Documentation

Lean.Compiler.IR.Basic

Implements (extended) λPure and λRc proposed in the article "Counting Immutable Beans", Sebastian Ullrich and Leonardo de Moura.

The Lean to IR transformation produces λPure code, and this part is implemented in C++. The procedures described in the paper above are implemented in Lean.

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Function identifier

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      structure Lean.IR.VarId :

      Variable identifier

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        Join point identifier

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                inductive Lean.IR.IRType :

                Low Level IR types. Most are self explanatory.

                • usize represents the C++ size_t Type. We have it here because it is 32-bit in 32-bit machines, and 64-bit in 64-bit machines, and we want the C++ backend for our Compiler to generate platform independent code.

                • irrelevant for Lean types, propositions and proofs.

                • object a pointer to a value in the heap.

                • tobject a pointer to a value in the heap or tagged pointer (i.e., the least significant bit is 1) storing a scalar value.

                • struct and union are used to return small values (e.g., Option, Prod, Except) on the stack.

                Remark: the RC operations for tobject are slightly more expensive because we first need to test whether the tobject is really a pointer or not.

                Remark: the Lean runtime assumes that sizeof(void*) == sizeof(sizeT). Lean cannot be compiled on old platforms where this is not True.

                Since values of type struct and union are only used to return values, We assume they must be used/consumed "linearly". We use the term "linear" here to mean "exactly once" in each execution. That is, given x : S, where S is a struct, then one of the following must hold in each (execution) branch. 1- x occurs only at a single ret x instruction. That is, it is being consumed by being returned. 2- x occurs only at a single ctor. That is, it is being "consumed" by being stored into another struct/union. 3- We extract (aka project) every single field of x exactly once. That is, we are consuming x by consuming each of one of its components. Minor refinement: we don't need to consume scalar fields or struct/union fields that do not contain object fields.

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                    inductive Lean.IR.Arg :

                    Arguments to applications, constructors, etc. We use irrelevant for Lean types, propositions and proofs that have been erased. Recall that for a Function f, we also generate f._rarg which does not take irrelevant arguments. However, f._rarg is only safe to be used in full applications.

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                      @[export lean_ir_mk_var_arg]
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                        inductive Lean.IR.LitVal :
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                          Constructor information.

                          • name is the Name of the Constructor in Lean.
                          • cidx is the Constructor index (aka tag).
                          • size is the number of arguments of type object/tobject.
                          • usize is the number of arguments of type usize.
                          • ssize is the number of bytes used to store scalar values.

                          Recall that a Constructor object contains a header, then a sequence of pointers to other Lean objects, a sequence of USize (i.e., size_t) scalar values, and a sequence of other scalar values.

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                            • info.isScalar = !info.isRef
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                              inductive Lean.IR.Expr :
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                                @[export lean_ir_mk_ctor_expr]
                                def Lean.IR.mkCtorExpr (n : Lean.Name) (cidx size usize ssize : Nat) (ys : Array Lean.IR.Arg) :
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                                  @[export lean_ir_mk_proj_expr]
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                                    @[export lean_ir_mk_uproj_expr]
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                                      @[export lean_ir_mk_sproj_expr]
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                                        @[export lean_ir_mk_fapp_expr]
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                                          @[export lean_ir_mk_papp_expr]
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                                            @[export lean_ir_mk_app_expr]
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                                              @[export lean_ir_mk_num_expr]
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                                                @[export lean_ir_mk_str_expr]
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                                                  structure Lean.IR.Param :
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                                                      inductive Lean.IR.AltCore (FnBody : Type) :
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                                                        inductive Lean.IR.FnBody :
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                                                            @[export lean_ir_mk_vdecl]
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                                                              @[export lean_ir_mk_jdecl]
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                                                                @[export lean_ir_mk_uset]
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                                                                  @[export lean_ir_mk_sset]
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                                                                    @[export lean_ir_mk_case]
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                                                                      @[export lean_ir_mk_ret]
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                                                                        @[export lean_ir_mk_jmp]
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                                                                          @[export lean_ir_mk_unreachable]
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                                                                                          If b is a non terminal, then return a pair (c, b') s.t. b == c <;> b', and c.body == FnBody.nil

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                                                                                          • b.split = (b.resetBody, b.body)
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                                                                                                  @[export lean_ir_mk_alt]
                                                                                                  def Lean.IR.mkAlt (n : Lean.Name) (cidx size usize ssize : Nat) (b : Lean.IR.FnBody) :
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                                                                                                    Extra information associated with a declaration.

                                                                                                    • sorryDep? : Option Lean.Name

                                                                                                      If some <blame>, then declaration depends on <blame> which uses a sorry axiom.

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                                                                                                          @[export lean_ir_mk_decl]
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                                                                                                            @[export lean_ir_mk_extern_decl]
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                                                                                                              @[export lean_ir_mk_dummy_extern_decl]
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                                                                                                                Set of variable and join point names

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                                                                                                                          class Lean.IR.AlphaEqv (α : Type) :
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