[LoopAccesses] Create the analysis pass

This is a function pass that runs the analysis on demand.  The analysis
can be initiated by querying the loop access info via LAA::getInfo.  It
either returns the cached info or runs the analysis.

Symbolic stride information continues to reside outside of this analysis
pass. We may move it inside later but it's not a priority for me right
now.  The idea is that Loop Distribution won't support run-time stride
checking at least initially.

This means that when querying the analysis, symbolic stride information
can be provided optionally.  Whether stride information is used can
invalidate the cache entry and rerun the analysis.  Note that if the
loop does not have any symbolic stride, the entry should be preserved
across Loop Distribution and LV.

Since currently the only user of the pass is LV, I just check that the
symbolic stride information didn't change when using a cached result.

On the LV side, LoopVectorizationLegality requests the info object
corresponding to the loop from the analysis pass.  A large chunk of the
diff is due to LAI becoming a pointer from a reference.

A test will be added as part of the -analyze patch.

Also tested that with AVX, we generate identical assembly output for the
testsuite (including the external testsuite) before and after.

This is part of the patchset that converts LoopAccessAnalysis into an
actual analysis pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229893 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/LoopAccessAnalysis.h b/include/llvm/Analysis/LoopAccessAnalysis.h
index 3867b896504b2e835e8cbf688bf994488b7d3425..48c990a3e86a7acf04552f9860bc5cfd73f36f9b 100644 (file)
--- a/include/llvm/Analysis/LoopAccessAnalysis.h
+++ b/include/llvm/Analysis/LoopAccessAnalysis.h
@@ -22,6 +22,7 @@
 #include "llvm/Analysis/AliasSetTracker.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/IR/ValueHandle.h"
+#include "llvm/Pass.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace llvm {
@@ -138,12 +139,7 @@ public:
 
   LoopAccessInfo(Loop *L, ScalarEvolution *SE, const DataLayout *DL,
                  const TargetLibraryInfo *TLI, AliasAnalysis *AA,
-                 DominatorTree *DT) :
-      TheLoop(L), SE(SE), DL(DL), TLI(TLI), AA(AA), DT(DT), NumLoads(0),
-      NumStores(0), MaxSafeDepDistBytes(-1U), CanVecMem(false) {}
-
-  /// \brief Analyze the loop.  Replaces symbolic strides using Strides.
-  void analyzeLoop(ValueToValueMap &Strides);
+                 DominatorTree *DT, ValueToValueMap &Strides);
 
   /// Return true we can analyze the memory accesses in the loop and there are
   /// no memory dependence cycles.
@@ -174,7 +170,15 @@ public:
   /// couldn't analyze the loop.
   Optional<VectorizationReport> &getReport() { return Report; }
 
+  /// \brief Used to ensure that if the analysis was run with speculating the
+  /// value of symbolic strides, the client queries it with the same assumption.
+  /// Only used in DEBUG build but we don't want NDEBUG-depedent ABI.
+  unsigned NumSymbolicStrides;
+
 private:
+  /// \brief Analyze the loop.  Substitute symbolic strides using Strides.
+  void analyzeLoop(ValueToValueMap &Strides);
+
   void emitAnalysis(VectorizationReport &Message);
 
   /// We need to check that all of the pointers in this list are disjoint
@@ -212,6 +216,49 @@ const SCEV *replaceSymbolicStrideSCEV(ScalarEvolution *SE,
                                       ValueToValueMap &PtrToStride,
                                       Value *Ptr, Value *OrigPtr = nullptr);
 
