Question

Previously I had asked how to write then read back IR to/from a file. The read code looked like:

LLVMContext ctx;
SMDiagnostic diag;
Module *m = ParseIRFile( "my_file", diag, ctx );

However, the code I’m trying to retrofit LLVM IR into passes me just a std::istream&. How can I read IR from a std::istream?

I figured out how to use raw_os_ostream to adapt a std::ostream to a raw_ostream for writing a module, but there’s no obvious way to adapt the code for reading, e.g., no MemoryBuffer that adapts a std::istream (unless I missed it).

Answer 1

You should use ParseIR() instead of ParseIRFile(). It gets a MemoryBuffer as parameter, instead of a file name. You can create a MemoryBuffer from a StringRef via its getMemBuffer() factory method:

/// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
/// that InputData must be null terminated if RequiresNullTerminator is true.
static MemoryBuffer *getMemBuffer(StringRef InputData,
                                  StringRef BufferName = "",
                                  bool RequiresNullTerminator = true);

And since a StringRef can be (even implicitly) constructed from an std::string, all you need to do is convert your std::istream to std::string.