[llvm] [AArch64][GISel] Assign registers into FPR if they feed into FP instructions indirectly via PHI (PR #94618)

[via llvm-commits]

Him188 wrote:

> Which RegisterBank uses this phi? Which RegisterBank uses this select? Which RegisterBank uses this G_LOAD?

We don't always know these during RBS, because RBS assigns each instruction one by one and the defs might come from another block that is visited after we assign phi.

But it is possible to add a combiner instead to detect the pattern. 


https://github.com/llvm/llvm-project/pull/94618