The code would cause LLVM to emit a jump table for the switch in the loop over
the dynamic tags. That jump table was far enough away that the compiler decided
to go through the GOT, which would of course break at this early stage as we
haven't applied MIPS's local GOT relocations yet, nor can we until we've walked
through the _DYNAMIC array.
The first attempt at rewriting this used code like this:
var sorted_dynv = [_]elf.Addr{0} ** elf.DT_NUM;
But this is also problematic as it results in a memcpy() call. Instead, we
explicitly initialize it to undefined and use a loop of volatile stores to
clear it.
This prevents it from trying to access thread local storage before it
has set up thread local storage, particularly when code coverage
instrumentation is enabled.
`Elf*_Rela` relocations store their argument in `r_addend`, including for `R_*_RELATIVE` relocations. Unlike `Elf*_Rel` relocations, they are not applied as a delta to the destination virtual address. Instead, they are computed from `base_address + r_addend` directly.
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
* Don't skip the TLS initialization (Fixes#9083)
* Add a test case where a PIE program is built and run
* Refactor the common initialization code in the Linux startup
sequence.
