From e507961b12b9fbf606a3c87082409b42e284376a Mon Sep 17 00:00:00 2001
From: Jishnu Bhattacharya <jishnub.github@gmail.com>
Date: Fri, 4 Apr 2025 19:44:20 +0530
Subject: [PATCH 1/3] Generic path in ldiv! for Diagonal

---
 src/diagonal.jl | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/diagonal.jl b/src/diagonal.jl
index 7311f6e1..fa1d5804 100644
--- a/src/diagonal.jl
+++ b/src/diagonal.jl
@@ -601,10 +601,10 @@ function _rdiv!(B::AbstractVecOrMat, A::AbstractVecOrMat, D::Diagonal)
     if (k = length(dd)) != n
         throw(DimensionMismatch(lazy"left hand side has $n columns but D is $k by $k"))
     end
-    @inbounds for j in 1:n
+    @inbounds for j in axes(A,2)
         ddj = dd[j]
         iszero(ddj) && throw(SingularException(j))
-        for i in 1:m
+        @simd for i in axes(A,1)
             B[i, j] = A[i, j] / ddj
         end
     end
@@ -629,8 +629,20 @@ function ldiv!(B::AbstractVecOrMat, D::Diagonal, A::AbstractVecOrMat)
     (m, n) == (m′, n′) || throw(DimensionMismatch(lazy"expect output to be $m by $n, but got $m′ by $n′"))
     j = findfirst(iszero, D.diag)
     isnothing(j) || throw(SingularException(j))
-    @inbounds for j = 1:n, i = 1:m
-        B[i, j] = dd[i] \ A[i, j]
+    _ldiv_Diagonal_loop!(B, D, A)
+    B
+end
+function _ldiv_Diagonal_loop!(B::AbstractVecOrMat, D::Diagonal, A::AbstractVecOrMat)
+    dd = D.diag
+    @. B = dd \ A
+    B
+end
+function _ldiv_Diagonal_loop!(B::StridedVecOrMat, D::Diagonal, A::StridedVecOrMat)
+    dd = D.diag
+    @inbounds for j in axes(A,2)
+        @simd for i in axes(A,1)
+            B[i, j] = dd[i] \ A[i, j]
+        end
     end
     B
 end

From d760b6a35566057a9dd62859a8fe38404415fb0d Mon Sep 17 00:00:00 2001
From: Jishnu Bhattacharya <jishnub.github@gmail.com>
Date: Fri, 4 Apr 2025 20:56:58 +0530
Subject: [PATCH 2/3] Revert rdiv!

---
 src/diagonal.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/diagonal.jl b/src/diagonal.jl
index fa1d5804..850e2a53 100644
--- a/src/diagonal.jl
+++ b/src/diagonal.jl
@@ -604,7 +604,7 @@ function _rdiv!(B::AbstractVecOrMat, A::AbstractVecOrMat, D::Diagonal)
     @inbounds for j in axes(A,2)
         ddj = dd[j]
         iszero(ddj) && throw(SingularException(j))
-        @simd for i in axes(A,1)
+        for i in axes(A,1)
             B[i, j] = A[i, j] / ddj
         end
     end

From 548cc056ebfc3d8f9f6201d1223a3b7dcca619be Mon Sep 17 00:00:00 2001
From: Jishnu Bhattacharya <jishnub.github@gmail.com>
Date: Fri, 4 Apr 2025 21:04:20 +0530
Subject: [PATCH 3/3] Remove simd annotation in ldiv!

---
 src/diagonal.jl | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/diagonal.jl b/src/diagonal.jl
index 850e2a53..c919f360 100644
--- a/src/diagonal.jl
+++ b/src/diagonal.jl
@@ -639,10 +639,8 @@ function _ldiv_Diagonal_loop!(B::AbstractVecOrMat, D::Diagonal, A::AbstractVecOr
 end
 function _ldiv_Diagonal_loop!(B::StridedVecOrMat, D::Diagonal, A::StridedVecOrMat)
     dd = D.diag
-    @inbounds for j in axes(A,2)
-        @simd for i in axes(A,1)
-            B[i, j] = dd[i] \ A[i, j]
-        end
+    @inbounds for j in axes(A,2), i in axes(A,1)
+        B[i, j] = dd[i] \ A[i, j]
     end
     B
 end