Concurrency support for PNaCl ABI

lib/Transforms/NaCl/ResolvePNaClIntrinsics.cpp

 //===- ResolvePNaClIntrinsics.cpp - Resolve calls to PNaCl intrinsics ----====//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass resolves calls to PNaCl stable bitcode intrinsics. It is
 // normally run in the PNaCl translator.
 //
-// Running AddPNaClExternalDeclsPass is a precondition for running this pass.
-// They are separate because one is a ModulePass and the other is a
-// FunctionPass.
+// Running AddPNaClExternalDeclsPass is a precondition for running this
+// pass. They are separate because one is a ModulePass and the other is
+// a FunctionPass.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/IR/Constant.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
+#include "llvm/IR/NaClIntrinsics.h"
+#include "llvm/IR/Value.h"
 #include "llvm/Pass.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Transforms/NaCl.h"
 
 using namespace llvm;
 
 namespace {
-  class ResolvePNaClIntrinsics : public FunctionPass {
+class ResolvePNaClIntrinsics : public FunctionPass {
+public:
+  ResolvePNaClIntrinsics() : FunctionPass(ID) {
+    initializeResolvePNaClIntrinsicsPass(*PassRegistry::getPassRegistry());
+  }
+
+  static char ID;
+  virtual bool runOnFunction(Function &F);
+
+  // Interface specifying how calls should be resolved.

[eliben, 2013/07/03 16:06:05]

Explain how it's used and what has to be implemented by subclasses

[JF, 2013/07/03 20:58:35]

Done. I edited this comment and a few others, and 's/walk/visit/g'.

