Enable streaming of bitcode

This CL delays reading of function bodies from initial parse until
materialization, allowing overlap of compilation with bitcode download.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149918 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/StreamableMemoryObject.cpp

@@ -0,0 +1,137 @@
+//===- StreamableMemoryObject.cpp - Streamable data interface - -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/StreamableMemoryObject.h"
+#include <cassert>
+#include <cstring>
+
+
+using namespace llvm;
+
+namespace {
+
+class RawMemoryObject : public StreamableMemoryObject {
+public:
+  RawMemoryObject(const unsigned char *Start, const unsigned char *End) :
+    FirstChar(Start), LastChar(End) {
+    assert(LastChar > FirstChar && "Invalid start/end range");
+  }
+
+  virtual uint64_t getBase() const { return 0; }
+  virtual uint64_t getExtent() { return LastChar - FirstChar; }
+  virtual int readByte(uint64_t address, uint8_t* ptr);
+  virtual int readBytes(uint64_t address,
+                        uint64_t size,
+                        uint8_t* buf,
+                        uint64_t* copied);
+  virtual const uint8_t *getPointer(uint64_t address, uint64_t size);
+  virtual bool isValidAddress(uint64_t address) {return validAddress(address);}
+  virtual bool isObjectEnd(uint64_t address) {return objectEnd(address);}
+
+private:
+  const uint8_t* const FirstChar;
+  const uint8_t* const LastChar;
+
+  // These are implemented as inline functions here to avoid multiple virtual
+  // calls per public function
+  bool validAddress(uint64_t address) {
+    return static_cast<ptrdiff_t>(address) < LastChar - FirstChar;
+  }
+  bool objectEnd(uint64_t address) {
+    return static_cast<ptrdiff_t>(address) == LastChar - FirstChar;
+  }
+
+  RawMemoryObject(const RawMemoryObject&);  // DO NOT IMPLEMENT
+  void operator=(const RawMemoryObject&);  // DO NOT IMPLEMENT
+};
+
+int RawMemoryObject::readByte(uint64_t address, uint8_t* ptr) {
+  if (!validAddress(address)) return -1;
+  *ptr = *((uint8_t *)(uintptr_t)(address + FirstChar));
+  return 0;
+}
+
+int RawMemoryObject::readBytes(uint64_t address,
+                               uint64_t size,
+                               uint8_t* buf,
+                               uint64_t* copied) {
+  if (!validAddress(address) || !validAddress(address + size - 1)) return -1;
+  memcpy(buf, (uint8_t *)(uintptr_t)(address + FirstChar), size);
+  if (copied) *copied = size;
+  return size;
+}
+
+const uint8_t *RawMemoryObject::getPointer(uint64_t address, uint64_t size) {
+  return FirstChar + address;
+}
+} // anonymous namespace
+
+namespace llvm {
+// If the bitcode has a header, then its size is known, and we don't have to
+// block until we actually want to read it.
+bool StreamingMemoryObject::isValidAddress(uint64_t address) {
+  if (ObjectSize && address < ObjectSize) return true;
+    return fetchToPos(address);
+}
+
+bool StreamingMemoryObject::isObjectEnd(uint64_t address) {
+  if (ObjectSize) return address == ObjectSize;
+  fetchToPos(address);
+  return address == ObjectSize && address != 0;
+}
+
+uint64_t StreamingMemoryObject::getExtent() {
+  if (ObjectSize) return ObjectSize;
+  size_t pos = BytesRead + kChunkSize;
+  // keep fetching until we run out of bytes
+  while (fetchToPos(pos)) pos += kChunkSize;
+  return ObjectSize;
+}
+
+int StreamingMemoryObject::readByte(uint64_t address, uint8_t* ptr) {
+  if (!fetchToPos(address)) return -1;
+  *ptr = Bytes[address + BytesSkipped];
+  return 0;
+}
+
+int StreamingMemoryObject::readBytes(uint64_t address,
+                                     uint64_t size,
+                                     uint8_t* buf,
+                                     uint64_t* copied) {
+  if (!fetchToPos(address + size - 1)) return -1;
+  memcpy(buf, &Bytes[address + BytesSkipped], size);
+  if (copied) *copied = size;
+  return 0;
+}
+
+bool StreamingMemoryObject::dropLeadingBytes(size_t s) {
+  if (BytesRead < s) return true;
+  BytesSkipped = s;
+  BytesRead -= s;
+  return false;
+}
+
+void StreamingMemoryObject::setKnownObjectSize(size_t size) {
+  ObjectSize = size;
+  Bytes.reserve(size);
+}
+
+StreamableMemoryObject *getNonStreamedMemoryObject(
+    const unsigned char *Start, const unsigned char *End) {
+  return new RawMemoryObject(Start, End);
+}
+
+StreamableMemoryObject::~StreamableMemoryObject() { }
+
+StreamingMemoryObject::StreamingMemoryObject(DataStreamer *streamer) :
+  Bytes(kChunkSize), Streamer(streamer), BytesRead(0), BytesSkipped(0),
+  ObjectSize(0), EOFReached(false) {
+  BytesRead = streamer->GetBytes(&Bytes[0], kChunkSize);
+}
+}