[LVI] Cache lookup of experimental.guard intrinsic (NFC)

[nikic]

Summary

When LVI is performing assume intersections, it also checks for llvm.experimental.guard intrinsics. To avoid unnecessary block scans, it first checks whether this intrinsic is declared in the module at all. I've noticed that we end up spending quite a lot of time lookup up that function again and again...

Avoid this by only looking it up once when LazyValueInfo is constructed. This of course assumes that we don't introduce new guard intrinsics (which is the case for all existing uses of LVI -- and even if it weren't, it would not introduce miscompiles, just potentially lose optimization power.)

Most of the patch is threading through the Module into getImpl().

Compile-time numbers: https://llvm-compile-time-tracker.com/compare.php?from=d449cb81232e38d1175b0c9c316129c4637d3cbc&to=35c3e576fa3bc961223d4d45ca2aa8fc6db2b1cf&stat=instructions

[nikic]

llvm/lib/Analysis/LazyValueInfo.cpp

370

The indentation in this class is messed up. I'll address that separately.

[fhahn]

LGTM, thanks! Looks like a straight-forward improvement.

llvm/lib/Analysis/LazyValueInfo.cpp

bool pushBlockValue(const std::pair<BasicBlock *, Value *> &BV) {
                         << BV.first->getName() << "\n");
       BlockValueStack.push_back(BV);
       return true;
     }
 
     AssumptionCache *AC;  ///< A pointer to the cache of @llvm.assume calls.
     const DataLayout &DL; ///< A mandatory DataLayout
 
+    /// Declaration of the llvm.experimental.guard() intrinsic,
+    /// if it exists in the module.
+    Function *GuardDecl;
+
   Optional<ValueLatticeElement> getBlockValue(Value *Val, BasicBlock *BB);
   Optional<ValueLatticeElement> getEdgeValue(Value *V, BasicBlock *F,
                                 BasicBlock *T, Instruction *CxtI = nullptr);
 
   // These methods process one work item and may add more. A false value
   // returned means that the work item was not completely processed and must
   // be revisited after going through the new items.
   bool solveBlockValue(Value *Val, BasicBlock *BB);
public:
     void eraseBlock(BasicBlock *BB) {
       TheCache.eraseBlock(BB);
     }
 
     /// This is the update interface to inform the cache that an edge from
     /// PredBB to OldSucc has been threaded to be from PredBB to NewSucc.
     void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
 
-    LazyValueInfoImpl(AssumptionCache *AC, const DataLayout &DL)
-        : AC(AC), DL(DL) {}
+    LazyValueInfoImpl(AssumptionCache *AC, const DataLayout &DL,
+                      Function *GuardDecl)
+        : AC(AC), DL(DL), GuardDecl(GuardDecl) {}
   };
 } // end anonymous namespace
 
 
 void LazyValueInfoImpl::solve() {
   SmallVector<std::pair<BasicBlock *, Value *>, 8> StartingStack(
       BlockValueStack.begin(), BlockValueStack.end());
 
for (auto &AssumeVH : AC->assumptionsFor(Val)) {
     auto *I = cast<CallInst>(AssumeVH);
     if (I->getParent() != BB || !isValidAssumeForContext(I, BBI))
       continue;
 
     BBLV = intersect(BBLV, getValueFromCondition(Val, I->getArgOperand(0)));
   }
 
   // If guards are not used in the module, don't spend time looking for them
-  auto *GuardDecl = BBI->getModule()->getFunction(
-          Intrinsic::getName(Intrinsic::experimental_guard));
   if (!GuardDecl || GuardDecl->use_empty())
     return;
 
   if (BBI->getIterator() == BB->begin())
     return;
   for (Instruction &I : make_range(std::next(BBI->getIterator().getReverse()),
                                    BB->rend())) {
     Value *Cond = nullptr;

 }
 
 //===----------------------------------------------------------------------===//
 //                            LazyValueInfo Impl
 //===----------------------------------------------------------------------===//
 
