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-rw-r--r--include/llvm/Transforms/Utils/GlobalStatus.h82
1 files changed, 82 insertions, 0 deletions
diff --git a/include/llvm/Transforms/Utils/GlobalStatus.h b/include/llvm/Transforms/Utils/GlobalStatus.h
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+++ b/include/llvm/Transforms/Utils/GlobalStatus.h
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+//===- GlobalStatus.h - Compute status info for globals ---------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_GLOBALSTATUS_H
+#define LLVM_TRANSFORMS_UTILS_GLOBALSTATUS_H
+
+#include "llvm/IR/Instructions.h"
+
+namespace llvm {
+class Value;
+class Function;
+
+/// It is safe to destroy a constant iff it is only used by constants itself.
+/// Note that constants cannot be cyclic, so this test is pretty easy to
+/// implement recursively.
+///
+bool isSafeToDestroyConstant(const Constant *C);
+
+/// As we analyze each global, keep track of some information about it. If we
+/// find out that the address of the global is taken, none of this info will be
+/// accurate.
+struct GlobalStatus {
+ /// True if the global's address is used in a comparison.
+ bool IsCompared;
+
+ /// True if the global is ever loaded. If the global isn't ever loaded it
+ /// can be deleted.
+ bool IsLoaded;
+
+ /// Keep track of what stores to the global look like.
+ enum StoredType {
+ /// There is no store to this global. It can thus be marked constant.
+ NotStored,
+
+ /// This global is stored to, but the only thing stored is the constant it
+ /// was initialized with. This is only tracked for scalar globals.
+ InitializerStored,
+
+ /// This global is stored to, but only its initializer and one other value
+ /// is ever stored to it. If this global isStoredOnce, we track the value
+ /// stored to it in StoredOnceValue below. This is only tracked for scalar
+ /// globals.
+ StoredOnce,
+
+ /// This global is stored to by multiple values or something else that we
+ /// cannot track.
+ Stored
+ } StoredType;
+
+ /// If only one value (besides the initializer constant) is ever stored to
+ /// this global, keep track of what value it is.
+ Value *StoredOnceValue;
+
+ /// These start out null/false. When the first accessing function is noticed,
+ /// it is recorded. When a second different accessing function is noticed,
+ /// HasMultipleAccessingFunctions is set to true.
+ const Function *AccessingFunction;
+ bool HasMultipleAccessingFunctions;
+
+ /// Set to true if this global has a user that is not an instruction (e.g. a
+ /// constant expr or GV initializer).
+ bool HasNonInstructionUser;
+
+ /// Set to the strongest atomic ordering requirement.
+ AtomicOrdering Ordering;
+
+ /// Look at all uses of the global and fill in the GlobalStatus structure. If
+ /// the global has its address taken, return true to indicate we can't do
+ /// anything with it.
+ static bool analyzeGlobal(const Value *V, GlobalStatus &GS);
+
+ GlobalStatus();
+};
+}
+
+#endif