[CodeGen] Generate follow-up metadata for loops with more than one transformation.

Before this patch, CGLoop would dump all transformations for a loop into
a single LoopID without encoding any order in which to apply them.
rL348944 added the possibility to encode a transformation order using
followup-attributes.

When a loop has more than one transformation, use the follow-up
attribute define the order in which they are applied. The emitted order
is the defacto order as defined by the current LLVM pass pipeline,
which is:

  LoopFullUnrollPass
  LoopDistributePass
  LoopVectorizePass
  LoopUnrollAndJamPass
  LoopUnrollPass
  MachinePipeliner

This patch should therefore not change the assembly output, assuming
that all explicit transformations can be applied, and no implicit
transformations in-between. In the former case,
WarnMissedTransformationsPass should emit a warning (except for
MachinePipeliner which is not implemented yet). The latter could be
avoided by adding 'llvm.loop.disable_nonforced' attributes.

Because LoopUnrollAndJamPass processes a loop nest, generation of the
MDNode is delayed to after the inner loop metadata have been processed.
A temporary LoopID is therefore used to annotate instructions and
RAUW'ed by the actual LoopID later.

Differential Revision: https://reviews.llvm.org/D57978

llvm-svn: 357415

1 files changed, 449 insertions, 91 deletions

diff --git a/clang/lib/CodeGen/CGLoopInfo.cpp b/clang/lib/CodeGen/CGLoopInfo.cpp
index 36ae39b6fe4..b2bc42bfa01 100644
--- a/clang/lib/CodeGen/CGLoopInfo.cpp
+++ b/clang/lib/CodeGen/CGLoopInfo.cpp
@@ -18,138 +18,396 @@
 using namespace clang::CodeGen;
 using namespace llvm;
 
-static MDNode *createMetadata(LLVMContext &Ctx, const LoopAttributes &Attrs,
-                              const llvm::DebugLoc &StartLoc,
-                              const llvm::DebugLoc &EndLoc, MDNode *&AccGroup) {
+MDNode *
+LoopInfo::createLoopPropertiesMetadata(ArrayRef<Metadata *> LoopProperties) {
+  LLVMContext &Ctx = Header->getContext();
+  SmallVector<Metadata *, 4> NewLoopProperties;
+  TempMDTuple TempNode = MDNode::getTemporary(Ctx, None);
+  NewLoopProperties.push_back(TempNode.get());
+  NewLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+
+  MDNode *LoopID = MDNode::getDistinct(Ctx, NewLoopProperties);
+  LoopID->replaceOperandWith(0, LoopID);
+  return LoopID;
+}
 
-  if (!Attrs.IsParallel && Attrs.VectorizeWidth == 0 &&
-      Attrs.InterleaveCount == 0 && Attrs.UnrollCount == 0 &&
-      Attrs.UnrollAndJamCount == 0 && !Attrs.PipelineDisabled &&
-      Attrs.PipelineInitiationInterval == 0 &&
-      Attrs.VectorizeEnable == LoopAttributes::Unspecified &&
-      Attrs.UnrollEnable == LoopAttributes::Unspecified &&
-      Attrs.UnrollAndJamEnable == LoopAttributes::Unspecified &&
-      Attrs.DistributeEnable == LoopAttributes::Unspecified && !StartLoc &&
-      !EndLoc)
-    return nullptr;
+MDNode *LoopInfo::createPipeliningMetadata(const LoopAttributes &Attrs,
+                                           ArrayRef<Metadata *> LoopProperties,
+                                           bool &HasUserTransforms) {
+  LLVMContext &Ctx = Header->getContext();
+
+  Optional<bool> Enabled;
+  if (Attrs.PipelineDisabled)
+    Enabled = false;
+  else if (Attrs.PipelineInitiationInterval != 0)
+    Enabled = true;
+
+  if (Enabled != true) {
+    SmallVector<Metadata *, 4> NewLoopProperties;
+    if (Enabled == false) {
+      NewLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+      NewLoopProperties.push_back(
+          MDNode::get(Ctx, {MDString::get(Ctx, "llvm.loop.pipeline.disable"),
+                            ConstantAsMetadata::get(ConstantInt::get(
+                                llvm::Type::getInt1Ty(Ctx), 1))}));
+      LoopProperties = NewLoopProperties;
+    }
+    return createLoopPropertiesMetadata(LoopProperties);
+  }
 
