Don't assert about missing profile info in createProfileWeightsForLoop

[hans]

Summary

The compiler shouldn't crash if the profile info is slightly off. We hit this in Chromium.

[thakis]

Could there be a test for this? Or is that difficult?

[hans]

In D79417#2020607, @thakis wrote:

Could there be a test for this? Or is that difficult?

I think it would be a bit of a pain, which is why I skipped it. It also wouldn't be a very interesting test, just "don't assert here", really.

[thakis]

Fair enough :)

clang/lib/CodeGen/CodeGenPGO.cpp

CodeGenFunction::createProfileWeights(ArrayRef<uint64_t> Weights) {
   return MDHelper.createBranchWeights(ScaledWeights);
 }
 
 llvm::MDNode *CodeGenFunction::createProfileWeightsForLoop(const Stmt *Cond,
                                                            uint64_t LoopCount) {
   if (!PGO.haveRegionCounts())
     return nullptr;
   Optional<uint64_t> CondCount = PGO.getStmtCount(Cond);
-  assert(CondCount.hasValue() && "missing expected loop condition count");
-  if (*CondCount == 0)
+  if (!CondCount || *CondCount == 0)
     return nullptr;
   return createProfileWeights(LoopCount,
                               std::max(*CondCount, LoopCount) - LoopCount);
 }