Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release:

MFC r309142 (by emaste):

Add WITH_LLD_AS_LD build knob

If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation

MFC r310840:

Reapply 310775, now it also builds correctly if lldb is disabled:

Move llvm-objdump from CLANG_EXTRAS to installed by default

We currently install three tools from binutils 2.17.50: as, ld, and
objdump. Work is underway to migrate to a permissively-licensed
tool-chain, with one goal being the retirement of binutils 2.17.50.

LLVM's llvm-objdump is intended to be compatible with GNU objdump
although it is currently missing some options and may have formatting
differences. Enable it by default for testing and further investigation.
It may later be changed to install as /usr/bin/objdump, it becomes a
fully viable replacement.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D8879

MFC r312855 (by emaste):

Rename LLD_AS_LD to LLD_IS_LD, for consistency with CLANG_IS_CC

Reported by:	Dan McGregor <dan.mcgregor usask.ca>

MFC r313559 | glebius | 2017-02-10 18:34:48 +0100 (Fri, 10 Feb 2017) | 5 lines

Don't check struct rtentry on FreeBSD, it is an internal kernel structure.
On other systems it may be API structure for SIOCADDRT/SIOCDELRT.

Reviewed by:	emaste, dim

MFC r314152 (by jkim):

Remove an assembler flag, which is redundant since r309124.  The upstream
took care of it by introducing a macro NO_EXEC_STACK_DIRECTIVE.

http://llvm.org/viewvc/llvm-project?rev=273500&view=rev

Reviewed by:	dim

MFC r314564:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
4.0.0 (branches/release_40 296509).  The release will follow soon.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Also note that as of 4.0.0, lld should be able to link the base system
on amd64 and aarch64.  See the WITH_LLD_IS_LLD setting in src.conf(5).
Though please be aware that this is work in progress.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/4.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Jan Beich, Antoine Brodin and Eric Fiselier for
their help.

Relnotes:	yes
Exp-run:	antoine
PR:		215969, 216008

MFC r314708:

For now, revert r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

This commit is the cause of excessive compile times on skein_block.c
(and possibly other files) during kernel builds on amd64.

We never saw the problematic behavior described in this upstream commit,
so for now it is better to revert it.  An upstream bug has been filed
here: https://bugs.llvm.org/show_bug.cgi?id=32142

Reported by:	mjg

MFC r314795:

Reapply r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

Pull in r296992 from upstream llvm trunk (by Sanjoy Das):

  [SCEV] Decrease the recursion threshold for CompareValueComplexity

  Fixes PR32142.

  r287232 accidentally increased the recursion threshold for
  CompareValueComplexity from 2 to 32.  This change reverses that
  change by introducing a separate flag for CompareValueComplexity's
  threshold.

The latter revision fixes the excessive compile times for skein_block.c.

MFC r314907 | mmel | 2017-03-08 12:40:27 +0100 (Wed, 08 Mar 2017) | 7 lines

Unbreak ARMv6 world.

The new compiler_rt library imported with clang 4.0.0 have several fatal
issues (non-functional __udivsi3 for example) with ARM specific instrict
functions. As temporary workaround, until upstream solve these problems,
disable all thumb[1][2] related feature.

MFC r315016:

Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release.
We were already very close to the last release candidate, so this is a
pretty minor update.

Relnotes:	yes

MFC r316005:

Revert r314907, and pull in r298713 from upstream compiler-rt trunk (by
Weiming Zhao):

  builtins: Select correct code fragments when compiling for Thumb1/Thum2/ARM ISA.

  Summary:
  Value of __ARM_ARCH_ISA_THUMB isn't based on the actual compilation
  mode (-mthumb, -marm), it reflect's capability of given CPU.

  Due to this:
   - use  __tbumb__ and __thumb2__ insteand of __ARM_ARCH_ISA_THUMB
   - use '.thumb' directive consistently  in all affected files
   - decorate all thumb functions using
     DEFINE_COMPILERRT_THUMB_FUNCTION()

  ---------
  Note: This patch doesn't fix broken Thumb1 variant of __udivsi3 !

