[Refactor] Have getNonLocalPointerDependency take the query instruction

Previously, MemoryDependenceAnalysis::getNonLocalPointerDependency was taking a list of properties about the instruction being queried. Since I'm about to need one more property to be passed down through the infrastructure - I need to know a query instruction is non-volatile in an inner helper - fix the interface once and for all.

I also added some assertions and behaviour clarifications around volatile and ordered field accesses. At the moment, this is mostly to document expected behaviour. The only non-standard instructions which can currently reach this are atomic, but unordered, loads and stores. Neither ordered or volatile accesses can reach here.

The call in GVN is protected by an isSimple check when it first considers the load. The calls in MemDepPrinter are protected by isUnordered checks. Both utilities also check isVolatile for loads and stores.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225481 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/MemoryDependenceAnalysis.h

@@ -366,12 +366,13 @@ namespace llvm {
 
 
     /// getNonLocalPointerDependency - Perform a full dependency query for an
-    /// access to the specified (non-volatile) memory location, returning the
+    /// access to the QueryInst's specified (non-volatile) memory location,
-    /// set of instructions that either define or clobber the value.
+    /// returning the set of instructions that either define or clobber
+    /// the value.
     ///
-    /// This method assumes the pointer has a "NonLocal" dependency within BB.
+    /// This method assumes the pointer has a "NonLocal" dependency within
-    void getNonLocalPointerDependency(const AliasAnalysis::Location &Loc,
+    /// QueryInst's parent basic block.
-                                      bool isLoad, BasicBlock *BB,
+    void getNonLocalPointerDependency(Instruction *QueryInst,
                                     SmallVectorImpl<NonLocalDepResult> &Result);
 
     /// removeInstruction - Remove an instruction from the dependence analysis,

lib/Analysis/MemDepPrinter.cpp

@@ -92,7 +92,6 @@ const char *const MemDepPrinter::DepTypeStr[]
 
 bool MemDepPrinter::runOnFunction(Function &F) {
   this->F = &F;
-  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
   MemoryDependenceAnalysis &MDA = getAnalysis<MemoryDependenceAnalysis>();
 
   // All this code uses non-const interfaces because MemDep is not
@@ -126,8 +125,7 @@ bool MemDepPrinter::runOnFunction(Function &F) {
                                            static_cast<BasicBlock *>(nullptr)));
           continue;
         }
-        AliasAnalysis::Location Loc = AA.getLocation(LI);
+        MDA.getNonLocalPointerDependency(LI, NLDI);
-        MDA.getNonLocalPointerDependency(Loc, true, LI->getParent(), NLDI);
       } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
         if (!SI->isUnordered()) {
           // FIXME: Handle atomic/volatile stores.
@@ -135,11 +133,9 @@ bool MemDepPrinter::runOnFunction(Function &F) {
                                            static_cast<BasicBlock *>(nullptr)));
           continue;
         }
-        AliasAnalysis::Location Loc = AA.getLocation(SI);
+        MDA.getNonLocalPointerDependency(SI, NLDI);
-        MDA.getNonLocalPointerDependency(Loc, false, SI->getParent(), NLDI);
       } else if (VAArgInst *VI = dyn_cast<VAArgInst>(Inst)) {
-        AliasAnalysis::Location Loc = AA.getLocation(VI);
+        MDA.getNonLocalPointerDependency(VI, NLDI);
-        MDA.getNonLocalPointerDependency(Loc, false, VI->getParent(), NLDI);
       } else {
         llvm_unreachable("Unknown memory instruction!");
       }

lib/Analysis/MemoryDependenceAnalysis.cpp

@@ -859,9 +859,53 @@ MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
 /// own block.
 ///
 void MemoryDependenceAnalysis::
-getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad,
+getNonLocalPointerDependency(Instruction *QueryInst,
-                             BasicBlock *FromBB,
                              SmallVectorImpl<NonLocalDepResult> &Result) {
+
+  auto getLocation = [](AliasAnalysis *AA, Instruction *Inst) {
+    if (auto *I = dyn_cast<LoadInst>(Inst))
+      return AA->getLocation(I);
+    else if (auto *I = dyn_cast<StoreInst>(Inst))
+      return AA->getLocation(I);
+    else if (auto *I = dyn_cast<VAArgInst>(Inst))
+      return AA->getLocation(I);
+    else if (auto *I = dyn_cast<AtomicCmpXchgInst>(Inst))
+      return AA->getLocation(I);
+    else if (auto *I = dyn_cast<AtomicRMWInst>(Inst))
+      return AA->getLocation(I);
+    else
+      llvm_unreachable("unsupported memory instruction");
+  };
+   
+  const AliasAnalysis::Location Loc = getLocation(AA, QueryInst);
+  bool isLoad = isa<LoadInst>(QueryInst);
+  BasicBlock *FromBB = QueryInst->getParent();
+  assert(FromBB);
+  
+  // This routine does not expect to deal with volatile instructions.  Doing so
+  // would require piping through the QueryInst all the way through.
+  // TODO: volatiles can't be elided, but they can be reordered with other
+  // non-volatile accesses.  
+  if (LoadInst *LI = dyn_cast<LoadInst>(QueryInst)) {
+    assert(!LI->isVolatile());
+  } else if (StoreInst *SI = dyn_cast<StoreInst>(QueryInst)) {
+    assert(!SI->isVolatile());
+  }
+
+
+  // We currently give up on any instruction which is ordered, but we do handle
+  // atomic instructions which are unordered.
+  // TODO: Handle ordered instructions
+  auto isOrdered = [](Instruction *Inst) {
+    if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
+      return !LI->isUnordered();
+    } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+      return !SI->isUnordered();
+    }
+    return false;
+  };
+  assert(!isOrdered(QueryInst) && "ordered instructions not expected");
+
   assert(Loc.Ptr->getType()->isPointerTy() &&
          "Can't get pointer deps of a non-pointer!");
   Result.clear();

lib/Transforms/Scalar/GVN.cpp

@@ -1707,8 +1707,7 @@ bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
 bool GVN::processNonLocalLoad(LoadInst *LI) {
   // Step 1: Find the non-local dependencies of the load.
   LoadDepVect Deps;
-  AliasAnalysis::Location Loc = VN.getAliasAnalysis()->getLocation(LI);
+  MD->getNonLocalPointerDependency(LI, Deps);
-  MD->getNonLocalPointerDependency(Loc, true, LI->getParent(), Deps);
 
   // If we had to process more than one hundred blocks to find the
   // dependencies, this load isn't worth worrying about.  Optimizing