[LLVMdev] MSVC-style RTTI and LLVM IR

David Majnemer david.majnemer at gmail.com
Fri Jan 3 17:51:49 PST 2014

Hello all,

MSVC-style RTTI when targeting x86_64 requires creating references to
symbols using image-base relative relocations (IMAGE_REL_AMD64_ADDR32 in
PE/COFF, similar to ELF's R_X86_64_RELATIVE).  This is currently supported
at the MC layer, one may have:

    .quad foo at imgrel

This would create a symbol which points to it's own image-relative offset.

To my knowledge, LLVM IR gives no way to refer to the address of a symbol
using a relocation and thus the above result cannot be obtained.

Seeing as how we want to support MSVC-style RTTI from clang, how should we
represent image-relative relocations in the IR?


David Majnemer
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