+  class CallResolver {
   public:
-    ResolvePNaClIntrinsics() : FunctionPass(ID) {
-      initializeResolvePNaClIntrinsicsPass(*PassRegistry::getPassRegistry());
-    }
-
-    static char ID;
-    virtual bool runOnFunction(Function &F);
+    // Called once per call to the intrinsic in the module.
+    bool Resolve(IntrinsicInst *Call) {
+      // To be a well-behaving FunctionPass, don't touch uses in other
+      // functions. These will be handled when the pass manager gets to
+      // those functions.
+      if (Call->getParent()->getParent() == &F)
+        return DoResolve(Call);
+      return false;
+    }
+    Function *getDeclaration() const { return DoGetDeclaration(); }
+    std::string getName() { return Intrinsic::getName(IntrinsicID); }
+
+  protected:
+    Function &F;
+    Module *M;
+    Intrinsic::ID IntrinsicID;
+
+    CallResolver(Function &F, Intrinsic::ID IntrinsicID)
+        : F(F), M(F.getParent()), IntrinsicID(IntrinsicID) {}
+    virtual ~CallResolver() {}
+    virtual Function *DoGetDeclaration() const = 0;
+    virtual bool DoResolve(IntrinsicInst *Call) = 0;
+
   private:
-    // Some intrinsic calls are resolved simply by replacing the call with a
-    // call to an alternative function with exactly the same type.
-    bool resolveSimpleCall(Function &F, Intrinsic::ID IntrinsicID,
-                           const char *TargetFunctionName);
+    CallResolver(const CallResolver &) LLVM_DELETED_FUNCTION;
+    CallResolver &operator=(const CallResolver &) LLVM_DELETED_FUNCTION;
   };
+
+private:
+  // Walk calls matching the resolver's declaration, and invoke the
+  // CallResolver methods on each of them.
+  bool walkCalls(CallResolver &Resolver);
+};
+
+// Rewrite intrinsic calls to another function.
+class SimpleCallResolver : public ResolvePNaClIntrinsics::CallResolver {
+public:
+  SimpleCallResolver(Function &F, Intrinsic::ID IntrinsicID,
+                     const char *TargetFunctionName)
+      : CallResolver(F, IntrinsicID),
+        TargetFunction(M->getFunction(TargetFunctionName)) {
+    // Expect to find the target function for this intrinsic already
+    // declared, even if it is never used.
+    if (!TargetFunction)
+      report_fatal_error(std::string(
+          "Expected to find external declaration of ") + TargetFunctionName);
+  }
+  virtual ~SimpleCallResolver() {}
+
+private:
+  Function *TargetFunction;
+
+  virtual Function *DoGetDeclaration() const {
+    return Intrinsic::getDeclaration(M, IntrinsicID);
+  }
+
+  virtual bool DoResolve(IntrinsicInst *Call) {
+    Call->setCalledFunction(TargetFunction);
+    return true;
+  }
+
+  SimpleCallResolver(const SimpleCallResolver &) LLVM_DELETED_FUNCTION;
+  SimpleCallResolver &operator=(const SimpleCallResolver &)
+  LLVM_DELETED_FUNCTION;
+};
+
+// Rewrite atomic intrinsics to LLVM IR instructions.
+class AtomicCallResolver : public ResolvePNaClIntrinsics::CallResolver {
+public:
+  AtomicCallResolver(Function &F, NaCl::AtomicIntrinsics::const_iterator I)
+      : CallResolver(F, I->ID), AI(I) {}
+  virtual ~AtomicCallResolver() {}
+
+private:
+  NaCl::AtomicIntrinsics::const_iterator AI;
+
+  virtual Function *DoGetDeclaration() const { return AI->getDeclaration(M); }
+
+  virtual bool DoResolve(IntrinsicInst *Call) {
+    // Assume the @llvm.nacl.atomic.* intrinsics follow the PNaCl ABI:
+    // this should have been checked by the verifier.
+    const Twine Name("");
+    bool isVolatile = false;
+    SynchronizationScope SS = CrossThread;
+    Instruction *I;
+
+    switch (Call->getIntrinsicID()) {
+    default:
+      llvm_unreachable("unknown atomic intrinsic");
+    case Intrinsic::nacl_atomic_load:
+      I = new LoadInst(Call->getArgOperand(0), Name, isVolatile,
+                       alignmentFromPointer(Call->getArgOperand(0)),
+                       thawMemoryOrder(Call->getArgOperand(1)), SS, Call);
+      break;
+    case Intrinsic::nacl_atomic_store:
+      I = new StoreInst(Call->getArgOperand(0), Call->getArgOperand(1),
+                        isVolatile,
+                        alignmentFromPointer(Call->getArgOperand(1)),
+                        thawMemoryOrder(Call->getArgOperand(2)), SS, Call);
+      break;
+    case Intrinsic::nacl_atomic_rmw:
+      I = new AtomicRMWInst(thawRMWOperation(Call->getArgOperand(0)),
+                            Call->getArgOperand(1), Call->getArgOperand(2),
+                            thawMemoryOrder(Call->getArgOperand(3)), SS, Call);
+      break;
+    case Intrinsic::nacl_atomic_cmpxchg:
+      // TODO LLVM currently doesn't support specifying separate memory
+      //      orders for compare exchange's success and failure cases:
+      //      LLVM IR implicitly drops the Release part of the specified
+      //      memory order on failure. It is therefore correct to map
+      //      the success memory order onto the LLVM IR and ignore the
+      //      failure one.
+      I = new AtomicCmpXchgInst(Call->getArgOperand(0), Call->getArgOperand(1),
+                                Call->getArgOperand(2),
+                                thawMemoryOrder(Call->getArgOperand(3)), SS,
+                                Call);
+      break;
+    case Intrinsic::nacl_atomic_fence:
+      I = new FenceInst(M->getContext(),
+                        thawMemoryOrder(Call->getArgOperand(0)), SS, Call);
+      break;
+    }
+    I->setDebugLoc(Call->getDebugLoc());
+    Call->replaceAllUsesWith(I);
+    Call->eraseFromParent();
+
+    return true;
+  }
+
+  unsigned alignmentFromPointer(const Value *Ptr) const {
+    unsigned BitWidth = cast<IntegerType>(
+        cast<PointerType>(Ptr->getType())->getElementType())->getBitWidth();
+    return 1 << (CountTrailingZeros_32(BitWidth) - 3);
+  }
+
+  AtomicOrdering thawMemoryOrder(const Value *MemoryOrder) const {
+    NaCl::MemoryOrder MO = (NaCl::MemoryOrder)
+        cast<Constant>(MemoryOrder)->getUniqueInteger().getLimitedValue();
+    switch (MO) {
+    // Only valid values should pass validation.
+    default: llvm_unreachable("unknown memory order");
+    case NaCl::MemoryOrderRelaxed: return Monotonic;
+    // TODO Consume is unspecified by LLVM's internal IR.
+    case NaCl::MemoryOrderConsume: return SequentiallyConsistent;
+    case NaCl::MemoryOrderAcquire: return Acquire;
+    case NaCl::MemoryOrderRelease: return Release;
+    case NaCl::MemoryOrderAcquireRelease: return AcquireRelease;
+    case NaCl::MemoryOrderSequentiallyConsistent: return SequentiallyConsistent;
+    }
+  }
+
+  AtomicRMWInst::BinOp thawRMWOperation(const Value *Operation) const {
+    NaCl::AtomicRMWOperation Op = (NaCl::AtomicRMWOperation)
+        cast<Constant>(Operation)->getUniqueInteger().getLimitedValue();
+    switch (Op) {
+    // Only valid values should pass validation.
+    default: llvm_unreachable("unknown atomic RMW operation");
+    case NaCl::AtomicAdd: return AtomicRMWInst::Add;
+    case NaCl::AtomicSub: return AtomicRMWInst::Sub;
+    case NaCl::AtomicOr:  return AtomicRMWInst::Or;
+    case NaCl::AtomicAnd: return AtomicRMWInst::And;
+    case NaCl::AtomicXor: return AtomicRMWInst::Xor;
+    case NaCl::AtomicExchange: return AtomicRMWInst::Xchg;
+    }
+  }
+
+  AtomicCallResolver(const AtomicCallResolver &);
+  AtomicCallResolver &operator=(const AtomicCallResolver &);
+};
 }
 
