[BOLT] Restrict ICP for functions with unknown control flow

[Amir]

Summary

ICP has two modes: jump table promotion and indirect call promotion.
The selection is based on whether an instruction has a jump table or not.
An instruction with unknown control flow doesn't have a jump table and will
fall under indirect call promotion policy which might be incorrect/unsafe
(if an instruction is not a tail call, i.e. has local jump targets).

Prevent ICP for functions containing instructions with unknown control flow.

Follow-up to https://reviews.llvm.org/D128870.

bolt/include/bolt/Passes/IndirectCallPromotion.h

 public:
   explicit IndirectCallPromotion(const cl::opt<bool> &PrintPass)
       : BinaryFunctionPass(PrintPass) {}
 
   const char *getName() const override { return "indirect-call-promotion"; }
   bool shouldPrint(const BinaryFunction &BF) const override {
     return BinaryFunctionPass::shouldPrint(BF) && Modified.count(&BF) > 0;
   }
+  bool shouldOptimize(const BinaryFunction &BF) const override {
+    return BF.isSimple() && !BF.isIgnored() && BF.hasProfile() &&
+           !BF.hasUnknownControlFlow();
+  }
   void runOnFunctions(BinaryContext &BC) override;
 };
 
 } // namespace bolt
 } // namespace llvm
 
 #endif

bolt/lib/Passes/IndirectCallPromotion.cpp

if (opts::ICPTopCallsites == 0) {
     using IndirectCallsite = std::tuple<uint64_t, MCInst *, BinaryFunction *>;
     std::vector<IndirectCallsite> IndirectCalls;
     size_t TotalIndirectCalls = 0;
 
     // Find all the indirect callsites.
     for (auto &BFIt : BFs) {
       BinaryFunction &Function = BFIt.second;
 
-      if (!Function.isSimple() || Function.isIgnored() ||
-          !Function.hasProfile())
+      if (!shouldOptimize(Function))
         continue;
 
       const bool HasLayout = !Function.getLayout().block_empty();
 
       for (BinaryBasicBlock &BB : Function) {
         if (HasLayout && Function.isSplit() && BB.isCold())
           continue;
 
if (opts::ICPTopCallsites == 0) {
     outs() << "BOLT-INFO: ICP Total indirect calls = " << TotalIndirectCalls
            << ", " << Num << " callsites cover " << opts::ICPTopCallsites
            << "% of all indirect calls\n";
   }
 
   for (BinaryFunction *FuncPtr : Functions) {
     BinaryFunction &Function = *FuncPtr;
 
-    if (!Function.isSimple() || Function.isIgnored() || !Function.hasProfile())
+    if (!shouldOptimize(Function))
       continue;
 
     const bool HasLayout = !Function.getLayout().block_empty();
 
     // Total number of indirect calls issued from the current Function.
     // (a fraction of TotalIndirectCalls)
     uint64_t FuncTotalIndirectCalls = 0;
     uint64_t FuncTotalIndirectJmps = 0;