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NikolajDanger
2022-06-09 11:13:16 +02:00
parent 41ed1788cb
commit 5ff8dd409a
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41
Fasto/CopyConstPropFold.fs
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@ -22,22 +22,12 @@ let rec copyConstPropFoldExp (vtable : VarTable)
(* Copy propagation is handled entirely in the following three
cases for variables, array indexing, and let-bindings. *)
| Var (name, pos) ->
(* TODO project task 3:
Should probably look in the symbol table to see if
a binding corresponding to the current variable `name`
exists and if so, it should replace the current expression
with the variable or constant to be propagated.
*)
let name' = SymTab.lookup name vtable
match name' with
| Some (ConstProp x) -> Constant (x, pos)
| Some (VarProp x) -> Var (x, pos)
| _ -> Var (name, pos)
| Index (name, e2, t, pos) ->
(* TODO project task 3:
Should probably do the same as the `Var` case, for
the array name, and optimize the index expression `e` as well.
*)
let name' = SymTab.lookup name vtable
let e2' = copyConstPropFoldExp vtable e2
match name' with
@ -48,37 +38,14 @@ let rec copyConstPropFoldExp (vtable : VarTable)
let e' = copyConstPropFoldExp vtable e
match e' with
| Var (name', _) ->
(* TODO project task 3:
Hint: I have discovered a variable-copy statement `let x = a`.
I should probably record it in the `vtable` by
associating `x` with a variable-propagatee binding,
and optimize the `body` of the let.
*)
let vtable' = SymTab.bind name (VarProp name') vtable
let body' = copyConstPropFoldExp vtable' body
Let (Dec (name, e', decpos), body', pos)
| Constant (constval, _) ->
(* TODO project task 3:
Hint: I have discovered a constant-copy statement `let x = 5`.
I should probably record it in the `vtable` by
associating `x` with a constant-propagatee binding,
and optimize the `body` of the let.
*)
let vtable' = SymTab.bind name (ConstProp constval) vtable
let body' = copyConstPropFoldExp vtable' body
Let (Dec (name, e', decpos), body', pos)
| Let (Dec (name2, e2, decpos2), body2, pos2) ->
(* TODO project task 3:
Hint: this has the structure
`let y = (let x = e1 in e2) in e3`
Problem is, in this form, `e2` may simplify
to a variable or constant, but I will miss
identifying the resulting variable/constant-copy
statement on `y`.
A potential solution is to optimize directly the
restructured, semantically-equivalent expression:
`let x = e1 in let y = e2 in e3`
*)
let e2' = copyConstPropFoldExp vtable e2
let body2' = copyConstPropFoldExp vtable body2
let body' = copyConstPropFoldExp vtable body
@ -88,12 +55,6 @@ let rec copyConstPropFoldExp (vtable : VarTable)
Let (Dec (name, e', decpos), body', pos)
| Times (e1, e2, pos) ->
(* TODO project task 3: implement as many safe algebraic
simplifications as you can think of. You may inspire
yourself from the case of `Plus`. For example:
1 * x = ?
x * 0 = ?
*)
let e1' = copyConstPropFoldExp vtable e1
let e2' = copyConstPropFoldExp vtable e2
match (e1', e2') with
@ -109,8 +70,6 @@ let rec copyConstPropFoldExp (vtable : VarTable)
e1'
| _ -> Times (e1, e2, pos)
| And (e1, e2, pos) ->
(* TODO project task 3: see above. You may inspire yourself from
`Or` below, but that only scratches the surface of what's possible *)
let e1' = copyConstPropFoldExp vtable e1
let e2' = copyConstPropFoldExp vtable e2
match (e1', e2') with