Revision 1f2b5f48c99fc53008a14c5a1bcd0d5872a6dbab authored by Sebastian Stock on 10 August 2020, 13:38:07 UTC, committed by KristofferC on 19 August 2020, 12:00:53 UTC
(cherry picked from commit 00f2133d8354f1032f83d62c6921a19d8a5c8d69)
1 parent 27408bc
expr.jl
# This file is a part of Julia. License is MIT: https://julialang.org/license
## symbols ##
"""
gensym([tag])
Generates a symbol which will not conflict with other variable names.
"""
gensym() = ccall(:jl_gensym, Ref{Symbol}, ())
gensym(s::String) = ccall(:jl_tagged_gensym, Ref{Symbol}, (Ptr{UInt8}, Int32), s, sizeof(s))
gensym(ss::String...) = map(gensym, ss)
gensym(s::Symbol) =
ccall(:jl_tagged_gensym, Ref{Symbol}, (Ptr{UInt8}, Int32), s, ccall(:strlen, Csize_t, (Ptr{UInt8},), s))
"""
@gensym
Generates a gensym symbol for a variable. For example, `@gensym x y` is transformed into
`x = gensym("x"); y = gensym("y")`.
"""
macro gensym(names...)
blk = Expr(:block)
for name in names
push!(blk.args, :($(esc(name)) = gensym($(string(name)))))
end
push!(blk.args, :nothing)
return blk
end
## expressions ##
function copy(e::Expr)
n = Expr(e.head)
n.args = copy_exprargs(e.args)
return n
end
# copy parts of an AST that the compiler mutates
copy_exprs(@nospecialize(x)) = x
copy_exprs(x::Expr) = copy(x)
function copy_exprs(x::PhiNode)
new_values = Vector{Any}(undef, length(x.values))
for i = 1:length(x.values)
isassigned(x.values, i) || continue
new_values[i] = copy_exprs(x.values[i])
end
return PhiNode(copy(x.edges), new_values)
end
function copy_exprs(x::PhiCNode)
new_values = Vector{Any}(undef, length(x.values))
for i = 1:length(x.values)
isassigned(x.values, i) || continue
new_values[i] = copy_exprs(x.values[i])
end
return PhiCNode(new_values)
end
copy_exprargs(x::Array{Any,1}) = Any[copy_exprs(x[i]) for i in 1:length(x)]
# create copies of the CodeInfo definition, and any mutable fields
function copy(c::CodeInfo)
cnew = ccall(:jl_copy_code_info, Ref{CodeInfo}, (Any,), c)
cnew.code = copy_exprargs(cnew.code)
cnew.slotnames = copy(cnew.slotnames)
cnew.slotflags = copy(cnew.slotflags)
cnew.codelocs = copy(cnew.codelocs)
cnew.linetable = copy(cnew.linetable)
cnew.ssaflags = copy(cnew.ssaflags)
cnew.edges = cnew.edges === nothing ? nothing : copy(cnew.edges)
ssavaluetypes = cnew.ssavaluetypes
ssavaluetypes isa Vector{Any} && (cnew.ssavaluetypes = copy(ssavaluetypes))
return cnew
end
==(x::Expr, y::Expr) = x.head === y.head && isequal(x.args, y.args)
==(x::QuoteNode, y::QuoteNode) = isequal(x.value, y.value)
"""
macroexpand(m::Module, x; recursive=true)
Take the expression `x` and return an equivalent expression with all macros removed (expanded)
for executing in module `m`.
The `recursive` keyword controls whether deeper levels of nested macros are also expanded.
This is demonstrated in the example below:
```julia-repl
julia> module M
macro m1()
42
end
macro m2()
:(@m1())
end
end
M
julia> macroexpand(M, :(@m2()), recursive=true)
42
julia> macroexpand(M, :(@m2()), recursive=false)
:(#= REPL[16]:6 =# M.@m1)
```
"""
function macroexpand(m::Module, @nospecialize(x); recursive=true)
if recursive
ccall(:jl_macroexpand, Any, (Any, Any), x, m)
else
ccall(:jl_macroexpand1, Any, (Any, Any), x, m)
end
end
"""
@macroexpand
Return equivalent expression with all macros removed (expanded).
