[CodeGen] Generate llvm.loop.parallel_accesses instead of llvm.mem.parallel_loop_access metadata.

Instead of generating llvm.mem.parallel_loop_access metadata, generate
llvm.access.group on instructions and llvm.loop.parallel_accesses on
loops. There is one access group per generated loop.

This is clang part of D52116/r349725.

Differential Revision: https://reviews.llvm.org/D52117

llvm-svn: 349823

2 files changed, 29 insertions, 16 deletions

diff --git a/clang/lib/CodeGen/CGLoopInfo.cpp b/clang/lib/CodeGen/CGLoopInfo.cpp
index 169ae4fcde1..6cbf801ae61 100644
--- a/clang/lib/CodeGen/CGLoopInfo.cpp
+++ b/clang/lib/CodeGen/CGLoopInfo.cpp
@@ -21,7 +21,7 @@ using namespace llvm;
 
 static MDNode *createMetadata(LLVMContext &Ctx, const LoopAttributes &Attrs,
                               const llvm::DebugLoc &StartLoc,
-                              const llvm::DebugLoc &EndLoc) {
+                              const llvm::DebugLoc &EndLoc, MDNode *&AccGroup) {
 
   if (!Attrs.IsParallel && Attrs.VectorizeWidth == 0 &&
       Attrs.InterleaveCount == 0 && Attrs.UnrollCount == 0 &&
@@ -122,6 +122,12 @@ static MDNode *createMetadata(LLVMContext &Ctx, const LoopAttributes &Attrs,
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
+  if (Attrs.IsParallel) {
+    AccGroup = MDNode::getDistinct(Ctx, {});
+    Args.push_back(MDNode::get(
+        Ctx, {MDString::get(Ctx, "llvm.loop.parallel_accesses"), AccGroup}));
+  }
+
   // Set the first operand to itself.
   MDNode *LoopID = MDNode::get(Ctx, Args);
   LoopID->replaceOperandWith(0, LoopID);
@@ -150,7 +156,8 @@ 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);
+  LoopID =
+      createMetadata(Header->getContext(), Attrs, StartLoc, EndLoc, AccGroup);
 }
 
 void LoopInfoStack::push(BasicBlock *Header, const llvm::DebugLoc &StartLoc,
@@ -328,6 +335,21 @@ void LoopInfoStack::pop() {
 }
 
 void LoopInfoStack::InsertHelper(Instruction *I) const {
+  if (I->mayReadOrWriteMemory()) {
+    SmallVector<Metadata *, 4> AccessGroups;
+    for (const LoopInfo &AL : Active) {
+      // Here we assume that every loop that has an access group is parallel.
+      if (MDNode *Group = AL.getAccessGroup())
+        AccessGroups.push_back(Group);
+    }
+    MDNode *UnionMD = nullptr;
+    if (AccessGroups.size() == 1)
+      UnionMD = cast<MDNode>(AccessGroups[0]);
+    else if (AccessGroups.size() >= 2)
+      UnionMD = MDNode::get(I->getContext(), AccessGroups);
+    I->setMetadata("llvm.access.group", UnionMD);
+  }
+
   if (!hasInfo())
     return;
 
@@ -343,18 +365,4 @@ void LoopInfoStack::InsertHelper(Instruction *I) const {
       }
     return;
   }
-
-  if (I->mayReadOrWriteMemory()) {
-    SmallVector<Metadata *, 2> ParallelLoopIDs;
-    for (const LoopInfo &AL : Active)
-      if (AL.getAttributes().IsParallel)
-        ParallelLoopIDs.push_back(AL.getLoopID());
-
-    MDNode *ParallelMD = nullptr;
-    if (ParallelLoopIDs.size() == 1)
-      ParallelMD = cast<MDNode>(ParallelLoopIDs[0]);
-    else if (ParallelLoopIDs.size() >= 2)
-      ParallelMD = MDNode::get(I->getContext(), ParallelLoopIDs);
-    I->setMetadata("llvm.mem.parallel_loop_access", ParallelMD);
-  }
 }
diff --git a/clang/lib/CodeGen/CGLoopInfo.h b/clang/lib/CodeGen/CGLoopInfo.h
index 466fdc9fedd..201cbb7894b 100644
--- a/clang/lib/CodeGen/CGLoopInfo.h
+++ b/clang/lib/CodeGen/CGLoopInfo.h
@@ -84,6 +84,9 @@ public:
   /// Get the set of attributes active for this loop.
   const LoopAttributes &getAttributes() const { return Attrs; }
 
+  /// Return this loop's access group or nullptr if it does not have one.
+  llvm::MDNode *getAccessGroup() const { return AccGroup; }
+
 private:
   /// Loop ID metadata.
   llvm::MDNode *LoopID;
@@ -91,6 +94,8 @@ private:
   llvm::BasicBlock *Header;
   /// The attributes for this loop.
   LoopAttributes Attrs;
+  /// The access group for memory accesses parallel to this loop.
+  llvm::MDNode *AccGroup = nullptr;
 };
 
 /// A stack of loop information corresponding to loop nesting levels.