[LoopDist] Port to new PM

Summary:
The direct motivation for the port is to ensure that the OptRemarkEmitter
tests work with the new PM.

This remains a function pass because we not only create multiple loops
but could also version the original loop.

In the test I need to invoke opt
with -passes='require<aa>,loop-distribute'.  LoopDistribute does not
directly depend on AA however LAA does.  LAA uses getCachedResult so
I *think* we need manually pull in 'aa'.

Reviewers: davidxl, silvas

Subscribers: sanjoy, llvm-commits, mzolotukhin

Differential Revision: https://reviews.llvm.org/D22437

llvm-svn: 275811

include/llvm/InitializePasses.h

@@ -177,7 +177,7 @@ void initializeLocalStackSlotPassPass(PassRegistry&);
 void initializeLoopAccessLegacyAnalysisPass(PassRegistry&);
 void initializeLoopDataPrefetchPass(PassRegistry&);
 void initializeLoopDeletionLegacyPassPass(PassRegistry&);
-void initializeLoopDistributePass(PassRegistry&);
+void initializeLoopDistributeLegacyPass(PassRegistry&);
 void initializeLoopExtractorPass(PassRegistry&);
 void initializeLoopIdiomRecognizeLegacyPassPass(PassRegistry&);
 void initializeLoopInfoWrapperPassPass(PassRegistry&);

include/llvm/Transforms/Scalar/LoopDistribute.h

@@ -0,0 +1,30 @@
+//===- LoopDistribute.cpp - Loop Distribution Pass --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Loop Distribution Pass.  Its main focus is to
+// distribute loops that cannot be vectorized due to dependence cycles.  It
+// tries to isolate the offending dependences into a new loop allowing
+// vectorization of the remaining parts.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_LOOPDISTRIBUTE_H
+#define LLVM_TRANSFORMS_SCALAR_LOOPDISTRIBUTE_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+class LoopDistributePass : public PassInfoMixin<LoopDistributePass> {
+public:
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_SCALAR_LOOPDISTRIBUTE_H

lib/Passes/PassBuilder.cpp

@@ -92,6 +92,7 @@
 #include "llvm/Transforms/Scalar/JumpThreading.h"
 #include "llvm/Transforms/Scalar/LICM.h"
 #include "llvm/Transforms/Scalar/LoopDeletion.h"
+#include "llvm/Transforms/Scalar/LoopDistribute.h"
 #include "llvm/Transforms/Scalar/LoopIdiomRecognize.h"
 #include "llvm/Transforms/Scalar/LoopInstSimplify.h"
 #include "llvm/Transforms/Scalar/LoopRotation.h"

lib/Passes/PassRegistry.def

@@ -151,6 +151,7 @@ FUNCTION_PASS("mldst-motion", MergedLoadStoreMotionPass())
 FUNCTION_PASS("jump-threading", JumpThreadingPass())
 FUNCTION_PASS("partially-inline-libcalls", PartiallyInlineLibCallsPass())
 FUNCTION_PASS("lcssa", LCSSAPass())
+FUNCTION_PASS("loop-distribute", LoopDistributePass())
 FUNCTION_PASS("loop-vectorize", LoopVectorizePass())
 FUNCTION_PASS("print", PrintFunctionPass(dbgs()))
 FUNCTION_PASS("print<assumptions>", AssumptionPrinterPass(dbgs()))

lib/Transforms/Scalar/LoopDistribute.cpp

@@ -22,6 +22,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Transforms/Scalar/LoopDistribute.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/EquivalenceClasses.h"
 #include "llvm/ADT/STLExtras.h"
@@ -29,6 +30,7 @@
 #include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/Analysis/LoopAccessAnalysis.h"
 #include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPassManager.h"
 #include "llvm/Analysis/OptimizationDiagnosticInfo.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Dominators.h"
@@ -597,7 +599,7 @@ public:
   }
 
   /// \brief Try to distribute an inner-most loop.
-  bool processLoop(LoopAccessLegacyAnalysis *LAA) {
+  bool processLoop(std::function<const LoopAccessInfo &(Loop &)> &GetLAA) {
     assert(L->empty() && "Only process inner loops.");
 
     DEBUG(dbgs() << "\nLDist: In \"" << L->getHeader()->getParent()->getName()
@@ -610,7 +612,7 @@ public:
       return fail("multiple exit blocks");
 
