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e30173ac33
function with a new NumLowBitsAvailable enum, which makes the value available as an integer constant expression. Add PointerLikeTypeTraits specializations for Instruction* and Use** since they are only guaranteed 4-byte aligned. Enhance PointerIntPair to know about (and enforce) the alignment specified by PointerLikeTypeTraits. This should allow things like PointerIntPair<PointerIntPair<void*, 1,bool>, 1, bool> because the inner one knows that 2 low bits are free. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67979 91177308-0d34-0410-b5e6-96231b3b80d8
62 lines
2.0 KiB
C++
62 lines
2.0 KiB
C++
//===- llvm/Support/PointerLikeTypeTraits.h - Pointer Traits ----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the PointerLikeTypeTraits class. This allows data
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// structures to reason about pointers and other things that are pointer sized.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
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#define LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
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namespace llvm {
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/// PointerLikeTypeTraits - This is a traits object that is used to handle
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/// pointer types and things that are just wrappers for pointers as a uniform
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/// entity.
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template <typename T>
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class PointerLikeTypeTraits {
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// getAsVoidPointer
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// getFromVoidPointer
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// getNumLowBitsAvailable
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};
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// Provide PointerLikeTypeTraits for non-cvr pointers.
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template<typename T>
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class PointerLikeTypeTraits<T*> {
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public:
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static inline void *getAsVoidPointer(T* P) { return P; }
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static inline T *getFromVoidPointer(void *P) {
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return static_cast<T*>(P);
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}
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/// Note, we assume here that malloc returns objects at least 8-byte aligned.
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/// However, this may be wrong, or pointers may be from something other than
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/// malloc. In this case, you should specialize this template to reduce this.
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///
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/// All clients should use assertions to do a run-time check to ensure that
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/// this is actually true.
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enum { NumLowBitsAvailable = 3 };
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};
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// Provide PointerLikeTypeTraits for const pointers.
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template<typename T>
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class PointerLikeTypeTraits<const T*> {
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public:
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static inline const void *getAsVoidPointer(const T* P) { return P; }
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static inline const T *getFromVoidPointer(const void *P) {
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return static_cast<const T*>(P);
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}
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enum { NumLowBitsAvailable = 3 };
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};
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} // end namespace llvm
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#endif
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