+/// \brief This analysis provides dependence information for the memory accesses
+/// of a loop.
+///
+/// It runs the analysis for a loop on demand.  This can be initiated by
+/// querying the loop access info via LAA::getInfo.  getInfo return a
+/// LoopAccessInfo object.  See this class for the specifics of what information
+/// is provided.
+class LoopAccessAnalysis : public FunctionPass {
+public:
+  static char ID;
+
+  LoopAccessAnalysis() : FunctionPass(ID) {
+    initializeLoopAccessAnalysisPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  /// \brief Query the result of the loop access information for the loop \p L.
+  ///
+  /// If the client speculates (and then issues run-time checks) for the values
+  /// of symbolic strides, \p Strides provides the mapping (see
+  /// replaceSymbolicStrideSCEV).  If there is no cached result available run
+  /// the analysis.
+  LoopAccessInfo &getInfo(Loop *L, ValueToValueMap &Strides);
+
+  void releaseMemory() override {
+    // Invalidate the cache when the pass is freed.
+    LoopAccessInfoMap.clear();
+  }
+
+private:
+  /// \brief The cache.
+  DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;
+
+  // The used analysis passes.
+  ScalarEvolution *SE;
+  const DataLayout *DL;
+  const TargetLibraryInfo *TLI;
+  AliasAnalysis *AA;
+  DominatorTree *DT;
+};
 } // End llvm namespace
 
 #endif

diff --git a/include/llvm/InitializePasses.h b/include/llvm/InitializePasses.h
index b2d609ccc7959ddaa2d04b40aa275600d63e910f..22e8739a0e09a4a4b12918d8d12fbabc5e227d1d 100644 (file)
--- a/include/llvm/InitializePasses.h
+++ b/include/llvm/InitializePasses.h
@@ -281,6 +281,7 @@ void initializeVirtRegRewriterPass(PassRegistry&);
 void initializeInstSimplifierPass(PassRegistry&);
 void initializeUnpackMachineBundlesPass(PassRegistry&);
 void initializeFinalizeMachineBundlesPass(PassRegistry&);
+void initializeLoopAccessAnalysisPass(PassRegistry&);
 void initializeLoopVectorizePass(PassRegistry&);
 void initializeSLPVectorizerPass(PassRegistry&);
 void initializeBBVectorizePass(PassRegistry&);

diff --git a/lib/Analysis/LoopAccessAnalysis.cpp b/lib/Analysis/LoopAccessAnalysis.cpp
index 5001b5fa3f1f798312b6404212918fe00e5885eb..73fdb9ca0362ee5d847a9ea0c85a97cb31a7c2c2 100644 (file)
--- a/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1230,3 +1230,64 @@ LoopAccessInfo::addRuntimeCheck(Instruction *Loc) {
   FirstInst = getFirstInst(FirstInst, Check, Loc);
   return std::make_pair(FirstInst, Check);
 }
+
+LoopAccessInfo::LoopAccessInfo(Loop *L, ScalarEvolution *SE,
+                               const DataLayout *DL,
+                               const TargetLibraryInfo *TLI, AliasAnalysis *AA,
+                               DominatorTree *DT, ValueToValueMap &Strides)
+    : TheLoop(L), SE(SE), DL(DL), TLI(TLI), AA(AA), DT(DT), NumLoads(0),
+      NumStores(0), MaxSafeDepDistBytes(-1U), CanVecMem(false) {
+  analyzeLoop(Strides);
+}
+
+LoopAccessInfo &LoopAccessAnalysis::getInfo(Loop *L, ValueToValueMap &Strides) {
+  auto &LAI = LoopAccessInfoMap[L];
+
+#ifndef NDEBUG
+  assert((!LAI || LAI->NumSymbolicStrides == Strides.size()) &&
+         "Symbolic strides changed for loop");
+#endif
+
+  if (!LAI) {
+    LAI = llvm::make_unique<LoopAccessInfo>(L, SE, DL, TLI, AA, DT, Strides);
+#ifndef NDEBUG
+    LAI->NumSymbolicStrides = Strides.size();
+#endif
+  }
+  return *LAI.get();
+}
+
+bool LoopAccessAnalysis::runOnFunction(Function &F) {
+  SE = &getAnalysis<ScalarEvolution>();
+  DL = F.getParent()->getDataLayout();
+  auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
+  TLI = TLIP ? &TLIP->getTLI() : nullptr;
+  AA = &getAnalysis<AliasAnalysis>();
+  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+
+  return false;
+}
+
+void LoopAccessAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.addRequired<ScalarEvolution>();
+    AU.addRequired<AliasAnalysis>();
+    AU.addRequired<DominatorTreeWrapperPass>();
+
+    AU.setPreservesAll();
+}
+
+char LoopAccessAnalysis::ID = 0;
+static const char laa_name[] = "Loop Access Analysis";
+#define LAA_NAME "loop-accesses"
+
+INITIALIZE_PASS_BEGIN(LoopAccessAnalysis, LAA_NAME, laa_name, false, true)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_END(LoopAccessAnalysis, LAA_NAME, laa_name, false, true)
+
+namespace llvm {
+  Pass *createLAAPass() {
+    return new LoopAccessAnalysis();
+  }
+}

