[X86] Use ISD::SIGN_EXTEND instead of X86ISD::VSEXT for mask to xmm/ymm/zmm conversion
There are a couple tricky things with this patch.
I had to add an override of isVectorLoadExtDesirable to stop DAG combine from combining sign_extend with loads after legalization since we legalize sextload using a load+sign_extend. Overriding this hook actually prevents a lot sextloads from being created in the first place.
I also had to add isel patterns because DAG combine blindly combines sign_extend+truncate to a smaller sign_extend which defeats what legalization was trying to do.
Differential Revision: https://reviews.llvm.org/D42407
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323301 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed