Rename Emitter.cpp -> JITEmitter.cpp

llvm-svn: 18132

1 files changed, 425 insertions, 0 deletions

diff --git a/llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp b/llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp
new file mode 100644
index 00000000000..0cd476984f2
--- /dev/null
+++ b/llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -0,0 +1,425 @@
+//===-- JITEmitter.cpp - Write machine code to executable memory ----------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This file defines a MachineCodeEmitter object that is used by the JIT to
+// write machine code to memory and remember where relocatable values are.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "jit"
+#include "JIT.h"
+#include "llvm/Constant.h"
+#include "llvm/Module.h"
+#include "llvm/CodeGen/MachineCodeEmitter.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/CodeGen/MachineRelocation.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetJITInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/System/Memory.h"
+using namespace llvm;
+
+namespace {
+  Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
+  JIT *TheJIT = 0;
+}
+
+
+//===----------------------------------------------------------------------===//
+// JITMemoryManager code.
+//
+namespace {
+  /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
+  /// sane way.  This splits a large block of MAP_NORESERVE'd memory into two
+  /// sections, one for function stubs, one for the functions themselves.  We
+  /// have to do this because we may need to emit a function stub while in the
+  /// middle of emitting a function, and we don't know how large the function we
+  /// are emitting is.  This never bothers to release the memory, because when
+  /// we are ready to destroy the JIT, the program exits.
+  class JITMemoryManager {
+    sys::MemoryBlock  MemBlock;  // Virtual memory block allocated RWX
+    unsigned char *MemBase;      // Base of block of memory, start of stub mem
+    unsigned char *FunctionBase; // Start of the function body area
+    unsigned char *CurStubPtr, *CurFunctionPtr;
+  public:
+    JITMemoryManager();
+    
+    inline unsigned char *allocateStub(unsigned StubSize);
+    inline unsigned char *startFunctionBody();
+    inline void endFunctionBody(unsigned char *FunctionEnd);    
+  };
+}
+
+JITMemoryManager::JITMemoryManager() {
+  // Allocate a 16M block of memory...
+  MemBlock = sys::Memory::AllocateRWX((16 << 20));
+  MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
+  FunctionBase = MemBase + 512*1024; // Use 512k for stubs
+
+  // Allocate stubs backwards from the function base, allocate functions forward
+  // from the function base.
+  CurStubPtr = CurFunctionPtr = FunctionBase;
+}
+
+unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
+  CurStubPtr -= StubSize;
+  if (CurStubPtr < MemBase) {
+    std::cerr << "JIT ran out of memory for function stubs!\n";
+    abort();
+  }
+  return CurStubPtr;
+}
+
+unsigned char *JITMemoryManager::startFunctionBody() {
+  // Round up to an even multiple of 8 bytes, this should eventually be target
+  // specific.
+  return (unsigned char*)(((intptr_t)CurFunctionPtr + 7) & ~7);
+}
+
+void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
+  assert(FunctionEnd > CurFunctionPtr);
+  CurFunctionPtr = FunctionEnd;
+}
+
+//===----------------------------------------------------------------------===//
+// JIT lazy compilation code.
+//
+namespace {
+  /// JITResolver - Keep track of, and resolve, call sites for functions that
+  /// have not yet been compiled.
+  class JITResolver {
+    /// MCE - The MachineCodeEmitter to use to emit stubs with.
+    MachineCodeEmitter &MCE;
+
+    /// LazyResolverFn - The target lazy resolver function that we actually
+    /// rewrite instructions to use.
+    TargetJITInfo::LazyResolverFn LazyResolverFn;
+
+    // FunctionToStubMap - Keep track of the stub created for a particular
+    // function so that we can reuse them if necessary.
+    std::map<Function*, void*> FunctionToStubMap;
+
+    // StubToFunctionMap - Keep track of the function that each stub corresponds
+    // to.
+    std::map<void*, Function*> StubToFunctionMap;
+
+  public:
+    JITResolver(MachineCodeEmitter &mce) : MCE(mce) {
+      LazyResolverFn =
+        TheJIT->getJITInfo().getLazyResolverFunction(JITCompilerFn);
+    }
+
+    /// getFunctionStub - This returns a pointer to a function stub, creating
+    /// one on demand as needed.