  Reviewers: weimingz, rengolin, compnerd

  Subscribers: aemerson, dim

  Differential Revision: https://reviews.llvm.org/D30938

Discussed with:	mmel

1 files changed, 189 insertions, 105 deletions

diff --git a/contrib/llvm/lib/Transforms/IPO/SampleProfile.cpp b/contrib/llvm/lib/Transforms/IPO/SampleProfile.cpp
index 39de108..6a43f8d 100644
--- a/contrib/llvm/lib/Transforms/IPO/SampleProfile.cpp
+++ b/contrib/llvm/lib/Transforms/IPO/SampleProfile.cpp
@@ -88,6 +88,52 @@ typedef DenseMap<Edge, uint64_t> EdgeWeightMap;
 typedef DenseMap<const BasicBlock *, SmallVector<const BasicBlock *, 8>>
     BlockEdgeMap;
 
+class SampleCoverageTracker {
+public:
+  SampleCoverageTracker() : SampleCoverage(), TotalUsedSamples(0) {}
+
+  bool markSamplesUsed(const FunctionSamples *FS, uint32_t LineOffset,
+                       uint32_t Discriminator, uint64_t Samples);
+  unsigned computeCoverage(unsigned Used, unsigned Total) const;
+  unsigned countUsedRecords(const FunctionSamples *FS) const;
+  unsigned countBodyRecords(const FunctionSamples *FS) const;
+  uint64_t getTotalUsedSamples() const { return TotalUsedSamples; }
+  uint64_t countBodySamples(const FunctionSamples *FS) const;
+  void clear() {
+    SampleCoverage.clear();
+    TotalUsedSamples = 0;
+  }
+
+private:
+  typedef std::map<LineLocation, unsigned> BodySampleCoverageMap;
+  typedef DenseMap<const FunctionSamples *, BodySampleCoverageMap>
+      FunctionSamplesCoverageMap;
+
+  /// Coverage map for sampling records.
+  ///
+  /// This map keeps a record of sampling records that have been matched to
+  /// an IR instruction. This is used to detect some form of staleness in
+  /// profiles (see flag -sample-profile-check-coverage).
+  ///
+  /// Each entry in the map corresponds to a FunctionSamples instance.  This is
+  /// another map that counts how many times the sample record at the
+  /// given location has been used.
+  FunctionSamplesCoverageMap SampleCoverage;
+
+  /// Number of samples used from the profile.
+  ///
+  /// When a sampling record is used for the first time, the samples from
+  /// that record are added to this accumulator.  Coverage is later computed
+  /// based on the total number of samples available in this function and
+  /// its callsites.
+  ///
+  /// Note that this accumulator tracks samples used from a single function
+  /// and all the inlined callsites. Strictly, we should have a map of counters
+  /// keyed by FunctionSamples pointers, but these stats are cleared after
+  /// every function, so we just need to keep a single counter.
+  uint64_t TotalUsedSamples;
+};
+
 /// \brief Sample profile pass.
 ///
 /// This pass reads profile data from the file specified by
@@ -110,9 +156,9 @@ protected:
   bool runOnFunction(Function &F);
   unsigned getFunctionLoc(Function &F);
   bool emitAnnotations(Function &F);
-  ErrorOr<uint64_t> getInstWeight(const Instruction &I) const;
-  ErrorOr<uint64_t> getBlockWeight(const BasicBlock *BB) const;
-  const FunctionSamples *findCalleeFunctionSamples(const CallInst &I) const;
+  ErrorOr<uint64_t> getInstWeight(const Instruction &I);
+  ErrorOr<uint64_t> getBlockWeight(const BasicBlock *BB);
+  const FunctionSamples *findCalleeFunctionSamples(const Instruction &I) const;
   const FunctionSamples *findFunctionSamples(const Instruction &I) const;
   bool inlineHotFunctions(Function &F);
   void printEdgeWeight(raw_ostream &OS, Edge E);
@@ -125,7 +171,7 @@ protected:
   void propagateWeights(Function &F);
   uint64_t visitEdge(Edge E, unsigned *NumUnknownEdges, Edge *UnknownEdge);
   void buildEdges(Function &F);
-  bool propagateThroughEdges(Function &F);
+  bool propagateThroughEdges(Function &F, bool UpdateBlockCount);
   void computeDominanceAndLoopInfo(Function &F);
   unsigned getOffset(unsigned L, unsigned H) const;
   void clearFunctionData();
@@ -169,6 +215,8 @@ protected:
   /// \brief Successors for each basic block in the CFG.
   BlockEdgeMap Successors;
 
