allow @nospecialize-d push! to take arbitrary items

base/array.jl

@@ -1053,9 +1053,19 @@ function push!(a::Array{T,1}, item) where T
     return a
 end
 
-function push!(a::Array{Any,1}, @nospecialize item)
+# specialize and optimize the single argument case
+function push!(a::Vector{Any}, @nospecialize x)
     _growend!(a, 1)
-    arrayset(true, a, item, length(a))
+    arrayset(true, a, x, length(a))
+    return a
+end
+function push!(a::Vector{Any}, @nospecialize x...)
+    na = length(a)
+    nx = length(x)
+    _growend!(a, nx)
+    for i = 1:nx
+        arrayset(true, a, x[i], na+i)
+    end
     return a
 end
 
@@ -1385,6 +1395,22 @@ function pushfirst!(a::Array{T,1}, item) where T
     return a
 end
 
+# specialize and optimize the single argument case
+function pushfirst!(a::Vector{Any}, @nospecialize x)
+    _growbeg!(a, 1)
+    a[1] = x
+    return a
+end
+function pushfirst!(a::Vector{Any}, @nospecialize x...)
+    na = length(a)
+    nx = length(x)
+    _growbeg!(a, nx)
+    for i = 1:nx
+        a[i] = x[i]
+    end
+    return a
+end
+
 """
     popfirst!(collection) -> item
 

test/compiler/inline.jl

@@ -1375,3 +1375,30 @@ let src = code_typed1() do
     @test count(isnew, src.code) == 1
     @test count(isinvoke(:noinline_finalizer), src.code) == 1
 end
+
+# optimize `[push!|pushfirst!](::Vector{Any}, x...)`
+@testset "optimize `$f(::Vector{Any}, x...)`" for f = Any[push!, pushfirst!]
+    @eval begin
+        let src = code_typed1((Vector{Any}, Any)) do xs, x
+                $f(xs, x)
+            end
+            @test count(iscall((src, $f)), src.code) == 0
+            @test count(src.code) do @nospecialize x
+                isa(x, Core.GotoNode) ||
+                isa(x, Core.GotoIfNot) ||
+                iscall((src, getfield))(x)
+            end == 0 # no loop should be involved for the common single arg case
+        end
+        let src = code_typed1((Vector{Any}, Any, Any)) do xs, x, y
+                $f(xs, x, y)
+            end
+            @test count(iscall((src, $f)), src.code) == 0
+        end
+        let xs = Any[]
+            $f(xs, :x, "y", 'z')
+            @test xs[1] === :x
+            @test xs[2] == "y"
+            @test xs[3] === 'z'
+        end
+    end
+end