[llvm] [PowerPC] Respect endianness when bitcasting to fp128 (PR #95931)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 approved this pull request.

LGTM. Thanks very much for fixing this.

For an i128 value, its higher 64 bit and its lower 64 bit are passed with different GPRs on 64-bit BE/LE, to make the bit order be same in the final VSR (what bitcast mean), the swap based on LE code generation looks correct to me.

https://github.com/llvm/llvm-project/pull/95931