Move Value.isDereferenceablePointer to ValueTracking [NFC]

Move isDereferenceablePointer function to Analysis. This function recursively tracks dereferencability over a chain of values like other functions in ValueTracking.

This refactoring is motivated by further changes to support dereferenceable_or_null attribute (http://reviews.llvm.org/D8650). isDereferenceablePointer will be extended to perform context-sensitive analysis and IR is not a good place to have such functionality.

Patch by: Artur Pilipenko <apilipenko@azulsystems.com>
Differential Revision: reviews.llvm.org/D9075




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235611 91177308-0d34-0410-b5e6-96231b3b80d8

9 files changed, 159 insertions, 147 deletions

diff --git a/include/llvm/Analysis/ValueTracking.h b/include/llvm/Analysis/ValueTracking.h
index 8955b7c7bd..ded756b8f1 100644
--- a/include/llvm/Analysis/ValueTracking.h
+++ b/include/llvm/Analysis/ValueTracking.h
@@ -186,6 +186,13 @@ namespace llvm {
   /// are lifetime markers.
   bool onlyUsedByLifetimeMarkers(const Value *V);
 
+  /// isDereferenceablePointer - Return true if this is always a dereferenceable 
+  /// pointer.
+  ///
+  /// Test if this value is always a pointer to allocated and suitably aligned
+  /// memory for a simple load or store.
+  bool isDereferenceablePointer(const Value *V, const DataLayout &DL);
+  
   /// isSafeToSpeculativelyExecute - Return true if the instruction does not
   /// have any effects besides calculating the result and does not have
   /// undefined behavior.
diff --git a/include/llvm/IR/Value.h b/include/llvm/IR/Value.h
index 8217ef7236..c03cb88524 100644
--- a/include/llvm/IR/Value.h
+++ b/include/llvm/IR/Value.h
@@ -446,12 +446,6 @@ public:
     return const_cast<Value*>(this)->stripInBoundsOffsets();
   }
 
-  /// \brief Check if this is always a dereferenceable pointer.
-  ///
-  /// Test if this value is always a pointer to allocated and suitably aligned
-  /// memory for a simple load or store.
-  bool isDereferenceablePointer(const DataLayout &DL) const;
-
   /// \brief Translate PHI node to its predecessor from the given basic block.
   ///
   /// If this value is a PHI node with CurBB as its parent, return the value in
diff --git a/lib/Analysis/MemDerefPrinter.cpp b/lib/Analysis/MemDerefPrinter.cpp
index 6119a3da61..5903dc5670 100644
--- a/lib/Analysis/MemDerefPrinter.cpp
+++ b/lib/Analysis/MemDerefPrinter.cpp
@@ -10,6 +10,7 @@
 #include "llvm/Analysis/Passes.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/InstIterator.h"
@@ -53,7 +54,7 @@ bool MemDerefPrinter::runOnFunction(Function &F) {
   for (auto &I: inst_range(F)) {
     if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
       Value *PO = LI->getPointerOperand();
-      if (PO->isDereferenceablePointer(DL))
+      if (isDereferenceablePointer(PO, DL))
         Vec.push_back(PO);
     }
   }
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 36513018ac..de175fc523 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -31,6 +31,7 @@
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/PatternMatch.h"
+#include "llvm/IR/Statepoint.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/MathExtras.h"
 #include <cstring>
@@ -2807,6 +2808,145 @@ bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
   return true;
 }
 