+    void *getFunctionStub(Function *F);
+
+    /// AddCallbackAtLocation - If the target is capable of rewriting an
+    /// instruction without the use of a stub, record the location of the use so
+    /// we know which function is being used at the location.
+    void *AddCallbackAtLocation(Function *F, void *Location) {
+      /// Get the target-specific JIT resolver function.
+      StubToFunctionMap[Location] = F;
+      return (void*)LazyResolverFn;
+    }
+
+    /// JITCompilerFn - This function is called to resolve a stub to a compiled
+    /// address.  If the LLVM Function corresponding to the stub has not yet
+    /// been compiled, this function compiles it first.
+    static void *JITCompilerFn(void *Stub);
+  };
+}
+
+/// getJITResolver - This function returns the one instance of the JIT resolver.
+///
+static JITResolver &getJITResolver(MachineCodeEmitter *MCE = 0) {
+  static JITResolver TheJITResolver(*MCE);
+  return TheJITResolver;
+}
+
+/// getFunctionStub - This returns a pointer to a function stub, creating
+/// one on demand as needed.
+void *JITResolver::getFunctionStub(Function *F) {
+  // If we already have a stub for this function, recycle it.
+  void *&Stub = FunctionToStubMap[F];
+  if (Stub) return Stub;
+
+  // Call the lazy resolver function unless we already KNOW it is an external
+  // function, in which case we just skip the lazy resolution step.
+  void *Actual = (void*)LazyResolverFn;
+  if (F->hasExternalLinkage())
+    Actual = TheJIT->getPointerToFunction(F);
+    
+  // Otherwise, codegen a new stub.  For now, the stub will call the lazy
+  // resolver function.
+  Stub = TheJIT->getJITInfo().emitFunctionStub(Actual, MCE);
+
+  if (F->hasExternalLinkage()) {
+    // If we are getting the stub for an external function, we really want the
+    // address of the stub in the GlobalAddressMap for the JIT, not the address
+    // of the external function.
+    TheJIT->updateGlobalMapping(F, Stub);
+  }
+
+  DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub << "] for function '"
+                  << F->getName() << "'\n");
+
+  // Finally, keep track of the stub-to-Function mapping so that the
+  // JITCompilerFn knows which function to compile!
+  StubToFunctionMap[Stub] = F;
+  return Stub;
+}
+
+/// JITCompilerFn - This function is called when a lazy compilation stub has
+/// been entered.  It looks up which function this stub corresponds to, compiles
+/// it if necessary, then returns the resultant function pointer.
+void *JITResolver::JITCompilerFn(void *Stub) {
+  JITResolver &JR = getJITResolver();
+  
+  // The address given to us for the stub may not be exactly right, it might be
+  // a little bit after the stub.  As such, use upper_bound to find it.
+  std::map<void*, Function*>::iterator I =
+    JR.StubToFunctionMap.upper_bound(Stub);
+  assert(I != JR.StubToFunctionMap.begin() && "This is not a known stub!");
+  Function *F = (--I)->second;
+
+  // The target function will rewrite the stub so that the compilation callback
+  // function is no longer called from this stub.
+  JR.StubToFunctionMap.erase(I);
+
+  DEBUG(std::cerr << "JIT: Lazily resolving function '" << F->getName()
+                  << "' In stub ptr = " << Stub << " actual ptr = "
+                  << I->first << "\n");
+
+  void *Result = TheJIT->getPointerToFunction(F);
+
+  // We don't need to reuse this stub in the future, as F is now compiled.
+  JR.FunctionToStubMap.erase(F);
+
+  // FIXME: We could rewrite all references to this stub if we knew them.
+  return Result;
+}
+
+
+//===----------------------------------------------------------------------===//
+// JITEmitter code.
+//
+namespace {
+  /// JITEmitter - The JIT implementation of the MachineCodeEmitter, which is
+  /// used to output functions to memory for execution.
