commit 488b40bd2e114094b70317ebfe11f8c4d689d79f
author Simon Pilgrim <llvm-dev@redking.me.uk> Fri Feb 01 16:02:12 2019 +0000
committer Simon Pilgrim <llvm-dev@redking.me.uk> Fri Feb 01 16:02:12 2019 +0000
tree 30ad6619accf318424d3cdf91a6731246694698f
parent e9dc79169d528635259dc0c1b0afa8c7e6eed1d7

[X86][SSE] Use PSLLDQ/PSRLDQ to mask out zeroable ends of a shuffle

As suggested on PR40318, this patch uses PSLLDQ/PSRLDQ to lower shuffles to zero out the ends of a vector, leaving a sequential inner section.

For pre-SSSE3 we do this for shuffles with zeros at either end (requiring up to 3 shifts), but once PSHUFB is available I've limited this to shuffles with a single zeroable end (2 shifts).

Differential Revision: https://reviews.llvm.org/D56784

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@352883 91177308-0d34-0410-b5e6-96231b3b80d8