Anayzling SixtyPical Programs

-> Tests for functionality "Analyze SixtyPical program"

-> Functionality "Analyze SixtyPical program" is implemented by
-> shell command "bin/sixtypical analyze %(test-file)"

Analysis determines what storage locations have been modified by a routine.

| reserve byte score
| routine main {
|   lda #4
|   sta score
| }
= main ([])
=   A: UpdatedWith (Immediate 4)
=   NamedLocation (Just Byte) "score": UpdatedWith A

A routine cannot expect registers which a called routine does not preserve, to be preserved.

| assign byte border_colour 4000
| reserve byte score
| routine update_score
| {
|   lda #8
|   sta score
| }
| routine main {
|   lda #4
|   jsr update_score
|   sta border_colour
| }
? routine does not preserve 'A'

But if it does it can.

| assign byte border_colour 4000
| reserve byte score
| routine update_score
| {
|   ldx score
|   inx
|   stx score
| }
| routine main {
|   lda #4
|   jsr update_score
|   sta border_colour
| }
= main ([])
=   A: UpdatedWith (Immediate 4)
=   X: PoisonedWith (Immediate 1)
=   NamedLocation (Just Byte) "border_colour": UpdatedWith A
=   NamedLocation (Just Byte) "score": PoisonedWith X
= 
= update_score ([])
=   X: UpdatedWith (Immediate 1)
=   NamedLocation (Just Byte) "score": UpdatedWith X

We can't expect to stay named variables to stay unmodified either.

| assign byte border_colour 4000
| reserve byte score
| routine update_score
| {
|   lda #8
|   sta score
| }
| routine main {
|   jsr update_score
|   ldx score
| }
? routine does not preserve 'NamedLocation (Just Byte) "score"'

What the solution to the above is to notate update_score as intentionally modifying score, as an "output" of the routine.

| assign byte border_colour 4000
| reserve byte score
| routine update_score outputs (score)
| {
|   lda #8
|   sta score
| }
| routine main {
|   ldx score
|   jsr update_score
|   ldx score
| }
= main ([])
=   A: PoisonedWith (Immediate 8)
=   X: UpdatedWith (NamedLocation (Just Byte) "score")
=   NamedLocation (Just Byte) "score": UpdatedWith A
= 
= update_score ([NamedLocation Nothing "score"])
=   A: UpdatedWith (Immediate 8)
=   NamedLocation (Just Byte) "score": UpdatedWith A

2.5 KiB Raw Blame History

Anayzling SixtyPical Programs

2.5 KiB

Raw Blame History