[X86][SSE] Recognise vXi1 boolean anyof/allof reduction patterns

Currently combineHorizontalPredicateResult only handles anyof/allof reduction patterns of legal types, which can be tricky to match as type legalization of bools can introduce bitcasts/truncs/extensions.

This patch extends combineHorizontalPredicateResult to recognise vXi1 bool reductions as well and uses the existing combineBitcastvxi1 helper to create the MOVMSK necessary to then compare the signmask result.

This ensures the accuracy of the reduction costs added in D60403 which assume the MOVMSK generation.

Differential Revision: https://reviews.llvm.org/D60610

llvm-svn: 358286