--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/IR/Operator.cpp	Tue Oct 13 17:48:58 2015 +0900
@@ -0,0 +1,44 @@
+#include "llvm/IR/Operator.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Type.h"
+
+#include "ConstantsContext.h"
+
+namespace llvm {
+Type *GEPOperator::getSourceElementType() const {
+  if (auto *I = dyn_cast<GetElementPtrInst>(this))
+    return I->getSourceElementType();
+  return cast<GetElementPtrConstantExpr>(this)->getSourceElementType();
+}
+
+bool GEPOperator::accumulateConstantOffset(const DataLayout &DL,
+                                           APInt &Offset) const {
+  assert(Offset.getBitWidth() ==
+             DL.getPointerSizeInBits(getPointerAddressSpace()) &&
+         "The offset must have exactly as many bits as our pointer.");
+
+  for (gep_type_iterator GTI = gep_type_begin(this), GTE = gep_type_end(this);
+       GTI != GTE; ++GTI) {
+    ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
+    if (!OpC)
+      return false;
+    if (OpC->isZero())
+      continue;
+
+    // Handle a struct index, which adds its field offset to the pointer.
+    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      unsigned ElementIdx = OpC->getZExtValue();
+      const StructLayout *SL = DL.getStructLayout(STy);
+      Offset += APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx));
+      continue;
+    }
+
+    // For array or vector indices, scale the index by the size of the type.
+    APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth());
+    Offset += Index * APInt(Offset.getBitWidth(),
+                            DL.getTypeAllocSize(GTI.getIndexedType()));
+  }
+  return true;
+}
+}