[PATCH] D41879: [X86] Added support for nocf_check attribute for indirect Branch Tracking

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: lib/Target/X86/X86InstrSystem.td:564
+let Predicates = [HasIBT] in
+  def : Pat<(X86nocf_check_calljmp), (DS_PREFIX)>;
+
----------------
I'm not sure I like feel very safe emitting the DS_PREFIX as a separate instruction. The glue won't exist after the SelectionDAG is converted to MIR so I'm not sure we would be guaranteed to keep it together.

I think I'd rather see special flavors of CALL*r/JMP*r that have a DS_PREFIX bit set in the TSFlags for their opcode and then the code emitter would know to emit the prefix. Basically what we do with LOCK and REP today. That way the instruction is one machine IR instruction that can never be separated.


Repository:
  rL LLVM

https://reviews.llvm.org/D41879