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/DataStream.cpp

@@ -0,0 +1,96 @@
+//===--- llvm/Support/DataStream.cpp - Lazy streamed Data               ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements DataStreamer, which fetches bytes of Data from
+// a stream source. It provides support for streaming (lazy reading) of
+// bitcode. An example implementation of streaming from a file or stdin
+// is included.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "Data-stream"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/DataStream.h"
+#include "llvm/Support/system_error.h"
+#include <string>
+#include <cerrno>
+#include <cstdio>
+#if !defined(_MSC_VER) && !defined(__MINGW32__)
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+#include <fcntl.h>
+using namespace llvm;
+
+// Interface goals:
+// * StreamableMemoryObject doesn't care about complexities like using
+//   threads/async callbacks to actually overlap download+compile
+// * Don't want to duplicate Data in memory
+// * Don't need to know total Data len in advance
+// Non-goals:
+// StreamableMemoryObject already has random access so this interface only does
+// in-order streaming (no arbitrary seeking, else we'd have to buffer all the
+// Data here in addition to MemoryObject).  This also means that if we want
+// to be able to to free Data, BitstreamBytes/BitcodeReader will implement it
+
+STATISTIC(NumStreamFetches, "Number of calls to Data stream fetch");
+
+namespace llvm {
+DataStreamer::~DataStreamer() {}
+}
+
+namespace {
+
+const static error_code success;
+
+// Very simple stream backed by a file. Mostly useful for stdin and debugging;
+// actual file access is probably still best done with mmap.
+class DataFileStreamer : public DataStreamer {
+ int Fd;
+public:
+  DataFileStreamer() : Fd(0) {}
+  virtual ~DataFileStreamer() {
+    close(Fd);
+  }
+  virtual size_t GetBytes(unsigned char *buf, size_t len) {
+    NumStreamFetches++;
+    return read(Fd, buf, len);
+  }
+
+  error_code OpenFile(const std::string &Filename) {
+    int OpenFlags = O_RDONLY;
+#ifdef O_BINARY
+    OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
+#endif
+    if (Filename == "-")
+      Fd = 0;
+    else
+      Fd = ::open(Filename.c_str(), OpenFlags);
+    if (Fd == -1) return error_code(errno, posix_category());
+      return success;
+  }
+};
+
+}
+
+namespace llvm {
+DataStreamer *getDataFileStreamer(const std::string &Filename,
+                                  std::string *StrError) {
+  DataFileStreamer *s = new DataFileStreamer();
+  error_code e = s->OpenFile(Filename);
+  if (e != success) {
+    *StrError = std::string("Could not open ") + Filename + ": " +
+        e.message() + "\n";
+    return NULL;
+  }
+  return s;
+}
+
+}