Teach the load analysis to allow finding available values which require

inttoptr or ptrtoint cast provided there is datalayout available.
Eventually, the datalayout can just be required but in practice it will
always be there today.

To go with the ability to expose available values requiring a ptrtoint
or inttoptr cast, helpers are added to perform one of these three casts.

These smarts are necessary to finish canonicalizing loads and stores to
the operational type requirements without regressing fundamental
combines.

I've added some test cases. These should actually improve as the load
combining and store combining improves, but they may fundamentally be
highlighting some missing combines for select in addition to exercising
the specific added logic to load analysis.

llvm-svn: 220277

4 files changed, 39 insertions, 9 deletions

diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index bb0d60e263e..5042eb9777a 100644
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -176,8 +176,13 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
 
   Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
 
-  // If we're using alias analysis to disambiguate get the size of *Ptr.
-  uint64_t AccessSize = AA ? AA->getTypeStoreSize(AccessTy) : 0;
+  // Try to get the DataLayout for this module. This may be null, in which case
+  // the optimizations will be limited.
+  const DataLayout *DL = ScanBB->getDataLayout();
+
+  // Try to get the store size for the type.
+  uint64_t AccessSize = DL ? DL->getTypeStoreSize(AccessTy)
+                           : AA ? AA->getTypeStoreSize(AccessTy) : 0;
 
   Value *StrippedPtr = Ptr->stripPointerCasts();
 
@@ -202,7 +207,7 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
     if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
       if (AreEquivalentAddressValues(
               LI->getPointerOperand()->stripPointerCasts(), StrippedPtr) &&
-          CastInst::isBitCastable(LI->getType(), AccessTy)) {
+          CastInst::isBitOrNoopPointerCastable(LI->getType(), AccessTy, DL)) {
         if (AATags)
           LI->getAAMetadata(*AATags);
         return LI;
@@ -214,7 +219,8 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
       // (This is true even if the store is volatile or atomic, although
       // those cases are unlikely.)
       if (AreEquivalentAddressValues(StorePtr, StrippedPtr) &&
-          CastInst::isBitCastable(SI->getValueOperand()->getType(), AccessTy)) {
+          CastInst::isBitOrNoopPointerCastable(SI->getValueOperand()->getType(),
+                                               AccessTy, DL)) {
         if (AATags)
           SI->getAAMetadata(*AATags);
         return SI->getOperand(0);
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index 1497aa885c5..9da0eb4a0d6 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -2559,6 +2559,17 @@ CastInst *CastInst::CreatePointerBitCastOrAddrSpaceCast(
   return Create(Instruction::BitCast, S, Ty, Name, InsertBefore);
 }
 
+CastInst *CastInst::CreateBitOrPointerCast(Value *S, Type *Ty,
+                                           const Twine &Name,
+                                           Instruction *InsertBefore) {
+  if (S->getType()->isPointerTy() && Ty->isIntegerTy())
+    return Create(Instruction::PtrToInt, S, Ty, Name, InsertBefore);
+  if (S->getType()->isIntegerTy() && Ty->isPointerTy())
+    return Create(Instruction::IntToPtr, S, Ty, Name, InsertBefore);
+
+  return Create(Instruction::BitCast, S, Ty, Name, InsertBefore);
+}
+
 CastInst *CastInst::CreateIntegerCast(Value *C, Type *Ty,
                                       bool isSigned, const Twine &Name,
                                       Instruction *InsertBefore) {
@@ -2716,6 +2727,18 @@ bool CastInst::isBitCastable(Type *SrcTy, Type *DestTy) {
   return true;
 }
 
+bool CastInst::isBitOrNoopPointerCastable(Type *SrcTy, Type *DestTy,
+                                          const DataLayout *DL) {
+  if (auto *PtrTy = dyn_cast<PointerType>(SrcTy))
+    if (auto *IntTy = dyn_cast<IntegerType>(DestTy))
+      return DL && IntTy->getBitWidth() >= DL->getPointerTypeSizeInBits(PtrTy);
+  if (auto *PtrTy = dyn_cast<PointerType>(DestTy))
+    if (auto *IntTy = dyn_cast<IntegerType>(SrcTy))
+      return DL && IntTy->getBitWidth() >= DL->getPointerTypeSizeInBits(PtrTy);
+
+  return isBitCastable(SrcTy, DestTy);
+}
+
 // Provide a way to get a "cast" where the cast opcode is inferred from the
 // types and size of the operand. This, basically, is a parallel of the
 // logic in the castIsValid function below.  This axiom should hold:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index 3557ad72f49..95ca1a6ff7a 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -417,7 +417,8 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
   BasicBlock::iterator BBI = &LI;
   if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6))
     return ReplaceInstUsesWith(
-        LI, Builder->CreateBitCast(AvailableVal, LI.getType()));
+        LI, Builder->CreateBitOrPointerCast(AvailableVal, LI.getType(),
+                                            LI.getName() + ".cast"));
 
   // load(gep null, ...) -> unreachable
   if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 25a8b0cdbd3..c37a4c91c66 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -902,8 +902,8 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
     // only happen in dead loops.
     if (AvailableVal == LI) AvailableVal = UndefValue::get(LI->getType());
     if (AvailableVal->getType() != LI->getType())
-      AvailableVal = CastInst::Create(CastInst::BitCast, AvailableVal,
-                                      LI->getType(), "", LI);
+      AvailableVal =
+          CastInst::CreateBitOrPointerCast(AvailableVal, LI->getType(), "", LI);
     LI->replaceAllUsesWith(AvailableVal);
     LI->eraseFromParent();
     return true;
@@ -1040,8 +1040,8 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
     // predecessor use the same bitcast.
     Value *&PredV = I->second;
     if (PredV->getType() != LI->getType())
-      PredV = CastInst::Create(CastInst::BitCast, PredV, LI->getType(), "",
-                               P->getTerminator());
+      PredV = CastInst::CreateBitOrPointerCast(PredV, LI->getType(), "",
+                                               P->getTerminator());
 
     PN->addIncoming(PredV, I->first);
   }