[llvm] [llvm][lit] Add option to run only the failed tests (PR #158043)

[Tomohiro Kashiwada via llvm-commits]

kikairoya wrote:

Hi, I found the cause of failure.

On Windows (with python <= 3.12 only, 3.13 works fine), the contents of `filter-failed.py.tmp/.lit_test_times.txt` after test ran is below:
```
-2.408028e-02 fail.txt
1.904011e-02 pass.txt
-0.000000e+00 unresolved.txt
2.004886e-02 xfail.txt
-2.453256e-02 xpass.txt
```

It says that unresolved.txt finished in 0 seconds. However, since [`previous_failure` is set by `time < 0`](https://github.com/llvm/llvm-project/blob/fbb587c65653395dc97a360e0cd0d1cf9ed0e875/llvm/utils/lit/lit/Test.py#L282), a test that finishes in 0 seconds is treated as a successful test.

All of failed tests should have a strictly negative elapsed time (or, modifying to `time <= 0` also might be an option.)
This patch works fine for me:
```diff
diff --git a/llvm/utils/lit/lit/TestTimes.py b/llvm/utils/lit/lit/TestTimes.py
index a2c0e0527b84..0c18e3e01582 100644
--- a/llvm/utils/lit/lit/TestTimes.py
+++ b/llvm/utils/lit/lit/TestTimes.py
@@ -22,7 +22,7 @@ def record_test_times(tests, lit_config):
             continue
         if not t.suite.exec_root in times_by_suite:
             times_by_suite[t.suite.exec_root] = read_test_times(t.suite)
-        time = -t.result.elapsed if t.isFailure() else t.result.elapsed
+        time = min(-t.result.elapsed, -1.0e-6) if t.isFailure() else t.result.elapsed
         # The "path" here is only used as a key into a dictionary. It is never
         # used as an actual path to a filesystem API, therefore we use '/' as
         # the canonical separator so that Unix and Windows machines can share
```

https://github.com/llvm/llvm-project/pull/158043