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Adds an extra field in `CodeInfo` that allows users (Cassette, et al.) to specify dependencies (as forward edges to `MethodInstance`s) that should be turned into backedges once the CodeInfo is passed over by inference. The test includes a minimal implementation of the Cassette mechansim to exercise this code path.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,110 @@ | ||
| module MiniCassette | ||
| # A minimal demonstration of the cassette mechanism. Doesn't support all the | ||
| # fancy features, but sufficient to exercise this code path in the compiler. | ||
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| using Core.Compiler: method_instances, retrieve_code_info, CodeInfo, | ||
| MethodInstance, SSAValue, GotoNode, Slot, SlotNumber, quoted, | ||
| signature_type | ||
| using Base: _methods_by_ftype | ||
| using Base.Meta: isexpr | ||
| using Test | ||
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| export Ctx, overdub | ||
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| struct Ctx; end | ||
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| # A no-op cassette-like transform | ||
| function transform_expr(expr, map_slot_number, map_ssa_value, sparams) | ||
| transform(expr) = transform_expr(expr, map_slot_number, map_ssa_value, sparams) | ||
| if isexpr(expr, :call) | ||
| return Expr(:call, overdub, SlotNumber(2), map(transform, expr.args)...) | ||
| elseif isexpr(expr, :gotoifnot) | ||
| return Expr(:gotoifnot, transform(expr.args[1]), map_ssa_value(SSAValue(expr.args[2])).id) | ||
| elseif isexpr(expr, :static_parameter) | ||
| return quoted(sparams[expr.args[1]]) | ||
| elseif isa(expr, Expr) | ||
| return Expr(expr.head, map(transform, expr.args)...) | ||
| elseif isa(expr, GotoNode) | ||
| return GotoNode(map_ssa_value(SSAValue(expr.label)).id) | ||
| elseif isa(expr, Slot) | ||
| return map_slot_number(expr.id) | ||
| elseif isa(expr, SSAValue) | ||
| return map_ssa_value(expr) | ||
| else | ||
| return expr | ||
| end | ||
| end | ||
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| function transform!(ci, nargs, sparams) | ||
| code = ci.code | ||
| ci.slotnames = Symbol[Symbol("#self#"), :ctx, :f, :args, ci.slotnames[nargs+1:end]...] | ||
| ci.slotflags = UInt8[(0x00 for i = 1:4)..., ci.slotflags[nargs+1:end]...] | ||
| # Insert one SSAValue for every argument statement | ||
| prepend!(code, [Expr(:call, getfield, SlotNumber(4), i) for i = 1:nargs]) | ||
| prepend!(ci.codelocs, [0 for i = 1:nargs]) | ||
| ci.ssavaluetypes += nargs | ||
| function map_slot_number(slot) | ||
| if slot == 1 | ||
| # self in the original function is now `f` | ||
| return SlotNumber(3) | ||
| elseif 2 <= slot <= nargs + 1 | ||
| # Arguments get inserted as ssa values at the top of the function | ||
| return SSAValue(slot - 1) | ||
| else | ||
| # The first non-argument slot will be 5 | ||
| return SlotNumber(slot - (nargs + 1) + 4) | ||
| end | ||
| end | ||
| map_ssa_value(ssa::SSAValue) = SSAValue(ssa.id + nargs) | ||
| for i = (nargs+1:length(code)) | ||
| code[i] = transform_expr(code[i], map_slot_number, map_ssa_value, sparams) | ||
| end | ||
| end | ||
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| function overdub_generator(self, c, f, args) | ||
| if f <: Core.Builtin || !isdefined(f, :instance) | ||
| return :(return f(args...)) | ||
| end | ||
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| tt = Tuple{f, args...} | ||
| mthds = _methods_by_ftype(tt, -1, typemax(UInt)) | ||
| @assert length(mthds) == 1 | ||
| mtypes, msp, m = mthds[1] | ||
| mi = ccall(:jl_specializations_get_linfo, Ref{MethodInstance}, (Any, Any, Any), m, mtypes, msp) | ||
| # Unsupported in this mini-cassette | ||
| @assert !mi.def.isva | ||
| code_info = retrieve_code_info(mi) | ||
| @assert isa(code_info, CodeInfo) | ||
| code_info = copy(code_info) | ||
| if isdefined(code_info, :edges) | ||
| code_info.edges = MethodInstance[mi] | ||
| end | ||
| transform!(code_info, length(args), msp) | ||
| code_info | ||
| end | ||
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| @eval function overdub(c::Ctx, f, args...) | ||
| $(Expr(:meta, :generated_only)) | ||
| $(Expr(:meta, | ||
| :generated, | ||
| Expr(:new, | ||
| Core.GeneratedFunctionStub, | ||
| :overdub_generator, | ||
| Any[:overdub, :ctx, :f, :args], | ||
| Any[], | ||
| @__LINE__, | ||
| QuoteNode(Symbol(@__FILE__)), | ||
| true))) | ||
| end | ||
| end | ||
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| using .MiniCassette | ||
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| # Test #265 for Cassette | ||
| f() = 1 | ||
| @test overdub(Ctx(), f) === 1 | ||
| f() = 2 | ||
| @test overdub(Ctx(), f) === 2 | ||
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| # Test that MiniCassette is at least somewhat capable by overdubbing gcd | ||
| @test overdub(Ctx(), gcd, 10, 20) === gcd(10, 20) |