   SmallVector<Metadata *, 4> Args;
-  // Reserve operand 0 for loop id self reference.
-  auto TempNode = MDNode::getTemporary(Ctx, None);
+  TempMDTuple TempNode = MDNode::getTemporary(Ctx, None);
   Args.push_back(TempNode.get());
+  Args.append(LoopProperties.begin(), LoopProperties.end());
 
-  // If we have a valid start debug location for the loop, add it.
-  if (StartLoc) {
-    Args.push_back(StartLoc.getAsMDNode());
-
-    // If we also have a valid end debug location for the loop, add it.
-    if (EndLoc)
-      Args.push_back(EndLoc.getAsMDNode());
-  }
-
-  // Setting vectorize.width
-  if (Attrs.VectorizeWidth > 0) {
-    Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.vectorize.width"),
-                        ConstantAsMetadata::get(ConstantInt::get(
-                            Type::getInt32Ty(Ctx), Attrs.VectorizeWidth))};
+  if (Attrs.PipelineInitiationInterval > 0) {
+    Metadata *Vals[] = {
+        MDString::get(Ctx, "llvm.loop.pipeline.initiationinterval"),
+        ConstantAsMetadata::get(ConstantInt::get(
+            llvm::Type::getInt32Ty(Ctx), Attrs.PipelineInitiationInterval))};
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  // Setting interleave.count
-  if (Attrs.InterleaveCount > 0) {
-    Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.interleave.count"),
-                        ConstantAsMetadata::get(ConstantInt::get(
-                            Type::getInt32Ty(Ctx), Attrs.InterleaveCount))};
-    Args.push_back(MDNode::get(Ctx, Vals));
+  // No follow-up: This is the last transformation.
+
+  MDNode *LoopID = MDNode::getDistinct(Ctx, Args);
+  LoopID->replaceOperandWith(0, LoopID);
+  HasUserTransforms = true;
+  return LoopID;
+}
+
+MDNode *
+LoopInfo::createPartialUnrollMetadata(const LoopAttributes &Attrs,
+                                      ArrayRef<Metadata *> LoopProperties,
+                                      bool &HasUserTransforms) {
+  LLVMContext &Ctx = Header->getContext();
+
+  Optional<bool> Enabled;
+  if (Attrs.UnrollEnable == LoopAttributes::Disable)
+    Enabled = false;
+  else if (Attrs.UnrollEnable == LoopAttributes::Full)
+    Enabled = None;
+  else if (Attrs.UnrollEnable != LoopAttributes::Unspecified ||
+           Attrs.UnrollCount != 0)
+    Enabled = true;
+
+  if (Enabled != true) {
+    // createFullUnrollMetadata will already have added llvm.loop.unroll.disable
+    // if unrolling is disabled.
+    return createPipeliningMetadata(Attrs, LoopProperties, HasUserTransforms);
   }
 
+  SmallVector<Metadata *, 4> FollowupLoopProperties;
+
+  // Apply all loop properties to the unrolled loop.
+  FollowupLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+
+  // Don't unroll an already unrolled loop.
+  FollowupLoopProperties.push_back(
+      MDNode::get(Ctx, MDString::get(Ctx, "llvm.loop.unroll.disable")));
+
+  bool FollowupHasTransforms = false;
+  MDNode *Followup = createPipeliningMetadata(Attrs, FollowupLoopProperties,
+                                              FollowupHasTransforms);
+
+  SmallVector<Metadata *, 4> Args;
+  TempMDTuple TempNode = MDNode::getTemporary(Ctx, None);
+  Args.push_back(TempNode.get());
+  Args.append(LoopProperties.begin(), LoopProperties.end());
+
   // Setting unroll.count
   if (Attrs.UnrollCount > 0) {
     Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.unroll.count"),
                         ConstantAsMetadata::get(ConstantInt::get(
-                            Type::getInt32Ty(Ctx), Attrs.UnrollCount))};
+                            llvm::Type::getInt32Ty(Ctx), Attrs.UnrollCount))};
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  // Setting unroll_and_jam.count
-  if (Attrs.UnrollAndJamCount > 0) {
-    Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.unroll_and_jam.count"),
-                        ConstantAsMetadata::get(ConstantInt::get(
-                            Type::getInt32Ty(Ctx), Attrs.UnrollAndJamCount))};
+  // Setting unroll.full or unroll.disable
+  if (Attrs.UnrollEnable == LoopAttributes::Enable) {
+    Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.unroll.enable")};
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  // Setting vectorize.enable
-  if (Attrs.VectorizeEnable != LoopAttributes::Unspecified) {
-    Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.vectorize.enable"),
-                        ConstantAsMetadata::get(ConstantInt::get(
-                            Type::getInt1Ty(Ctx), (Attrs.VectorizeEnable ==
-                                                   LoopAttributes::Enable)))};
-    Args.push_back(MDNode::get(Ctx, Vals));
-  }
+  if (FollowupHasTransforms)
+    Args.push_back(MDNode::get(
+        Ctx, {MDString::get(Ctx, "llvm.loop.unroll.followup_all"), Followup}));
 
