Vectorization of product of flipped vectors

I'm looking for how to vectorize this loop :

r=zeros(1,length(r1));
for i=1:length(r1);
r(i)=sum(r1(1:i).*r2(i:-1:1));
end

r1 and r2 are two vectors of the same size.

Answer 1

[Teja Muppirala]

Faster for long vectors, slower for short ones:

r = conv(r1,r2);
r = r(1:numel(r1));

[Tétef]

thx !