85 lines
3.0 KiB
C
85 lines
3.0 KiB
C
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//===- GlobalStatus.h - Compute status info for globals ---------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_GLOBALSTATUS_H
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#define LLVM_TRANSFORMS_UTILS_GLOBALSTATUS_H
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#include "llvm/Support/AtomicOrdering.h"
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namespace llvm {
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class Constant;
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class Function;
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class Value;
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/// It is safe to destroy a constant iff it is only used by constants itself.
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/// Note that constants cannot be cyclic, so this test is pretty easy to
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/// implement recursively.
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///
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bool isSafeToDestroyConstant(const Constant *C);
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/// As we analyze each global, keep track of some information about it. If we
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/// find out that the address of the global is taken, none of this info will be
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/// accurate.
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struct GlobalStatus {
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/// True if the global's address is used in a comparison.
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bool IsCompared = false;
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/// True if the global is ever loaded. If the global isn't ever loaded it
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/// can be deleted.
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bool IsLoaded = false;
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/// Keep track of what stores to the global look like.
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enum StoredType {
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/// There is no store to this global. It can thus be marked constant.
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NotStored,
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/// This global is stored to, but the only thing stored is the constant it
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/// was initialized with. This is only tracked for scalar globals.
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InitializerStored,
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/// This global is stored to, but only its initializer and one other value
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/// is ever stored to it. If this global isStoredOnce, we track the value
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/// stored to it in StoredOnceValue below. This is only tracked for scalar
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/// globals.
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StoredOnce,
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/// This global is stored to by multiple values or something else that we
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/// cannot track.
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Stored
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} StoredType = NotStored;
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/// If only one value (besides the initializer constant) is ever stored to
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/// this global, keep track of what value it is.
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Value *StoredOnceValue = nullptr;
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/// These start out null/false. When the first accessing function is noticed,
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/// it is recorded. When a second different accessing function is noticed,
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/// HasMultipleAccessingFunctions is set to true.
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const Function *AccessingFunction = nullptr;
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bool HasMultipleAccessingFunctions = false;
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/// Set to true if this global has a user that is not an instruction (e.g. a
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/// constant expr or GV initializer).
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bool HasNonInstructionUser = false;
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/// Set to the strongest atomic ordering requirement.
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AtomicOrdering Ordering = AtomicOrdering::NotAtomic;
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GlobalStatus();
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/// Look at all uses of the global and fill in the GlobalStatus structure. If
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/// the global has its address taken, return true to indicate we can't do
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/// anything with it.
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static bool analyzeGlobal(const Value *V, GlobalStatus &GS);
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_UTILS_GLOBALSTATUS_H
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