[X86] Emit 11-byte or 15-byte NOPs on recent AMD targets, else default to 10-byte NOPs (PR22965)
We currently emit up to 15-byte NOPs on all targets (apart from Silvermont), which stalls performance on some targets with decoders that struggle with 2 or 3 more '66' prefixes.
This patch flags recent AMD targets (btver1/znver1) to still emit 15-byte NOPs and bdver* targets to emit 11-byte NOPs. All other targets now emit 10-byte NOPs apart from SilverMont CPUs which still emit 7-byte NOPS.
Differential Revision: https://reviews.llvm.org/D42616
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323693 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed