[llvm] [Mips] Fix R6 floating-point condition register handling (PR #226838)

[via llvm-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 142817 tests passed
* 3382 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### LLVM
<details>
<summary>LLVM.CodeGen/MIR/Mips/mips32r6-copyPhysReg-fcmp-f64-to-gpr.mir</summary>

```
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 1
c:\_work\llvm-project\llvm-project\build\bin\llc.exe -mtriple=mipsisa32r6-linux-gnu --start-before=mips-set-machine-register-flags -verify-machineinstrs C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\MIR\Mips\mips32r6-copyPhysReg-fcmp-f64-to-gpr.mir -o - | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\MIR\Mips\mips32r6-copyPhysReg-fcmp-f64-to-gpr.mir
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\llc.exe' -mtriple=mipsisa32r6-linux-gnu --start-before=mips-set-machine-register-flags -verify-machineinstrs 'C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\MIR\Mips\mips32r6-copyPhysReg-fcmp-f64-to-gpr.mir' -o -
# .---command stderr------------
# | LLVM ERROR: "mips-set-machine-register-flags" pass is not registered.
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
# | Stack dump:
# | 0.	Program arguments: c:\\_work\\llvm-project\\llvm-project\\build\\bin\\llc.exe -mtriple=mipsisa32r6-linux-gnu --start-before=mips-set-machine-register-flags -verify-machineinstrs C:\\_work\\llvm-project\\llvm-project\\llvm\\test\\CodeGen\\MIR\\Mips\\mips32r6-copyPhysReg-fcmp-f64-to-gpr.mir -o -
# `-----------------------------
# error: command failed with exit status: 1
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' 'C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\MIR\Mips\mips32r6-copyPhysReg-fcmp-f64-to-gpr.mir'
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\MIR\Mips\mips32r6-copyPhysReg-fcmp-f64-to-gpr.mir
# `-----------------------------
# error: command failed with exit status: 2

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/226838