[llvm] [TableGen] Avoid assignmentInAssert warning (PR #139715)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `arc-builder` running on `arc-worker` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/3/builds/15859

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: TableGen/GlobalISelCombinerEmitter/match-table-imms.td' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
/buildbot/worker/arc-folder/build/bin/llvm-tblgen -I /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/../../../include -gen-global-isel-combiner      -combiners=MyCombiner /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/match-table-imms.td |  /buildbot/worker/arc-folder/build/bin/FileCheck /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/match-table-imms.td # RUN: at line 1
+ /buildbot/worker/arc-folder/build/bin/FileCheck /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/match-table-imms.td
+ /buildbot/worker/arc-folder/build/bin/llvm-tblgen -I /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/../../../include -gen-global-isel-combiner -combiners=MyCombiner /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/match-table-imms.td
llvm-tblgen: /buildbot/worker/arc-folder/llvm-project/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp:2615: virtual void {anonymous}::GICombinerEmitter::emitTestSimplePredicate(llvm::raw_ostream&): Assertion `ExpectedID == ID && "combine rules are not ordered!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /buildbot/worker/arc-folder/build/bin/llvm-tblgen -I /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/../../../include -gen-global-isel-combiner -combiners=MyCombiner /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/match-table-imms.td
 #0 0x000000000075f638 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/buildbot/worker/arc-folder/build/bin/llvm-tblgen+0x75f638)
 #1 0x000000000075ced5 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #2 0x00007fc522f66630 __restore_rt sigaction.c:0:0
 #3 0x00007fc521cb63d7 raise (/usr/lib64/libc.so.6+0x363d7)
 #4 0x00007fc521cb7ac8 abort (/usr/lib64/libc.so.6+0x37ac8)
 #5 0x00007fc521caf1a6 __assert_fail_base (/usr/lib64/libc.so.6+0x2f1a6)
 #6 0x00007fc521caf252 (/usr/lib64/libc.so.6+0x2f252)
 #7 0x000000000062331b (/buildbot/worker/arc-folder/build/bin/llvm-tblgen+0x62331b)
 #8 0x000000000047aca5 llvm::GlobalISelMatchTableExecutorEmitter::emitExecutorImpl(llvm::raw_ostream&, llvm::gi::MatchTable const&, llvm::ArrayRef<llvm::gi::LLTCodeGen>, llvm::ArrayRef<llvm::gi::RuleMatcher>, llvm::ArrayRef<llvm::Record const*>, llvm::ArrayRef<llvm::StringRef>, llvm::StringRef) (/buildbot/worker/arc-folder/build/bin/llvm-tblgen+0x47aca5)
 #9 0x000000000063b9ba EmitGICombiner(llvm::RecordKeeper const&, llvm::raw_ostream&) GlobalISelCombinerEmitter.cpp:0:0
#10 0x000000000079b6bb llvm::TableGen::Emitter::ApplyCallback(llvm::RecordKeeper const&, llvm::raw_ostream&) (/buildbot/worker/arc-folder/build/bin/llvm-tblgen+0x79b6bb)
#11 0x000000000076a8f0 llvm::TableGenMain(char const*, std::function<bool (llvm::raw_ostream&, llvm::RecordKeeper const&)>) (/buildbot/worker/arc-folder/build/bin/llvm-tblgen+0x76a8f0)
#12 0x00000000004464ff tblgen_main(int, char**) (/buildbot/worker/arc-folder/build/bin/llvm-tblgen+0x4464ff)
#13 0x00007fc521ca2555 __libc_start_main (/usr/lib64/libc.so.6+0x22555)
#14 0x000000000040b7de _start (/buildbot/worker/arc-folder/build/bin/llvm-tblgen+0x40b7de)
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /buildbot/worker/arc-folder/build/bin/FileCheck /buildbot/worker/arc-folder/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/match-table-imms.td

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/139715