vendor/llvm/llvm-release_39-r276489

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diff --git a/include/llvm/Transforms/IPO/DeadArgumentElimination.h b/include/llvm/Transforms/IPO/DeadArgumentElimination.h
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+++ b/include/llvm/Transforms/IPO/DeadArgumentElimination.h
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+//===- DeadArgumentElimination.h - Eliminate Dead Args ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass deletes dead arguments from internal functions.  Dead argument
+// elimination removes arguments which are directly dead, as well as arguments
+// only passed into function calls as dead arguments of other functions.  This
+// pass also deletes dead return values in a similar way.
+//
+// This pass is often useful as a cleanup pass to run after aggressive
+// interprocedural passes, which add possibly-dead arguments or return values.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_IPO_DEADARGUMENTELIMINATION_H
+#define LLVM_TRANSFORMS_IPO_DEADARGUMENTELIMINATION_H
+
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+
+#include <map>
+#include <set>
+#include <string>
+
+namespace llvm {
+
+/// Eliminate dead arguments (and return values) from functions.
+class DeadArgumentEliminationPass
+    : public PassInfoMixin<DeadArgumentEliminationPass> {
+public:
+  /// Struct that represents (part of) either a return value or a function
+  /// argument.  Used so that arguments and return values can be used
+  /// interchangeably.
+  struct RetOrArg {
+    RetOrArg(const Function *F, unsigned Idx, bool IsArg)
+        : F(F), Idx(Idx), IsArg(IsArg) {}
+    const Function *F;
+    unsigned Idx;
+    bool IsArg;
+
+    /// Make RetOrArg comparable, so we can put it into a map.
+    bool operator<(const RetOrArg &O) const {
+      return std::tie(F, Idx, IsArg) < std::tie(O.F, O.Idx, O.IsArg);
+    }
+
+    /// Make RetOrArg comparable, so we can easily iterate the multimap.
+    bool operator==(const RetOrArg &O) const {
+      return F == O.F && Idx == O.Idx && IsArg == O.IsArg;
+    }
+
+    std::string getDescription() const {
+      return (Twine(IsArg ? "Argument #" : "Return value #") + Twine(Idx) +
+              " of function " + F->getName())
+          .str();
+    }
+  };
+
+  /// Liveness enum - During our initial pass over the program, we determine
+  /// that things are either alive or maybe alive. We don't mark anything
+  /// explicitly dead (even if we know they are), since anything not alive
+  /// with no registered uses (in Uses) will never be marked alive and will
+  /// thus become dead in the end.
+  enum Liveness { Live, MaybeLive };
+
+  /// Convenience wrapper
+  RetOrArg CreateRet(const Function *F, unsigned Idx) {
+    return RetOrArg(F, Idx, false);
+  }
+  /// Convenience wrapper
+  RetOrArg CreateArg(const Function *F, unsigned Idx) {
+    return RetOrArg(F, Idx, true);
+  }
+
+  typedef std::multimap<RetOrArg, RetOrArg> UseMap;
+  /// This maps a return value or argument to any MaybeLive return values or
+  /// arguments it uses. This allows the MaybeLive values to be marked live
+  /// when any of its users is marked live.
+  /// For example (indices are left out for clarity):
+  ///  - Uses[ret F] = ret G
+  ///    This means that F calls G, and F returns the value returned by G.
+  ///  - Uses[arg F] = ret G
+  ///    This means that some function calls G and passes its result as an
+  ///    argument to F.
+  ///  - Uses[ret F] = arg F
+  ///    This means that F returns one of its own arguments.
+  ///  - Uses[arg F] = arg G
+  ///    This means that G calls F and passes one of its own (G's) arguments
+  ///    directly to F.
+  UseMap Uses;
+
+  typedef std::set<RetOrArg> LiveSet;
+  typedef std::set<const Function *> LiveFuncSet;
+
+  /// This set contains all values that have been determined to be live.
+  LiveSet LiveValues;
+  /// This set contains all values that are cannot be changed in any way.
+  LiveFuncSet LiveFunctions;
+
+  typedef SmallVector<RetOrArg, 5> UseVector;
+
+  /// This allows this pass to do double-duty as the dead arg hacking pass
+  /// (used only by bugpoint).
+  bool ShouldHackArguments = false;
+
+public:
+  DeadArgumentEliminationPass(bool ShouldHackArguments_ = false)
+      : ShouldHackArguments(ShouldHackArguments_) {}
+  PreservedAnalyses run(Module &M, ModuleAnalysisManager &);
+
+private:
+  Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
+  Liveness SurveyUse(const Use *U, UseVector &MaybeLiveUses,
+                     unsigned RetValNum = -1U);
+  Liveness SurveyUses(const Value *V, UseVector &MaybeLiveUses);
+
+  void SurveyFunction(const Function &F);
+  void MarkValue(const RetOrArg &RA, Liveness L,
+                 const UseVector &MaybeLiveUses);
+  void MarkLive(const RetOrArg &RA);
+  void MarkLive(const Function &F);
+  void PropagateLiveness(const RetOrArg &RA);
+  bool RemoveDeadStuffFromFunction(Function *F);
+  bool DeleteDeadVarargs(Function &Fn);
+  bool RemoveDeadArgumentsFromCallers(Function &Fn);
+};
+}
+
+#endif // LLVM_TRANSFORMS_IPO_DEADARGUMENTELIMINATION_H