     // LAA will check that we only have a single exiting block.
-    LAI = &LAA->getInfo(L);
+    LAI = &GetLAA(*L);
 
     // Currently, we only distribute to isolate the part of the loop with
     // dependence cycles to enable partial vectorization.
@@ -860,19 +862,50 @@ private:
   Optional<bool> IsForced;
 };
 
+/// Shared implementation between new and old PMs.
+static bool runImpl(Function &F, LoopInfo *LI, DominatorTree *DT,
+                    ScalarEvolution *SE, OptimizationRemarkEmitter *ORE,
+                    std::function<const LoopAccessInfo &(Loop &)> &GetLAA,
+                    bool ProcessAllLoops) {
+  // Build up a worklist of inner-loops to vectorize. This is necessary as the
+  // act of distributing a loop creates new loops and can invalidate iterators
+  // across the loops.
+  SmallVector<Loop *, 8> Worklist;
+
+  for (Loop *TopLevelLoop : *LI)
+    for (Loop *L : depth_first(TopLevelLoop))
+      // We only handle inner-most loops.
+      if (L->empty())
+        Worklist.push_back(L);
+
+  // Now walk the identified inner loops.
+  bool Changed = false;
+  for (Loop *L : Worklist) {
+    LoopDistributeForLoop LDL(L, &F, LI, DT, SE, ORE);
+
+    // If distribution was forced for the specific loop to be
+    // enabled/disabled, follow that.  Otherwise use the global flag.
+    if (LDL.isForced().getValueOr(ProcessAllLoops))
+      Changed |= LDL.processLoop(GetLAA);
+  }
+
+  // Process each loop nest in the function.
+  return Changed;
+}
+
 /// \brief The pass class.
-class LoopDistribute : public FunctionPass {
+class LoopDistributeLegacy : public FunctionPass {
 public:
   /// \p ProcessAllLoopsByDefault specifies whether loop distribution should be
   /// performed by default.  Pass -enable-loop-distribute={0,1} overrides this
   /// default.  We use this to keep LoopDistribution off by default when invoked
   /// from the optimization pipeline but on when invoked explicitly from opt.
-  LoopDistribute(bool ProcessAllLoopsByDefault = true)
+  LoopDistributeLegacy(bool ProcessAllLoopsByDefault = true)
       : FunctionPass(ID), ProcessAllLoops(ProcessAllLoopsByDefault) {
     // The default is set by the caller.
     if (EnableLoopDistribute.getNumOccurrences() > 0)
       ProcessAllLoops = EnableLoopDistribute;
-    initializeLoopDistributePass(*PassRegistry::getPassRegistry());
+    initializeLoopDistributeLegacyPass(*PassRegistry::getPassRegistry());
   }
 
   bool runOnFunction(Function &F) override {
@@ -884,31 +917,10 @@ public:
     auto *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
     auto *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
     auto *ORE = &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
+    std::function<const LoopAccessInfo &(Loop &)> GetLAA =
+        [&](Loop &L) -> const LoopAccessInfo & { return LAA->getInfo(&L); };
 
-    // Build up a worklist of inner-loops to vectorize. This is necessary as the
-    // act of distributing a loop creates new loops and can invalidate iterators
-    // across the loops.
-    SmallVector<Loop *, 8> Worklist;
-
-    for (Loop *TopLevelLoop : *LI)
-      for (Loop *L : depth_first(TopLevelLoop))
-        // We only handle inner-most loops.
-        if (L->empty())
-          Worklist.push_back(L);
-
-    // Now walk the identified inner loops.
-    bool Changed = false;
-    for (Loop *L : Worklist) {
-      LoopDistributeForLoop LDL(L, &F, LI, DT, SE, ORE);
-
-      // If distribution was forced for the specific loop to be
-      // enabled/disabled, follow that.  Otherwise use the global flag.
-      if (LDL.isForced().getValueOr(ProcessAllLoops))
-        Changed |= LDL.processLoop(LAA);
-    }
-
-    // Process each loop nest in the function.
-    return Changed;
+    return runImpl(F, LI, DT, SE, ORE, GetLAA, ProcessAllLoops);
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
@@ -930,19 +942,49 @@ private:
 };
 } // anonymous namespace
 
