[BOLT] Introduce BinaryFunction::canClone()

In some scenarios, we want to allow execution of the original function
code together with its rewritten (optimized) copy. We used to limit such
capability when the function uses C++ exceptions, since we cannot
duplicate exception tables. There's more metadata that cannot be
duplicated, and this PR adds more checks via the introduction of
canClone() function that checks all such limitations.

Author: maksfb

bolt/include/bolt/Core/BinaryFunction.h

@@ -1375,6 +1375,11 @@ class BinaryFunction {
   /// Return true if the function should not have associated symbol table entry.
   bool isAnonymous() const { return IsAnonymous; }
 
+  /// Return true if we can allow the execution of the original body of the
+  /// function together with its rewritten copy. This means, e.g., that metadata
+  /// associated with the function can be duplicated/cloned.
+  bool canClone() const;
+
   /// If this function was folded, return the function it was folded into.
   BinaryFunction *getFoldedIntoFunction() const { return FoldedIntoFunction; }
 

bolt/lib/Core/BinaryFunction.cpp

@@ -3744,6 +3744,16 @@ void BinaryFunction::postProcessBranches() {
   assert(validateCFG() && "invalid CFG");
 }
 
+bool BinaryFunction::canClone() const {
+  // For instrumentation, we need to restrict the execution to the rewritten
+  // version of the function.
+  if (opts::Instrument)
+    return false;
+
+  // Check for the presence of metadata that cannot be duplicated.
+  return !hasEHRanges() && !hasSDTMarker() && !hasPseudoProbe() && !hasORC();
+}
+
 MCSymbol *BinaryFunction::addEntryPointAtOffset(uint64_t Offset) {
   assert(Offset && "cannot add primary entry point");
   assert(CurrentState == State::Empty || CurrentState == State::Disassembled);

bolt/lib/Passes/PatchEntries.cpp

@@ -65,7 +65,7 @@ Error PatchEntries::runOnFunctions(BinaryContext &BC) {
       continue;
 
     // Check if we can skip patching the function.
-    if (!opts::ForcePatch && !Function.hasEHRanges() &&
+    if (!opts::ForcePatch && Function.canClone() &&
         Function.getSize() < PatchThreshold)
       continue;