Set alpha to true if unused

Author: jishnub

src/generic.jl

@@ -211,11 +211,9 @@ _lscale_add!(C::StridedArray, s::Number, X::StridedArray, alpha::Number, beta::N
 end
 function _lscale_add_nonzeroalpha!(C::AbstractArray, s::Number, X::AbstractArray, alpha::Number, beta::Number)
     if isone(alpha)
-        if iszero(beta)
-            @. C = s * X
-        else
-            @. C = s * X + C * beta
-        end
+        # since alpha is unused, we might as well set to `true` to avoid recompiling
+        # the branch if a different type is used
+        _lscale_add_nonzeroalpha!(C, s, X, true, beta)
     else
         if iszero(beta)
             @. C = s * X * alpha

test/generic.jl

@@ -862,6 +862,11 @@ end
     w = similar(v)
     @test mul!(w, 2, v) == 2v
     @test mul!(w, v, 2) == 2v
+    # 5-arg equivalent to the 3-arg method, but with non-Bool alpha
+    @test mul!(copy!(similar(v), v), 2, v, 1, 0) == 2v
+    @test mul!(copy!(similar(v), v), v, 2, 1, 0) == 2v
+    @test mul!(copy!(similar(v), v), 2, v, true, 1) == 3v
+    @test mul!(copy!(similar(v), v), v, 2, true, 1) == 3v
     @test mul!(copy!(similar(v), v), 2, v, 1, 3) == 5v
     @test mul!(copy!(similar(v), v), v, 2, 1, 3) == 5v
     @test mul!(copy!(similar(v), v), 2, v, 2, 3) == 7v