Problems with barrier function

Level Zero's SPIRV barrier function is not working on my Intel(R) UHD Graphics P630 [0x9bf6]

The kernel I'm looking at implements a reduction (sum) within a workgroup (local). It sums over the elements of an array of floats and stores the intermediate results in local memory. The required synchronization within the workgroup is implemented via

```
call void @_Z7barrierj(i32 3)

declare spir_func void @_Z7barrierj(i32) #0
attributes #0 = { readnone }

```
However, the kernel doesn't work correctly. It's result is off a little bit from the correct value. This is a typical symptom when the barrier function is not working correctly.

The kernel gets translated to SPIRV and then loaded and launched with Intel Level Zero/compute-runtime. And that's when the barrier is not working. I don't know at what stage it gets messed up.

I have tried passing '1' and '2' to the barrier function and not issuing the call at all: Exactly the same outcome. This hints to the fact that the barrier is not called at all.

This is what Clang generates for the following statement:

```
barrier(CLK_LOCAL_MEM_FENCE | CLK_GLOBAL_MEM_FENCE);

tail call spir_func void @_Z7barrierj(i32 3) #4

declare spir_func void @_Z7barrierj(i32) local_unnamed_addr #2
attributes #2 = { convergent "frame-pointer"="none" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
attributes #4 = { convergent nounwind }

```
I don't think the additional attributes matter here.

Any ideas?

Begin with the provided LLVM IR and trace the barrier through SPIR-V translation and the Level Zero/compute-runtime launch; compare behavior for barrier arguments 1, 2, and 3 and with the call omitted. Done means locating the stage where synchronization is lost and documenting a reproducible result for the reduction kernel.

Written by the indexing model from the issue text.