+  SampleCoverageTracker CoverageTracker;
+
   /// \brief Profile reader object.
   std::unique_ptr<SampleProfileReader> Reader;
 
@@ -176,7 +224,7 @@ protected:
   FunctionSamples *Samples;
 
   /// \brief Name of the profile file to load.
-  StringRef Filename;
+  std::string Filename;
 
   /// \brief Flag indicating whether the profile input loaded successfully.
   bool ProfileIsValid;
@@ -204,64 +252,17 @@ public:
   bool doInitialization(Module &M) override {
     return SampleLoader.doInitialization(M);
   }
-  const char *getPassName() const override { return "Sample profile pass"; }
+  StringRef getPassName() const override { return "Sample profile pass"; }
   bool runOnModule(Module &M) override;
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<AssumptionCacheTracker>();
   }
-private:
-  SampleProfileLoader SampleLoader;
-};
-
-class SampleCoverageTracker {
-public:
-  SampleCoverageTracker() : SampleCoverage(), TotalUsedSamples(0) {}
-
-  bool markSamplesUsed(const FunctionSamples *FS, uint32_t LineOffset,
-                       uint32_t Discriminator, uint64_t Samples);
-  unsigned computeCoverage(unsigned Used, unsigned Total) const;
-  unsigned countUsedRecords(const FunctionSamples *FS) const;
-  unsigned countBodyRecords(const FunctionSamples *FS) const;
-  uint64_t getTotalUsedSamples() const { return TotalUsedSamples; }
-  uint64_t countBodySamples(const FunctionSamples *FS) const;
-  void clear() {
-    SampleCoverage.clear();
-    TotalUsedSamples = 0;
-  }
 
 private:
-  typedef std::map<LineLocation, unsigned> BodySampleCoverageMap;
-  typedef DenseMap<const FunctionSamples *, BodySampleCoverageMap>
-      FunctionSamplesCoverageMap;
-
-  /// Coverage map for sampling records.
-  ///
-  /// This map keeps a record of sampling records that have been matched to
-  /// an IR instruction. This is used to detect some form of staleness in
-  /// profiles (see flag -sample-profile-check-coverage).
-  ///
-  /// Each entry in the map corresponds to a FunctionSamples instance.  This is
-  /// another map that counts how many times the sample record at the
-  /// given location has been used.
-  FunctionSamplesCoverageMap SampleCoverage;
-
-  /// Number of samples used from the profile.
-  ///
-  /// When a sampling record is used for the first time, the samples from
-  /// that record are added to this accumulator.  Coverage is later computed
-  /// based on the total number of samples available in this function and
-  /// its callsites.
-  ///
-  /// Note that this accumulator tracks samples used from a single function
-  /// and all the inlined callsites. Strictly, we should have a map of counters
-  /// keyed by FunctionSamples pointers, but these stats are cleared after
-  /// every function, so we just need to keep a single counter.
-  uint64_t TotalUsedSamples;
+  SampleProfileLoader SampleLoader;
 };
 
-SampleCoverageTracker CoverageTracker;
-
 /// Return true if the given callsite is hot wrt to its caller.
 ///
 /// Functions that were inlined in the original binary will be represented
@@ -451,7 +452,7 @@ void SampleProfileLoader::printBlockWeight(raw_ostream &OS,
 ///
 /// \returns the weight of \p Inst.
 ErrorOr<uint64_t>
-SampleProfileLoader::getInstWeight(const Instruction &Inst) const {
+SampleProfileLoader::getInstWeight(const Instruction &Inst) {
   const DebugLoc &DLoc = Inst.getDebugLoc();
   if (!DLoc)
     return std::error_code();
@@ -460,18 +461,28 @@ SampleProfileLoader::getInstWeight(const Instruction &Inst) const {
   if (!FS)
     return std::error_code();
 