+  class JITEmitter : public MachineCodeEmitter {
+    JITMemoryManager MemMgr;
+
+    // CurBlock - The start of the current block of memory.  CurByte - The
+    // current byte being emitted to.
+    unsigned char *CurBlock, *CurByte;
+
+    // When outputting a function stub in the context of some other function, we
+    // save CurBlock and CurByte here.
+    unsigned char *SavedCurBlock, *SavedCurByte;
+
+    // ConstantPoolAddresses - Contains the location for each entry in the
+    // constant pool.
+    std::vector<void*> ConstantPoolAddresses;
+
+    /// Relocations - These are the relocations that the function needs, as
+    /// emitted.
+    std::vector<MachineRelocation> Relocations;
+  public:
+    JITEmitter(JIT &jit) { TheJIT = &jit; }
+
+    virtual void startFunction(MachineFunction &F);
+    virtual void finishFunction(MachineFunction &F);
+    virtual void emitConstantPool(MachineConstantPool *MCP);
+    virtual void startFunctionStub(unsigned StubSize);
+    virtual void* finishFunctionStub(const Function *F);
+    virtual void emitByte(unsigned char B);
+    virtual void emitWord(unsigned W);
+    virtual void emitWordAt(unsigned W, unsigned *Ptr);
+
+    virtual void addRelocation(const MachineRelocation &MR) {
+      Relocations.push_back(MR);
+    }
+
+    virtual uint64_t getCurrentPCValue();
+    virtual uint64_t getCurrentPCOffset();
+    virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
+
+  private:
+    void *getPointerToGlobal(GlobalValue *GV, void *Reference, bool NoNeedStub);
+  };
+}
+
+MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
+  return new JITEmitter(jit);
+}
+
+void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
+                                     bool DoesntNeedStub) {
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
+    /// FIXME: If we straightened things out, this could actually emit the
+    /// global immediately instead of queuing it for codegen later!
+    GlobalVariable *GV = cast<GlobalVariable>(V);
+    return TheJIT->getOrEmitGlobalVariable(GV);
+  }
+
+  // If we have already compiled the function, return a pointer to its body.
+  Function *F = cast<Function>(V);
+  void *ResultPtr = TheJIT->getPointerToGlobalIfAvailable(F);
+  if (ResultPtr) return ResultPtr;
+
+  if (F->hasExternalLinkage()) {
+    // If this is an external function pointer, we can force the JIT to
+    // 'compile' it, which really just adds it to the map.
+    if (DoesntNeedStub)
+      return TheJIT->getPointerToFunction(F);
+
+    return getJITResolver(this).getFunctionStub(F);
+  }
+
+  // Okay, the function has not been compiled yet, if the target callback
+  // mechanism is capable of rewriting the instruction directly, prefer to do
+  // that instead of emitting a stub.
+  if (DoesntNeedStub)
+    return getJITResolver(this).AddCallbackAtLocation(F, Reference);
+
+  // Otherwise, we have to emit a lazy resolving stub.
+  return getJITResolver(this).getFunctionStub(F);
+}
+
+void JITEmitter::startFunction(MachineFunction &F) {
+  CurByte = CurBlock = MemMgr.startFunctionBody();
+  TheJIT->addGlobalMapping(F.getFunction(), CurBlock);
+}
+
+void JITEmitter::finishFunction(MachineFunction &F) {
+  MemMgr.endFunctionBody(CurByte);
+  ConstantPoolAddresses.clear();
+  NumBytes += CurByte-CurBlock;
+
+  if (!Relocations.empty()) {
+    // Resolve the relocations to concrete pointers.
