fix non-real α

Author: araujoms

src/matmul.jl

@@ -585,7 +585,7 @@ Base.@constprop :aggressive function generic_matmatmul_wrapper!(C::StridedMatrix
         blasfn = _valtypeparam(val)
         if blasfn == BlasFlag.SYRK && T <: Union{Real,Complex} && (iszero(β) || issymmetric(C))
             return copytri!(generic_syrk!(C, A, false, aat, α, β), 'U')
-        elseif blasfn == BlasFlag.HERK && (iszero(β) || ishermitian(C))
+        elseif blasfn == BlasFlag.HERK && isreal(α) && isreal(β) && (iszero(β) || ishermitian(C))
             return copytri!(generic_syrk!(C, A, true, aat, α, β), 'U', true)
         end
     end

test/generic.jl

@@ -145,6 +145,17 @@ end
         mul!(cbig, transpose(a), a, α, false)
         LinearAlgebra._generic_matmatmul!(cbig_fallback, transpose(a), a, α, false)
         @test cbig ≈ cbig_fallback
+        if T <: Union{Real, Complex}
+            @test issymmetric(csmall)
+            @test issymmetric(cbig)
+        end
+        #make sure generic herk is not called for non-real α
+        mul!(csmall, a, a', α, false)
+        LinearAlgebra._generic_matmatmul!(csmall_fallback, a, a', α, false)
+        @test csmall ≈ csmall_fallback
+        mul!(cbig, a', a, α, false)
+        LinearAlgebra._generic_matmatmul!(cbig_fallback, a', a, α, false)
+        @test cbig ≈ cbig_fallback
     end
 end