There are differences between `@macroexpand` and [`macroexpand`](@ref).
* While [`macroexpand`](@ref) takes a keyword argument `recursive`, `@macroexpand`
is always recursive. For a non recursive macro version, see [`@macroexpand1`](@ref).
* While [`macroexpand`](@ref) has an explicit `module` argument, `@macroexpand` always
expands with respect to the module in which it is called.
This is best seen in the following example:
```julia-repl
julia> module M
macro m()
1
end
function f()
(@macroexpand(@m),
macroexpand(M, :(@m)),
macroexpand(Main, :(@m))
)
end
end
M
julia> macro m()
2
end
@m (macro with 1 method)
julia> M.f()
(1, 1, 2)
```
With `@macroexpand` the expression expands where `@macroexpand` appears in the code (module `M` in the example).
With `macroexpand` the expression expands in the module given as the first argument.
"""
macro macroexpand(code)
return :(macroexpand($__module__, $(QuoteNode(code)), recursive=true))
end
"""
@macroexpand1
Non recursive version of [`@macroexpand`](@ref).
"""
macro macroexpand1(code)
return :(macroexpand($__module__, $(QuoteNode(code)), recursive=false))
end
## misc syntax ##
"""
Core.eval(m::Module, expr)
Evaluate an expression in the given module and return the result.
"""
Core.eval
"""
@inline
Give a hint to the compiler that this function is worth inlining.
Small functions typically do not need the `@inline` annotation,
as the compiler does it automatically. By using `@inline` on bigger functions,
an extra nudge can be given to the compiler to inline it.
This is shown in the following example:
```julia
@inline function bigfunction(x)
#=
Function Definition
=#
end
```
"""
macro inline(ex)
esc(isa(ex, Expr) ? pushmeta!(ex, :inline) : ex)
end
"""
@noinline
Give a hint to the compiler that it should not inline a function.
Small functions are typically inlined automatically.
By using `@noinline` on small functions, auto-inlining can be
prevented. This is shown in the following example:
```julia
@noinline function smallfunction(x)
#=
Function Definition
=#
end
If the function is trivial (for example returning a constant) it might get inlined anyway.
```
"""
macro noinline(ex)
esc(isa(ex, Expr) ? pushmeta!(ex, :noinline) : ex)
end
"""
@pure ex
@pure(ex)
`@pure` gives the compiler a hint for the definition of a pure function,
helping for type inference.
A pure function can only depend on immutable information.
This also means a `@pure` function cannot use any global mutable state, including
generic functions. Calls to generic functions depend on method tables which are
mutable global state.
Use with caution, incorrect `@pure` annotation of a function may introduce
hard to identify bugs. Double check for calls to generic functions.
This macro is intended for internal compiler use and may be subject to changes.
"""
macro pure(ex)
esc(isa(ex, Expr) ? pushmeta!(ex, :pure) : ex)
end
"""
@propagate_inbounds
Tells the compiler to inline a function while retaining the caller's inbounds context.
"""
macro propagate_inbounds(ex)
if isa(ex, Expr)
pushmeta!(ex, :inline)
pushmeta!(ex, :propagate_inbounds)
end
esc(ex)
end
"""
@polly
Tells the compiler to apply the polyhedral optimizer Polly to a function.
