diff --git a/src/compiler.jl b/src/compiler.jl
index 36ba2c8656..bb7ec835f8 100644
--- a/src/compiler.jl
+++ b/src/compiler.jl
@@ -3207,7 +3207,20 @@ function annotate!(mod, mode)
     )
         if haskey(fns, fname)
             fn = fns[fname]
-            push!(function_attributes(fn), LLVM.EnumAttribute("readonly", 0))
+            if LLVM.version().major <= 15
+                push!(function_attributes(fn), LLVM.EnumAttribute("readonly", 0))
+            else
+                push!(function_attributes(fn), 
+                    EnumAttribute(
+                        "memory",
+                        MemoryEffect(
+                            (MRI_Ref << getLocationPos(ArgMem)) |
+                            (MRI_NoModRef << getLocationPos(InaccessibleMem)) |
+                            (MRI_NoModRef << getLocationPos(Other)),
+                        ).data,
+                    )
+                )
+            end
             for u in LLVM.uses(fn)
                 c = LLVM.user(u)
                 if !isa(c, LLVM.CallInst)
diff --git a/src/compiler/optimize.jl b/src/compiler/optimize.jl
index 86760b423f..a35de5608f 100644
--- a/src/compiler/optimize.jl
+++ b/src/compiler/optimize.jl
@@ -828,13 +828,14 @@ function nodecayed_phis!(mod::LLVM.Module)
                                             base_1, off_1, _ = get_base_and_offset(operands(v)[1])
 
                                             if o2 == rhs && base_1 == base_2 && off_1 == off_2
-                                                return v2, offset, true
+                                                return operands(v)[1], offset, true
                                             end
 
                                             rhs = ptrtoint!(b, get_memory_data(b, operands(v)[1]), offty)
                                             lhs = ptrtoint!(b, operands(v)[2], offty)
-                                            off2 = nuwsub!(b, rhs, lhs)
-                                            return v2, nuwadd!(b, offset, off2), true
+                                            off2 = nuwsub!(b, lhs, rhs)
+                                            add = nuwadd!(b, offset, off2)
+                                            return operands(v)[1], add, true
                                         end
                                     end
                                 end
@@ -905,8 +906,12 @@ function nodecayed_phis!(mod::LLVM.Module)
                             end
 
                             if isa(v, LLVM.BitCastInst)
+                                preop = operands(v)[1]
+                                while isa(preop, LLVM.BitCastInst)
+                                    preop = operands(preop)[1]
+                                end
                                 v2, offset, skipload =
-                                    getparent(operands(v)[1], offset, hasload)
+                                    getparent(preop, offset, hasload)
                                 v2 = bitcast!(
                                     b,
                                     v2,
@@ -1059,7 +1064,7 @@ function nodecayed_phis!(mod::LLVM.Module)
                     end
 
                     nb = IRBuilder()
-                    position!(nb, inst)
+                    position!(nb, nonphi)
 
                     offset = goffsets[inst]
                     append!(LLVM.incoming(offset), offsets)
@@ -1068,15 +1073,26 @@ function nodecayed_phis!(mod::LLVM.Module)
                     end
 
                     nphi = nextvs[inst]
-                    if !all(x -> x[1] == nvs[1][1], nvs)
-                        append!(LLVM.incoming(nphi), nvs)
-                    else
-                        replace_uses!(nphi, nvs[1][1])
+
+                    function ogbc(x)
+                        while isa(x, LLVM.BitCastInst)
+                            x = operands(x)[1]
+                        end
+                        return x
+                    end
+
+                    if all(x -> ogbc(x[1]) == ogbc(nvs[1][1]), nvs)
+                        bc = ogbc(nvs[1][1])
+                        if value_type(bc) != value_type(nphi)
+                            bc = bitcast!(nb, bc, value_type(nphi))
+                        end
+                        replace_uses!(nphi, bc)
                         LLVM.API.LLVMInstructionEraseFromParent(nphi)
-                        nphi = nvs[1][1]
+                        nphi = bc
+                    else
+                        append!(LLVM.incoming(nphi), nvs)
                     end
 
-                    position!(nb, nonphi)
                     if addr == 13
                         @static if VERSION < v"1.11-"
                             nphi = bitcast!(nb, nphi, LLVM.PointerType(ty, 10))
diff --git a/test/optimize.jl b/test/optimize.jl
new file mode 100644
index 0000000000..a4fcc1768f
--- /dev/null
+++ b/test/optimize.jl
@@ -0,0 +1,46 @@
+using Enzyme, LinearAlgebra, Test
+
+function gcloaded_fixup(dest, src)
+    N = size(src)
+    dat = src.data
+    len = N[1]
+
+    i = 1
+    while true
+        j = 1
+        while true
+            ld = @inbounds if i <= j
+                dat[(i-1) * 2 + j]
+            else
+                dat[(j-1) * 2 + i]
+            end
+            @inbounds dest[(i-1) * 2 + j] = ld
+            if j == len
+                break
+            end
+            j += 1
+        end
+        if i == len
+            break
+        end
+        i += 1
+    end
+    return nothing
+end
+
+@testset "GCLoaded fixup" begin
+	H = Hermitian(Matrix([4.0 1.0; 2.0 5.0]))
+	dest = Matrix{Float64}(undef, 2, 2)
+
+	Enzyme.autodiff(
+	    ForwardWithPrimal,
+	    gcloaded_fixup,
+	    Const,
+	    Const(dest),
+	    Const(H),
+	)[1]
+    @test dest ≈ [4.0 2.0; 2.0 5.0]
+    dest = Matrix{Float64}(undef, 2, 2)
+    gcloaded_fixup(dest, H)
+    @test dest ≈ [4.0 2.0; 2.0 5.0]
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index 8c7ca39abc..b3a64a2a21 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -73,6 +73,7 @@ end
 
 include("abi.jl")
 include("typetree.jl")
+include("optimize.jl")
 
 include("rules.jl")
 include("rrules.jl")