-  // Setting unroll.full or unroll.disable
-  if (Attrs.UnrollEnable != LoopAttributes::Unspecified) {
-    std::string Name;
-    if (Attrs.UnrollEnable == LoopAttributes::Enable)
-      Name = "llvm.loop.unroll.enable";
-    else if (Attrs.UnrollEnable == LoopAttributes::Full)
-      Name = "llvm.loop.unroll.full";
-    else
-      Name = "llvm.loop.unroll.disable";
-    Metadata *Vals[] = {MDString::get(Ctx, Name)};
-    Args.push_back(MDNode::get(Ctx, Vals));
+  MDNode *LoopID = MDNode::getDistinct(Ctx, Args);
+  LoopID->replaceOperandWith(0, LoopID);
+  HasUserTransforms = true;
+  return LoopID;
+}
+
+MDNode *
+LoopInfo::createUnrollAndJamMetadata(const LoopAttributes &Attrs,
+                                     ArrayRef<Metadata *> LoopProperties,
+                                     bool &HasUserTransforms) {
+  LLVMContext &Ctx = Header->getContext();
+
+  Optional<bool> Enabled;
+  if (Attrs.UnrollAndJamEnable == LoopAttributes::Disable)
+    Enabled = false;
+  else if (Attrs.UnrollAndJamEnable == LoopAttributes::Enable ||
+           Attrs.UnrollAndJamCount != 0)
+    Enabled = true;
+
+  if (Enabled != true) {
+    SmallVector<Metadata *, 4> NewLoopProperties;
+    if (Enabled == false) {
+      NewLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+      NewLoopProperties.push_back(MDNode::get(
+          Ctx, MDString::get(Ctx, "llvm.loop.unroll_and_jam.disable")));
+      LoopProperties = NewLoopProperties;
+    }
+    return createPartialUnrollMetadata(Attrs, LoopProperties,
+                                       HasUserTransforms);
   }
 
