[llvm] [VPlan] Replace reverse RPOT with PO traversal (NFC) (PR #151757)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `fuchsia-x86_64-linux` running on `fuchsia-debian-64-us-central1-a-1` while building `llvm` at step 4 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/11/builds/20943

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

```
Step 4 (annotate) failure: 'python ../llvm-zorg/zorg/buildbot/builders/annotated/fuchsia-linux.py ...' (failure)
...
[678/1397] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/ImmutableMapTest.cpp.o
[679/1397] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o
[680/1397] Linking CXX executable bin/yaml2obj
[680/1397] Running lld test suite
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld.lld: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/ld.lld
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using lld-link: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld64.lld: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/ld64.lld
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using wasm-ld: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/wasm-ld
-- Testing: 3130 tests, 60 workers --
Testing:  0..
FAIL: lld :: COFF/import_weak_alias.test (262 of 3130)
******************** TEST 'lld :: COFF/import_weak_alias.test' FAILED ********************
Exit Code: 139

Command Output (stderr):
--
split-file /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/lld/test/COFF/import_weak_alias.test /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir # RUN: at line 3
+ split-file /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/lld/test/COFF/import_weak_alias.test /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/foo.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj # RUN: at line 4
+ /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/foo.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/qux.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj # RUN: at line 5
+ /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/qux.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj -out:/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dll -dll # RUN: at line 6
+ /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj -out:/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dll -dll
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.script: line 4: 3898585 Segmentation fault      (core dumped) /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj -out:/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dll -dll

--

********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90.. 
********************
Failed Tests (1):
  lld :: COFF/import_weak_alias.test


Testing Time: 24.68s

Total Discovered Tests: 3130
  Unsupported:  568 (18.15%)
  Passed     : 2561 (81.82%)
  Failed     :    1 (0.03%)
[826/1397] Building CXX object unittests/Analysis/CMakeFiles/AnalysisTests.dir/CtxProfAnalysisTest.cpp.o
FAILED: tools/lld/test/CMakeFiles/check-lld /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/CMakeFiles/check-lld 
cd /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test && /usr/bin/python3.10 /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/./bin/llvm-lit -sv /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test
[828/1397] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/STLExtrasTest.cpp.o
[829/1397] Building CXX object unittests/Analysis/CMakeFiles/AnalysisTests.dir/LazyCallGraphTest.cpp.o
[830/1397] Building CXX object unittests/Analysis/CMakeFiles/AnalysisTests.dir/ValueTrackingTest.cpp.o
[831/1397] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/CCStateTest.cpp.o
[832/1397] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/GCMetadata.cpp.o
Step 7 (check) failure: check (failure)
...
[678/1397] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/ImmutableMapTest.cpp.o
[679/1397] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o
[680/1397] Linking CXX executable bin/yaml2obj
[680/1397] Running lld test suite
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld.lld: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/ld.lld
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using lld-link: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld64.lld: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/ld64.lld
llvm-lit: /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using wasm-ld: /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/wasm-ld
-- Testing: 3130 tests, 60 workers --
Testing:  0..
FAIL: lld :: COFF/import_weak_alias.test (262 of 3130)
******************** TEST 'lld :: COFF/import_weak_alias.test' FAILED ********************
Exit Code: 139

Command Output (stderr):
--
split-file /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/lld/test/COFF/import_weak_alias.test /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir # RUN: at line 3
+ split-file /var/lib/buildbot/fuchsia-x86_64-linux/llvm-project/lld/test/COFF/import_weak_alias.test /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/foo.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj # RUN: at line 4
+ /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/foo.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/qux.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj # RUN: at line 5
+ /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/llvm-mc --filetype=obj -triple=x86_64-windows-msvc /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dir/qux.s -o /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj -out:/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dll -dll # RUN: at line 6
+ /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj -out:/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dll -dll
/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.script: line 4: 3898585 Segmentation fault      (core dumped) /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/bin/lld-link /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.qux.obj /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.foo.obj -out:/var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/COFF/Output/import_weak_alias.test.tmp.dll -dll

--

********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90.. 
********************
Failed Tests (1):
  lld :: COFF/import_weak_alias.test


Testing Time: 24.68s

Total Discovered Tests: 3130
  Unsupported:  568 (18.15%)
  Passed     : 2561 (81.82%)
  Failed     :    1 (0.03%)
[826/1397] Building CXX object unittests/Analysis/CMakeFiles/AnalysisTests.dir/CtxProfAnalysisTest.cpp.o
FAILED: tools/lld/test/CMakeFiles/check-lld /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test/CMakeFiles/check-lld 
cd /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test && /usr/bin/python3.10 /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/./bin/llvm-lit -sv /var/lib/buildbot/fuchsia-x86_64-linux/build/llvm-build-f74gchkm/tools/lld/test
[828/1397] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/STLExtrasTest.cpp.o
[829/1397] Building CXX object unittests/Analysis/CMakeFiles/AnalysisTests.dir/LazyCallGraphTest.cpp.o
[830/1397] Building CXX object unittests/Analysis/CMakeFiles/AnalysisTests.dir/ValueTrackingTest.cpp.o
[831/1397] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/CCStateTest.cpp.o
[832/1397] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/GCMetadata.cpp.o

```

</details>

https://github.com/llvm/llvm-project/pull/151757