[llvm] r269190 - NFC. Introduce Value::isPointerDereferenceable

[Artur Pilipenko via llvm-commits]

Author: apilipenko
Date: Wed May 11 09:43:28 2016
New Revision: 269190

URL: http://llvm.org/viewvc/llvm-project?rev=269190&view=rev
Log:
NFC. Introduce Value::isPointerDereferenceable
    
Extract a part of isDereferenceableAndAlignedPointer functionality to Value:
    
Reviewed By: hfinkel, sanjoy
    
Differential Revision: http://reviews.llvm.org/D17611

Modified:
    llvm/trunk/include/llvm/IR/Value.h
    llvm/trunk/lib/Analysis/Loads.cpp
    llvm/trunk/lib/IR/Value.cpp

Modified: llvm/trunk/include/llvm/IR/Value.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Value.h?rev=269190&r1=269189&r2=269190&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Value.h (original)
+++ llvm/trunk/include/llvm/IR/Value.h Wed May 11 09:43:28 2016
@@ -511,6 +511,12 @@ public:
   /// dereferenceable up to the returned number of bytes.
   unsigned getPointerDereferenceableBytes(bool &CanBeNull) const;
 
+  /// \brief Returns true if the pointer value is fully dereferenceable.
+  ///
+  /// Sets CanBeNull to true if the pointer is either null or can be fully
+  /// dereferenceable.
+  bool isPointerDereferenceable(bool &CanBeNull) const;
+
   /// \brief Returns an alignment of the pointer value.
   ///
   /// Returns an alignment which is either specified explicitly, e.g. via

Modified: llvm/trunk/lib/Analysis/Loads.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/Loads.cpp?rev=269190&r1=269189&r2=269190&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/Loads.cpp (original)
+++ llvm/trunk/lib/Analysis/Loads.cpp Wed May 11 09:43:28 2016
@@ -91,9 +91,12 @@ static bool isDereferenceableAndAlignedP
   // Note that it is not safe to speculate into a malloc'd region because
   // malloc may return null.
 
-  // These are obviously ok if aligned.
-  if (isa<AllocaInst>(V))
+  bool CheckForNonNull;
+  if (V->isPointerDereferenceable(CheckForNonNull)) {
+    if (CheckForNonNull && !isKnownNonNullAt(V, CtxI, DT, TLI))
+      return false;
     return isAligned(V, Align, DL);
+  }
 
   // It's not always safe to follow a bitcast, for example:
   //   bitcast i8* (alloca i8) to i32*
@@ -112,16 +115,6 @@ static bool isDereferenceableAndAlignedP
                                                 CtxI, DT, TLI, Visited);
   }
 
-  // Global variables which can't collapse to null are ok.
-  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
-    if (!GV->hasExternalWeakLinkage())
-      return isAligned(V, Align, DL);
-
-  // byval arguments are okay.
-  if (const Argument *A = dyn_cast<Argument>(V))
-    if (A->hasByValAttr())
-      return isAligned(V, Align, DL);
-
   if (isDereferenceableFromAttribute(V, DL, CtxI, DT, TLI))
     return isAligned(V, Align, DL);
 

Modified: llvm/trunk/lib/IR/Value.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Value.cpp?rev=269190&r1=269189&r2=269190&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Value.cpp (original)
+++ llvm/trunk/lib/IR/Value.cpp Wed May 11 09:43:28 2016
@@ -559,6 +559,29 @@ unsigned Value::getPointerDereferenceabl
   return DerefBytes;
 }
 
+bool Value::isPointerDereferenceable(bool &CanBeNull) const {
+  assert(getType()->isPointerTy() && "must be pointer");
+
+  CanBeNull = false;
+
+  // These are obviously ok.
+  if (isa<AllocaInst>(this))
+    return true;
+
+  // Global variables which can't collapse to null are ok.
+  // TODO: return true for those but set CanBeNull flag
+  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
+    if (!GV->hasExternalWeakLinkage())
+      return true;
+
+  // byval arguments are okay.
+  if (const Argument *A = dyn_cast<Argument>(this))
+    if (A->hasByValAttr())
+      return true;
+
+  return false;
+}
+
 unsigned Value::getPointerAlignment(const DataLayout &DL) const {
   assert(getType()->isPointerTy() && "must be pointer");