[llvm] [X86] Use unsigned comparison for stack clash probing loop (PR #192355)

[Nick Desaulniers via llvm-commits]

nickdesaulniers wrote:

> Did you check if we have the same issue on other non-intel architectures?

It looks like only `X86TargetLowering` has the method `EmitLoweredProbedAlloca`.

I took a quick peek at:
*   `llvm-project/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp`
*   `llvm-project/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp`
*   `llvm-project/llvm/lib/Target/RISCV/RISCVISelLowering.cpp`
*   `llvm-project/llvm/lib/Target/PowerPC/PPCISelLowering.cpp`
*   `llvm-project/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp`

which reference `*PROBED_ALLOCA*`.

It looks like RISCV 32b has the same issue; it's using `BLT` instead of `BLTU`.  I'll post a second patch for that.

https://github.com/llvm/llvm-project/pull/192355