"""
macro polly(ex)
esc(isa(ex, Expr) ? pushmeta!(ex, :polly) : ex)
end
## some macro utilities ##
function pushmeta!(ex::Expr, sym::Symbol, args::Any...)
if isempty(args)
tag = sym
else
tag = Expr(sym, args...)
end
inner = ex
while inner.head === :macrocall
inner = inner.args[end]::Expr
end
idx, exargs = findmeta(inner)
if idx != 0
push!(exargs[idx].args, tag)
else
body::Expr = inner.args[2]
pushfirst!(body.args, Expr(:meta, tag))
end
ex
end
popmeta!(body, sym) = _getmeta(body, sym, true)
peekmeta(body, sym) = _getmeta(body, sym, false)
function _getmeta(body::Expr, sym::Symbol, delete::Bool)
body.head === :block || return false, []
_getmeta(body.args, sym, delete)
end
_getmeta(arg, sym, delete::Bool) = (false, [])
function _getmeta(body::Array{Any,1}, sym::Symbol, delete::Bool)
idx, blockargs = findmeta_block(body, args -> findmetaarg(args,sym)!=0)
if idx == 0
return false, []
end
metaargs = blockargs[idx].args
i = findmetaarg(blockargs[idx].args, sym)
if i == 0
return false, []
end
ret = isa(metaargs[i], Expr) ? (metaargs[i]::Expr).args : []
if delete
deleteat!(metaargs, i)
isempty(metaargs) && deleteat!(blockargs, idx)
end
true, ret
end
# Find index of `sym` in a meta expression argument list, or 0.
function findmetaarg(metaargs, sym)
for i = 1:length(metaargs)
arg = metaargs[i]
if (isa(arg, Symbol) && (arg::Symbol) == sym) ||
(isa(arg, Expr) && (arg::Expr).head == sym)
return i
end
end
return 0
end
function is_short_function_def(ex)
ex.head === :(=) || return false
while length(ex.args) >= 1 && isa(ex.args[1], Expr)
(ex.args[1].head === :call) && return true
(ex.args[1].head === :where || ex.args[1].head === :(::)) || return false
ex = ex.args[1]
end
return false
end
function findmeta(ex::Expr)
if ex.head === :function || is_short_function_def(ex) || ex.head === :->
body::Expr = ex.args[2]
body.head === :block || error(body, " is not a block expression")
return findmeta_block(ex.args)
end
error(ex, " is not a function expression")
end
findmeta(ex::Array{Any,1}) = findmeta_block(ex)
function findmeta_block(exargs, argsmatch=args->true)
for i = 1:length(exargs)
a = exargs[i]
if isa(a, Expr)
if (a::Expr).head === :meta && argsmatch((a::Expr).args)
return i, exargs
elseif (a::Expr).head === :block
idx, exa = findmeta_block(a.args, argsmatch)
if idx != 0
return idx, exa
end
end
end
end
return 0, []
end
remove_linenums!(ex) = ex
function remove_linenums!(ex::Expr)
if ex.head === :block || ex.head === :quote
# remove line number expressions from metadata (not argument literal or inert) position
filter!(ex.args) do x
isa(x, Expr) && x.head === :line && return false
isa(x, LineNumberNode) && return false
return true
end
end
for subex in ex.args
subex isa Expr && remove_linenums!(subex)
end
return ex
end
function remove_linenums!(src::CodeInfo)
src.codelocs .= 0
length(src.linetable) > 1 && resize!(src.linetable, 1)
return src
end
macro generated()
return Expr(:generated)
end
"""
@generated f
@generated(f)
`@generated` is used to annotate a function which will be generated.
In the body of the generated function, only types of arguments can be read
(not the values). The function returns a quoted expression evaluated when the
function is called. The `@generated` macro should not be used on functions mutating
the global scope or depending on mutable elements.
See [Metaprogramming](@ref) for further details.
## Example:
```julia
julia> @generated function bar(x)
if x <: Integer
return :(x ^ 2)
else
return :(x)
end
end
bar (generic function with 1 method)
julia> bar(4)
16
julia> bar("baz")
"baz"
```
"""
macro generated(f)
if isa(f, Expr) && (f.head === :function || is_short_function_def(f))
body = f.args[2]
lno = body.args[1]
return Expr(:escape,
Expr(f.head, f.args[1],
Expr(:block,
lno,
Expr(:if, Expr(:generated),
body,
Expr(:block,
Expr(:meta, :generated_only),
Expr(:return, nothing))))))
else
error("invalid syntax; @generated must be used with a function definition")
end
end
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