diff options
| -rw-r--r-- | include/llvm/Constants.h | 5 | ||||
| -rw-r--r-- | lib/VMCore/Constants.cpp | 12 |
2 files changed, 17 insertions, 0 deletions
diff --git a/include/llvm/Constants.h b/include/llvm/Constants.h index e26bb62c35..a66773c0b5 100644 --- a/include/llvm/Constants.h +++ b/include/llvm/Constants.h @@ -602,6 +602,11 @@ public: /// independent way (Note: the return type is an i64). /// static Constant* getSizeOf(const Type* Ty); + + /// getOffsetOf constant expr - computes the offset of a field in a target + /// independent way (Note: the return type is an i64). + /// + static Constant* getOffsetOf(const StructType* Ty, unsigned FieldNo); static Constant* getNeg(Constant* C); static Constant* getFNeg(Constant* C); diff --git a/lib/VMCore/Constants.cpp b/lib/VMCore/Constants.cpp index 647bc1225a..f820033932 100644 --- a/lib/VMCore/Constants.cpp +++ b/lib/VMCore/Constants.cpp @@ -1391,6 +1391,18 @@ Constant* ConstantExpr::getAlignOf(const Type* Ty) { Type::getInt32Ty(Ty->getContext())); } +Constant* ConstantExpr::getOffsetOf(const StructType* STy, unsigned FieldNo) { + // offsetof is implemented as: (i64) gep (Ty*)null, 0, FieldNo + // Note that a non-inbounds gep is used, as null isn't within any object. + Constant *GEPIdx[] = { + ConstantInt::get(Type::getInt64Ty(STy->getContext()), 0), + ConstantInt::get(Type::getInt32Ty(STy->getContext()), FieldNo) + }; + Constant *GEP = getGetElementPtr( + Constant::getNullValue(PointerType::getUnqual(STy)), GEPIdx, 2); + return getCast(Instruction::PtrToInt, GEP, + Type::getInt64Ty(STy->getContext())); +} Constant *ConstantExpr::getCompare(unsigned short pred, Constant *C1, Constant *C2) { |