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Diffstat (limited to 'llvm/docs/LangRef.rst')
| -rw-r--r-- | llvm/docs/LangRef.rst | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index 3cdddcb1eb6..25bf9cccb09 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -12293,6 +12293,60 @@ Overview: The ``llvm.type.test`` intrinsic tests whether the given pointer is associated with the given type identifier. +'``llvm.type.checked.load``' Intrinsic +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Syntax: +""""""" + +:: + + declare {i8*, i1} @llvm.type.checked.load(i8* %ptr, i32 %offset, metadata %type) argmemonly nounwind readonly + + +Arguments: +"""""""""" + +The first argument is a pointer from which to load a function pointer. The +second argument is the byte offset from which to load the function pointer. The +third argument is a metadata object representing a :doc:`type identifier +<TypeMetadata>`. + +Overview: +""""""""" + +The ``llvm.type.checked.load`` intrinsic safely loads a function pointer from a +virtual table pointer using type metadata. This intrinsic is used to implement +control flow integrity in conjunction with virtual call optimization. The +virtual call optimization pass will optimize away ``llvm.type.checked.load`` +intrinsics associated with devirtualized calls, thereby removing the type +check in cases where it is not needed to enforce the control flow integrity +constraint. + +If the given pointer is associated with a type metadata identifier, this +function returns true as the second element of its return value. (Note that +the function may also return true if the given pointer is not associated +with a type metadata identifier.) If the function's return value's second +element is true, the following rules apply to the first element: + +- If the given pointer is associated with the given type metadata identifier, + it is the function pointer loaded from the given byte offset from the given + pointer. + +- If the given pointer is not associated with the given type metadata + identifier, it is one of the following (the choice of which is unspecified): + + 1. The function pointer that would have been loaded from an arbitrarily chosen + (through an unspecified mechanism) pointer associated with the type + metadata. + + 2. If the function has a non-void return type, a pointer to a function that + returns an unspecified value without causing side effects. + +If the function's return value's second element is false, the value of the +first element is undefined. + + '``llvm.donothing``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
