Hi Bill, On Fri, Jul 15, 2016 at 08:55:08AM -0500, Bill Schmidt wrote: > This patch is a follow-up to Richard's patch of > https://gcc.gnu.org/ml/gcc-patches/2016-06/msg00584.html. The cost of a > vec_construct (initialization of an N-way vector by N scalars) is too low, > which can cause too-aggressive vectorization in particular for N=8 or > higher. Richard changed the default cost to N-1, which is generally > sensible. For powerpc I am going with a slightly higher cost of N, which > will keep us from being less conservative than the previous values when N=2.
> In any case, the purpose of this patch is simply to avoid vectorizing > things we shouldn't when we've undercounted the cost of a vec_construct. > Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no > regressions (hence the vectorization decisions in the test suite have > not changed). Is this ok for trunk? Do you also have a testcase where it does matter? It would be good to add that, then. Or is it fixing a regression? I know nothing about the cost model, so someone else will have to review, or I can just say "okay" ;-) Segher
