Revert "[FunctionAttrs] deduce attr cold on functions if all CG paths call a cold function"

This reverts commit b7eac8c.

Causing a test failure. Not 100% sure the issue so to reverting to
unblock pipeline.

Author: goldsteinn

llvm/lib/Transforms/IPO/FunctionAttrs.cpp

@@ -82,7 +82,6 @@ STATISTIC(NumNoUnwind, "Number of functions marked as nounwind");
 STATISTIC(NumNoFree, "Number of functions marked as nofree");
 STATISTIC(NumWillReturn, "Number of functions marked as willreturn");
 STATISTIC(NumNoSync, "Number of functions marked as nosync");
-STATISTIC(NumCold, "Number of functions marked as cold");
 
 STATISTIC(NumThinLinkNoRecurse,
           "Number of functions marked as norecurse during thinlink");
@@ -1746,7 +1745,6 @@ static bool canReturn(Function &F) {
   return false;
 }
 
-
 // Set the noreturn function attribute if possible.
 static void addNoReturnAttrs(const SCCNodeSet &SCCNodes,
                              SmallSet<Function *, 8> &Changed) {
@@ -1762,72 +1760,6 @@ static void addNoReturnAttrs(const SCCNodeSet &SCCNodes,
   }
 }
 
-static bool
-allBBPathsGoThroughCold(BasicBlock *BB,
-                        SmallDenseMap<BasicBlock *, bool, 16> &Visited) {
-  // If BB contains a cold callsite this path through the CG is cold.
-  // Ignore whether the instructions actually are guranteed to transfer
-  // execution. Divergent behavior is considered unlikely.
-  if (any_of(*BB, [](Instruction &I) {
-        if (auto *CB = dyn_cast<CallBase>(&I))
-          return CB->hasFnAttr(Attribute::Cold);
-        return false;
-      })) {
-    Visited[BB] = true;
-    return true;
-  }
-
-  auto Succs = successors(BB);
-  // We found a path that doesn't go through any cold callsite.
-  if (Succs.empty())
-    return false;
-
-  // We didn't find a cold callsite in this BB, so check that all successors
-  // contain a cold callsite (or that their successors do).
-  // Potential TODO: We could use static branch hints to assume certain
-  // successor paths are inherently cold, irrespective of if they contain a cold
-  // callsite.
-  for (auto *Succ : Succs) {
-    // Start with false, this is necessary to ensure we don't turn loops into
-    // cold.
-    auto R = Visited.try_emplace(Succ, false);
-    if (!R.second) {
-      if (R.first->second)
-        continue;
-      return false;
-    }
-    if (!allBBPathsGoThroughCold(Succ, Visited))
-      return false;
-    Visited[Succ] = true;
-  }
-
-  return true;
-}
-
-static bool allPathsGoThroughCold(Function &F) {
-  SmallDenseMap<BasicBlock *, bool, 16> Visited;
-  Visited[&F.front()] = false;
-  return allBBPathsGoThroughCold(&F.front(), Visited);
-}
-
-// Set the cold function attribute if possible.
-static void addColdAttrs(const SCCNodeSet &SCCNodes,
-                         SmallSet<Function *, 8> &Changed) {
-  for (Function *F : SCCNodes) {
-    if (!F || !F->hasExactDefinition() || F->hasFnAttribute(Attribute::Naked) ||
-        F->hasFnAttribute(Attribute::Cold) || F->hasFnAttribute(Attribute::Hot))
-      continue;
-
-    // Potential TODO: We could add attribute `cold` on functions with `coldcc`.
-    if (allPathsGoThroughCold(*F)) {
-      F->addFnAttr(Attribute::Cold);
-      ++NumCold;
-      Changed.insert(F);
-      continue;
-    }
-  }
-}
-
 static bool functionWillReturn(const Function &F) {
   // We can infer and propagate function attributes only when we know that the
   // definition we'll get at link time is *exactly* the definition we see now.
@@ -1921,7 +1853,6 @@ deriveAttrsInPostOrder(ArrayRef<Function *> Functions, AARGetterT &&AARGetter,
   addArgumentAttrs(Nodes.SCCNodes, Changed);
   inferConvergent(Nodes.SCCNodes, Changed);
   addNoReturnAttrs(Nodes.SCCNodes, Changed);
-  addColdAttrs(Nodes.SCCNodes, Changed);
   addWillReturn(Nodes.SCCNodes, Changed);
   addNoUndefAttrs(Nodes.SCCNodes, Changed);