Support: Implement StreamingMemoryObject::getPointer

The implementation is fairly obvious.  This is preparation for using
some blobs in bitcode.

For clarity (and perhaps future-proofing?), I moved the call to
JumpToBit in BitstreamCursor::readRecord ahead of calling
MemoryObject::getPointer, since JumpToBit can theoretically (a) read
bytes, which (b) invalidates the blob pointer.

This isn't strictly necessary the two memory objects we have:

  - The return of RawMemoryObject::getPointer is valid until the memory
    object is destroyed.

  - StreamingMemoryObject::getPointer is valid until the next chunk is
    read from the stream.  Since the JumpToBit call is only going ahead
    to a word boundary, we'll never load another chunk.

However, reordering makes it clear by inspection that the blob returned
by BitstreamCursor::readRecord will be valid.

I added some tests for StreamingMemoryObject::getPointer and
BitstreamCursor::readRecord.

llvm-svn: 264549

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Support/StreamingMemoryObject.cpp b/llvm/lib/Support/StreamingMemoryObject.cpp
index 5a44e62..fb56617 100644
--- a/llvm/lib/Support/StreamingMemoryObject.cpp
+++ b/llvm/lib/Support/StreamingMemoryObject.cpp
@@ -104,6 +104,12 @@ uint64_t StreamingMemoryObject::readBytes(uint8_t *Buf, uint64_t Size,
   return Size;
 }
 
+const uint8_t *StreamingMemoryObject::getPointer(uint64_t Address,
+                                                 uint64_t Size) const {
+  fetchToPos(Address + Size - 1);
+  return &Bytes[Address + BytesSkipped];
+}
+
 bool StreamingMemoryObject::dropLeadingBytes(size_t s) {
   if (BytesRead < s) return true;
   BytesSkipped = s;