198 lines
7.7 KiB
Text
198 lines
7.7 KiB
Text
/-
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Copyright (c) 2019 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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import init.lean.name init.lean.kvmap
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prelude
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/-
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Implements (extended) λ_pure and λ_RC proposed in the article
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"Counting Immutable Beans", Sebastian Ullrich and Leonardo de Moura.
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The Lean to IR transformation produces λ_pure code. That is,
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then transformed using the procedures described in the paper above.
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-/
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namespace lean
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namespace ir
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/- Variable identifier -/
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abbreviation varid := name
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/- Function identifier -/
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abbreviation fid := name
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/- Join point identifier -/
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abbreviation jpid := name
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/- Low level IR types. Most are self explanatory.
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- `usize` represents the C++ `size_t` type. We have it here
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because it is 32-bit in 32-bit machines, and 64-bit in 64-bit machines,
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and we want the C++ backend for our compiler to generate platform independent code.
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- `irrelevant` for Lean types, propositions and proofs.
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- `object` a pointer to a value in the heap.
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- `tobject` a pointer to a value in the heap or tagged pointer
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(i.e., the least significant bit is 1) storing a scalar value.
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Remark: the RC operations for `tobject` are slightly more expensive because we
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first need to test whether the `tobject` is really a pointer or not.
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Remark: the Lean runtime assumes that sizeof(void*) == sizeof(size_t).
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Lean cannot be compiled on old platforms where this is not true. -/
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inductive type
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| float | uint8 | uint16 | uint32 | uint64 | usize
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| irrelevant | object | tobject
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/- Arguments to applications, constructors, etc.
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We use `irrelevant` for Lean types, propositions and proofs that have been erased.
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Recall that for a function `f`, we also generate `f._rarg` which does not take
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`irrelevant` arguments. However, `f._rarg` is only safe to be used in full applications. -/
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inductive arg
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| var (id : varid)
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| irrelevant
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inductive litval
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| num (v : nat)
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| str (v : string)
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/- Constructor information.
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- `id` is the name of the constructor in Lean.
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- `cidx` is the constructor index (aka tag).
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- `usize` is the number of arguments of type `usize`.
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- `ssize` is the number of bytes used to store scalar values.
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Recall that a constructor object contains a header, then a sequence of
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pointers to other Lean objects, a sequence of `usize` (i.e., `size_t`)
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scalar values, and a sequence of other scalar values. -/
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structure ctor_info :=
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(id : name) (cidx : nat) (usize : nat) (ssize : nat)
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def ctor_info.beq : ctor_info → ctor_info → bool
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| ⟨id₁, cidx₁, usize₁, ssize₁⟩ ⟨id₂, cidx₂, usize₂, ssize₂⟩ :=
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id₁ = id₂ && cidx₁ = cidx₂ && usize₁ = usize₂ && ssize₁ = ssize₂
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inductive expr
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| ctor (i : ctor_info) (ys : list arg)
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| reset (x : varid)
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/- `reuse x in ctor_i ys` instruction in the paper. -/
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| reuse (x : varid) (i : ctor_info) (ys : list arg)
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/- Extract the `tobject` value at position `sizeof(void)*i` from `x`. -/
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| proj (i : nat) (x : varid)
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/- Extract the `usize` value at position `sizeof(void)*i` from `x`. -/
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| uproj (i : nat) (x : varid)
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/- Extract the scalar value at position `n` (in bytes) from `x`. -/
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| sproj (n : nat) (x : varid)
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/- Full application. -/
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| fap (c : fid) (ys : list arg)
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/- Partial application that creates a `pap` value (aka closure in our nonstandard terminology). -/
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| pap (c : fid) (ys : list arg)
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/- Application. `x` must be a `pap` value. -/
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| ap (x : varid) (ys : list arg)
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/- Given `x : ty` where `ty` is a scalar type, this operation returns a value of type `tobject`.
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For small scalar values, the result is a tagged pointer, and no memory allocation is performed. -/
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| box (ty : type) (x : varid)
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/- Given `x : [t]object`, obtain the scalar value. -/
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| unbox (x : varid)
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| lit (v : litval)
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/- Return `1 : uint8` iff `RC(x) > 1` -/
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| is_shared (x : varid)
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/- Return `1 : uint8` iff `x : tobject` is a tagged pointer (storing a scalar value). -/
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| is_tagged_ptr (x : varid)
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structure param :=
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(x : name) (borrowed : bool) (ty : type)
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inductive alt (fnbody : Type) : Type
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| ctor (info : ctor_info) (b : fnbody) : alt
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| default (b : fnbody) : alt
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inductive fnbody
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/- `let x : ty := e; b` -/
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| vdecl (x : varid) (ty : type) (e : expr) (b : fnbody)
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/- Join point declaration `let j (xs) : ty := e; b` -/
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| jdecl (j : jpid) (xs : list param) (ty : type) (e : expr) (b : fnbody)
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/- Store `y` at position `sizeof(void*)*i` in `x`. `x` must be a constructor object and `RC(x)` must be 1.