-  // Setting unroll_and_jam.full or unroll_and_jam.disable
-  if (Attrs.UnrollAndJamEnable != LoopAttributes::Unspecified) {
-    std::string Name;
-    if (Attrs.UnrollAndJamEnable == LoopAttributes::Enable)
-      Name = "llvm.loop.unroll_and_jam.enable";
-    else if (Attrs.UnrollAndJamEnable == LoopAttributes::Full)
-      Name = "llvm.loop.unroll_and_jam.full";
-    else
-      Name = "llvm.loop.unroll_and_jam.disable";
-    Metadata *Vals[] = {MDString::get(Ctx, Name)};
+  SmallVector<Metadata *, 4> FollowupLoopProperties;
+  FollowupLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+  FollowupLoopProperties.push_back(
+      MDNode::get(Ctx, MDString::get(Ctx, "llvm.loop.unroll_and_jam.disable")));
+
+  bool FollowupHasTransforms = false;
+  MDNode *Followup = createPartialUnrollMetadata(Attrs, FollowupLoopProperties,
+                                                 FollowupHasTransforms);
+
+  SmallVector<Metadata *, 4> Args;
+  TempMDTuple TempNode = MDNode::getTemporary(Ctx, None);
+  Args.push_back(TempNode.get());
+  Args.append(LoopProperties.begin(), LoopProperties.end());
+
+  // Setting unroll_and_jam.count
+  if (Attrs.UnrollAndJamCount > 0) {
+    Metadata *Vals[] = {
+        MDString::get(Ctx, "llvm.loop.unroll_and_jam.count"),
+        ConstantAsMetadata::get(ConstantInt::get(llvm::Type::getInt32Ty(Ctx),
+                                                 Attrs.UnrollAndJamCount))};
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  if (Attrs.DistributeEnable != LoopAttributes::Unspecified) {
-    Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.distribute.enable"),
-                        ConstantAsMetadata::get(ConstantInt::get(
-                            Type::getInt1Ty(Ctx), (Attrs.DistributeEnable ==
-                                                   LoopAttributes::Enable)))};
+  if (Attrs.UnrollAndJamEnable == LoopAttributes::Enable) {
+    Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.unroll_and_jam.enable")};
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  if (Attrs.IsParallel) {
-    AccGroup = MDNode::getDistinct(Ctx, {});
+  if (FollowupHasTransforms)
     Args.push_back(MDNode::get(
-        Ctx, {MDString::get(Ctx, "llvm.loop.parallel_accesses"), AccGroup}));
+        Ctx, {MDString::get(Ctx, "llvm.loop.unroll_and_jam.followup_outer"),
+              Followup}));
+
+  if (UnrollAndJamInnerFollowup)
+    Args.push_back(MDNode::get(
+        Ctx, {MDString::get(Ctx, "llvm.loop.unroll_and_jam.followup_inner"),
+              UnrollAndJamInnerFollowup}));
+
+  MDNode *LoopID = MDNode::getDistinct(Ctx, Args);
+  LoopID->replaceOperandWith(0, LoopID);
+  HasUserTransforms = true;
+  return LoopID;
+}
+
+MDNode *
+LoopInfo::createLoopVectorizeMetadata(const LoopAttributes &Attrs,
+                                      ArrayRef<Metadata *> LoopProperties,
+                                      bool &HasUserTransforms) {
+  LLVMContext &Ctx = Header->getContext();
+
+  Optional<bool> Enabled;
+  if (Attrs.VectorizeEnable == LoopAttributes::Disable)
+    Enabled = false;
+  else if (Attrs.VectorizeEnable != LoopAttributes::Unspecified ||
+           Attrs.InterleaveCount != 0 || Attrs.VectorizeWidth != 0)
+    Enabled = true;
+
+  if (Enabled != true) {
+    SmallVector<Metadata *, 4> NewLoopProperties;
+    if (Enabled == false) {
+      NewLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+      NewLoopProperties.push_back(
+          MDNode::get(Ctx, {MDString::get(Ctx, "llvm.loop.vectorize.enable"),
+                            ConstantAsMetadata::get(ConstantInt::get(
+                                llvm::Type::getInt1Ty(Ctx), 0))}));
+      LoopProperties = NewLoopProperties;
+    }
+    return createUnrollAndJamMetadata(Attrs, LoopProperties, HasUserTransforms);
+  }
+
+  // Apply all loop properties to the vectorized loop.
+  SmallVector<Metadata *, 4> FollowupLoopProperties;
+  FollowupLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+
+  // Don't vectorize an already vectorized loop.
+  FollowupLoopProperties.push_back(
+      MDNode::get(Ctx, MDString::get(Ctx, "llvm.loop.isvectorized")));
+
+  bool FollowupHasTransforms = false;
+  MDNode *Followup = createUnrollAndJamMetadata(Attrs, FollowupLoopProperties,
+                                                FollowupHasTransforms);
+
+  SmallVector<Metadata *, 4> Args;
+  TempMDTuple TempNode = MDNode::getTemporary(Ctx, None);
+  Args.push_back(TempNode.get());
+  Args.append(LoopProperties.begin(), LoopProperties.end());
+
+  // Setting vectorize.width
+  if (Attrs.VectorizeWidth > 0) {
+    Metadata *Vals[] = {
+        MDString::get(Ctx, "llvm.loop.vectorize.width"),
+        ConstantAsMetadata::get(ConstantInt::get(llvm::Type::getInt32Ty(Ctx),
+                                                 Attrs.VectorizeWidth))};
+    Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  if (Attrs.PipelineDisabled) {
+  // Setting interleave.count