diff --git a/lib/Transforms/Scalar/Scalar.cpp b/lib/Transforms/Scalar/Scalar.cpp
index f0728dccd24f141412c7fbdce476eb59b769918d..c8a7a2c27b048d70ccbb0abfd5713cedcbd6bac4 100644 (file)
--- a/lib/Transforms/Scalar/Scalar.cpp
+++ b/lib/Transforms/Scalar/Scalar.cpp
@@ -46,6 +46,7 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializeJumpThreadingPass(Registry);
   initializeLICMPass(Registry);
   initializeLoopDeletionPass(Registry);
+  initializeLoopAccessAnalysisPass(Registry);
   initializeLoopInstSimplifyPass(Registry);
   initializeLoopRotatePass(Registry);
   initializeLoopStrengthReducePass(Registry);

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 2ba7913119fd46c0e4410d152b058d90cc39a72d..6caaa236836562ece45b501f1ae38ca1044d28e6 100644 (file)
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -531,12 +531,11 @@ public:
   LoopVectorizationLegality(Loop *L, ScalarEvolution *SE, const DataLayout *DL,
                             DominatorTree *DT, TargetLibraryInfo *TLI,
                             AliasAnalysis *AA, Function *F,
-                            const TargetTransformInfo *TTI)
+                            const TargetTransformInfo *TTI,
+                            LoopAccessAnalysis *LAA)
       : NumPredStores(0), TheLoop(L), SE(SE), DL(DL),
-        TLI(TLI), TheFunction(F), TTI(TTI), DT(DT), Induction(nullptr),
-        WidestIndTy(nullptr),
-        LAI(L, SE, DL, TLI, AA, DT),
-        HasFunNoNaNAttr(false) {}
+        TLI(TLI), TheFunction(F), TTI(TTI), DT(DT), LAA(LAA), LAI(nullptr),
+        Induction(nullptr), WidestIndTy(nullptr), HasFunNoNaNAttr(false) {}
 
   /// This enum represents the kinds of reductions that we support.
   enum ReductionKind {
@@ -722,18 +721,18 @@ public:
 
   /// Returns the information that we collected about runtime memory check.
   LoopAccessInfo::RuntimePointerCheck *getRuntimePointerCheck() {
-    return LAI.getRuntimePointerCheck();
+    return LAI->getRuntimePointerCheck();
   }
 
   LoopAccessInfo *getLAI() {
-    return &LAI;
+    return LAI;
   }
 
   /// This function returns the identity element (or neutral element) for
   /// the operation K.
   static Constant *getReductionIdentity(ReductionKind K, Type *Tp);
 
-  unsigned getMaxSafeDepDistBytes() { return LAI.getMaxSafeDepDistBytes(); }
+  unsigned getMaxSafeDepDistBytes() { return LAI->getMaxSafeDepDistBytes(); }
 
   bool hasStride(Value *V) { return StrideSet.count(V); }
   bool mustCheckStrides() { return !StrideSet.empty(); }
@@ -758,10 +757,10 @@ public:
     return (MaskedOp.count(I) != 0);
   }
   unsigned getNumStores() const {
-    return LAI.getNumStores();
+    return LAI->getNumStores();
   }
   unsigned getNumLoads() const {
-    return LAI.getNumLoads();
+    return LAI->getNumLoads();
   }
   unsigned getNumPredStores() const {
     return NumPredStores;
@@ -836,6 +835,11 @@ private:
   const TargetTransformInfo *TTI;
   /// Dominator Tree.
   DominatorTree *DT;
+  // LoopAccess analysis.
+  LoopAccessAnalysis *LAA;
+  // And the loop-accesses info corresponding to this loop.  This pointer is
+  // null until canVectorizeMemory sets it up.
+  LoopAccessInfo *LAI;
 
