 [ main::a#2 main::b#1 ] { }  ) always clobbers reg byte a 
Statement [11] (byte) main::a#1 ← (byte) main::a#2 - (byte) main::b#2 [ main::b#2 main::a#1 ] ( main:2 [ main::b#2 main::a#1 ] { }  ) always clobbers reg byte a 
Potential registers zp[1]:2 [ main::a#2 main::a#1 ] : zp[1]:2 , reg byte x , reg byte y , 
Potential registers zp[1]:3 [ main::b#2 main::b#1 ] : zp[1]:3 , reg byte x , reg byte y , 

REGISTER UPLIFT SCOPES
Uplift Scope [main] 381.5: zp[1]:2 [ main::a#2 main::a#1 ] 378.75: zp[1]:3 [ main::b#2 main::b#1 ] 
Uplift Scope [] 

Uplifting [main] best 568 combination zp[1]:2 [ main::a#2 main::a#1 ] reg byte x [ main::b#2 main::b#1 ] 
Uplifting [] best 568 combination 
Attempting to uplift remaining variables inzp[1]:2 [ main::a#2 main::a#1 ]
Uplifting [main] best 568 combination zp[1]:2 [ main::a#2 main::a#1 ] 

ASSEMBLER BEFORE OPTIMIZATION
  // File Comments
// Demonstrates a problem where wrong alive ranges result in clobbering an alive variable
// The compiler does not realize that A is alive in the statement b=b-a - and thus can clobber it.
  // Upstart
.pc = $801 "Basic"
:BasicUpstart(main)
.pc = $80d "Program"
  // Global Constants & labels
  .label SCREEN = $400
  // @begin
__bbegin:
  // [1] phi from @begin to @1 [phi:@begin->@1]
__b1_from___bbegin:
  jmp __b1
  // @1
__b1:
  // [2] call main 
  // [4] phi from @1 to main [phi:@1->main]
main_from___b1:
  jsr main
  // [3] phi from @1 to @end [phi:@1->@end]
__bend_from___b1:
  jmp __bend
  // @end
__bend:
  // main
main: {
    .label a = 2
    // [5] phi from main to main::@1 [phi:main->main::@1]
  __b1_from_main:
    // [5] phi (byte) main::b#2 = (byte) 2 [phi:main->main::@1#0] -- vbuxx=vbuc1 
    ldx #2
    // [5] phi (byte) main::a#2 = (byte) $80 [phi:main->main::@1#1] -- vbuz1=vbuc1 
    lda #$80
    sta.z a
    jmp __b1
    // main::@1
  __b1:
    // [6] if((byte) main::a#2!=(byte) main::b#2) goto main::@2 -- vbuz1_neq_vbuxx_then_la1 
    cpx.z a
    bne __b2
    jmp __b3
    // main::@3
  __b3:
    // [7] *((const byte*) SCREEN) ← (byte) main::a#2 -- _deref_pbuc1=vbuz1 
    lda.z a
    sta SCREEN
    jmp __breturn
    // main::@return
  __breturn:
    // [8] return 
    rts
    // main::@2
  __b2:
    // [9] if((byte) main::a#2>(byte) main::b#2) goto main::@4 -- vbuz1_gt_vbuxx_then_la1 
    cpx.z a
    bcc __b4
    jmp __b5
    // main::@5
  __b5:
    // [10] (byte) main::b#1 ← (byte) main::b#2 - (byte) main::a#2 -- vbuxx=vbuxx_minus_vbuz1 
    txa
    sec
    sbc.z a
    tax
    // [5] phi from main::@4 main::@5 to main::@1 [phi:main::@4/main::@5->main::@1]
  __b1_from___b4:
  __b1_from___b5:
    // [5] phi (byte) main::b#2 = (byte) main::b#2 [phi:main::@4/main::@5->main::@1#0] -- register_copy 
    // [5] phi (byte) main::a#2 = (byte) main::a#1 [phi:main::@4/main::@5->main::@1#1] -- register_copy 
    jmp __b1
    // main::@4
  __b4:
    // [11] (byte) main::a#1 ← (byte) main::a#2 - (byte) main::b#2 -- vbuz1=vbuz1_minus_vbuxx 
    txa
    eor #$ff
    sec
    adc.z a
    sta.z a
    jmp __b1_from___b4
}
  // File Data