-  // Ignore all dbg_value intrinsics.
-  const IntrinsicInst *II = dyn_cast<IntrinsicInst>(&Inst);
-  if (II && II->getIntrinsicID() == Intrinsic::dbg_value)
+  // Ignore all intrinsics and branch instructions.
+  // Branch instruction usually contains debug info from sources outside of
+  // the residing basic block, thus we ignore them during annotation.
+  if (isa<BranchInst>(Inst) || isa<IntrinsicInst>(Inst))
     return std::error_code();
 
+  // If a call/invoke instruction is inlined in profile, but not inlined here,
+  // it means that the inlined callsite has no sample, thus the call
+  // instruction should have 0 count.
+  bool IsCall = isa<CallInst>(Inst) || isa<InvokeInst>(Inst);
+  if (IsCall && findCalleeFunctionSamples(Inst))
+    return 0;
+
   const DILocation *DIL = DLoc;
   unsigned Lineno = DLoc.getLine();
   unsigned HeaderLineno = DIL->getScope()->getSubprogram()->getLine();
 
   uint32_t LineOffset = getOffset(Lineno, HeaderLineno);
   uint32_t Discriminator = DIL->getDiscriminator();
-  ErrorOr<uint64_t> R = FS->findSamplesAt(LineOffset, Discriminator);
+  ErrorOr<uint64_t> R = IsCall
+                            ? FS->findCallSamplesAt(LineOffset, Discriminator)
+                            : FS->findSamplesAt(LineOffset, Discriminator);
   if (R) {
     bool FirstMark =
         CoverageTracker.markSamplesUsed(FS, LineOffset, Discriminator, R.get());
@@ -488,13 +499,6 @@ SampleProfileLoader::getInstWeight(const Instruction &Inst) const {
                  << Inst << " (line offset: " << Lineno - HeaderLineno << "."
                  << DIL->getDiscriminator() << " - weight: " << R.get()
                  << ")\n");
-  } else {
-    // If a call instruction is inlined in profile, but not inlined here,
-    // it means that the inlined callsite has no sample, thus the call
-    // instruction should have 0 count.
-    const CallInst *CI = dyn_cast<CallInst>(&Inst);
-    if (CI && findCalleeFunctionSamples(*CI))
-      R = 0;
   }
   return R;
 }
@@ -508,23 +512,17 @@ SampleProfileLoader::getInstWeight(const Instruction &Inst) const {
 ///
 /// \returns the weight for \p BB.
 ErrorOr<uint64_t>
-SampleProfileLoader::getBlockWeight(const BasicBlock *BB) const {
-  DenseMap<uint64_t, uint64_t> CM;
+SampleProfileLoader::getBlockWeight(const BasicBlock *BB) {
+  uint64_t Max = 0;
+  bool HasWeight = false;
   for (auto &I : BB->getInstList()) {
     const ErrorOr<uint64_t> &R = getInstWeight(I);
-    if (R) CM[R.get()]++;
-  }
-  if (CM.size() == 0) return std::error_code();
-  uint64_t W = 0, C = 0;
-  for (const auto &C_W : CM) {
-    if (C_W.second == W) {
-      C = std::max(C, C_W.first);
-    } else if (C_W.second > W) {
-      C = C_W.first;
-      W = C_W.second;
+    if (R) {
+      Max = std::max(Max, R.get());
+      HasWeight = true;
     }
   }
-  return C;
+  return HasWeight ? ErrorOr<uint64_t>(Max) : std::error_code();
 }
 
 /// \brief Compute and store the weights of every basic block.
@@ -551,18 +549,18 @@ bool SampleProfileLoader::computeBlockWeights(Function &F) {
 
