I moved these functions to X86InstrInfo.cpp so I can use them in another
pass I'm working on. Thanks for the suggestion, Craig!
Tested via llvm-lit llvm/test/CodeGen/X86/speculative-load-hardening*
As noted in the FIXMEs that I moved along with the fuctions, these
should eventually be moved to the tablegen instruction tables. There
didn't seem a straightforward way to do that due to the difficulties
trying to handle the check for when EFLAGS is dead for target