[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

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 {