[Bug tree-optimization/54855] Unnecessary duplication when performing scalar operation on vector element

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54855



--- Comment #5 from Marc Glisse <glisse at gcc dot gnu.org> 2012-10-12 18:08:45 
UTC ---

Doing the optimization that late is a bit fragile though. For instance:

    v[0] += 3.0;

    v[0] -= 1.0;

is back to decomposing the vector, doing the operations and reconstructing it

(I didn't use -fassociative-math so it couldn't turn that into += 2.0). But

doing more looks too complicated.