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This operation is not part of λ_pure is only used during optimization. -/
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| set (x : varid) (i : nat) (y : varid) (b : fnbody)
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/- Store `y : usize` at position `sizeof(void*)*i` in `x`. `x` must be a constructor object and `RC(x)` must be 1. -/
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| uset (x : varid) (i : nat) (y : varid) (b : fnbody)
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/- Store `y : ty` at position `sizeof(void*)*i + offset` in `x`. `x` must be a constructor object and `RC(x)` must be 1.
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`ty` must not be `object`, `tobject`, `irrelevant` nor `usize`. -/
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| sset (x : varid) (i : nat) (offset : nat) (y : varid) (ty : type) (b : fnbody)
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| release (x : varid) (i : nat) (b : fnbody)
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/- RC increment for `object` -/
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| inc (x : varid) (n : nat) (b : fnbody)
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/- RC decrement for `object` -/
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| dec (x : varid) (n : nat) (b : fnbody)
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/- RC increment for `tobject` -/
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| tinc (x : varid) (n : nat) (b : fnbody)
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/- RC decrement for `tobject` -/
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| tdec (x : varid) (n : nat) (b : fnbody)
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| mdata (d : kvmap) (b : fnbody)
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| case (tid : name) (cs : list (alt fnbody))
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| ret (x : varid)
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/- Jump to join point `j` -/
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| jmp (j : jpid) (ys : list arg)
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| unreachable
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inductive decl
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| fdecl (f : fid) (xs : list param) (ty : type) (b : fnbody)
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| extern (f : fid) (xs : list param) (ty : type)
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/-- `expr.is_pure e` return `tt` iff `e` is in the `λ_pure` fragment. -/
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def expr.is_pure : expr → bool
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| (expr.ctor _ _) := tt
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| (expr.proj _ _) := tt
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| (expr.uproj _ _) := tt
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| (expr.sproj _ _) := tt
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| (expr.fap _ _) := tt
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| (expr.pap _ _) := tt
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| (expr.ap _ _) := tt
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| (expr.lit _) := tt
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| _ := ff
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/-- `fnbody.is_pure b` return `tt` iff `b` is in the `λ_pure` fragment. -/
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mutual def fnbody.is_pure, alts.is_pure, alt.is_pure
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with fnbody.is_pure : fnbody → bool
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| (fnbody.vdecl _ _ e b) := e.is_pure && b.is_pure
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| (fnbody.jdecl _ _ _ e b) := e.is_pure && b.is_pure
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| (fnbody.uset _ _ _ b) := b.is_pure
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| (fnbody.sset _ _ _ _ _ b) := b.is_pure
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| (fnbody.mdata _ b) := b.is_pure
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| (fnbody.case _ cs) := alts.is_pure cs
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| (fnbody.ret _) := tt
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| (fnbody.jmp _ _) := tt
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| fnbody.unreachable := tt
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| _ := ff
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with alts.is_pure : list (alt fnbody) → bool
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| [] := tt
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| (a::as) := a.is_pure && alts.is_pure as
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with alt.is_pure : alt fnbody → bool
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| (alt.ctor _ b) := b.is_pure
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| (alt.default b) := ff
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def varid.alpha_eqv (ρ : name_map name) (v₁ v₂ : varid) : bool :=
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v₁ = v₂ || ρ.find v₁ = v₂
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def arg.alpha_eqv (ρ : name_map name) : arg → arg → bool
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| (arg.var v₁) (arg.var v₂) := varid.alpha_eqv ρ v₁ v₂
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| arg.irrelevant arg.irrelevant := tt
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| _ _ := ff
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def args.alpha_eqv (ρ : name_map name) : list arg → list arg → bool
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| [] [] := tt
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| (a::as) (b::bs) := arg.alpha_eqv ρ a b && args.alpha_eqv as bs
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| _ _ := ff
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def expr.alpha_eqv (ρ : name_map name) : expr → expr → bool
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| (expr.ctor i₁ ys₁) (expr.ctor i₂ ys₂) := ctor_info.beq i₁ i₂ && args.alpha_eqv ρ ys₁ ys₂
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| (expr.reset x₁) (expr.reset x₂) := varid.alpha_eqv ρ x₁ x₂
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| (expr.reuse x₁ i₁ ys₁) (expr.reuse x₂ i₂ ys₂) := varid.alpha_eqv ρ x₁ x₂ && ctor_info.beq i₁ i₂ && args.alpha_eqv ρ ys₁ ys₂
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-- TODO(Leo): remaining cases
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| _ _ := ff
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end ir
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end lean
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