Add a new attribute called 'jumptable' that creates jump-instruction tables for functions marked with this attribute.

It includes a pass that rewrites all indirect calls to jumptable functions to pass through these tables.

This also adds backend support for generating the jump-instruction tables on ARM and X86.
Note that since the jumptable attribute creates a second function pointer for a
function, any function marked with jumptable must also be marked with unnamed_addr.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210280 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/JumpInstrTableInfo.h

@@ -0,0 +1,60 @@
+//===-- JumpInstrTableInfo.h: Info for Jump-Instruction Tables --*- C++ -*-===//
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Information about jump-instruction tables that have been created by
+/// JumpInstrTables pass.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_JUMPINSTRTABLEINFO_H
+#define LLVM_ANALYSIS_JUMPINSTRTABLEINFO_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Pass.h"
+
+#include <vector>
+
+namespace llvm {
+class Function;
+class FunctionType;
+
+/// This class stores information about jump-instruction tables created by the
+/// JumpInstrTables pass (in lib/CodeGen/JumpInstrTables.cpp). Each table is a
+/// map from a function type to a vector of pairs. The first element of each
+/// pair is the function that has the jumptable annotation. The second element
+/// is a function that was declared by JumpInstrTables and used to replace all
+/// address-taking sites for the original function.
+///
+/// The information in this pass is used in AsmPrinter
+/// (lib/CodeGen/AsmPrinter/AsmPrinter.cpp) to generate the required assembly
+/// for the jump-instruction tables.
+class JumpInstrTableInfo : public ImmutablePass {
+public:
+  static char ID;
+
+  JumpInstrTableInfo();
+  virtual ~JumpInstrTableInfo();
+  const char *getPassName() const override {
+    return "Jump-Instruction Table Info";
+  }
+
+  typedef std::pair<Function *, Function *> JumpPair;
+  typedef DenseMap<FunctionType *, std::vector<JumpPair> > JumpTables;
+
+  /// Inserts an entry in a table, adding the table if it doesn't exist.
+  void insertEntry(FunctionType *TableFunTy, Function *Target, Function *Jump);
+
+  /// Gets the tables.
+  const JumpTables &getTables() const { return Tables; }
+
+private:
+  JumpTables Tables;
+};
+}
+
+#endif /* LLVM_ANALYSIS_JUMPINSTRTABLEINFO_H */

include/llvm/Analysis/Passes.h

@@ -142,6 +142,10 @@ namespace llvm {
   // information and prints it with -analyze.
   //
   FunctionPass *createMemDepPrinter();
+
+  // createJumpInstrTableInfoPass - This creates a pass that stores information
+  // about the jump tables created by JumpInstrTables
+  ImmutablePass *createJumpInstrTableInfoPass();
 }
 
 #endif