+static bool isDereferenceableFromAttribute(const Value *BV, APInt Offset,
+                                           Type *Ty, const DataLayout &DL) {
+  assert(Offset.isNonNegative() && "offset can't be negative");
+  assert(Ty->isSized() && "must be sized");
+  
+  APInt DerefBytes(Offset.getBitWidth(), 0);
+  if (const Argument *A = dyn_cast<Argument>(BV)) {
+    DerefBytes = A->getDereferenceableBytes();
+  } else if (auto CS = ImmutableCallSite(BV)) {
+    DerefBytes = CS.getDereferenceableBytes(0);
+  }
+  
+  if (DerefBytes.getBoolValue())
+    if (DerefBytes.uge(Offset + DL.getTypeStoreSize(Ty)))
+      return true;
+  
+  return false;
+}
+
+static bool isDereferenceableFromAttribute(const Value *V, 
+                                           const DataLayout &DL) {
+  Type *VTy = V->getType();
+  Type *Ty = VTy->getPointerElementType();
+  if (!Ty->isSized())
+    return false;
+  
+  APInt Offset(DL.getTypeStoreSizeInBits(VTy), 0);
+  return isDereferenceableFromAttribute(V, Offset, Ty, DL);
+}
+
+/// Return true if Value is always a dereferenceable pointer.
+///
+/// Test if V is always a pointer to allocated and suitably aligned memory for
+/// a simple load or store.
+static bool isDereferenceablePointer(const Value *V, const DataLayout &DL,
+                                     SmallPtrSetImpl<const Value *> &Visited) {
+  // Note that it is not safe to speculate into a malloc'd region because
+  // malloc may return null.
+
+  // These are obviously ok.
+  if (isa<AllocaInst>(V)) return true;
+
+  // It's not always safe to follow a bitcast, for example:
+  //   bitcast i8* (alloca i8) to i32*
+  // would result in a 4-byte load from a 1-byte alloca. However,
+  // if we're casting from a pointer from a type of larger size
+  // to a type of smaller size (or the same size), and the alignment
+  // is at least as large as for the resulting pointer type, then
+  // we can look through the bitcast.
+  if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) {
+    Type *STy = BC->getSrcTy()->getPointerElementType(),
+         *DTy = BC->getDestTy()->getPointerElementType();
+    if (STy->isSized() && DTy->isSized() &&
+        (DL.getTypeStoreSize(STy) >= DL.getTypeStoreSize(DTy)) &&
+        (DL.getABITypeAlignment(STy) >= DL.getABITypeAlignment(DTy)))
+      return isDereferenceablePointer(BC->getOperand(0), DL, Visited);
+  }
+
+  // Global variables which can't collapse to null are ok.
+  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
+    return !GV->hasExternalWeakLinkage();
+
+  // byval arguments are okay.
+  if (const Argument *A = dyn_cast<Argument>(V))
+    if (A->hasByValAttr())
+      return true;
+    
+  if (isDereferenceableFromAttribute(V, DL))
+    return true;
+
+  // For GEPs, determine if the indexing lands within the allocated object.
+  if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
+    // Conservatively require that the base pointer be fully dereferenceable.
+    if (!Visited.insert(GEP->getOperand(0)).second)
+      return false;
+    if (!isDereferenceablePointer(GEP->getOperand(0), DL, Visited))
