lib/CodeGen/ShadowStackGC.cpp

   1 //===-- ShadowStackGC.cpp - GC support for uncooperative targets ----------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements lowering for the llvm.gc* intrinsics for targets that do
  11 // not natively support them (which includes the C backend). Note that the code
  12 // generated is not quite as efficient as algorithms which generate stack maps
  13 // to identify roots.
  14 //
  15 // This pass implements the code transformation described in this paper:
  16 //   "Accurate Garbage Collection in an Uncooperative Environment"
  17 //   Fergus Henderson, ISMM, 2002
  18 //
  19 // In runtime/GC/SemiSpace.cpp is a prototype runtime which is compatible with
  20 // ShadowStackGC.
  21 //
  22 // In order to support this particular transformation, all stack roots are
  23 // coallocated in the stack. This allows a fully target-independent stack map
  24 // while introducing only minor runtime overhead.
  25 //
  26 //===----------------------------------------------------------------------===//
  27
  28 #include "llvm/CodeGen/GCs.h"
  29 #include "llvm/ADT/StringExtras.h"
  30 #include "llvm/CodeGen/GCStrategy.h"
  31 #include "llvm/IR/CallSite.h"
  32 #include "llvm/IR/IRBuilder.h"
  33 #include "llvm/IR/IntrinsicInst.h"
  34 #include "llvm/IR/Module.h"
  35
  36 using namespace llvm;
  37
  38 #define DEBUG_TYPE "shadowstackgc"
  39
  40 namespace {
  41 class ShadowStackGC : public GCStrategy {
  42 public:
  43   ShadowStackGC();
  44 };
  45 }
  46
  47 static GCRegistry::Add<ShadowStackGC>
  48     X("shadow-stack", "Very portable GC for uncooperative code generators");
  49
  50 void llvm::linkShadowStackGC() {}
  51
  52 ShadowStackGC::ShadowStackGC() {
  53   InitRoots = true;
  54   CustomRoots = true;
  55 }