From 2e80c0d2645f48a4b3a8884b342339c302844ede Mon Sep 17 00:00:00 2001
From: Zentrik <Zentrik@users.noreply.github.com>
Date: Thu, 4 May 2023 11:26:06 +0100
Subject: [PATCH] Inline StepRange construction (#49270)

This can improve performance when iterating over a range with a step as currently steprange_last is not inlined. About a 12ns improvement

I don't think this should slow anything down as at worst you're making a call which is what you'd have to do without inlining. Also, it should be unlikely that branch is taken.
This should allow for better automatic inlining.
---
 base/multidimensional.jl |  2 +-
 base/range.jl            |  3 ++-
 test/ranges.jl           | 25 +++++++++++++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/base/multidimensional.jl b/base/multidimensional.jl
index 70b7354c18bd2..ce1b6c39adb43 100644
--- a/base/multidimensional.jl
+++ b/base/multidimensional.jl
@@ -526,7 +526,7 @@ module IteratorsMD
         dimrev = ntuple(i -> sum(==(i), dims; init = 0) == 1, Val(length(indices)))
         length(dims) == sum(dimrev) || throw(ArgumentError(Base.LazyString("invalid dimensions ", dims, " in reverse")))
         length(dims) == length(indices) && return Base._reverse(iter, :)
-        indices′ = map((i, f) -> f ? reverse(i) : i, indices, dimrev)
+        indices′ = map((i, f) -> f ? (@noinline reverse(i)) : i, indices, dimrev)
         return CartesianIndices(indices′)
     end
 
diff --git a/base/range.jl b/base/range.jl
index ea29516f64d24..80693a8e94a0c 100644
--- a/base/range.jl
+++ b/base/range.jl
@@ -350,7 +350,8 @@ function steprange_last(start, step, stop)::typeof(stop)
             # Compute remainder as a nonnegative number:
             if absdiff isa Signed && absdiff < zero(absdiff)
                 # unlikely, but handle the signed overflow case with unsigned rem
-                remain = convert(typeof(absdiff), unsigned(absdiff) % absstep)
+                overflow_case(absdiff, absstep) = (@noinline; convert(typeof(absdiff), unsigned(absdiff) % absstep))
+                remain = overflow_case(absdiff, absstep)
             else
                 remain = convert(typeof(absdiff), absdiff % absstep)
             end
diff --git a/test/ranges.jl b/test/ranges.jl
index bbdd303adb3c5..04c2cdcb47ac4 100644
--- a/test/ranges.jl
+++ b/test/ranges.jl
@@ -1,6 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 using Base.Checked: checked_length
+using InteractiveUtils: code_llvm
 
 @testset "range construction" begin
     @test_throws ArgumentError range(start=1, step=1, stop=2, length=10)
@@ -2400,3 +2401,27 @@ end
     @test test_firstindex(StepRange{Union{Int64,Int128},Int}(Int64(1), 1, Int128(1)))
     @test test_firstindex(StepRange{Union{Int64,Int128},Int}(Int64(1), 1, Int128(0)))
 end
+
+@testset "Inline StepRange Construction #49270" begin
+    x = rand(Float32, 80)
+    a = rand(round(Int, length(x) / 2):length(x), 10^6)
+
+    function test(x, a)
+        c = zero(Float32)
+
+        @inbounds for j in a
+            for i in 1:8:j
+                c += x[i]
+            end
+        end
+
+        return c
+    end
+
+    llvm_ir(f, args) = sprint((io, args...) -> code_llvm(io, args...; debuginfo=:none), f, Base.typesof(args...))
+
+    ir = llvm_ir(test, (x, a))
+    @test !occursin("steprange_last", ir)
+    @test !occursin("_colon", ir)
+    @test !occursin("StepRange", ir)
+end