+  if (Attrs.InterleaveCount > 0) {
     Metadata *Vals[] = {
-        MDString::get(Ctx, "llvm.loop.pipeline.disable"),
-        ConstantAsMetadata::get(ConstantInt::get(
-            Type::getInt1Ty(Ctx), (Attrs.PipelineDisabled == true)))};
+        MDString::get(Ctx, "llvm.loop.interleave.count"),
+        ConstantAsMetadata::get(ConstantInt::get(llvm::Type::getInt32Ty(Ctx),
+                                                 Attrs.InterleaveCount))};
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  if (Attrs.PipelineInitiationInterval > 0) {
+  // Setting vectorize.enable
+  if (Attrs.VectorizeEnable != LoopAttributes::Unspecified) {
     Metadata *Vals[] = {
-        MDString::get(Ctx, "llvm.loop.pipeline.initiationinterval"),
+        MDString::get(Ctx, "llvm.loop.vectorize.enable"),
         ConstantAsMetadata::get(ConstantInt::get(
-            Type::getInt32Ty(Ctx), Attrs.PipelineInitiationInterval))};
+            llvm::Type::getInt1Ty(Ctx),
+            (Attrs.VectorizeEnable == LoopAttributes::Enable)))};
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
-  // Set the first operand to itself.
+  if (FollowupHasTransforms)
+    Args.push_back(MDNode::get(
+        Ctx,
+        {MDString::get(Ctx, "llvm.loop.vectorize.followup_all"), Followup}));
+
+  MDNode *LoopID = MDNode::get(Ctx, Args);
+  LoopID->replaceOperandWith(0, LoopID);
+  HasUserTransforms = true;
+  return LoopID;
+}
+
+MDNode *
+LoopInfo::createLoopDistributeMetadata(const LoopAttributes &Attrs,
+                                       ArrayRef<Metadata *> LoopProperties,
+                                       bool &HasUserTransforms) {
+  LLVMContext &Ctx = Header->getContext();
+
+  Optional<bool> Enabled;
+  if (Attrs.DistributeEnable == LoopAttributes::Disable)
+    Enabled = false;
+  if (Attrs.DistributeEnable == LoopAttributes::Enable)
+    Enabled = true;
+
+  if (Enabled != true) {
+    SmallVector<Metadata *, 4> NewLoopProperties;
+    if (Enabled == false) {
+      NewLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+      NewLoopProperties.push_back(
+          MDNode::get(Ctx, {MDString::get(Ctx, "llvm.loop.distribute.enable"),
+                            ConstantAsMetadata::get(ConstantInt::get(
+                                llvm::Type::getInt1Ty(Ctx), 0))}));
+      LoopProperties = NewLoopProperties;
+    }
+    return createLoopVectorizeMetadata(Attrs, LoopProperties,
+                                       HasUserTransforms);
+  }
+
+  bool FollowupHasTransforms = false;
+  MDNode *Followup =
+      createLoopVectorizeMetadata(Attrs, LoopProperties, FollowupHasTransforms);
+
+  SmallVector<Metadata *, 4> Args;
+  TempMDTuple TempNode = MDNode::getTemporary(Ctx, None);
+  Args.push_back(TempNode.get());
+  Args.append(LoopProperties.begin(), LoopProperties.end());
+
+  Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.distribute.enable"),
+                      ConstantAsMetadata::get(ConstantInt::get(
+                          llvm::Type::getInt1Ty(Ctx),
+                          (Attrs.DistributeEnable == LoopAttributes::Enable)))};
+  Args.push_back(MDNode::get(Ctx, Vals));
+
+  if (FollowupHasTransforms)
+    Args.push_back(MDNode::get(
+        Ctx,
+        {MDString::get(Ctx, "llvm.loop.distribute.followup_all"), Followup}));
+
   MDNode *LoopID = MDNode::get(Ctx, Args);
   LoopID->replaceOperandWith(0, LoopID);
+  HasUserTransforms = true;
+  return LoopID;
+}
+
+MDNode *LoopInfo::createFullUnrollMetadata(const LoopAttributes &Attrs,
+                                           ArrayRef<Metadata *> LoopProperties,
+                                           bool &HasUserTransforms) {
+  LLVMContext &Ctx = Header->getContext();
+
+  Optional<bool> Enabled;
+  if (Attrs.UnrollEnable == LoopAttributes::Disable)
+    Enabled = false;
+  else if (Attrs.UnrollEnable == LoopAttributes::Full)
+    Enabled = true;
+
+  if (Enabled != true) {
+    SmallVector<Metadata *, 4> NewLoopProperties;
+    if (Enabled == false) {
+      NewLoopProperties.append(LoopProperties.begin(), LoopProperties.end());
+      NewLoopProperties.push_back(
+          MDNode::get(Ctx, MDString::get(Ctx, "llvm.loop.unroll.disable")));
+      LoopProperties = NewLoopProperties;
+    }
+    return createLoopDistributeMetadata(Attrs, LoopProperties,
+                                        HasUserTransforms);
+  }
+
+  SmallVector<Metadata *, 4> Args;
+  TempMDTuple TempNode = MDNode::getTemporary(Ctx, None);
+  Args.push_back(TempNode.get());
+  Args.append(LoopProperties.begin(), LoopProperties.end());
+  Args.push_back(MDNode::get(Ctx, MDString::get(Ctx, "llvm.loop.unroll.full")));
+
+  // No follow-up: there is no loop after full unrolling.
+  // TODO: Warn if there are transformations after full unrolling.
+
+  MDNode *LoopID = MDNode::getDistinct(Ctx, Args);
+  LoopID->replaceOperandWith(0, LoopID);
+  HasUserTransforms = true;
   return LoopID;
 }
 
