3 files changed, 26 insertions, 5 deletions

diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index 3d57acf06e74..93eab680ca6b 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2026,6 +2026,24 @@ OptimizeFunctions(Module &M, TargetLibraryInfo *TLI,
       continue;
     }
 
+    // LLVM's definition of dominance allows instructions that are cyclic
+    // in unreachable blocks, e.g.:
+    // %pat = select i1 %condition, @global, i16* %pat
+    // because any instruction dominates an instruction in a block that's
+    // not reachable from entry.
+    // So, remove unreachable blocks from the function, because a) there's
+    // no point in analyzing them and b) GlobalOpt should otherwise grow
+    // some more complicated logic to break these cycles.
+    // Removing unreachable blocks might invalidate the dominator so we
+    // recalculate it.
+    if (!F->isDeclaration()) {
+      if (removeUnreachableBlocks(*F)) {
+        auto &DT = LookupDomTree(*F);
+        DT.recalculate(*F);
+        Changed = true;
+      }
+    }
+
     Changed |= processGlobal(*F, TLI, LookupDomTree);
 
     if (!F->hasLocalLinkage())
diff --git a/lib/Transforms/IPO/Inliner.cpp b/lib/Transforms/IPO/Inliner.cpp
index 00ddb93df830..317770d133b3 100644
--- a/lib/Transforms/IPO/Inliner.cpp
+++ b/lib/Transforms/IPO/Inliner.cpp
@@ -909,7 +909,7 @@ PreservedAnalyses InlinerPass::run(LazyCallGraph::SCC &InitialC,
         // To check this we also need to nuke any dead constant uses (perhaps
         // made dead by this operation on other functions).
         Callee.removeDeadConstantUsers();
-        if (Callee.use_empty()) {
+        if (Callee.use_empty() && !CG.isLibFunction(Callee)) {
           Calls.erase(
               std::remove_if(Calls.begin() + i + 1, Calls.end(),
                              [&Callee](const std::pair<CallSite, int> &Call) {
diff --git a/lib/Transforms/IPO/SampleProfile.cpp b/lib/Transforms/IPO/SampleProfile.cpp
index ac4765f96075..6baada2c1ae1 100644
--- a/lib/Transforms/IPO/SampleProfile.cpp
+++ b/lib/Transforms/IPO/SampleProfile.cpp
@@ -173,8 +173,10 @@ protected:
   void printBlockEquivalence(raw_ostream &OS, const BasicBlock *BB);
   bool computeBlockWeights(Function &F);
   void findEquivalenceClasses(Function &F);
+  template <bool IsPostDom>
   void findEquivalencesFor(BasicBlock *BB1, ArrayRef<BasicBlock *> Descendants,
-                           DominatorTreeBase<BasicBlock> *DomTree);
+                           DominatorTreeBase<BasicBlock, IsPostDom> *DomTree);
+
   void propagateWeights(Function &F);
   uint64_t visitEdge(Edge E, unsigned *NumUnknownEdges, Edge *UnknownEdge);
   void buildEdges(Function &F);
@@ -217,7 +219,7 @@ protected:
 
   /// \brief Dominance, post-dominance and loop information.
   std::unique_ptr<DominatorTree> DT;
-  std::unique_ptr<DominatorTreeBase<BasicBlock>> PDT;
+  std::unique_ptr<PostDomTreeBase<BasicBlock>> PDT;
   std::unique_ptr<LoopInfo> LI;
 
   AssumptionCacheTracker *ACT;
@@ -773,9 +775,10 @@ bool SampleProfileLoader::inlineHotFunctions(
 /// \param DomTree  Opposite dominator tree. If \p Descendants is filled
 ///                 with blocks from \p BB1's dominator tree, then
 ///                 this is the post-dominator tree, and vice versa.
+template <bool IsPostDom>
 void SampleProfileLoader::findEquivalencesFor(
     BasicBlock *BB1, ArrayRef<BasicBlock *> Descendants,
-    DominatorTreeBase<BasicBlock> *DomTree) {
+    DominatorTreeBase<BasicBlock, IsPostDom> *DomTree) {
   const BasicBlock *EC = EquivalenceClass[BB1];
   uint64_t Weight = BlockWeights[EC];
   for (const auto *BB2 : Descendants) {
@@ -1283,7 +1286,7 @@ void SampleProfileLoader::computeDominanceAndLoopInfo(Function &F) {
   DT.reset(new DominatorTree);
   DT->recalculate(F);
 
-  PDT.reset(new DominatorTreeBase<BasicBlock>(true));
+  PDT.reset(new PostDomTreeBase<BasicBlock>());
   PDT->recalculate(F);
 
   LI.reset(new LoopInfo);