Restrict dest in 5-arg mul! (#825)

Author: mateuszbaran

src/matrix_multiply_add.jl

@@ -204,10 +204,18 @@ Base.transpose(::TSize{S,:any}) where {S,T} = TSize{reverse(S),:transpose}()
 @inline mul_parent(A::StaticMatrix) = A
 @inline mul_parent(A::StaticVector) = A
 
+# Using the full StaticVecOrMatLike in dest of that one method of mul! takes a lot of load time
+const StaticVecOrMatLikeForFiveArgMulDest{T} = Union{
+    StaticVector{<:Any, T},
+    StaticMatrix{<:Any, <:Any, T},
+    Transpose{T, <:StaticVecOrMat{T}},
+    Adjoint{T, <:StaticVecOrMat{T}}
+}
+
 # 5-argument matrix multiplication
 #    To avoid allocations, strip away Transpose type and store tranpose info in Size
-@inline LinearAlgebra.mul!(dest::StaticVecOrMatLike, A::StaticVecOrMatLike, B::StaticVecOrMatLike,
-    α::Real, β::Real) = _mul!(TSize(dest), mul_parent(dest), Size(A), Size(B), A, B,
+@inline LinearAlgebra.mul!(dest::StaticVecOrMatLikeForFiveArgMulDest, A::StaticVecOrMatLike, B::StaticVecOrMatLike,
+    α::Number, β::Number) = _mul!(TSize(dest), mul_parent(dest), Size(A), Size(B), A, B,
     AlphaBeta(α,β))
 
 @inline function LinearAlgebra.mul!(dest::StaticVecOrMatLike{TDest}, A::StaticVecOrMatLike{TA},
@@ -601,3 +609,4 @@ end
 @inline mul_blas!(Sc::TSize{<:Any,:transpose}, c::StaticMatrix, Sa::TSize, Sb::TSize,
         a::StaticMatrix, b::StaticMatrix, _add::MulAddMul) =
     mul_blas!(transpose(Sc), c, transpose(Sb), transpose(Sa), b, a, _add)
+