`@threads` with `@simd` performance regression on `0.7.0-alpha`

General Usage
2

Ahhh, I think it is issue #15276 again (I don’t understand why @simd was triggering it thought)! I thought that was presumably fixed in:

https://github.com/JuliaLang/julia/pull/24688

This fixes it:

 function fillat!(a)
     Threads.@thread for i2 in 1:size(a,2)
           let i2=i2
              @simd for i1 in 1:size(a,1)
                      @inbounds  a[i1,i2]=i1/i2
              end
          end
     end
end
[(n=10^i;a1=rand(n,n);a2=rand(n,n);t1=@elapsed filla!(a1);t2=@elapsed fillat!(a2);(t1,t2/t1,vecnorm(a2-a1))) for i=1:4]
 (7.24e-7, 4.593922651933702, 0.0)     
 (3.2617e-5, 1.0026366618634455, 0.0)  
 (0.003374422, 0.984838885000157, 0.0) 
 (0.336461036, 0.9935467089270926, 0.0)

In case this proves useful to anyone :slight_smile:

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