1 files changed, 48 insertions, 46 deletions

diff --git a/gnu/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/gnu/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index 71980e85e8c..76fe91884c7 100644
--- a/gnu/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/gnu/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -210,7 +210,7 @@ namespace {
 
     bool runOnLoop(Loop *L, LPPassManager &LPM) override;
     bool processCurrentLoop();
-
+    bool isUnreachableDueToPreviousUnswitching(BasicBlock *);
     /// This transformation requires natural loop information & requires that
     /// loop preheaders be inserted into the CFG.
     ///
@@ -483,6 +483,35 @@ bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) {
   return Changed;
 }
 
+// Return true if the BasicBlock BB is unreachable from the loop header.
+// Return false, otherwise.
+bool LoopUnswitch::isUnreachableDueToPreviousUnswitching(BasicBlock *BB) {
+  auto *Node = DT->getNode(BB)->getIDom();
+  BasicBlock *DomBB = Node->getBlock();
+  while (currentLoop->contains(DomBB)) {
+    BranchInst *BInst = dyn_cast<BranchInst>(DomBB->getTerminator());
+
+    Node = DT->getNode(DomBB)->getIDom();
+    DomBB = Node->getBlock();
+
+    if (!BInst || !BInst->isConditional())
+      continue;
+
+    Value *Cond = BInst->getCondition();
+    if (!isa<ConstantInt>(Cond))
+      continue;
+
+    BasicBlock *UnreachableSucc =
+        Cond == ConstantInt::getTrue(Cond->getContext())
+            ? BInst->getSuccessor(1)
+            : BInst->getSuccessor(0);
+
+    if (DT->dominates(UnreachableSucc, BB))
+      return true;
+  }
+  return false;
+}
+
 /// Do actual work and unswitch loop if possible and profitable.
 bool LoopUnswitch::processCurrentLoop() {
   bool Changed = false;
@@ -593,6 +622,12 @@ bool LoopUnswitch::processCurrentLoop() {
       continue;
 
     if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+      // Some branches may be rendered unreachable because of previous
+      // unswitching.
+      // Unswitch only those branches that are reachable.
+      if (isUnreachableDueToPreviousUnswitching(*I))
+        continue;
+ 
       // If this isn't branching on an invariant condition, we can't unswitch
       // it.
       if (BI->isConditional()) {
@@ -742,42 +777,6 @@ static Loop *CloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM,
   return &New;
 }
 
-static void copyMetadata(Instruction *DstInst, const Instruction *SrcInst,
-                         bool Swapped) {
-  if (!SrcInst || !SrcInst->hasMetadata())
-    return;
-
-  SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
-  SrcInst->getAllMetadata(MDs);
-  for (auto &MD : MDs) {
-    switch (MD.first) {
-    default:
-      break;
-    case LLVMContext::MD_prof:
-      if (Swapped && MD.second->getNumOperands() == 3 &&
-          isa<MDString>(MD.second->getOperand(0))) {
-        MDString *MDName = cast<MDString>(MD.second->getOperand(0));
-        if (MDName->getString() == "branch_weights") {
-          auto *ValT = cast_or_null<ConstantAsMetadata>(
-                           MD.second->getOperand(1))->getValue();
-          auto *ValF = cast_or_null<ConstantAsMetadata>(
-                           MD.second->getOperand(2))->getValue();
-          assert(ValT && ValF && "Invalid Operands of branch_weights");
-          auto NewMD =
-              MDBuilder(DstInst->getParent()->getContext())
-                  .createBranchWeights(cast<ConstantInt>(ValF)->getZExtValue(),
-                                       cast<ConstantInt>(ValT)->getZExtValue());
-          MD.second = NewMD;
-        }
-      }
-      // fallthrough.
-    case LLVMContext::MD_make_implicit:
-    case LLVMContext::MD_dbg:
-      DstInst->setMetadata(MD.first, MD.second);
-    }
-  }
-}
-
 /// Emit a conditional branch on two values if LIC == Val, branch to TrueDst,
 /// otherwise branch to FalseDest. Insert the code immediately before InsertPt.
 void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
@@ -799,8 +798,10 @@ void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
   }
 
   // Insert the new branch.
-  BranchInst *BI = BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt);
-  copyMetadata(BI, TI, Swapped);
+  BranchInst *BI =
+      IRBuilder<>(InsertPt).CreateCondBr(BranchVal, TrueDest, FalseDest, TI);
+  if (Swapped)
+    BI->swapProfMetadata();
 
   // If either edge is critical, split it. This helps preserve LoopSimplify
   // form for enclosing loops.
@@ -1078,10 +1079,6 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
                                 F->getBasicBlockList(),
                                 NewBlocks[0]->getIterator(), F->end());
 
-  // FIXME: We could register any cloned assumptions instead of clearing the
-  // whole function's cache.
-  AC->clear();
-
   // Now we create the new Loop object for the versioned loop.
   Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM);
 
@@ -1131,10 +1128,15 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
   }
 
   // Rewrite the code to refer to itself.
-  for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i)
-    for (Instruction &I : *NewBlocks[i])
+  for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i) {
+    for (Instruction &I : *NewBlocks[i]) {
       RemapInstruction(&I, VMap,
                        RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
+      if (auto *II = dyn_cast<IntrinsicInst>(&I))
+        if (II->getIntrinsicID() == Intrinsic::assume)
+          AC->registerAssumption(II);
+    }
+  }
 
   // Rewrite the original preheader to select between versions of the loop.
   BranchInst *OldBR = cast<BranchInst>(loopPreheader->getTerminator());
@@ -1380,8 +1382,8 @@ void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L) {
         Pred->getInstList().splice(BI->getIterator(), Succ->getInstList(),
                                    Succ->begin(), Succ->end());
         LPM->deleteSimpleAnalysisValue(BI, L);
-        BI->eraseFromParent();
         RemoveFromWorklist(BI, Worklist);
+        BI->eraseFromParent();
 
         // Remove Succ from the loop tree.
         LI->removeBlock(Succ);