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Add a generalized form of ConstantExpr::getOffsetOf which works for

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array types as well as struct types, and which accepts arbitrary
Constant indicies.  

llvm-svn: 94981
This commit is contained in:
Dan Gohman 2010-02-01 16:37:38 +00:00
parent 7099d40968
commit 9026a494ae
2 changed files with 17 additions and 7 deletions
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11
include/llvm/Constants.h
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@ -652,10 +652,15 @@ public:
///
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).
/// getOffsetOf constant expr - computes the offset of a struct field in a
/// target independent way (Note: the return type is an i64).
///
static Constant *getOffsetOf(const StructType* Ty, unsigned FieldNo);
static Constant *getOffsetOf(const StructType* STy, unsigned FieldNo);
/// getOffsetOf constant expr - This is a generalized form of getOffsetOf,
/// which supports any aggregate type, and any Constant index.
///
static Constant *getOffsetOf(const Type* Ty, Constant *FieldNo);
static Constant *getNeg(Constant *C);
static Constant *getFNeg(Constant *C);

13
lib/VMCore/Constants.cpp
View File

@ -1493,16 +1493,21 @@ Constant* ConstantExpr::getAlignOf(const Type* Ty) {
}
Constant* ConstantExpr::getOffsetOf(const StructType* STy, unsigned FieldNo) {
return getOffsetOf(STy, ConstantInt::get(Type::getInt32Ty(STy->getContext()),
FieldNo));
}
Constant* ConstantExpr::getOffsetOf(const Type* Ty, Constant *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)
ConstantInt::get(Type::getInt64Ty(Ty->getContext()), 0),
FieldNo
};
Constant *GEP = getGetElementPtr(
Constant::getNullValue(PointerType::getUnqual(STy)), GEPIdx, 2);
Constant::getNullValue(PointerType::getUnqual(Ty)), GEPIdx, 2);
return getCast(Instruction::PtrToInt, GEP,
Type::getInt64Ty(STy->getContext()));
Type::getInt64Ty(Ty->getContext()));
}
Constant *ConstantExpr::getCompare(unsigned short pred,