Changes

[BPF] add "llvm." prefix to BPF internally created globals
Currently, BPF backend creates some global variables with name like
 <type_name>:<reloc_type>:<patch_imm>$<access_str> to carry certain
information to BPF backend.
With direct clang compilation, the following code in
  llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp is triggered and the above
globals are emitted to the ELF file.
(clang enabled this as opt flag -faddrsig is on by default.)
  if (TM.Options.EmitAddrsig) {
   // Emit address-significance attributes for all globals.
   OutStreamer->EmitAddrsig();
   for (const GlobalValue &GV : M.global_values())
     if (!GV.use_empty() && !GV.isThreadLocal() &&
         !GV.hasDLLImportStorageClass() &&
!GV.getName().startswith("llvm.") &&
         !GV.hasAtLeastLocalUnnamedAddr())
       OutStreamer->EmitAddrsigSym(getSymbol(&GV));
 }
...
10162: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT   UND
tcp_sock:0:2048$0:117
10163: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT   UND
tcp_sock:0:2112$0:126:0
10164: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT   UND
tcp_sock:1:8$0:31:6
... While in llc, those globals are not emited since EmitAddrsig default
option is false for llc. The llc flag "-addrsig" can be used to enable
the above code.
This patch added "llvm." prefix to these internal globals so that they
can be ignored in the above codes and possible other places.
Differential Revision: https://reviews.llvm.org/D70703

[X86] Updated strict fp scalar tests and add fp80 tests for D68857, NFC.