+      return false;
+    // Check the indices.
+    gep_type_iterator GTI = gep_type_begin(GEP);
+    for (User::const_op_iterator I = GEP->op_begin()+1,
+         E = GEP->op_end(); I != E; ++I) {
+      Value *Index = *I;
+      Type *Ty = *GTI++;
+      // Struct indices can't be out of bounds.
+      if (isa<StructType>(Ty))
+        continue;
+      ConstantInt *CI = dyn_cast<ConstantInt>(Index);
+      if (!CI)
+        return false;
+      // Zero is always ok.
+      if (CI->isZero())
+        continue;
+      // Check to see that it's within the bounds of an array.
+      ArrayType *ATy = dyn_cast<ArrayType>(Ty);
+      if (!ATy)
+        return false;
+      if (CI->getValue().getActiveBits() > 64)
+        return false;
+      if (CI->getZExtValue() >= ATy->getNumElements())
+        return false;
+    }
+    // Indices check out; this is dereferenceable.
+    return true;
+  }
+
+  // For gc.relocate, look through relocations
+  if (const IntrinsicInst *I = dyn_cast<IntrinsicInst>(V))
+    if (I->getIntrinsicID() == Intrinsic::experimental_gc_relocate) {
+      GCRelocateOperands RelocateInst(I);
+      return isDereferenceablePointer(RelocateInst.derivedPtr(), DL, Visited);
+    }
+
+  if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
+    return isDereferenceablePointer(ASC->getOperand(0), DL, Visited);
+
+  // If we don't know, assume the worst.
+  return false;
+}
+
+bool llvm::isDereferenceablePointer(const Value *V, const DataLayout &DL) {
+  // When dereferenceability information is provided by a dereferenceable
+  // attribute, we know exactly how many bytes are dereferenceable. If we can
+  // determine the exact offset to the attributed variable, we can use that
+  // information here.
+  Type *VTy = V->getType();
+  Type *Ty = VTy->getPointerElementType();
+  if (Ty->isSized()) {
+    APInt Offset(DL.getTypeStoreSizeInBits(VTy), 0);
+    const Value *BV = V->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
+    
+    if (Offset.isNonNegative())
+      if (isDereferenceableFromAttribute(BV, Offset, Ty, DL))
+        return true;
+  }
+
+  SmallPtrSet<const Value *, 32> Visited;
+  return ::isDereferenceablePointer(V, DL, Visited);
+}
+
 bool llvm::isSafeToSpeculativelyExecute(const Value *V) {
   const Operator *Inst = dyn_cast<Operator>(V);
   if (!Inst)
@@ -2854,7 +2994,7 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V) {
         LI->getParent()->getParent()->hasFnAttribute(Attribute::SanitizeThread))
       return false;
     const DataLayout &DL = LI->getModule()->getDataLayout();
-    return LI->getPointerOperand()->isDereferenceablePointer(DL);
+    return isDereferenceablePointer(LI->getPointerOperand(), DL);
   }
   case Instruction::Call: {
     if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
diff --git a/lib/IR/Value.cpp b/lib/IR/Value.cpp
index f6eb4273a5..18f6b1e9c3 100644
--- a/lib/IR/Value.cpp
+++ b/lib/IR/Value.cpp
@@ -477,137 +477,6 @@ Value *Value::stripInBoundsOffsets() {
   return stripPointerCastsAndOffsets<PSK_InBounds>(this);
 }
 