 /// This lazily constructs the LazyValueInfoImpl.
 static LazyValueInfoImpl &getImpl(void *&PImpl, AssumptionCache *AC,
-                                  const DataLayout *DL) {
+                                  const Module *M) {
   if (!PImpl) {
-    assert(DL && "getCache() called with a null DataLayout");
-    PImpl = new LazyValueInfoImpl(AC, *DL);
+    assert(M && "getCache() called with a null Module");
+    const DataLayout &DL = M->getDataLayout();
+    Function *GuardDecl = M->getFunction(
+        Intrinsic::getName(Intrinsic::experimental_guard));
+    PImpl = new LazyValueInfoImpl(AC, DL, GuardDecl);
   }
   return *static_cast<LazyValueInfoImpl*>(PImpl);
 }
 
 bool LazyValueInfoWrapperPass::runOnFunction(Function &F) {
   Info.AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
-  const DataLayout &DL = F.getParent()->getDataLayout();
   Info.TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
 
   if (Info.PImpl)
-    getImpl(Info.PImpl, Info.AC, &DL).clear();
+    getImpl(Info.PImpl, Info.AC, F.getParent()).clear();
 
   // Fully lazy.
   return false;
 }
 
 void LazyValueInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
   AU.addRequired<AssumptionCacheTracker>();

 }
 
 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB,
                                      Instruction *CxtI) {
   // Bail out early if V is known not to be a Constant.
   if (isKnownNonConstant(V))
     return nullptr;
 
-  const DataLayout &DL = BB->getModule()->getDataLayout();
   ValueLatticeElement Result =
-      getImpl(PImpl, AC, &DL).getValueInBlock(V, BB, CxtI);
+      getImpl(PImpl, AC, BB->getModule()).getValueInBlock(V, BB, CxtI);
 
   if (Result.isConstant())
     return Result.getConstant();
   if (Result.isConstantRange()) {
     const ConstantRange &CR = Result.getConstantRange();
     if (const APInt *SingleVal = CR.getSingleElement())
       return ConstantInt::get(V->getContext(), *SingleVal);
   }
   return nullptr;
 }
 
 ConstantRange LazyValueInfo::getConstantRange(Value *V, BasicBlock *BB,
                                               Instruction *CxtI,
                                               bool UndefAllowed) {
   assert(V->getType()->isIntegerTy());
   unsigned Width = V->getType()->getIntegerBitWidth();
-  const DataLayout &DL = BB->getModule()->getDataLayout();
   ValueLatticeElement Result =
-      getImpl(PImpl, AC, &DL).getValueInBlock(V, BB, CxtI);
+      getImpl(PImpl, AC, BB->getModule()).getValueInBlock(V, BB, CxtI);
   if (Result.isUnknown())
     return ConstantRange::getEmpty(Width);
   if (Result.isConstantRange(UndefAllowed))
     return Result.getConstantRange(UndefAllowed);
   // We represent ConstantInt constants as constant ranges but other kinds
   // of integer constants, i.e. ConstantExpr will be tagged as constants
   assert(!(Result.isConstant() && isa<ConstantInt>(Result.getConstant())) &&
          "ConstantInt value must be represented as constantrange");
   return ConstantRange::getFull(Width);
 }
 
 /// Determine whether the specified value is known to be a
 /// constant on the specified edge. Return null if not.
 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
                                            BasicBlock *ToBB,
                                            Instruction *CxtI) {
-  const DataLayout &DL = FromBB->getModule()->getDataLayout();
+  Module *M = FromBB->getModule();
   ValueLatticeElement Result =
-      getImpl(PImpl, AC, &DL).getValueOnEdge(V, FromBB, ToBB, CxtI);
+      getImpl(PImpl, AC, M).getValueOnEdge(V, FromBB, ToBB, CxtI);
 
   if (Result.isConstant())
     return Result.getConstant();
   if (Result.isConstantRange()) {
     const ConstantRange &CR = Result.getConstantRange();
     if (const APInt *SingleVal = CR.getSingleElement())
       return ConstantInt::get(V->getContext(), *SingleVal);
   }
   return nullptr;
 }
 
 ConstantRange LazyValueInfo::getConstantRangeOnEdge(Value *V,
                                                     BasicBlock *FromBB,
                                                     BasicBlock *ToBB,
                                                     Instruction *CxtI) {
   unsigned Width = V->getType()->getIntegerBitWidth();
-  const DataLayout &DL = FromBB->getModule()->getDataLayout();
+  Module *M = FromBB->getModule();
   ValueLatticeElement Result =
-      getImpl(PImpl, AC, &DL).getValueOnEdge(V, FromBB, ToBB, CxtI);
+      getImpl(PImpl, AC, M).getValueOnEdge(V, FromBB, ToBB, CxtI);
 
   if (Result.isUnknown())
     return ConstantRange::getEmpty(Width);
   if (Result.isConstantRange())
     return Result.getConstantRange();
   // We represent ConstantInt constants as constant ranges but other kinds
   // of integer constants, i.e. ConstantExpr will be tagged as constants
   assert(!(Result.isConstant() && isa<ConstantInt>(Result.getConstant())) &&

