[BOLT] Adapted policy checks for stripped binaries

[Amir]

Summary

Stripped binaries do not have relocation and symbol name.
Relax sibling and entry point policy checks for stripped binaries.

Test Plan:

ninja check-bolt

[Amir]

LGTM

[Amir]

bolt/lib/Core/BinaryContext.cpp

1132

Please remove --> in comments.

[nhuhuan]

Updated comment

[nhuhuan]

Clarify that it will not affect the correctness in processing nonstripped
binaries.

[Amir]

Reject stripped binaries as a policy (D142686).

bolt/lib/Core/BinaryContext.cpp

if (NumCollisions) {
     if (!opts::Verbosity)
       errs() << ". Use -v=1 to see the list.";
     errs() << '\n';
   }
 }
 
 bool BinaryContext::registerFragment(BinaryFunction &TargetFunction,
                                      BinaryFunction &Function) const {
-  if (!isPotentialFragmentByName(TargetFunction, Function))
+  // Only use symbol name matching for non-stripped binaries
+  if (!IsStripped && !isPotentialFragmentByName(TargetFunction, Function))
     return false;
   assert(TargetFunction.isFragment() && "TargetFunction must be a fragment");
   if (TargetFunction.isParentFragment(&Function))
     return true;
   TargetFunction.addParentFragment(Function);
   Function.addFragment(TargetFunction);
-  if (!HasRelocations) {
+
+  // Stripped binaries mostly don't have .rela.text section
+  // Without .rela.text, BOLT cannot reliably move code
+  // Relaxing for stripped binaries only, not affect nonstripped binaries
+  if (!IsStripped && !HasRelocations) {
     TargetFunction.setSimple(false);
     Function.setSimple(false);
   }
   if (opts::Verbosity >= 1) {
     outs() << "BOLT-INFO: marking " << TargetFunction << " as a fragment of "
            << Function << '\n';
   }
   return true;

bolt/lib/Core/BinaryFunction.cpp

void BinaryFunction::postProcessEntryPoints() {
   if (!isSimple())
     return;
 
   for (auto &KV : Labels) {
     MCSymbol *Label = KV.second;
     if (!getSecondaryEntryPointSymbol(Label))
       continue;
 
-    // In non-relocation mode there's potentially an external undetectable
-    // reference to the entry point and hence we cannot move this entry
-    // point. Optimizing without moving could be difficult.
-    if (!BC.HasRelocations)
+    // Stripped binaries mostly don't have .rela.text section
+    // Without .rela.text, BOLT cannot reliably move code
+    // Relaxing for stripped binaries only, not affect nonstripped binaries
+    if (!BC.IsStripped && !BC.HasRelocations)
       setSimple(false);
 
     const uint32_t Offset = KV.first;
 
     // If we are at Offset 0 and there is no instruction associated with it,
     // this means this is an empty function. Just ignore. If we find an
     // instruction at this offset, this entry point is valid.
     if (!Offset || getInstructionAtOffset(Offset))