Add a new helper method to Value to strip in-bounds constant offsets of

pointers, but accumulate the offset into an APInt in the process of
stripping it.

This is a pretty handy thing to have, such as when trying to determine
if two pointers are at some constant relative offset. I'll be committing
a patch shortly to use it for exactly that purpose.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189000 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 31 insertions, 12 deletions

diff --git a/include/llvm/IR/Value.h b/include/llvm/IR/Value.h
index e667b87f03..e1361fef35 100644
--- a/include/llvm/IR/Value.h
+++ b/include/llvm/IR/Value.h
@@ -22,26 +22,29 @@
 
 namespace llvm {
 
-class Constant;
+class APInt;
 class Argument;
-class Instruction;
+class AssemblyAnnotationWriter;
 class BasicBlock;
-class GlobalValue;
+class Constant;
+class DataLayout;
 class Function;
-class GlobalVariable;
 class GlobalAlias;
+class GlobalValue;
+class GlobalVariable;
 class InlineAsm;
-class ValueSymbolTable;
-template<typename ValueTy> class StringMapEntry;
-typedef StringMapEntry<Value*> ValueName;
-class raw_ostream;
-class AssemblyAnnotationWriter;
-class ValueHandleBase;
+class Instruction;
 class LLVMContext;
-class Twine;
 class MDNode;
-class Type;
 class StringRef;
+class Twine;
+class Type;
+class ValueHandleBase;
+class ValueSymbolTable;
+class raw_ostream;
+
+template<typename ValueTy> class StringMapEntry;
+typedef StringMapEntry<Value*> ValueName;
 
 //===----------------------------------------------------------------------===//
 //                                 Value Class
@@ -287,6 +290,22 @@ public:
     return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
   }
 
+  /// \brief Strips like \c stripInBoundsConstantOffsets but also accumulates
+  /// the constant offset stripped.
+  ///
+  /// Stores the resulting constant offset stripped into the APInt provided.
+  /// The provided APInt will be extended or truncated as needed to be the
+  /// correct bitwidth for an offset of this pointer type.
+  ///
+  /// If this is called on a non-pointer value, it returns 'this'.
+  Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
+                                                   APInt &Offset);
+  const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
+                                                         APInt &Offset) const {
+    return const_cast<Value *>(this)
+        ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
+  }
+
   /// \brief Strips off unneeded pointer casts and any in-bounds offsets from
   /// the specified value, returning the original pointer value.
   ///