+
+ /// \brief Accumulate the constant address offset of this GEP if possible.
+ ///
+ /// This routine accepts an APInt into which it will accumulate the constant
+ /// offset of this GEP if the GEP is in fact constant. If the GEP is not
+ /// all-constant, it returns false and the value of the offset APInt is
+ /// undefined (it is *not* preserved!). The APInt passed into this routine
+ /// must be at least as wide as the IntPtr type for the address space of
+ /// the base GEP pointer.
+ bool 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;