-/// \brief Check if Value is always a dereferenceable pointer.
-///
-/// Test if V is always a pointer to allocated and suitably aligned memory for
-/// a simple load or store.
-static bool isDereferenceablePointer(const Value *V, const DataLayout &DL,
-                                     SmallPtrSetImpl<const Value *> &Visited) {
-  // Note that it is not safe to speculate into a malloc'd region because
-  // malloc may return null.
-
-  // These are obviously ok.
-  if (isa<AllocaInst>(V)) return true;
-
-  // It's not always safe to follow a bitcast, for example:
-  //   bitcast i8* (alloca i8) to i32*
-  // would result in a 4-byte load from a 1-byte alloca. However,
-  // if we're casting from a pointer from a type of larger size
-  // to a type of smaller size (or the same size), and the alignment
-  // is at least as large as for the resulting pointer type, then
-  // we can look through the bitcast.
-  if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) {
-    Type *STy = BC->getSrcTy()->getPointerElementType(),
-         *DTy = BC->getDestTy()->getPointerElementType();
-    if (STy->isSized() && DTy->isSized() &&
-        (DL.getTypeStoreSize(STy) >= DL.getTypeStoreSize(DTy)) &&
-        (DL.getABITypeAlignment(STy) >= DL.getABITypeAlignment(DTy)))
-      return isDereferenceablePointer(BC->getOperand(0), DL, Visited);
-  }
-
-  // Global variables which can't collapse to null are ok.
-  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
-    return !GV->hasExternalWeakLinkage();
-
-  // byval arguments are okay. Arguments specifically marked as
-  // dereferenceable are okay too.
-  if (const Argument *A = dyn_cast<Argument>(V)) {
-    if (A->hasByValAttr())
-      return true;
-    else if (uint64_t Bytes = A->getDereferenceableBytes()) {
-      Type *Ty = V->getType()->getPointerElementType();
-      if (Ty->isSized() && DL.getTypeStoreSize(Ty) <= Bytes)
-        return true;
-    }
-
-    return false;
-  }
-
-  // Return values from call sites specifically marked as dereferenceable are
-  // also okay.
-  if (auto CS = ImmutableCallSite(V)) {
-    if (uint64_t Bytes = CS.getDereferenceableBytes(0)) {
-      Type *Ty = V->getType()->getPointerElementType();
-      if (Ty->isSized() && DL.getTypeStoreSize(Ty) <= Bytes)
-        return true;
-    }
-  }
-
-  // For GEPs, determine if the indexing lands within the allocated object.
-  if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
-    // Conservatively require that the base pointer be fully dereferenceable.
-    if (!Visited.insert(GEP->getOperand(0)).second)
-      return false;
-    if (!isDereferenceablePointer(GEP->getOperand(0), DL, Visited))
-      return false;
-    // Check the indices.
-    gep_type_iterator GTI = gep_type_begin(GEP);
-    for (User::const_op_iterator I = GEP->op_begin()+1,
-         E = GEP->op_end(); I != E; ++I) {
-      Value *Index = *I;
-      Type *Ty = *GTI++;
-      // Struct indices can't be out of bounds.
-      if (isa<StructType>(Ty))
-        continue;
-      ConstantInt *CI = dyn_cast<ConstantInt>(Index);
-      if (!CI)
-        return false;
-      // Zero is always ok.
-      if (CI->isZero())
-        continue;
-      // Check to see that it's within the bounds of an array.
-      ArrayType *ATy = dyn_cast<ArrayType>(Ty);
-      if (!ATy)
-        return false;
-      if (CI->getValue().getActiveBits() > 64)
-        return false;
-      if (CI->getZExtValue() >= ATy->getNumElements())
-        return false;
-    }
-    // Indices check out; this is dereferenceable.
-    return true;
-  }
-
-  // For gc.relocate, look through relocations
-  if (const IntrinsicInst *I = dyn_cast<IntrinsicInst>(V))
-    if (I->getIntrinsicID() == Intrinsic::experimental_gc_relocate) {
-      GCRelocateOperands RelocateInst(I);
-      return isDereferenceablePointer(RelocateInst.derivedPtr(), DL, Visited);
-    }
-
-  if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
-    return isDereferenceablePointer(ASC->getOperand(0), DL, Visited);
-
-  // If we don't know, assume the worst.
-  return false;
-}
-
-bool Value::isDereferenceablePointer(const DataLayout &DL) const {
-  // When dereferenceability information is provided by a dereferenceable
-  // attribute, we know exactly how many bytes are dereferenceable. If we can
-  // determine the exact offset to the attributed variable, we can use that
-  // information here.
-  Type *Ty = getType()->getPointerElementType();
-  if (Ty->isSized()) {
-    APInt Offset(DL.getTypeStoreSizeInBits(getType()), 0);
-    const Value *BV = stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
-
-    APInt DerefBytes(Offset.getBitWidth(), 0);
-    if (const Argument *A = dyn_cast<Argument>(BV))
-      DerefBytes = A->getDereferenceableBytes();
-    else if (auto CS = ImmutableCallSite(BV))
-      DerefBytes = CS.getDereferenceableBytes(0);
-
-    if (DerefBytes.getBoolValue() && Offset.isNonNegative()) {
-      if (DerefBytes.uge(Offset + DL.getTypeStoreSize(Ty)))
-        return true;
-    }
-  }
-
-  SmallPtrSet<const Value *, 32> Visited;
-  return ::isDereferenceablePointer(this, DL, Visited);
-}
-
 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
                                const BasicBlock *PredBB) {
   PHINode *PN = dyn_cast<PHINode>(this);
diff --git a/lib/Transforms/IPO/ArgumentPromotion.cpp b/lib/Transforms/IPO/ArgumentPromotion.cpp
index eee5a6a284..79e15bd5e7 100644
--- a/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ b/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -36,6 +36,7 @@
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/CallGraphSCCPass.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constants.h"
@@ -321,7 +322,7 @@ static bool AllCallersPassInValidPointerForArgument(Argument *Arg) {
     CallSite CS(U);
     assert(CS && "Should only have direct calls!");
 
