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Add a getAlignOf helper for getting the ABI alignment of a

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type as a target independent constant expression.  I confess
that I didn't check that this method works as intended (though
I did test the equivalent hand-written IR a little).  But what
could possibly go wrong!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72213 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2009-05-21 15:52:21 +00:00
parent e3e51c0038
commit ef854af5bd
4 changed files with 28 additions and 1 deletions
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8
bindings/ocaml/llvm/llvm.mli
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@ -514,9 +514,15 @@ external const_vector : llvalue array -> llvalue = "llvm_const_vector"
(** {7 Constant expressions} *)
(** [align_of ty] returns the alignof constant for the type [ty]. This is
equivalent to [const_ptrtoint (const_gep (const_null (pointer_type {i8,ty}))
(const_int i32_type 0) (const_int i32_type 1)) i32_type], but considerably
more readable. See the method [llvm::ConstantExpr::getAlignOf]. *)
external align_of : lltype -> llvalue = "LLVMAlignOf"
(** [size_of ty] returns the sizeof constant for the type [ty]. This is
equivalent to [const_ptrtoint (const_gep (const_null (pointer_type ty))
(const_int i64_type 1)) i64_type], but considerably more readable.
(const_int i32_type 1)) i64_type], but considerably more readable.
See the method [llvm::ConstantExpr::getSizeOf]. *)
external size_of : lltype -> llvalue = "LLVMSizeOf"

6
include/llvm/Constants.h
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@ -680,6 +680,12 @@ public:
return getSelectTy(V1->getType(), C, V1, V2);
}
/// getAlignOf constant expr - computes the alignment of a type in a target
/// independent way (Note: the return type is an i32; Note: assumes that i8
/// is byte aligned).
///
static Constant *getAlignOf(const Type *Ty);
/// getSizeOf constant expr - computes the size of a type in a target
/// independent way (Note: the return type is an i64).
///

11
lib/VMCore/Constants.cpp
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@ -2082,6 +2082,17 @@ Constant *ConstantExpr::getBitCast(Constant *C, const Type *DstTy) {
return getFoldedCast(Instruction::BitCast, C, DstTy);
}
Constant *ConstantExpr::getAlignOf(const Type *Ty) {
// alignof is implemented as: (i64) gep ({i8,Ty}*)null, 0, 1
const Type *AligningTy = StructType::get(Type::Int8Ty, Ty, NULL);
Constant *NullPtr = getNullValue(AligningTy->getPointerTo());
Constant *Zero = ConstantInt::get(Type::Int32Ty, 0);
Constant *One = ConstantInt::get(Type::Int32Ty, 1);
Constant *Indices[2] = { Zero, One };
Constant *GEP = getGetElementPtr(NullPtr, Indices, 2);
return getCast(Instruction::PtrToInt, GEP, Type::Int32Ty);
}
Constant *ConstantExpr::getSizeOf(const Type *Ty) {
// sizeof is implemented as: (i64) gep (Ty*)null, 1
Constant *GEPIdx = ConstantInt::get(Type::Int32Ty, 1);

4
lib/VMCore/Core.cpp
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@ -356,6 +356,10 @@ LLVMValueRef LLVMConstVector(LLVMValueRef *ScalarConstantVals, unsigned Size) {
/*--.. Constant expressions ................................................--*/
LLVMValueRef LLVMAlignOf(LLVMTypeRef Ty) {
return wrap(ConstantExpr::getAlignOf(unwrap(Ty)));
}
LLVMValueRef LLVMSizeOf(LLVMTypeRef Ty) {
return wrap(ConstantExpr::getSizeOf(unwrap(Ty)));
}