 }
 
 /// Determine whether the specified value comparison with a constant is known to
 /// be true or false on the specified CFG edge. Pred is a CmpInst predicate.
 LazyValueInfo::Tristate
 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
                                   BasicBlock *FromBB, BasicBlock *ToBB,
                                   Instruction *CxtI) {
-  const DataLayout &DL = FromBB->getModule()->getDataLayout();
+  Module *M = FromBB->getModule();
   ValueLatticeElement Result =
-      getImpl(PImpl, AC, &DL).getValueOnEdge(V, FromBB, ToBB, CxtI);
+      getImpl(PImpl, AC, M).getValueOnEdge(V, FromBB, ToBB, CxtI);
 
-  return getPredicateResult(Pred, C, Result, DL, TLI);
+  return getPredicateResult(Pred, C, Result, M->getDataLayout(), TLI);
 }
 
 LazyValueInfo::Tristate
 LazyValueInfo::getPredicateAt(unsigned Pred, Value *V, Constant *C,
                               Instruction *CxtI) {
   // Is or is not NonNull are common predicates being queried. If
   // isKnownNonZero can tell us the result of the predicate, we can
   // return it quickly. But this is only a fastpath, and falling
   // through would still be correct.
-  const DataLayout &DL = CxtI->getModule()->getDataLayout();
+  Module *M = CxtI->getModule();
+  const DataLayout &DL = M->getDataLayout();
   if (V->getType()->isPointerTy() && C->isNullValue() &&
       isKnownNonZero(V->stripPointerCastsSameRepresentation(), DL)) {
     if (Pred == ICmpInst::ICMP_EQ)
       return LazyValueInfo::False;
     else if (Pred == ICmpInst::ICMP_NE)
       return LazyValueInfo::True;
   }
-  ValueLatticeElement Result = getImpl(PImpl, AC, &DL).getValueAt(V, CxtI);
+  ValueLatticeElement Result = getImpl(PImpl, AC, M).getValueAt(V, CxtI);
   Tristate Ret = getPredicateResult(Pred, C, Result, DL, TLI);
   if (Ret != Unknown)
     return Ret;
 
   // Note: The following bit of code is somewhat distinct from the rest of LVI;
   // LVI as a whole tries to compute a lattice value which is conservatively
   // correct at a given location.  In this case, we have a predicate which we
   // weren't able to prove about the merged result, and we're pushing that
if (CxtI) {
     }
   }
   return Unknown;
 }
 
 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
                                BasicBlock *NewSucc) {
   if (PImpl) {
-    const DataLayout &DL = PredBB->getModule()->getDataLayout();
-    getImpl(PImpl, AC, &DL).threadEdge(PredBB, OldSucc, NewSucc);
+    getImpl(PImpl, AC, PredBB->getModule())
+        .threadEdge(PredBB, OldSucc, NewSucc);
   }
 }
 
 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
   if (PImpl) {
-    const DataLayout &DL = BB->getModule()->getDataLayout();
-    getImpl(PImpl, AC, &DL).eraseBlock(BB);
+    getImpl(PImpl, AC, BB->getModule()).eraseBlock(BB);
   }
 }
 
 
 void LazyValueInfo::printLVI(Function &F, DominatorTree &DTree, raw_ostream &OS) {
   if (PImpl) {
-    getImpl(PImpl, AC, DL).printLVI(F, DTree, OS);
+    getImpl(PImpl, AC, F.getParent()).printLVI(F, DTree, OS);
   }
 }
 
 // Print the LVI for the function arguments at the start of each basic block.
 void LazyValueInfoAnnotatedWriter::emitBasicBlockStartAnnot(
     const BasicBlock *BB, formatted_raw_ostream &OS) {
   // Find if there are latticevalues defined for arguments of the function.
   auto *F = BB->getParent();