+    for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
+      MachineRelocation &MR = Relocations[i];
+      void *ResultPtr;
+      if (MR.isString())
+        ResultPtr = TheJIT->getPointerToNamedFunction(MR.getString());
+      else
+        ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
+                                       CurBlock+MR.getMachineCodeOffset(),
+                                       MR.doesntNeedFunctionStub());
+      MR.setResultPointer(ResultPtr);
+    }
+
+    TheJIT->getJITInfo().relocate(CurBlock, &Relocations[0],
+                                  Relocations.size());
+  }
+
+  DEBUG(std::cerr << "JIT: Finished CodeGen of [" << (void*)CurBlock
+                  << "] Function: " << F.getFunction()->getName()
+                  << ": " << CurByte-CurBlock << " bytes of text, "
+                  << Relocations.size() << " relocations\n");
+  Relocations.clear();
+}
+
+void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
+  const std::vector<Constant*> &Constants = MCP->getConstants();
+  if (Constants.empty()) return;
+
+  std::vector<unsigned> ConstantOffset;
+  ConstantOffset.reserve(Constants.size());
+
+  // Calculate how much space we will need for all the constants, and the offset
+  // each one will live in.
+  unsigned TotalSize = 0;
+  for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
+    const Type *Ty = Constants[i]->getType();
+    unsigned Size      = TheJIT->getTargetData().getTypeSize(Ty);
+    unsigned Alignment = TheJIT->getTargetData().getTypeAlignment(Ty);
+    // Make sure to take into account the alignment requirements of the type.
+    TotalSize = (TotalSize + Alignment-1) & ~(Alignment-1);
+
+    // Remember the offset this element lives at.
+    ConstantOffset.push_back(TotalSize);
+    TotalSize += Size;   // Reserve space for the constant.
+  }
+
+  // Now that we know how much memory to allocate, do so.
+  char *Pool = new char[TotalSize];
+
+  // Actually output all of the constants, and remember their addresses.
+  for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
+    void *Addr = Pool + ConstantOffset[i];
+    TheJIT->InitializeMemory(Constants[i], Addr);
+    ConstantPoolAddresses.push_back(Addr);
+  }
+}
+
+void JITEmitter::startFunctionStub(unsigned StubSize) {
+  SavedCurBlock = CurBlock;  SavedCurByte = CurByte;
+  CurByte = CurBlock = MemMgr.allocateStub(StubSize);
+}
+
+void *JITEmitter::finishFunctionStub(const Function *F) {
+  NumBytes += CurByte-CurBlock;
+  std::swap(CurBlock, SavedCurBlock);
+  CurByte = SavedCurByte;
+  return SavedCurBlock;
+}
+
+void JITEmitter::emitByte(unsigned char B) {
+  *CurByte++ = B;   // Write the byte to memory
+}
+
+void JITEmitter::emitWord(unsigned W) {
+  // This won't work if the endianness of the host and target don't agree!  (For
+  // a JIT this can't happen though.  :)
+  *(unsigned*)CurByte = W;
+  CurByte += sizeof(unsigned);
+}
+
+void JITEmitter::emitWordAt(unsigned W, unsigned *Ptr) {
+  *Ptr = W;
+}
+
+// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
+// in the constant pool that was last emitted with the 'emitConstantPool'
+// method.
+//
+uint64_t JITEmitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
+  assert(ConstantNum < ConstantPoolAddresses.size() &&
+	 "Invalid ConstantPoolIndex!");
+  return (intptr_t)ConstantPoolAddresses[ConstantNum];
+}
+
+// getCurrentPCValue - This returns the address that the next emitted byte
+// will be output to.
+//
+uint64_t JITEmitter::getCurrentPCValue() {
+  return (intptr_t)CurByte;
+}
+
+uint64_t JITEmitter::getCurrentPCOffset() {
+  return (intptr_t)CurByte-(intptr_t)CurBlock;
+}
+
+// getPointerToNamedFunction - This function is used as a global wrapper to
+// JIT::getPointerToNamedFunction for the purpose of resolving symbols when
+// bugpoint is debugging the JIT. In that scenario, we are loading an .so and
+// need to resolve function(s) that are being mis-codegenerated, so we need to
+// resolve their addresses at runtime, and this is the way to do it.
+extern "C" {
+  void *getPointerToNamedFunction(const char *Name) {
+    Module &M = TheJIT->getModule();
+    if (Function *F = M.getNamedFunction(Name))
+      return TheJIT->getPointerToFunction(F);
+    return TheJIT->getPointerToNamedFunction(Name);
+  }
+}