-bool ResolvePNaClIntrinsics::resolveSimpleCall(Function &F,
-                                               Intrinsic::ID IntrinsicID,
-                                               const char *TargetFunctionName) {
-  Module *M = F.getParent();
+bool ResolvePNaClIntrinsics::walkCalls(
+    ResolvePNaClIntrinsics::CallResolver &Resolver) {
   bool Changed = false;
-  Function *IntrinsicFunction = Intrinsic::getDeclaration(M, IntrinsicID);
-
-  if (!IntrinsicFunction) {
+  Function *IntrinsicFunction = Resolver.getDeclaration();
+  if (!IntrinsicFunction)
     return false;
-  }
-
-  // Expect to find the target function for this intrinsic already declared
-  Function *TargetFunction = M->getFunction(TargetFunctionName);
-  if (!TargetFunction) {
-    report_fatal_error(
-        std::string("Expected to find external declaration of ") +
-        TargetFunctionName);
-  }
 
   for (Value::use_iterator UI = IntrinsicFunction->use_begin(),
-                           UE = IntrinsicFunction->use_end(); UI != UE;) {
+                           UE = IntrinsicFunction->use_end();
+       UI != UE;) {
     // At this point, the only uses of the intrinsic can be calls, since
     // we assume this pass runs on bitcode that passed ABI verification.
-    CallInst *Call = dyn_cast<CallInst>(*UI++);
-
-    if (!Call) {
-      report_fatal_error(
-          std::string("Expected use of intrinsic to be a call: ") +
-          Intrinsic::getName(IntrinsicID));
-    }
-
-    // To be a well-behaving FunctionPass, don't touch uses in other
-    // functions. These will be handled when the pass manager gets to those
-    // functions.
-    if (Call->getParent()->getParent() == &F) {
-      Call->setCalledFunction(TargetFunction);
-      Changed = true;
-    }
+    IntrinsicInst *Call = dyn_cast<IntrinsicInst>(*UI++);
+    if (!Call)
+      report_fatal_error("Expected use of intrinsic to be a call: " +
+                         Resolver.getName());
+
+    Changed |= Resolver.Resolve(Call);
   }
 
   return Changed;
 }
 
 bool ResolvePNaClIntrinsics::runOnFunction(Function &F) {
-  bool Changed = resolveSimpleCall(F, Intrinsic::nacl_setjmp, "setjmp");
-  Changed |= resolveSimpleCall(F, Intrinsic::nacl_longjmp, "longjmp");
+  bool Changed = false;
+
+  SimpleCallResolver SetJmpResolver(F, Intrinsic::nacl_setjmp, "setjmp");
+  SimpleCallResolver LongJmpResolver(F, Intrinsic::nacl_longjmp, "longjmp");
+  Changed |= walkCalls(SetJmpResolver);
+  Changed |= walkCalls(LongJmpResolver);
+
+  NaCl::AtomicIntrinsics AI(F.getParent()->getContext());
+  for (NaCl::AtomicIntrinsics::const_iterator I = AI.begin(), E = AI.end();
+       I != E; ++I) {
+    AtomicCallResolver AtomicResolver(F, I);
+    Changed |= walkCalls(AtomicResolver);
+  }
+
   return Changed;
 }
 
 char ResolvePNaClIntrinsics::ID = 0;
 INITIALIZE_PASS(ResolvePNaClIntrinsics, "resolve-pnacl-intrinsics",
                 "Resolve PNaCl intrinsic calls", false, false)
 
 FunctionPass *llvm::createResolvePNaClIntrinsicsPass() {
   return new ResolvePNaClIntrinsics();
 }