+MDNode *LoopInfo::createMetadata(
+    const LoopAttributes &Attrs,
+    llvm::ArrayRef<llvm::Metadata *> AdditionalLoopProperties,
+    bool &HasUserTransforms) {
+  SmallVector<Metadata *, 3> LoopProperties;
+
+  // If we have a valid start debug location for the loop, add it.
+  if (StartLoc) {
+    LoopProperties.push_back(StartLoc.getAsMDNode());
+
+    // If we also have a valid end debug location for the loop, add it.
+    if (EndLoc)
+      LoopProperties.push_back(EndLoc.getAsMDNode());
+  }
+
+  assert(!!AccGroup == Attrs.IsParallel &&
+         "There must be an access group iff the loop is parallel");
+  if (Attrs.IsParallel) {
+    LLVMContext &Ctx = Header->getContext();
+    LoopProperties.push_back(MDNode::get(
+        Ctx, {MDString::get(Ctx, "llvm.loop.parallel_accesses"), AccGroup}));
+  }
+
+  LoopProperties.insert(LoopProperties.end(), AdditionalLoopProperties.begin(),
+                        AdditionalLoopProperties.end());
+  return createFullUnrollMetadata(Attrs, LoopProperties, HasUserTransforms);
+}
+
 LoopAttributes::LoopAttributes(bool IsParallel)
     : IsParallel(IsParallel), VectorizeEnable(LoopAttributes::Unspecified),
       UnrollEnable(LoopAttributes::Unspecified),
@@ -173,15 +431,114 @@ void LoopAttributes::clear() {
 }
 
