LLVM fork for squiid.
https://github.com/llvm/llvm-project/
ccbbb8f8b9
Summary: After basic block reordering, it may be possible that the reordered function is now larger than the original because of the following reasons: - jump offsets may change, forcing some jump instructions to use 4-byte immediate operand instead of the 1-byte, shorter version. - fall-throughs change, forcing us to emit an extra jump instruction to jump to the original fall-through at the end of a basic block. Since we currently do not change function addresses, we need to rewrite the function back in the binary in the original location. If it doesn't fit, we were dropping the function. This patch adds a flag -split-functions that tells llvm-flo to split hot functions into hot and cold separate regions. The hot region is written back in the original function location, while the cold region is written in a separate, far-away region reserved to flo via a linker script. This patch also adds the logic to create and extra FDE to supply unwinding information to the cold part of the function. Owing to this, we now need to rewrite .eh_frame_hdr to another location and patch the EH_FRAME ELF segment to point to this new .eh_frame_hdr. (cherry picked from FBD2677996) |
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