[BOLT] Refactor --keep-nops option. NFC. (#72228)

Run RemoveNops pass only if --keep-nops is set to false (default).

Author: maksfb

bolt/include/bolt/Core/BinaryFunction.h

@@ -1296,7 +1296,7 @@ class BinaryFunction {
   /// Return true if the function body is non-contiguous.
   bool isSplit() const { return isSimple() && getLayout().isSplit(); }
 
-  bool shouldPreserveNops() const;
+  bool shouldPreserveNops() const { return PreserveNops; }
 
   /// Return true if the function has exception handling tables.
   bool hasEHRanges() const { return HasEHRanges; }

bolt/lib/Core/BinaryFunction.cpp

@@ -4367,10 +4367,6 @@ MCInst *BinaryFunction::getInstructionAtOffset(uint64_t Offset) {
   }
 }
 
-bool BinaryFunction::shouldPreserveNops() const {
-  return PreserveNops || opts::KeepNops;
-}
-
 void BinaryFunction::printLoopInfo(raw_ostream &OS) const {
   if (!opts::shouldPrint(*this))
     return;

bolt/lib/Rewrite/BinaryPassManager.cpp

@@ -72,6 +72,11 @@ static cl::opt<bool> JTFootprintReductionFlag(
              "instructions at jump sites"),
     cl::cat(BoltOptCategory));
 
+static cl::opt<bool>
+    KeepNops("keep-nops",
+             cl::desc("keep no-op instructions. By default they are removed."),
+             cl::Hidden, cl::cat(BoltOptCategory));
+
 cl::opt<bool> NeverPrint("never-print", cl::desc("never print"),
                          cl::ReallyHidden, cl::cat(BoltOptCategory));
 
@@ -359,7 +364,8 @@ void BinaryFunctionPassManager::runAllPasses(BinaryContext &BC) {
 
   Manager.registerPass(std::make_unique<ShortenInstructions>(NeverPrint));
 
-  Manager.registerPass(std::make_unique<RemoveNops>(NeverPrint));
+  Manager.registerPass(std::make_unique<RemoveNops>(NeverPrint),
+                       !opts::KeepNops);
 
   Manager.registerPass(std::make_unique<NormalizeCFG>(PrintNormalized));
 

bolt/lib/Utils/CommandLineOpts.cpp

@@ -129,11 +129,6 @@ cl::opt<bool>
                cl::desc("instrument code to generate accurate profile data"),
                cl::cat(BoltOptCategory));
 
-cl::opt<bool>
-    KeepNops("keep-nops",
-             cl::desc("keep no-op instructions. By default they are removed."),
-             cl::Hidden, cl::cat(BoltOptCategory));
-
 cl::opt<std::string>
 OutputFilename("o",
   cl::desc("<output file>"),