-    if (!CS.getArgument(ArgNo)->isDereferenceablePointer(DL))
+    if (!isDereferenceablePointer(CS.getArgument(ArgNo), DL))
       return false;
   }
   return true;
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 56b6cd3017..1505ff073b 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1204,7 +1204,7 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
       II->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
 
     // isDereferenceablePointer -> deref attribute
-    if (DerivedPtr->isDereferenceablePointer(DL)) {
+    if (isDereferenceablePointer(DerivedPtr, DL)) {
       if (Argument *A = dyn_cast<Argument>(DerivedPtr)) {
         uint64_t Bytes = A->getDereferenceableBytes();
         II->addDereferenceableAttr(AttributeSet::ReturnIndex, Bytes);
diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp
index e11ab33b0f..66aed8dbf8 100644
--- a/lib/Transforms/Scalar/SROA.cpp
+++ b/lib/Transforms/Scalar/SROA.cpp
@@ -1406,7 +1406,7 @@ static bool isSafePHIToSpeculate(PHINode &PN) {
     // If this pointer is always safe to load, or if we can prove that there
     // is already a load in the block, then we can move the load to the pred
     // block.
-    if (InVal->isDereferenceablePointer(DL) ||
+    if (isDereferenceablePointer(InVal, DL) ||
         isSafeToLoadUnconditionally(InVal, TI, MaxAlign))
       continue;
 
@@ -1476,8 +1476,8 @@ static bool isSafeSelectToSpeculate(SelectInst &SI) {
   Value *TValue = SI.getTrueValue();
   Value *FValue = SI.getFalseValue();
   const DataLayout &DL = SI.getModule()->getDataLayout();
-  bool TDerefable = TValue->isDereferenceablePointer(DL);
-  bool FDerefable = FValue->isDereferenceablePointer(DL);
+  bool TDerefable = isDereferenceablePointer(TValue, DL);
+  bool FDerefable = isDereferenceablePointer(FValue, DL);
 
   for (User *U : SI.users()) {
     LoadInst *LI = dyn_cast<LoadInst>(U);
diff --git a/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 03fff1df5d..5b47ef9d73 100644
--- a/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -1140,8 +1140,8 @@ public:
 /// the select can be loaded unconditionally.
 static bool isSafeSelectToSpeculate(SelectInst *SI) {
   const DataLayout &DL = SI->getModule()->getDataLayout();
-  bool TDerefable = SI->getTrueValue()->isDereferenceablePointer(DL);
-  bool FDerefable = SI->getFalseValue()->isDereferenceablePointer(DL);
+  bool TDerefable = isDereferenceablePointer(SI->getTrueValue(), DL);
+  bool FDerefable = isDereferenceablePointer(SI->getFalseValue(), DL);
 
   for (User *U : SI->users()) {
     LoadInst *LI = dyn_cast<LoadInst>(U);
@@ -1228,7 +1228,7 @@ static bool isSafePHIToSpeculate(PHINode *PN) {
 
     // If this pointer is always safe to load, or if we can prove that there is
     // already a load in the block, then we can move the load to the pred block.
-    if (InVal->isDereferenceablePointer(DL) ||
+    if (isDereferenceablePointer(InVal, DL) ||
         isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign))
       continue;