 /// \brief Get the FunctionSamples for a call instruction.
 ///
-/// The FunctionSamples of a call instruction \p Inst is the inlined
+/// The FunctionSamples of a call/invoke instruction \p Inst is the inlined
 /// instance in which that call instruction is calling to. It contains
 /// all samples that resides in the inlined instance. We first find the
 /// inlined instance in which the call instruction is from, then we
 /// traverse its children to find the callsite with the matching
-/// location and callee function name.
+/// location.
 ///
-/// \param Inst Call instruction to query.
+/// \param Inst Call/Invoke instruction to query.
 ///
 /// \returns The FunctionSamples pointer to the inlined instance.
 const FunctionSamples *
-SampleProfileLoader::findCalleeFunctionSamples(const CallInst &Inst) const {
+SampleProfileLoader::findCalleeFunctionSamples(const Instruction &Inst) const {
   const DILocation *DIL = Inst.getDebugLoc();
   if (!DIL) {
     return nullptr;
@@ -611,7 +609,6 @@ SampleProfileLoader::findFunctionSamples(const Instruction &Inst) const {
   return FS;
 }
 
-
 /// \brief Iteratively inline hot callsites of a function.
 ///
 /// Iteratively traverse all callsites of the function \p F, and find if
@@ -627,22 +624,36 @@ SampleProfileLoader::findFunctionSamples(const Instruction &Inst) const {
 bool SampleProfileLoader::inlineHotFunctions(Function &F) {
   bool Changed = false;
   LLVMContext &Ctx = F.getContext();
+  std::function<AssumptionCache &(Function &)> GetAssumptionCache = [&](
+      Function &F) -> AssumptionCache & { return ACT->getAssumptionCache(F); };
   while (true) {
     bool LocalChanged = false;
-    SmallVector<CallInst *, 10> CIS;
+    SmallVector<Instruction *, 10> CIS;
     for (auto &BB : F) {
+      bool Hot = false;
+      SmallVector<Instruction *, 10> Candidates;
       for (auto &I : BB.getInstList()) {
-        CallInst *CI = dyn_cast<CallInst>(&I);
-        if (CI && callsiteIsHot(Samples, findCalleeFunctionSamples(*CI)))
-          CIS.push_back(CI);
+        const FunctionSamples *FS = nullptr;
+        if ((isa<CallInst>(I) || isa<InvokeInst>(I)) &&
+            (FS = findCalleeFunctionSamples(I))) {
+          Candidates.push_back(&I);
+          if (callsiteIsHot(Samples, FS))
+            Hot = true;
+        }
+      }
+      if (Hot) {
+        CIS.insert(CIS.begin(), Candidates.begin(), Candidates.end());
       }
     }
-    for (auto CI : CIS) {
-      InlineFunctionInfo IFI(nullptr, ACT);
-      Function *CalledFunction = CI->getCalledFunction();
-      DebugLoc DLoc = CI->getDebugLoc();
-      uint64_t NumSamples = findCalleeFunctionSamples(*CI)->getTotalSamples();
-      if (InlineFunction(CI, IFI)) {
+    for (auto I : CIS) {
+      InlineFunctionInfo IFI(nullptr, ACT ? &GetAssumptionCache : nullptr);
+      CallSite CS(I);
+      Function *CalledFunction = CS.getCalledFunction();
+      if (!CalledFunction || !CalledFunction->getSubprogram())
+        continue;
+      DebugLoc DLoc = I->getDebugLoc();
+      uint64_t NumSamples = findCalleeFunctionSamples(*I)->getTotalSamples();
+      if (InlineFunction(CS, IFI)) {
         LocalChanged = true;
         emitOptimizationRemark(Ctx, DEBUG_TYPE, F, DLoc,
                                Twine("inlined hot callee '") +
@@ -693,6 +704,10 @@ void SampleProfileLoader::findEquivalencesFor(
     bool IsInSameLoop = LI->getLoopFor(BB1) == LI->getLoopFor(BB2);
     if (BB1 != BB2 && IsDomParent && IsInSameLoop) {
       EquivalenceClass[BB2] = EC;
+      // If BB2 is visited, then the entire EC should be marked as visited.
+      if (VisitedBlocks.count(BB2)) {
+        VisitedBlocks.insert(EC);
+      }
 
       // If BB2 is heavier than BB1, make BB2 have the same weight
       // as BB1.
@@ -705,7 +720,11 @@ void SampleProfileLoader::findEquivalencesFor(
       Weight = std::max(Weight, BlockWeights[BB2]);
     }
   }
-  BlockWeights[EC] = Weight;
+  if (EC == &EC->getParent()->getEntryBlock()) {
+    BlockWeights[EC] = Samples->getHeadSamples() + 1;
+  } else {
+    BlockWeights[EC] = Weight;
+  }
 }
 
