When trying to combine a DAG that builds a vector out of sign-extensions of
vector extracts, the code assumes legal input types. Due to that, we have to
disable this combine prior to legalization.
In some cases, the DAG will look slightly different after legalization so
account for that in the matching code.
This is a fix for https://bugs.llvm.org/show_bug.cgi?id=38087
Differential Revision: https://reviews.llvm.org/D49080
llvm-svn: 339769
Nemanja Ivanovic