Make sure to lower the first op in a collection first. Fixes #280.

Author: chriselrod

src/codegen/lower_load.jl

@@ -332,16 +332,21 @@ function _lower_load!(
     q::Expr, ls::LoopSet, op::Operation, td::UnrollArgs, mask::Bool, inds_calc_by_ptr_offset::Vector{Bool} = indices_calculated_by_pointer_offsets(ls, op.ref)
 )
   if rejectinterleave(op)
-    lower_load_no_optranslation!(q, ls, op, td, mask, inds_calc_by_ptr_offset)
+    return lower_load_no_optranslation!(q, ls, op, td, mask, inds_calc_by_ptr_offset)
   else
     omop = offsetloadcollection(ls)
     @unpack opids, opidcollectionmap, batchedcollections, batchedcollectionmap = omop
     batchid, opind = batchedcollectionmap[identifier(op)]
-    if opind == 1
-      collectionid, copind = opidcollectionmap[identifier(op)]
-      opidmap = opids[collectionid]
-      idsformap = batchedcollections[batchid]
-      lower_load_collection!(q, ls, opidmap, idsformap, td, mask, inds_calc_by_ptr_offset)
+    for (bid, oid) ∈ batchedcollectionmap # this relies on `for op ∈ ops` in codegen/operation_evaluation_order.jl
+      if bid == batchid
+        if oid == opind
+          collectionid, copind = opidcollectionmap[identifier(op)]
+          opidmap = opids[collectionid]
+          idsformap = batchedcollections[batchid]
+          lower_load_collection!(q, ls, opidmap, idsformap, td, mask, inds_calc_by_ptr_offset)
+        end
+        return nothing
+      end
     end
   end
   return nothing

test/copy.jl

@@ -151,20 +151,25 @@ using LoopVectorization, OffsetArrays, Test
     H
   end
 
-  function issue!(output, input, idx)
+  function issue279!(output, input, idx)
     @turbo for j in axes(output, 2), i in axes(output, 1)
       output[i, j, idx] = input[1, 1, i, j, idx]
     end
     output
   end
 
-  function issue_plain!(output, input, idx)
+  function issue279_plain!(output, input, idx)
     for j in axes(output, 2), i in axes(output, 1)
       output[i, j, idx] = input[1, 1, i, j, idx]
     end
     output
   end
-
+  function issue280!(dest, src)
+    @turbo for i in indices((dest, src), (2, 2))
+      dest[1, i] = src[2, i]
+      dest[2, i] = src[1, i]
+    end
+  end
 
     for T ∈ (Float32, Float64, Int32, Int64)
         @show T, @__LINE__
@@ -250,7 +255,16 @@ using LoopVectorization, OffsetArrays, Test
 
       input = rand(R, 2, 2, 5, 5, 1); output = Array{T}(undef, size(input)[3:end]...); output_plain = similar(output);
 
-      @test issue!(output, input, 1) ≈ issue_plain!(output_plain, input, 1)
+      @test issue279!(output, input, 1) ≈ issue279_plain!(output_plain, input, 1)
 
+      src = rand(R, 2, 17); dest = similar(src);
+      issue280!(dest, src)
+      @test dest ≈ vcat(view(src,2,:)',view(src,1,:)')
+      if VERSION ≥ v"1.6"
+        src2 = reinterpret(reshape,R,Vector{Tuple{T,T}}(undef, 17)); src2 .= src;
+        dest2 = reinterpret(reshape,R,Vector{Tuple{T,T}}(undef, 17));
+        issue280!(dest2, src2)
+        @test dest2 ≈ vcat(view(src,2,:)',view(src,1,:)')
+      end
     end
 end