From 6ba78767d79bee06686bc40c6239f6231ec28c16 Mon Sep 17 00:00:00 2001
From: Kristoffer Carlsson <kristoffer.carlsson@chalmers.se>
Date: Thu, 6 Sep 2018 14:03:05 -0400
Subject: [PATCH] work around a splatting penalty in twiceprecision (#29060)

* work around a splatting penalty in twiceprecision

* add allocation test

(cherry picked from commit 88d536a1ea8903dfdfd78f86a5be75eedcfddf5a)
---
 base/twiceprecision.jl | 7 +++++--
 test/ranges.jl         | 7 +++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/base/twiceprecision.jl b/base/twiceprecision.jl
index cf61823ecc0f6..e80c87c2eb8e5 100644
--- a/base/twiceprecision.jl
+++ b/base/twiceprecision.jl
@@ -332,11 +332,14 @@ const F_or_FF = Union{AbstractFloat, Tuple{AbstractFloat,AbstractFloat}}
 asF64(x::AbstractFloat) = Float64(x)
 asF64(x::Tuple{AbstractFloat,AbstractFloat}) = Float64(x[1]) + Float64(x[2])
 
+# Defined to prevent splatting in the function below which here has a performance impact
+_TP(x) = TwicePrecision{Float64}(x)
+_TP(x::Tuple{Any, Any}) = TwicePrecision{Float64}(x[1], x[2])
 function steprangelen_hp(::Type{Float64}, ref::F_or_FF,
                          step::F_or_FF, nb::Integer,
                          len::Integer, offset::Integer)
-    StepRangeLen(TwicePrecision{Float64}(ref...),
-                 twiceprecision(TwicePrecision{Float64}(step...), nb), Int(len), offset)
+    StepRangeLen(_TP(ref),
+                 twiceprecision(_TP(step), nb), Int(len), offset)
 end
 
 function steprangelen_hp(::Type{T}, ref::F_or_FF,
diff --git a/test/ranges.jl b/test/ranges.jl
index 5817871b04050..ad720f7a2553f 100644
--- a/test/ranges.jl
+++ b/test/ranges.jl
@@ -1371,3 +1371,10 @@ end # module NonStandardIntegerRangeTest
         end
     end
 end
+
+@testset "allocation of TwicePrecision call" begin
+    0:286.493442:360
+    0:286:360
+    @test @allocated(0:286.493442:360) == 0
+    @test @allocated(0:286:360) == 0
+end