add @constprop for compatibility to 1.7

This also adds a depwarn for `@aggressive_constprop`, which seemed
sensible to me, given that it will be removed in 1.8.

replaces #42125

base/char.jl

@@ -45,10 +45,10 @@ represents a valid Unicode character.
 """
 Char
 
-@aggressive_constprop (::Type{T})(x::Number) where {T<:AbstractChar} = T(UInt32(x))
-@aggressive_constprop AbstractChar(x::Number) = Char(x)
-@aggressive_constprop (::Type{T})(x::AbstractChar) where {T<:Union{Number,AbstractChar}} = T(codepoint(x))
-@aggressive_constprop (::Type{T})(x::AbstractChar) where {T<:Union{Int32,Int64}} = codepoint(x) % T
+@constprop :aggressive (::Type{T})(x::Number) where {T<:AbstractChar} = T(UInt32(x))
+@constprop :aggressive AbstractChar(x::Number) = Char(x)
+@constprop :aggressive (::Type{T})(x::AbstractChar) where {T<:Union{Number,AbstractChar}} = T(codepoint(x))
+@constprop :aggressive (::Type{T})(x::AbstractChar) where {T<:Union{Int32,Int64}} = codepoint(x) % T
 (::Type{T})(x::T) where {T<:AbstractChar} = x
 
 """
@@ -75,7 +75,7 @@ return a different-sized integer (e.g. `UInt8`).
 """
 function codepoint end
 
-@aggressive_constprop codepoint(c::Char) = UInt32(c)
+@constprop :aggressive codepoint(c::Char) = UInt32(c)
 
 struct InvalidCharError{T<:AbstractChar} <: Exception
     char::T
@@ -124,7 +124,7 @@ See also [`decode_overlong`](@ref) and [`show_invalid`](@ref).
 """
 isoverlong(c::AbstractChar) = false
 
-@aggressive_constprop function UInt32(c::Char)
+@constprop :aggressive function UInt32(c::Char)
     # TODO: use optimized inline LLVM
     u = bitcast(UInt32, c)
     u < 0x80000000 && return u >> 24
@@ -148,7 +148,7 @@ that support overlong encodings should implement `Base.decode_overlong`.
 """
 function decode_overlong end
 
-@aggressive_constprop function decode_overlong(c::Char)
+@constprop :aggressive function decode_overlong(c::Char)
     u = bitcast(UInt32, c)
     l1 = leading_ones(u)
     t0 = trailing_zeros(u) & 56
@@ -158,7 +158,7 @@ function decode_overlong end
     ((u & 0x007f0000) >> 4) | ((u & 0x7f000000) >> 6)
 end
 
-@aggressive_constprop function Char(u::UInt32)
+@constprop :aggressive function Char(u::UInt32)
     u < 0x80 && return bitcast(Char, u << 24)
     u < 0x00200000 || throw_code_point_err(u)
     c = ((u << 0) & 0x0000003f) | ((u << 2) & 0x00003f00) |
@@ -169,14 +169,14 @@ end
     bitcast(Char, c)
 end
 
-@aggressive_constprop @noinline UInt32_cold(c::Char) = UInt32(c)
-@aggressive_constprop function (T::Union{Type{Int8},Type{UInt8}})(c::Char)
+@constprop :aggressive @noinline UInt32_cold(c::Char) = UInt32(c)
+@constprop :aggressive function (T::Union{Type{Int8},Type{UInt8}})(c::Char)
     i = bitcast(Int32, c)
     i ≥ 0 ? ((i >>> 24) % T) : T(UInt32_cold(c))
 end
 
-@aggressive_constprop @noinline Char_cold(b::UInt32) = Char(b)
-@aggressive_constprop function Char(b::Union{Int8,UInt8})
+@constprop :aggressive @noinline Char_cold(b::UInt32) = Char(b)
+@constprop :aggressive function Char(b::Union{Int8,UInt8})
     0 ≤ b ≤ 0x7f ? bitcast(Char, (b % UInt32) << 24) : Char_cold(UInt32(b))
 end
 

base/deprecated.jl

@@ -262,4 +262,18 @@ end
 # This function was marked as experimental and not exported.
 @deprecate catch_stack(task=current_task(); include_bt=true) current_exceptions(task; backtrace=include_bt) false
 
+"""
+    @aggressive_constprop ex
+    @aggressive_constprop(ex)
+
+`@aggressive_constprop` requests more aggressive interprocedural constant
+propagation for the annotated function. For a method where the return type
+depends on the value of the arguments, this can yield improved inference results
+at the cost of additional compile time.
+"""
+macro aggressive_constprop(ex)
+    depwarn("use `@constprop :aggressive ex` instead of `@aggressive_constprop ex`", :var"@aggressive_constprop")
+    esc(isa(ex, Expr) ? pushmeta!(ex, :aggressive_constprop) : ex)
+end
+
 # END 1.7 deprecations

base/expr.jl

@@ -240,16 +240,25 @@ macro pure(ex)
 end
 
 """
-    @aggressive_constprop ex
-    @aggressive_constprop(ex)
+    @constprop setting ex
+    @constprop(setting, ex)
 
-`@aggressive_constprop` requests more aggressive interprocedural constant
-propagation for the annotated function. For a method where the return type
-depends on the value of the arguments, this can yield improved inference results
-at the cost of additional compile time.
+`@constprop` controls the mode of interprocedural constant propagation for the
+annotated function. Only `:aggressive` is supported in 1.7:
+
+- `@constprop :aggressive ex`: apply constant propagation aggressively.
+  For a method where the return type depends on the value of the arguments,
+  this can yield improved inference results at the cost of additional compile time.
+
+`@constprop :none ex` is a no-op, but is allowed for compatibility with Julia 1.8.
 """
-macro aggressive_constprop(ex)
-    esc(isa(ex, Expr) ? pushmeta!(ex, :aggressive_constprop) : ex)
+macro constprop(setting, ex)
+    if isa(setting, QuoteNode)
+        setting = setting.value
+    end
+    setting === :aggressive && return esc(isa(ex, Expr) ? pushmeta!(ex, :aggressive_constprop) : ex)
+    setting === :none && return esc(ex)
+    throw(ArgumentError("@constprop $setting not supported"))
 end
 
 """

test/compiler/inference.jl

@@ -3172,14 +3172,20 @@ f_inf_error_bottom(x::Vector) = isempty(x) ? error(x[1]) : x
 # @aggressive_constprop
 @noinline g_nonaggressive(y, x) = Val{x}()
 @noinline @Base.aggressive_constprop g_aggressive(y, x) = Val{x}()
+@noinline @Base.constprop :none g_nonaggressive2(y, x) = Val{x}()
+@noinline @Base.constprop :aggressive g_aggressive2(y, x) = Val{x}()
 
 f_nonaggressive(x) = g_nonaggressive(x, 1)
 f_aggressive(x) = g_aggressive(x, 1)
+f_nonaggressive2(x) = g_nonaggressive2(x, 1)
+f_aggressive2(x) = g_aggressive2(x, 1)
 
 # The first test just makes sure that improvements to the compiler don't
 # render the annotation effectless.
 @test Base.return_types(f_nonaggressive, Tuple{Int})[1] == Val
 @test Base.return_types(f_aggressive, Tuple{Int})[1] == Val{1}
+@test Base.return_types(f_nonaggressive2, Tuple{Int})[1] == Val
+@test Base.return_types(f_aggressive2, Tuple{Int})[1] == Val{1}
 
 function splat_lotta_unions()
     a = Union{Tuple{Int},Tuple{String,Vararg{Int}},Tuple{Int,Vararg{Int}}}[(2,)][1]