[NFC] Do not track calls to inlined intrinsics in IFI.

[jeroen.dobbelaere]

Summary

Just like intrinsics are not tracked for IFI.InlinedCalls, they should not be tracked for IFI.InlinedCallSites.

In the current top-of-tree this change is a NFC, but the full restrict patches (D68484) potentially trigger an read-after-free
if intrinsics are also added to the InlindeCallSites, due to a late optimization potentially removing some of the inlined intrinsics.

Also see https://lists.llvm.org/pipermail/llvm-dev/2021-July/151722.html for a discussion about the problem.

[aeubanks]

lgtm with nit

llvm/lib/Transforms/Utils/InlineFunction.cpp

2442

not strictly true, I'd say something like "calls intrinsic aren't inlineable".

llvm/lib/Transforms/IPO/Inliner.cpp

while (!Calls->empty() && Calls->front().first->getCaller() == &F) {
 
       // Add any new callsites to defined functions to the worklist.
       if (!IFI.InlinedCallSites.empty()) {
         int NewHistoryID = InlineHistory.size();
         InlineHistory.push_back({&Callee, InlineHistoryID});
 
         for (CallBase *ICB : reverse(IFI.InlinedCallSites)) {
           Function *NewCallee = ICB->getCalledFunction();
+          assert(!(NewCallee && NewCallee->isIntrinsic()) &&
+                 "Intrinsic calls should not be tracked.");
           if (!NewCallee) {
             // Try to promote an indirect (virtual) call without waiting for
             // the post-inline cleanup and the next DevirtSCCRepeatedPass
             // iteration because the next iteration may not happen and we may
             // miss inlining it.
             if (tryPromoteCall(*ICB))
               NewCallee = ICB->getCalledFunction();
           }

llvm/lib/Transforms/Utils/InlineFunction.cpp

if (InlinedMustTailCalls) {
     // Leave behind the normal returns so we can merge control flow.
     std::swap(Returns, NormalReturns);
   }
 
   // Now that all of the transforms on the inlined code have taken place but
   // before we splice the inlined code into the CFG and lose track of which
   // blocks were actually inlined, collect the call sites. We only do this if
   // call graph updates weren't requested, as those provide value handle based
-  // tracking of inlined call sites instead.
+  // tracking of inlined call sites instead. Calls to intrinsics are not
+  // collected because we expect them to become inline code.
   if (InlinedFunctionInfo.ContainsCalls && !IFI.CG) {
     // Otherwise just collect the raw call sites that were inlined.
     for (BasicBlock &NewBB :
          make_range(FirstNewBlock->getIterator(), Caller->end()))
       for (Instruction &I : NewBB)
         if (auto *CB = dyn_cast<CallBase>(&I))
+          if (!(CB->getCalledFunction() &&
+                CB->getCalledFunction()->isIntrinsic()))
             IFI.InlinedCallSites.push_back(CB);
   }
 
   // If we cloned in _exactly one_ basic block, and if that block ends in a
   // return instruction, we splice the body of the inlined callee directly into
   // the calling basic block.
   if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
     // Move all of the instructions right before the call.
     OrigBB->getInstList().splice(CB.getIterator(), FirstNewBlock->getInstList(),