MCAsmBackend::applyFixup: Change `Data` to indicate the relocated location

`Data` now references the first byte of the fixup offset within the current fragment.

MCAssembler::layout asserts that the fixup offset is within either the
fixed-size content or the optional variable-size tail, as this is the
most the generic code can validate without knowing the target-specific
fixup size.

Many backends applyFixup assert
```
assert(Offset + Size <= F.getSize() && "Invalid fixup offset!");
```

This refactoring allows a subsequent change to move the fixed-size
content outside of MCSection::ContentStorage, fixing the
-fsanitize=pointer-overflow issue of #150846

Pull Request: https://github.com/llvm/llvm-project/pull/151724

0 files changed, 0 insertions, 0 deletions