[LLVM] Change ModulePass::skipModule to take a const reference

- Change `ModulePass::skipModule` to take const Module reference.
- Additionally, make `OptPassGate::shouldRunPass`  const as well as
  for most implementations its a const query. For `OptBisect`, make
  `LastBisectNum` mutable so it could be updated in `shouldRunPass`.
- Minor code cleanup.

Author: jurahul

llvm/include/llvm/IR/OptBisect.h

@@ -28,8 +28,8 @@ class OptPassGate {
 
   /// IRDescription is a textual description of the IR unit the pass is running
   /// over.
-  virtual bool shouldRunPass(const StringRef PassName,
-                             StringRef IRDescription) {
+  virtual bool shouldRunPass(StringRef PassName,
+                             StringRef IRDescription) const {
     return true;
   }
 
@@ -62,8 +62,8 @@ class LLVM_ABI OptBisect : public OptPassGate {
   /// Most passes should not call this routine directly. Instead, it is called
   /// through helper routines provided by the base classes of the pass. For
   /// instance, function passes should call FunctionPass::skipFunction().
-  bool shouldRunPass(const StringRef PassName,
-                     StringRef IRDescription) override;
+  bool shouldRunPass(StringRef PassName,
+                     StringRef IRDescription) const override;
 
   /// isEnabled() should return true before calling shouldRunPass().
   bool isEnabled() const override { return BisectLimit != Disabled; }
@@ -75,11 +75,11 @@ class LLVM_ABI OptBisect : public OptPassGate {
     LastBisectNum = 0;
   }
 
-  static const int Disabled = std::numeric_limits<int>::max();
+  static constexpr int Disabled = std::numeric_limits<int>::max();
 
 private:
   int BisectLimit = Disabled;
-  int LastBisectNum = 0;
+  mutable int LastBisectNum = 0;
 };
 
 /// Singleton instance of the OptBisect class, so multiple pass managers don't

llvm/include/llvm/Pass.h

@@ -271,7 +271,7 @@ class LLVM_ABI ModulePass : public Pass {
 protected:
   /// Optional passes call this function to check whether the pass should be
   /// skipped. This is the case when optimization bisect is over the limit.
-  bool skipModule(Module &M) const;
+  bool skipModule(const Module &M) const;
 };
 
 //===----------------------------------------------------------------------===//

llvm/lib/Analysis/LoopPass.cpp

@@ -373,7 +373,7 @@ bool LoopPass::skipLoop(const Loop *L) const {
   if (!F)
     return false;
   // Check the opt bisect limit.
-  OptPassGate &Gate = F->getContext().getOptPassGate();
+  const OptPassGate &Gate = F->getContext().getOptPassGate();
   if (Gate.isEnabled() &&
       !Gate.shouldRunPass(this->getPassName(), getDescription(*L)))
     return true;

llvm/lib/Analysis/RegionPass.cpp

@@ -282,7 +282,7 @@ static std::string getDescription(const Region &R) {
 
 bool RegionPass::skipRegion(Region &R) const {
   Function &F = *R.getEntry()->getParent();
-  OptPassGate &Gate = F.getContext().getOptPassGate();
+  const OptPassGate &Gate = F.getContext().getOptPassGate();
   if (Gate.isEnabled() &&
       !Gate.shouldRunPass(this->getPassName(), getDescription(R)))
     return true;

llvm/lib/IR/OptBisect.cpp

@@ -37,15 +37,15 @@ static cl::opt<bool> OptBisectVerbose(
     cl::desc("Show verbose output when opt-bisect-limit is set"), cl::Hidden,
     cl::init(true), cl::Optional);
 
-static void printPassMessage(const StringRef &Name, int PassNum,
-                             StringRef TargetDesc, bool Running) {
+static void printPassMessage(StringRef Name, int PassNum, StringRef TargetDesc,
+                             bool Running) {
   StringRef Status = Running ? "" : "NOT ";
-  errs() << "BISECT: " << Status << "running pass "
-         << "(" << PassNum << ") " << Name << " on " << TargetDesc << "\n";
+  errs() << "BISECT: " << Status << "running pass (" << PassNum << ") " << Name
+         << " on " << TargetDesc << '\n';
 }
 
-bool OptBisect::shouldRunPass(const StringRef PassName,
-                              StringRef IRDescription) {
+bool OptBisect::shouldRunPass(StringRef PassName,
+                              StringRef IRDescription) const {
   assert(isEnabled());
 
   int CurBisectNum = ++LastBisectNum;
@@ -55,6 +55,4 @@ bool OptBisect::shouldRunPass(const StringRef PassName,
   return ShouldRun;
 }
 
-const int OptBisect::Disabled;
-
 OptPassGate &llvm::getGlobalPassGate() { return getOptBisector(); }

llvm/lib/IR/Pass.cpp

@@ -60,8 +60,8 @@ static std::string getDescription(const Module &M) {
   return "module (" + M.getName().str() + ")";
 }
 
-bool ModulePass::skipModule(Module &M) const {
-  OptPassGate &Gate = M.getContext().getOptPassGate();
+bool ModulePass::skipModule(const Module &M) const {
+  const OptPassGate &Gate = M.getContext().getOptPassGate();
   return Gate.isEnabled() &&
          !Gate.shouldRunPass(this->getPassName(), getDescription(M));
 }

llvm/lib/Passes/StandardInstrumentations.cpp

@@ -1074,7 +1074,7 @@ bool OptPassGateInstrumentation::shouldRun(StringRef PassName, Any IR) {
 
 void OptPassGateInstrumentation::registerCallbacks(
     PassInstrumentationCallbacks &PIC) {
-  OptPassGate &PassGate = Context.getOptPassGate();
+  const OptPassGate &PassGate = Context.getOptPassGate();
   if (!PassGate.isEnabled())
     return;
 

llvm/unittests/IR/LegacyPassManagerTest.cpp

@@ -359,7 +359,8 @@ namespace llvm {
     struct CustomOptPassGate : public OptPassGate {
       bool Skip;
       CustomOptPassGate(bool Skip) : Skip(Skip) { }
-      bool shouldRunPass(const StringRef PassName, StringRef IRDescription) override {
+      bool shouldRunPass(StringRef PassName,
+                         StringRef IRDescription) const override {
         return !Skip;
       }
       bool isEnabled() const override { return true; }