1 files changed, 26 insertions, 6 deletions
diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index b5af210f1b92..a85869b16333 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -34,6 +34,7 @@
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/PassManager.h"
+#include "llvm/IR/PrintPasses.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -431,6 +432,10 @@ static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB,
     for (const Use &U : I.uses()) {
       const Instruction *UI = cast<Instruction>(U.getUser());
       const BasicBlock *UserBB = UI->getParent();
+
+      // For practical purposes, we consider that the use in a PHI
+      // occurs in the respective predecessor block. For more info,
+      // see the `phi` doc in LangRef and the LCSSA doc.
       if (const PHINode *P = dyn_cast<PHINode>(UI))
         UserBB = P->getIncomingBlock(U);
 
@@ -535,6 +540,22 @@ void Loop::setLoopAlreadyUnrolled() {
   setLoopID(NewLoopID);
 }
 
+void Loop::setLoopMustProgress() {
+  LLVMContext &Context = getHeader()->getContext();
+
+  MDNode *MustProgress = findOptionMDForLoop(this, "llvm.loop.mustprogress");
+
+  if (MustProgress)
+    return;
+
+  MDNode *MustProgressMD =
+      MDNode::get(Context, MDString::get(Context, "llvm.loop.mustprogress"));
+  MDNode *LoopID = getLoopID();
+  MDNode *NewLoopID =
+      makePostTransformationMetadata(Context, LoopID, {}, {MustProgressMD});
+  setLoopID(NewLoopID);
+}
+
 bool Loop::isAnnotatedParallel() const {
   MDNode *DesiredLoopIdMetadata = getLoopID();
 
@@ -546,7 +567,7 @@ bool Loop::isAnnotatedParallel() const {
   SmallPtrSet<MDNode *, 4>
       ParallelAccessGroups; // For scalable 'contains' check.
   if (ParallelAccesses) {
-    for (const MDOperand &MD : drop_begin(ParallelAccesses->operands(), 1)) {
+    for (const MDOperand &MD : drop_begin(ParallelAccesses->operands())) {
       MDNode *AccGroup = cast<MDNode>(MD.get());
       assert(isValidAsAccessGroup(AccGroup) &&
              "List item must be an access group");
@@ -764,7 +785,7 @@ void UnloopUpdater::removeBlocksFromAncestors() {
 
 /// Update the parent loop for all subloops directly nested within unloop.
 void UnloopUpdater::updateSubloopParents() {
-  while (!Unloop.empty()) {
+  while (!Unloop.isInnermost()) {
     Loop *Subloop = *std::prev(Unloop.end());
     Unloop.removeChildLoop(std::prev(Unloop.end()));
 
@@ -862,7 +883,7 @@ void LoopInfo::erase(Loop *Unloop) {
   auto InvalidateOnExit = make_scope_exit([&]() { destroy(Unloop); });
 
   // First handle the special case of no parent loop to simplify the algorithm.
-  if (!Unloop->getParentLoop()) {
+  if (Unloop->isOutermost()) {
     // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
     for (Loop::block_iterator I = Unloop->block_begin(),
                               E = Unloop->block_end();
@@ -887,7 +908,7 @@ void LoopInfo::erase(Loop *Unloop) {
     }
 
     // Move all of the subloops to the top-level.
-    while (!Unloop->empty())
+    while (!Unloop->isInnermost())
       addTopLevelLoop(Unloop->removeChildLoop(std::prev(Unloop->end())));
 
     return;
@@ -1017,8 +1038,7 @@ MDNode *llvm::makePostTransformationMetadata(LLVMContext &Context,
   SmallVector<Metadata *, 4> MDs;
 
   // Reserve first location for self reference to the LoopID metadata node.
-  TempMDTuple TempNode = MDNode::getTemporary(Context, None);
-  MDs.push_back(TempNode.get());
+  MDs.push_back(nullptr);
 
   // Remove metadata for the transformation that has been applied or that became
   // outdated.