1 files changed, 39 insertions, 8 deletions

diff --git a/lib/Transforms/Utils/LCSSA.cpp b/lib/Transforms/Utils/LCSSA.cpp
index 53d444b309d5..29e7c5260f46 100644
--- a/lib/Transforms/Utils/LCSSA.cpp
+++ b/lib/Transforms/Utils/LCSSA.cpp
@@ -1,9 +1,8 @@
 //===-- LCSSA.cpp - Convert loops into loop-closed SSA form ---------------===//
 //
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
@@ -32,11 +31,12 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/MemorySSA.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
-#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
@@ -45,6 +45,7 @@
 #include "llvm/IR/PredIteratorCache.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/Utils.h"
+#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/SSAUpdater.h"
 using namespace llvm;
@@ -198,6 +199,17 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
         continue;
       }
 
+      // If we added a single PHI, it must dominate all uses and we can directly
+      // rename it.
+      if (AddedPHIs.size() == 1) {
+        // Tell the VHs that the uses changed. This updates SCEV's caches.
+        // We might call ValueIsRAUWd multiple times for the same value.
+        if (UseToRewrite->get()->hasValueHandle())
+          ValueHandleBase::ValueIsRAUWd(*UseToRewrite, AddedPHIs[0]);
+        UseToRewrite->set(AddedPHIs[0]);
+        continue;
+      }
+
       // Otherwise, do full PHI insertion.
       SSAUpdate.RewriteUse(*UseToRewrite);
     }
@@ -211,9 +223,12 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
       BasicBlock *UserBB = DVI->getParent();
       if (InstBB == UserBB || L->contains(UserBB))
         continue;
-      // We currently only handle debug values residing in blocks where we have
-      // inserted a PHI instruction.
-      if (Value *V = SSAUpdate.FindValueForBlock(UserBB))
+      // We currently only handle debug values residing in blocks that were
+      // traversed while rewriting the uses. If we inserted just a single PHI,
+      // we will handle all relevant debug values.
+      Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
+                                       : SSAUpdate.FindValueForBlock(UserBB);
+      if (V)
         DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
     }
 
@@ -306,6 +321,12 @@ bool llvm::formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI,
                      ScalarEvolution *SE) {
   bool Changed = false;
 
+#ifdef EXPENSIVE_CHECKS
+  // Verify all sub-loops are in LCSSA form already.
+  for (Loop *SubLoop: L)
+    assert(SubLoop->isRecursivelyLCSSAForm(DT, *LI) && "Subloop not in LCSSA!");
+#endif
+
   SmallVector<BasicBlock *, 8> ExitBlocks;
   L.getExitBlocks(ExitBlocks);
   if (ExitBlocks.empty())
@@ -325,6 +346,10 @@ bool llvm::formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI,
   // Look at all the instructions in the loop, checking to see if they have uses
   // outside the loop.  If so, put them into the worklist to rewrite those uses.
   for (BasicBlock *BB : BlocksDominatingExits) {
+    // Skip blocks that are part of any sub-loops, they must be in LCSSA
+    // already.
+    if (LI->getLoopFor(BB) != &L)
+      continue;
     for (Instruction &I : *BB) {
       // Reject two common cases fast: instructions with no uses (like stores)
       // and instructions with one use that is in the same block as this.
@@ -419,6 +444,8 @@ struct LCSSAWrapperPass : public FunctionPass {
     AU.addPreserved<GlobalsAAWrapperPass>();
     AU.addPreserved<ScalarEvolutionWrapperPass>();
     AU.addPreserved<SCEVAAWrapperPass>();
+    AU.addPreserved<BranchProbabilityInfoWrapperPass>();
+    AU.addPreserved<MemorySSAWrapperPass>();
 
     // This is needed to perform LCSSA verification inside LPPassManager
     AU.addRequired<LCSSAVerificationPass>();
@@ -462,5 +489,9 @@ PreservedAnalyses LCSSAPass::run(Function &F, FunctionAnalysisManager &AM) {
   PA.preserve<GlobalsAA>();
   PA.preserve<SCEVAA>();
   PA.preserve<ScalarEvolutionAnalysis>();
+  // BPI maps terminators to probabilities, since we don't modify the CFG, no
+  // updates are needed to preserve it.
+  PA.preserve<BranchProbabilityAnalysis>();
+  PA.preserve<MemorySSAAnalysis>();
   return PA;
 }