ASSEMBLER OPTIMIZATIONS
Removing instruction jmp __b1
Removing instruction jmp __bend
Removing instruction jmp __b1
Removing instruction jmp __b3
Removing instruction jmp __breturn
Removing instruction jmp __b5
Succesful ASM optimization Pass5NextJumpElimination
Replacing label __b1_from___b4 with __b1_from___b5
Removing instruction __b1_from___bbegin:
Removing instruction __b1:
Removing instruction main_from___b1:
Removing instruction __bend_from___b1:
Removing instruction __b1_from___b4:
Succesful ASM optimization Pass5RedundantLabelElimination
Removing instruction __bbegin:
Removing instruction __bend:
Removing instruction __b1_from_main:
Removing instruction __b3:
Removing instruction __breturn:
Removing instruction __b5:
Succesful ASM optimization Pass5UnusedLabelElimination
Removing instruction jsr main
Succesful ASM optimization Pass5SkipBegin
Skipping double jump to __b1 in jmp __b1_from___b5
Succesful ASM optimization Pass5DoubleJumpElimination
Relabelling long label __b1_from___b5 to __b3
Succesful ASM optimization Pass5RelabelLongLabels
Removing instruction __b3:
Succesful ASM optimization Pass5UnusedLabelElimination

FINAL SYMBOL TABLE
(label) @1
(label) @begin
(label) @end
(const byte*) SCREEN = (byte*) 1024
(void()) main()
(label) main::@1
(label) main::@2
(label) main::@3
(label) main::@4
(label) main::@5
(label) main::@return
(byte) main::a
(byte) main::a#1 a zp[1]:2 202.0
(byte) main::a#2 a zp[1]:2 179.5
(byte) main::b
(byte) main::b#1 reg byte x 202.0
(byte) main::b#2 reg byte x 176.75

zp[1]:2 [ main::a#2 main::a#1 ]
reg byte x [ main::b#2 main::b#1 ]


FINAL ASSEMBLER
Score: 463

  // File Comments
// Demonstrates a problem where wrong alive ranges result in clobbering an alive variable
// The compiler does not realize that A is alive in the statement b=b-a - and thus can clobber it.
  // Upstart
.pc = $801 "Basic"
:BasicUpstart(main)
.pc = $80d "Program"
  // Global Constants & labels
  .label SCREEN = $400
  // @begin
  // [1] phi from @begin to @1 [phi:@begin->@1]
  // @1
  // [2] call main 
  // [4] phi from @1 to main [phi:@1->main]
  // [3] phi from @1 to @end [phi:@1->@end]
  // @end
  // main
main: {
    .label a = 2
    // [5] phi from main to main::@1 [phi:main->main::@1]
    // [5] phi (byte) main::b#2 = (byte) 2 [phi:main->main::@1#0] -- vbuxx=vbuc1 
    ldx #2
    // [5] phi (byte) main::a#2 = (byte) $80 [phi:main->main::@1#1] -- vbuz1=vbuc1 
    lda #$80
    sta.z a
    // main::@1
  __b1:
    // while (a!=b)
    // [6] if((byte) main::a#2!=(byte) main::b#2) goto main::@2 -- vbuz1_neq_vbuxx_then_la1 
    cpx.z a
    bne __b2
    // main::@3
    // *SCREEN = a
    // [7] *((const byte*) SCREEN) ← (byte) main::a#2 -- _deref_pbuc1=vbuz1 
    lda.z a
    sta SCREEN
    // main::@return
    // }
    // [8] return 
    rts
    // main::@2
  __b2:
    // if(a>b)
    // [9] if((byte) main::a#2>(byte) main::b#2) goto main::@4 -- vbuz1_gt_vbuxx_then_la1 
    cpx.z a
    bcc __b4
    // main::@5
    // b = b-a
    // [10] (byte) main::b#1 ← (byte) main::b#2 - (byte) main::a#2 -- vbuxx=vbuxx_minus_vbuz1 
    txa
    sec
    sbc.z a
    tax
    // [5] phi from main::@4 main::@5 to main::@1 [phi:main::@4/main::@5->main::@1]
    // [5] phi (byte) main::b#2 = (byte) main::b#2 [phi:main::@4/main::@5->main::@1#0] -- register_copy 
    // [5] phi (byte) main::a#2 = (byte) main::a#1 [phi:main::@4/main::@5->main::@1#1] -- register_copy 
    jmp __b1
    // main::@4
  __b4:
    // a = a-b
    // [11] (byte) main::a#1 ← (byte) main::a#2 - (byte) main::b#2 -- vbuz1=vbuz1_minus_vbuxx 
    txa
    eor #$ff
    sec
    adc.z a
    sta.z a
    jmp __b1
}
  // File Data