 /// \brief Find equivalence classes.
@@ -796,9 +815,12 @@ uint64_t SampleProfileLoader::visitEdge(Edge E, unsigned *NumUnknownEdges,
 /// count of the basic block, if needed.
 ///
 /// \param F  Function to process.
+/// \param UpdateBlockCount  Whether we should update basic block counts that
+///                          has already been annotated.
 ///
 /// \returns  True if new weights were assigned to edges or blocks.
-bool SampleProfileLoader::propagateThroughEdges(Function &F) {
+bool SampleProfileLoader::propagateThroughEdges(Function &F,
+                                                bool UpdateBlockCount) {
   bool Changed = false;
   DEBUG(dbgs() << "\nPropagation through edges\n");
   for (const auto &BI : F) {
@@ -890,11 +912,35 @@ bool SampleProfileLoader::propagateThroughEdges(Function &F) {
             EdgeWeights[UnknownEdge] = BBWeight - TotalWeight;
           else
             EdgeWeights[UnknownEdge] = 0;
+          const BasicBlock *OtherEC;
+          if (i == 0)
+            OtherEC = EquivalenceClass[UnknownEdge.first];
+          else
+            OtherEC = EquivalenceClass[UnknownEdge.second];
+          // Edge weights should never exceed the BB weights it connects.
+          if (VisitedBlocks.count(OtherEC) &&
+              EdgeWeights[UnknownEdge] > BlockWeights[OtherEC])
+            EdgeWeights[UnknownEdge] = BlockWeights[OtherEC];
           VisitedEdges.insert(UnknownEdge);
           Changed = true;
           DEBUG(dbgs() << "Set weight for edge: ";
                 printEdgeWeight(dbgs(), UnknownEdge));
         }
+      } else if (VisitedBlocks.count(EC) && BlockWeights[EC] == 0) {
+        // If a block Weights 0, all its in/out edges should weight 0.
+        if (i == 0) {
+          for (auto *Pred : Predecessors[BB]) {
+            Edge E = std::make_pair(Pred, BB);
+            EdgeWeights[E] = 0;
+            VisitedEdges.insert(E);
+          }
+        } else {
+          for (auto *Succ : Successors[BB]) {
+            Edge E = std::make_pair(BB, Succ);
+            EdgeWeights[E] = 0;
+            VisitedEdges.insert(E);
+          }
+        }
       } else if (SelfReferentialEdge.first && VisitedBlocks.count(EC)) {
         uint64_t &BBWeight = BlockWeights[BB];
         // We have a self-referential edge and the weight of BB is known.
@@ -907,6 +953,11 @@ bool SampleProfileLoader::propagateThroughEdges(Function &F) {
         DEBUG(dbgs() << "Set self-referential edge weight to: ";
               printEdgeWeight(dbgs(), SelfReferentialEdge));
       }
+      if (UpdateBlockCount && !VisitedBlocks.count(EC) && TotalWeight > 0) {
+        BlockWeights[EC] = TotalWeight;
+        VisitedBlocks.insert(EC);
+        Changed = true;
+      }
     }
   }
 
@@ -966,7 +1017,21 @@ void SampleProfileLoader::propagateWeights(Function &F) {
 
   // Add an entry count to the function using the samples gathered
   // at the function entry.
-  F.setEntryCount(Samples->getHeadSamples());
+  F.setEntryCount(Samples->getHeadSamples() + 1);
+
+  // If BB weight is larger than its corresponding loop's header BB weight,
+  // use the BB weight to replace the loop header BB weight.
+  for (auto &BI : F) {
+    BasicBlock *BB = &BI;
+    Loop *L = LI->getLoopFor(BB);
+    if (!L) {
+      continue;
+    }
+    BasicBlock *Header = L->getHeader();
+    if (Header && BlockWeights[BB] > BlockWeights[Header]) {
+      BlockWeights[Header] = BlockWeights[BB];
+    }
+  }
 
