Index: include/llvm/Transforms/Utils/LoopSimplify.h
===================================================================
--- include/llvm/Transforms/Utils/LoopSimplify.h
+++ include/llvm/Transforms/Utils/LoopSimplify.h
@@ -0,0 +1,53 @@
+//===- LoopSimplify.h - Loop Canonicalization Pass --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass performs several transformations to transform natural loops into a
+// simpler form, which makes subsequent analyses and transformations simpler and
+// more effective.
+//
+// Loop pre-header insertion guarantees that there is a single, non-critical
+// entry edge from outside of the loop to the loop header.  This simplifies a
+// number of analyses and transformations, such as LICM.
+//
+// Loop exit-block insertion guarantees that all exit blocks from the loop
+// (blocks which are outside of the loop that have predecessors inside of the
+// loop) only have predecessors from inside of the loop (and are thus dominated
+// by the loop header).  This simplifies transformations such as store-sinking
+// that are built into LICM.
+//
+// This pass also guarantees that loops will have exactly one backedge.
+//
+// Indirectbr instructions introduce several complications. If the loop
+// contains or is entered by an indirectbr instruction, it may not be possible
+// to transform the loop and make these guarantees. Client code should check
+// that these conditions are true before relying on them.
+//
+// Note that the simplifycfg pass will clean up blocks which are split out but
+// end up being unnecessary, so usage of this pass should not pessimize
+// generated code.
+//
+// This pass obviously modifies the CFG, but updates loop information and
+// dominator information.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
+#define LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+/// This pass is responsible for loop canonicalization.
+class LoopSimplifyPass : public PassInfoMixin<LoopSimplifyPass> {
+public:
+  PreservedAnalyses run(Function &F, AnalysisManager<Function> &AM);
+};
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
Index: lib/Passes/PassBuilder.cpp
===================================================================
--- lib/Passes/PassBuilder.cpp
+++ lib/Passes/PassBuilder.cpp
@@ -92,6 +92,7 @@
 #include "llvm/Transforms/Scalar/Sink.h"
 #include "llvm/Transforms/Scalar/SLPVectorizer.h"
 #include "llvm/Transforms/Utils/LCSSA.h"
+#include "llvm/Transforms/Utils/LoopSimplify.h"
 #include "llvm/Transforms/Utils/Mem2Reg.h"
 #include "llvm/Transforms/Utils/MemorySSA.h"
 
Index: lib/Passes/PassRegistry.def
===================================================================
--- lib/Passes/PassRegistry.def
+++ lib/Passes/PassRegistry.def
@@ -131,6 +131,7 @@
 FUNCTION_PASS("lower-expect", LowerExpectIntrinsicPass())
 FUNCTION_PASS("guard-widening", GuardWideningPass())
 FUNCTION_PASS("gvn", GVN())
+FUNCTION_PASS("loop-simplify", LoopSimplifyPass())
 FUNCTION_PASS("mem2reg", PromotePass())
 FUNCTION_PASS("memcpyopt", MemCpyOptPass())
 FUNCTION_PASS("mldst-motion", MergedLoadStoreMotionPass())
Index: lib/Transforms/Utils/LoopSimplify.cpp
===================================================================
--- lib/Transforms/Utils/LoopSimplify.cpp
+++ lib/Transforms/Utils/LoopSimplify.cpp
@@ -37,6 +37,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Transforms/Utils/LoopSimplify.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SetOperations.h"
@@ -805,6 +806,36 @@
   return Changed;
 }
 
+PreservedAnalyses LoopSimplifyPass::run(Function &F,
+                                        AnalysisManager<Function> &AM) {
+  bool Changed = false;
+  LoopInfo *LI = &AM.getResult<LoopAnalysis>(F);
+  DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
+  ScalarEvolution *SE = AM.getCachedResult<ScalarEvolutionAnalysis>(F);
+  AssumptionCache *AC = &AM.getResult<AssumptionAnalysis>(F);
+
+  // FIXME: This pass should verify that the loops on which it's operating
+  // are in canonical SSA form, and that the pass itself preserves this form.
+  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
+    Changed |= simplifyLoop(*I, DT, LI, SE, AC, true /* PreserveLCSSA */);
+
+  if (Changed)
+    PreservedAnalyses::none();
+  PreservedAnalyses PA;
+
+  // The old PM also preserved LCSSAID and BreakCriticalEdgesID.
+  // This makes no sense in the new PM so we omit those from the set
+  // of preserved passes.
+  PA.preserve<DominatorTreeAnalysis>();
+  PA.preserve<LoopAnalysis>();
+  PA.preserve<BasicAA>();
+  PA.preserve<GlobalsAA>();
+  PA.preserve<SCEVAA>();
+  PA.preserve<ScalarEvolutionAnalysis>();
+  PA.preserve<DependenceAnalysis>();
+  return PA;
+}
+
 // FIXME: Restore this code when we re-enable verification in verifyAnalysis
 // below.
 #if 0
Index: test/Transforms/LoopSimplify/basictest.ll
===================================================================
--- test/Transforms/LoopSimplify/basictest.ll
+++ test/Transforms/LoopSimplify/basictest.ll
@@ -1,4 +1,5 @@
 ; RUN: opt < %s -loop-simplify
+; RUN: opt < %s -passes=loop-simplify
 
 ; This function should get a preheader inserted before BB3, that is jumped
 ; to by BB1 & BB2