[llvm] [GlobalISel] Add G_SUB for computeNumSignBits (PR #158384)

[Simon Pilgrim via llvm-commits]

================
@@ -1,5 +1,5 @@
 # NOTE: Assertions have been autogenerated by utils/update_givaluetracking_test_checks.py UTC_ARGS: --version 5
-# RUN: llc -mtriple aarch64 -passes="print<gisel-value-tracking>" %s -o - 2>&1 | FileCheck %s
+# RUN: llc -mtriple=aarch64 -passes='print<gisel-value-tracking>' -filetype=null %s 2>&1 | FileCheck %s
----------------
RKSimon wrote:

This is my experience with update_test_checks.py calls from the visual studio command prompt (dos evaluation), using `'` instead of `"` around passes lists etc. causes it to fail:
```
Traceback (most recent call last):
  File "C:\LLVM\llvm-project\llvm\utils\update_test_checks.py", line 379, in main
    update_test(ti)
  File "C:\LLVM\llvm-project\llvm\utils\update_test_checks.py", line 113, in update_test
    raw_tool_output = common.invoke_tool(
                      ^^^^^^^^^^^^^^^^^^^
  File "C:\LLVM\llvm-project\llvm\utils\UpdateTestChecks\common.py", line 550, in invoke_tool
    stdout = subprocess.check_output(
             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python312\Lib\subprocess.py", line 466, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python312\Lib\subprocess.py", line 571, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command 'opt -passes='default<O2>' -S' returned non-zero exit status 1.
```

https://github.com/llvm/llvm-project/pull/158384