Reuse code in _rscale_add!

Author: jishnub

src/generic.jl

@@ -212,7 +212,7 @@ end
 function _lscale_add_nonzeroalpha!(C::AbstractArray, s::Number, X::AbstractArray, alpha::Number, beta::Number)
     if isone(alpha)
         # since alpha is unused, we might as well set to `true` to avoid recompiling
-        # the branch if a different type is used
+        # the branch if an `alpha` of a different type is used
         _lscale_add_nonzeroalpha!(C, s, X, true, beta)
     else
         if iszero(beta)
@@ -239,24 +239,26 @@ _rscale_add!(C::StridedArray, X::StridedArray, s::Number, alpha::Number, beta::N
 @inline function _rscale_add!(C::AbstractArray, X::AbstractArray, s::Number, alpha::Number, beta::Number)
     if axes(C) == axes(X)
         if isone(alpha)
-            if iszero(beta)
-                @. C = X * s
-            else
-                @. C = X * s + C * beta
-            end
+            # since alpha is unused, we might as well ignore it in this branch.
+            # This avoids recompiling the branch if an `alpha` of a different type is used
+            _rscale_add_alphaisone!(C, X, s, beta)
         else
             s_alpha = s * alpha
-            if iszero(beta)
-                @. C = X * s_alpha
-            else
-                @. C = X * s_alpha + C * beta
-            end
+            _rscale_add_alphaisone!(C, X, s_alpha, beta)
         end
     else
         generic_mul!(C, X, s, alpha, beta)
     end
     return C
 end
+function _rscale_add_alphaisone!(C::AbstractArray, X::AbstractArray, s::Number, beta::Number)
+    if iszero(beta)
+        @. C = X * s
+    else
+        @. C = X * s + C * beta
+    end
+    C
+end
 
 # For better performance when input and output are the same array
 # See https://github.com/JuliaLang/julia/issues/8415#issuecomment-56608729

test/generic.jl

@@ -865,8 +865,12 @@ end
     # 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
+    # 5-arg tests with alpha::Bool
     @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, false, 2) == 2v
+    @test mul!(copy!(similar(v), v), v, 2, false, 2) == 2v
+    # 5-arg tests
     @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