[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@229626 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/LoopAccessAnalysis.h b/include/llvm/Analysis/LoopAccessAnalysis.h
index 3fbdb8bb8512cdbd60f1baff3a6adb692157912d..615b052ed73996d1c2eb38a4752fa89efb0ed554 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 {
@@ -132,12 +133,7 @@ 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.
@@ -168,7 +164,15 @@ 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
@@ -206,6 +210,49 @@ 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 363937314861761bd15eba494c069f8e8cecb2af..3c69399aecf97d1f57067270e90f0921d8ae133f 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 ca6e7a83e57375c5cb102c51c9f96d14d0c2b7db..d3e82fee3c516706382d6097ccd7427ddf255a61 100644 (file)
--- a/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1196,3 +1196,64 @@ 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 = 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 1dc4041a30050327bbd43a7546dac143d32251b5..090b3d89a26b81df4a1a2ed81d726b38b7d7ce0c 100644 (file)
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -552,12 +552,11 @@ 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 {
@@ -743,18 +742,18 @@ 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(); }
@@ -779,10 +778,10 @@ 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;
@@ -857,6 +856,11 @@ 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 --- //
 
@@ -878,7 +882,7 @@ 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;
 
@@ -1259,6 +1263,7 @@ struct LoopVectorize : public FunctionPass {
   TargetLibraryInfo *TLI;
   AliasAnalysis *AA;
   AssumptionCache *AC;
+  LoopAccessAnalysis *LAA;
   bool DisableUnrolling;
   bool AlwaysVectorize;
 
@@ -1276,6 +1281,7 @@ 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.
@@ -1386,7 +1392,7 @@ 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);
@@ -1491,6 +1497,7 @@ 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>();
@@ -1662,7 +1669,7 @@ int LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
 }
 
 bool LoopVectorizationLegality::isUniform(Value *V) {
-  return LAI.isUniform(V);
+  return LAI->isUniform(V);
 }
 
 InnerLoopVectorizer::VectorParts&
@@ -3402,7 +3409,7 @@ 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");
 
@@ -3827,11 +3834,11 @@ 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,
@@ -5006,6 +5013,7 @@ 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 {