`shfl_down` intrinsic

[christiangnrd]

This may be all that's needed?

Could maybe add simdgroup (warps, subgroups) indexing intrinsics but I'd have to check if every backend supports this (I assume they would?)

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diff --git a/test/intrinsics.jl b/test/intrinsics.jl
index 68fa9e48..d27de5e9 100644
--- a/test/intrinsics.jl
+++ b/test/intrinsics.jl
@@ -36,10 +36,10 @@ function shfl_down_test_kernel(a, b)
         value = temp[idx]
 
         value = value + KI.shfl_down(value, 16)
-        value = value + KI.shfl_down(value,  8)
-        value = value + KI.shfl_down(value,  4)
-        value = value + KI.shfl_down(value,  2)
-        value = value + KI.shfl_down(value,  1)
+        value = value + KI.shfl_down(value, 8)
+        value = value + KI.shfl_down(value, 4)
+        value = value + KI.shfl_down(value, 2)
+        value = value + KI.shfl_down(value, 1)
 
         b[idx] = value
     end
@@ -152,7 +152,7 @@ function intrinsics_testsuite(backend, AT)
             dev_a = AT(a)
             dev_b = AT(zeros(T, 32))
 
-            KI.@kernel backend() workgroupsize=32 shfl_down_test_kernel(dev_a, dev_b)
+            KI.@kernel backend() workgroupsize = 32 shfl_down_test_kernel(dev_a, dev_b)
 
             b = Array(dev_b)
             @test sum(a) ≈ b[1]

[vchuravy]

So the backends that I am worried about is Metal and to a lesser extend Intel.

[christiangnrd]

So the backends that I am worried about is Metal and to a lesser extend Intel.

What are your worries?