   //  ---  vectorization state --- //
 
@@ -857,7 +861,7 @@ private:
   /// This set holds the variables which are known to be uniform after
   /// vectorization.
   SmallPtrSet<Instruction*, 4> Uniforms;
-  LoopAccessInfo LAI;
+
   /// Can we assume the absence of NaNs.
   bool HasFunNoNaNAttr;
 
@@ -1239,6 +1243,7 @@ struct LoopVectorize : public FunctionPass {
   TargetLibraryInfo *TLI;
   AliasAnalysis *AA;
   AssumptionCache *AC;
+  LoopAccessAnalysis *LAA;
   bool DisableUnrolling;
   bool AlwaysVectorize;
 
@@ -1256,6 +1261,7 @@ struct LoopVectorize : public FunctionPass {
     TLI = TLIP ? &TLIP->getTLI() : nullptr;
     AA = &getAnalysis<AliasAnalysis>();
     AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
+    LAA = &getAnalysis<LoopAccessAnalysis>();
 
     // Compute some weights outside of the loop over the loops. Compute this
     // using a BranchProbability to re-use its scaling math.
@@ -1366,7 +1372,7 @@ struct LoopVectorize : public FunctionPass {
     }
 
     // Check if it is legal to vectorize the loop.
-    LoopVectorizationLegality LVL(L, SE, DL, DT, TLI, AA, F, TTI);
+    LoopVectorizationLegality LVL(L, SE, DL, DT, TLI, AA, F, TTI, LAA);
     if (!LVL.canVectorize()) {
       DEBUG(dbgs() << "LV: Not vectorizing: Cannot prove legality.\n");
       emitMissedWarning(F, L, Hints);
@@ -1471,6 +1477,7 @@ struct LoopVectorize : public FunctionPass {
     AU.addRequired<ScalarEvolution>();
     AU.addRequired<TargetTransformInfoWrapperPass>();
     AU.addRequired<AliasAnalysis>();
+    AU.addRequired<LoopAccessAnalysis>();
     AU.addPreserved<LoopInfoWrapperPass>();
     AU.addPreserved<DominatorTreeWrapperPass>();
     AU.addPreserved<AliasAnalysis>();
@@ -1642,7 +1649,7 @@ int LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
 }
 
 bool LoopVectorizationLegality::isUniform(Value *V) {
-  return LAI.isUniform(V);
+  return LAI->isUniform(V);
 }
 
 InnerLoopVectorizer::VectorParts&
@@ -3382,7 +3389,7 @@ bool LoopVectorizationLegality::canVectorize() {
   collectLoopUniforms();
 
   DEBUG(dbgs() << "LV: We can vectorize this loop" <<
-        (LAI.getRuntimePointerCheck()->Need ? " (with a runtime bound check)" :
+        (LAI->getRuntimePointerCheck()->Need ? " (with a runtime bound check)" :
          "")
         <<"!\n");
 
@@ -3807,11 +3814,11 @@ void LoopVectorizationLegality::collectLoopUniforms() {
 }
 
 bool LoopVectorizationLegality::canVectorizeMemory() {
-  LAI.analyzeLoop(Strides);
-  auto &OptionalReport = LAI.getReport();
+  LAI = &LAA->getInfo(TheLoop, Strides);
+  auto &OptionalReport = LAI->getReport();
   if (OptionalReport)
     emitAnalysis(*OptionalReport);
-  return LAI.canVectorizeMemory();
+  return LAI->canVectorizeMemory();
 }
 
 static bool hasMultipleUsesOf(Instruction *I,
@@ -4986,6 +4993,7 @@ INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
 INITIALIZE_PASS_DEPENDENCY(LCSSA)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
+INITIALIZE_PASS_DEPENDENCY(LoopAccessAnalysis)
 INITIALIZE_PASS_END(LoopVectorize, LV_NAME, lv_name, false, false)
 
 namespace llvm {