[BOLT] Extract comparator for sorting functions by index into helper function

This change extracts the comparator for sorting functions by index into a helper
function `compareBinaryFunctionByIndex()`

Not sure why the comparator used in `BinaryContext::getSortedFunctions()` is not
same as the other two places. I think they should use the same comparator, so I
also change `BinaryContext::getSortedFunctions()` to use
`compareBinaryFunctionByIndex()` for sorting functions.

Author: Enna1

bolt/include/bolt/Core/BinaryFunction.h

@@ -2366,6 +2366,19 @@ inline raw_ostream &operator<<(raw_ostream &OS,
   return OS;
 }
 
+/// Compare function by index if it is valid, fall back to the original address
+/// otherwise.
+inline bool compareBinaryFunctionByIndex(const BinaryFunction *A,
+                                         const BinaryFunction *B) {
+  if (A->hasValidIndex() && B->hasValidIndex())
+    return A->getIndex() < B->getIndex();
+  if (A->hasValidIndex() && !B->hasValidIndex())
+    return true;
+  if (!A->hasValidIndex() && B->hasValidIndex())
+    return false;
+  return A->getAddress() < B->getAddress();
+}
+
 } // namespace bolt
 
 // GraphTraits specializations for function basic block graphs (CFGs)

bolt/lib/Core/BinaryContext.cpp

@@ -1607,13 +1607,7 @@ std::vector<BinaryFunction *> BinaryContext::getSortedFunctions() {
                   SortedFunctions.begin(),
                   [](BinaryFunction &BF) { return &BF; });
 
-  llvm::stable_sort(SortedFunctions,
-                    [](const BinaryFunction *A, const BinaryFunction *B) {
-                      if (A->hasValidIndex() && B->hasValidIndex()) {
-                        return A->getIndex() < B->getIndex();
-                      }
-                      return A->hasValidIndex();
-                    });
+  llvm::stable_sort(SortedFunctions, compareBinaryFunctionByIndex);
   return SortedFunctions;
 }
 

bolt/lib/Core/BinaryFunction.cpp

@@ -385,16 +385,7 @@ bool BinaryFunction::isForwardCall(const MCSymbol *CalleeSymbol) const {
   if (CalleeBF) {
     if (CalleeBF->isInjected())
       return true;
-
-    if (hasValidIndex() && CalleeBF->hasValidIndex()) {
-      return getIndex() < CalleeBF->getIndex();
-    } else if (hasValidIndex() && !CalleeBF->hasValidIndex()) {
-      return true;
-    } else if (!hasValidIndex() && CalleeBF->hasValidIndex()) {
-      return false;
-    } else {
-      return getAddress() < CalleeBF->getAddress();
-    }
+    return compareBinaryFunctionByIndex(this, CalleeBF);
   } else {
     // Absolute symbol.
     ErrorOr<uint64_t> CalleeAddressOrError = BC.getSymbolValue(*CalleeSymbol);

bolt/lib/Passes/ReorderFunctions.cpp

@@ -473,16 +473,7 @@ Error ReorderFunctions::runOnFunctions(BinaryContext &BC) {
                     [](BinaryFunction &BF) { return &BF; });
 
     // Sort functions by index.
-    llvm::stable_sort(SortedFunctions,
-                      [](const BinaryFunction *A, const BinaryFunction *B) {
-                        if (A->hasValidIndex() && B->hasValidIndex())
-                          return A->getIndex() < B->getIndex();
-                        if (A->hasValidIndex() && !B->hasValidIndex())
-                          return true;
-                        if (!A->hasValidIndex() && B->hasValidIndex())
-                          return false;
-                        return A->getAddress() < B->getAddress();
-                      });
+    llvm::stable_sort(SortedFunctions, compareBinaryFunctionByIndex);
 
     for (const BinaryFunction *Func : SortedFunctions) {
       if (!Func->hasValidIndex())