From b255933106293a3f2deedf77281eb55ef75ef76b Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Sat, 20 Nov 2021 21:56:46 +0800
Subject: [PATCH 1/2] add `@inline` for `Diagonal`'s 2-arg `l/rdiv!` to enable
 auto vectorization

---
 stdlib/LinearAlgebra/src/diagonal.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/stdlib/LinearAlgebra/src/diagonal.jl b/stdlib/LinearAlgebra/src/diagonal.jl
index 0025085b2e964..6273ab5df8b45 100644
--- a/stdlib/LinearAlgebra/src/diagonal.jl
+++ b/stdlib/LinearAlgebra/src/diagonal.jl
@@ -357,7 +357,7 @@ end
 
 /(A::AbstractVecOrMat, D::Diagonal) = _rdiv!(similar(A, promote_op(/, eltype(A), eltype(D)), size(A)), A, D)
 
-rdiv!(A::AbstractVecOrMat, D::Diagonal) = _rdiv!(A, A, D)
+rdiv!(A::AbstractVecOrMat, D::Diagonal) = @inline _rdiv!(A, A, D)
 # avoid copy when possible via internal 3-arg backend
 function _rdiv!(B::AbstractVecOrMat, A::AbstractVecOrMat, D::Diagonal)
     require_one_based_indexing(A)
@@ -378,7 +378,7 @@ end
 
 \(D::Diagonal, B::AbstractVecOrMat) = ldiv!(similar(B, promote_op(\, eltype(D), eltype(B)), size(B)), D, B)
 
-ldiv!(D::Diagonal, B::AbstractVecOrMat) = ldiv!(B, D, B)
+ldiv!(D::Diagonal, B::AbstractVecOrMat) = @inline ldiv!(B, D, B)
 function ldiv!(B::AbstractVecOrMat, D::Diagonal, A::AbstractVecOrMat)
     require_one_based_indexing(A, B)
     d = length(D.diag)

From aacdc08fba0f5eb5dee297d9427aeec6c4903148 Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Sat, 20 Nov 2021 22:35:54 +0800
Subject: [PATCH 2/2] Update diagonal.jl

replace broadcast with for loop.
---
 stdlib/LinearAlgebra/src/diagonal.jl | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/stdlib/LinearAlgebra/src/diagonal.jl b/stdlib/LinearAlgebra/src/diagonal.jl
index 6273ab5df8b45..09562615621a1 100644
--- a/stdlib/LinearAlgebra/src/diagonal.jl
+++ b/stdlib/LinearAlgebra/src/diagonal.jl
@@ -381,14 +381,18 @@ end
 ldiv!(D::Diagonal, B::AbstractVecOrMat) = @inline ldiv!(B, D, B)
 function ldiv!(B::AbstractVecOrMat, D::Diagonal, A::AbstractVecOrMat)
     require_one_based_indexing(A, B)
-    d = length(D.diag)
+    dd = D.diag
+    d = length(dd)
     m, n = size(A, 1), size(A, 2)
     m′, n′ = size(B, 1), size(B, 2)
     m == d || throw(DimensionMismatch("right hand side has $m rows but D is $d by $d"))
     (m, n) == (m′, n′) || throw(DimensionMismatch("expect output to be $m by $n, but got $m′ by $n′"))
     j = findfirst(iszero, D.diag)
     isnothing(j) || throw(SingularException(j))
-    B .= D.diag .\ A
+    @inbounds for j = 1:n, i = 1:m
+        B[i, j] = dd[i] \ A[i, j]
+    end
+    B
 end
 
 # Optimizations for \, / between Diagonals