 LoopInfo::LoopInfo(BasicBlock *Header, const LoopAttributes &Attrs,
-                   const llvm::DebugLoc &StartLoc, const llvm::DebugLoc &EndLoc)
-    : LoopID(nullptr), Header(Header), Attrs(Attrs) {
-  LoopID =
-      createMetadata(Header->getContext(), Attrs, StartLoc, EndLoc, AccGroup);
+                   const llvm::DebugLoc &StartLoc, const llvm::DebugLoc &EndLoc,
+                   LoopInfo *Parent)
+    : Header(Header), Attrs(Attrs), StartLoc(StartLoc), EndLoc(EndLoc),
+      Parent(Parent) {
+
+  if (Attrs.IsParallel) {
+    // Create an access group for this loop.
+    LLVMContext &Ctx = Header->getContext();
+    AccGroup = MDNode::getDistinct(Ctx, {});
+  }
+
+  if (!Attrs.IsParallel && Attrs.VectorizeWidth == 0 &&
+      Attrs.InterleaveCount == 0 && Attrs.UnrollCount == 0 &&
+      Attrs.UnrollAndJamCount == 0 && !Attrs.PipelineDisabled &&
+      Attrs.PipelineInitiationInterval == 0 &&
+      Attrs.VectorizeEnable == LoopAttributes::Unspecified &&
+      Attrs.UnrollEnable == LoopAttributes::Unspecified &&
+      Attrs.UnrollAndJamEnable == LoopAttributes::Unspecified &&
+      Attrs.DistributeEnable == LoopAttributes::Unspecified && !StartLoc &&
+      !EndLoc)
+    return;
+
+  TempLoopID = MDNode::getTemporary(Header->getContext(), None);
+}
+
+void LoopInfo::finish() {
+  // We did not annotate the loop body instructions because there are no
+  // attributes for this loop.
+  if (!TempLoopID)
+    return;
+
+  MDNode *LoopID;
+  LoopAttributes CurLoopAttr = Attrs;
+  LLVMContext &Ctx = Header->getContext();
+
+  if (Parent && (Parent->Attrs.UnrollAndJamEnable ||
+                 Parent->Attrs.UnrollAndJamCount != 0)) {
+    // Parent unroll-and-jams this loop.
+    // Split the transformations in those that happens before the unroll-and-jam
+    // and those after.
+
+    LoopAttributes BeforeJam, AfterJam;
+
+    BeforeJam.IsParallel = AfterJam.IsParallel = Attrs.IsParallel;
+
+    BeforeJam.VectorizeWidth = Attrs.VectorizeWidth;
+    BeforeJam.InterleaveCount = Attrs.InterleaveCount;
+    BeforeJam.VectorizeEnable = Attrs.VectorizeEnable;
+    BeforeJam.DistributeEnable = Attrs.DistributeEnable;
+
+    switch (Attrs.UnrollEnable) {
+    case LoopAttributes::Unspecified:
+    case LoopAttributes::Disable:
+      BeforeJam.UnrollEnable = Attrs.UnrollEnable;
+      AfterJam.UnrollEnable = Attrs.UnrollEnable;
+      break;
+    case LoopAttributes::Full:
+      BeforeJam.UnrollEnable = LoopAttributes::Full;
+      break;
+    case LoopAttributes::Enable:
+      AfterJam.UnrollEnable = LoopAttributes::Enable;
+      break;
+    }
+
+    AfterJam.UnrollCount = Attrs.UnrollCount;
+    AfterJam.PipelineDisabled = Attrs.PipelineDisabled;
+    AfterJam.PipelineInitiationInterval = Attrs.PipelineInitiationInterval;
+
+    // If this loop is subject of an unroll-and-jam by the parent loop, and has
+    // an unroll-and-jam annotation itself, we have to decide whether to first
+    // apply the parent's unroll-and-jam or this loop's unroll-and-jam. The
+    // UnrollAndJam pass processes loops from inner to outer, so we apply the
+    // inner first.
+    BeforeJam.UnrollAndJamCount = Attrs.UnrollAndJamCount;
+    BeforeJam.UnrollAndJamEnable = Attrs.UnrollAndJamEnable;
+
+    // Set the inner followup metadata to process by the outer loop. Only
+    // consider the first inner loop.
+    if (!Parent->UnrollAndJamInnerFollowup) {
+      // Splitting the attributes into a BeforeJam and an AfterJam part will
+      // stop 'llvm.loop.isvectorized' (generated by vectorization in BeforeJam)
+      // to be forwarded to the AfterJam part. We detect the situation here and
+      // add it manually.
+      SmallVector<Metadata *, 1> BeforeLoopProperties;
+      if (BeforeJam.VectorizeEnable != LoopAttributes::Unspecified ||
+          BeforeJam.InterleaveCount != 0 || BeforeJam.VectorizeWidth != 0)
+        BeforeLoopProperties.push_back(
+            MDNode::get(Ctx, MDString::get(Ctx, "llvm.loop.isvectorized")));
+
+      bool InnerFollowupHasTransform = false;
+      MDNode *InnerFollowup = createMetadata(AfterJam, BeforeLoopProperties,
+                                             InnerFollowupHasTransform);
+      if (InnerFollowupHasTransform)
+        Parent->UnrollAndJamInnerFollowup = InnerFollowup;
+    }
+
+    CurLoopAttr = BeforeJam;
+  }
+
+  bool HasUserTransforms = false;
+  LoopID = createMetadata(CurLoopAttr, {}, HasUserTransforms);
+  TempLoopID->replaceAllUsesWith(LoopID);
 }
 
 void LoopInfoStack::push(BasicBlock *Header, const llvm::DebugLoc &StartLoc,
                          const llvm::DebugLoc &EndLoc) {
-  Active.push_back(LoopInfo(Header, StagedAttrs, StartLoc, EndLoc));
+  Active.push_back(LoopInfo(Header, StagedAttrs, StartLoc, EndLoc,
+                            Active.empty() ? nullptr : &Active.back()));
   // Clear the attributes so nested loops do not inherit them.
   StagedAttrs.clear();
 }
@@ -364,6 +721,7 @@ void LoopInfoStack::push(BasicBlock *Header, clang::ASTContext &Ctx,
 
 void LoopInfoStack::pop() {
   assert(!Active.empty() && "No active loops to pop");
+  Active.back().finish();
   Active.pop_back();
 }