   // Before propagation starts, build, for each block, a list of
   // unique predecessors and successors. This is necessary to handle
@@ -977,7 +1042,23 @@ void SampleProfileLoader::propagateWeights(Function &F) {
 
   // Propagate until we converge or we go past the iteration limit.
   while (Changed && I++ < SampleProfileMaxPropagateIterations) {
-    Changed = propagateThroughEdges(F);
+    Changed = propagateThroughEdges(F, false);
+  }
+
+  // The first propagation propagates BB counts from annotated BBs to unknown
+  // BBs. The 2nd propagation pass resets edges weights, and use all BB weights
+  // to propagate edge weights.
+  VisitedEdges.clear();
+  Changed = true;
+  while (Changed && I++ < SampleProfileMaxPropagateIterations) {
+    Changed = propagateThroughEdges(F, false);
+  }
+
+  // The 3rd propagation pass allows adjust annotated BB weights that are
+  // obviously wrong.
+  Changed = true;
+  while (Changed && I++ < SampleProfileMaxPropagateIterations) {
+    Changed = propagateThroughEdges(F, true);
   }
 
   // Generate MD_prof metadata for every branch instruction using the
@@ -994,7 +1075,7 @@ void SampleProfileLoader::propagateWeights(Function &F) {
           if (!dyn_cast<IntrinsicInst>(&I)) {
             SmallVector<uint32_t, 1> Weights;
             Weights.push_back(BlockWeights[BB]);
-            CI->setMetadata(LLVMContext::MD_prof, 
+            CI->setMetadata(LLVMContext::MD_prof,
                             MDB.createBranchWeights(Weights));
           }
         }
@@ -1023,7 +1104,9 @@ void SampleProfileLoader::propagateWeights(Function &F) {
         DEBUG(dbgs() << " (saturated due to uint32_t overflow)");
         Weight = std::numeric_limits<uint32_t>::max();
       }
-      Weights.push_back(static_cast<uint32_t>(Weight));
+      // Weight is added by one to avoid propagation errors introduced by
+      // 0 weights.
+      Weights.push_back(static_cast<uint32_t>(Weight + 1));
       if (Weight != 0) {
         if (Weight > MaxWeight) {
           MaxWeight = Weight;
@@ -1192,10 +1275,10 @@ bool SampleProfileLoader::emitAnnotations(Function &F) {
 
 char SampleProfileLoaderLegacyPass::ID = 0;
 INITIALIZE_PASS_BEGIN(SampleProfileLoaderLegacyPass, "sample-profile",
-                "Sample Profile loader", false, false)
+                      "Sample Profile loader", false, false)
 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
 INITIALIZE_PASS_END(SampleProfileLoaderLegacyPass, "sample-profile",
-                "Sample Profile loader", false, false)
+                    "Sample Profile loader", false, false)
 
 bool SampleProfileLoader::doInitialization(Module &M) {
   auto &Ctx = M.getContext();
@@ -1232,12 +1315,13 @@ bool SampleProfileLoader::runOnModule(Module &M) {
       clearFunctionData();
       retval |= runOnFunction(F);
     }
-  M.setProfileSummary(Reader->getSummary().getMD(M.getContext()));
+  if (M.getProfileSummary() == nullptr)
+    M.setProfileSummary(Reader->getSummary().getMD(M.getContext()));
   return retval;
 }
 
 bool SampleProfileLoaderLegacyPass::runOnModule(Module &M) {
-  // FIXME: pass in AssumptionCache correctly for the new pass manager. 
+  // FIXME: pass in AssumptionCache correctly for the new pass manager.
   SampleLoader.setACT(&getAnalysis<AssumptionCacheTracker>());
   return SampleLoader.runOnModule(M);
 }
@@ -1251,7 +1335,7 @@ bool SampleProfileLoader::runOnFunction(Function &F) {
 }
 
 PreservedAnalyses SampleProfileLoaderPass::run(Module &M,
-                                               AnalysisManager<Module> &AM) {
+                                               ModuleAnalysisManager &AM) {
 
   SampleProfileLoader SampleLoader(SampleProfileFile);