-char LoopDistribute::ID;
+PreservedAnalyses LoopDistributePass::run(Function &F,
+                                          FunctionAnalysisManager &AM) {
+  // FIXME: This does not currently match the behavior from the old PM.
+  // ProcessAllLoops with the old PM defaults to true when invoked from opt and
+  // false when invoked from the optimization pipeline.
+  bool ProcessAllLoops = false;
+  if (EnableLoopDistribute.getNumOccurrences() > 0)
+    ProcessAllLoops = EnableLoopDistribute;
+
+  auto &LI = AM.getResult<LoopAnalysis>(F);
+  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
+  auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
+  auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
+
+  auto &LAM = AM.getResult<LoopAnalysisManagerFunctionProxy>(F).getManager();
+  std::function<const LoopAccessInfo &(Loop &)> GetLAA =
+      [&](Loop &L) -> const LoopAccessInfo & {
+    return LAM.getResult<LoopAccessAnalysis>(L);
+  };
+
+  bool Changed = runImpl(F, &LI, &DT, &SE, &ORE, GetLAA, ProcessAllLoops);
+  if (!Changed)
+    return PreservedAnalyses::all();
+  PreservedAnalyses PA;
+  PA.preserve<LoopAnalysis>();
+  PA.preserve<DominatorTreeAnalysis>();
+  return PA;
+}
+
+char LoopDistributeLegacy::ID;
 static const char ldist_name[] = "Loop Distribition";
 
-INITIALIZE_PASS_BEGIN(LoopDistribute, LDIST_NAME, ldist_name, false, false)
+INITIALIZE_PASS_BEGIN(LoopDistributeLegacy, LDIST_NAME, ldist_name, false,
+                      false)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(LoopAccessLegacyAnalysis)
 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
-INITIALIZE_PASS_END(LoopDistribute, LDIST_NAME, ldist_name, false, false)
+INITIALIZE_PASS_END(LoopDistributeLegacy, LDIST_NAME, ldist_name, false, false)
 
 namespace llvm {
 FunctionPass *createLoopDistributePass(bool ProcessAllLoopsByDefault) {
-  return new LoopDistribute(ProcessAllLoopsByDefault);
+  return new LoopDistributeLegacy(ProcessAllLoopsByDefault);
 }
 }

lib/Transforms/Scalar/Scalar.cpp

@@ -86,7 +86,7 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializePlaceBackedgeSafepointsImplPass(Registry);
   initializePlaceSafepointsPass(Registry);
   initializeFloat2IntLegacyPassPass(Registry);
-  initializeLoopDistributePass(Registry);
+  initializeLoopDistributeLegacyPass(Registry);
   initializeLoopLoadEliminationPass(Registry);
   initializeLoopSimplifyCFGLegacyPassPass(Registry);
   initializeLoopVersioningPassPass(Registry);

test/Transforms/LoopDistribute/diagnostics-with-hotness-lazy-BFI.ll

@@ -5,6 +5,11 @@
 ; RUN: opt -loop-distribute -S -pass-remarks-missed=loop-distribute \
 ; RUN:     -debug-only=block-freq                            < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
 
+; RUN: opt -passes='require<aa>,loop-distribute' -S -pass-remarks-missed=loop-distribute \
+; RUN:     -debug-only=block-freq -pass-remarks-with-hotness < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
+; RUN: opt -passes='require<aa>,loop-distribute' -S -pass-remarks-missed=loop-distribute \
+; RUN:     -debug-only=block-freq                            < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
+
 ; REQUIRES: asserts
 
 ; HOTNESS: block-frequency: forced

test/Transforms/LoopDistribute/diagnostics-with-hotness.ll

@@ -3,6 +3,11 @@
 ; RUN: opt -loop-distribute -S -pass-remarks-missed=loop-distribute \
 ; RUN:                                < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
 
+; RUN: opt -passes='require<aa>,loop-distribute' -S -pass-remarks-missed=loop-distribute \
+; RUN:     -pass-remarks-with-hotness < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
+; RUN: opt -passes='require<aa>,loop-distribute' -S -pass-remarks-missed=loop-distribute \
+; RUN:                                < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
+
 ; REQUIRES: asserts
 
 ; This is the input program: