[llvm] [RISCV] Vectorize phi for loop carried @llvm.vp.reduce.* (PR #131974)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve-vla` running on `linaro-g3-04` while building `llvm` at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/17/builds/6891

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

```
Step 7 (ninja check 1) failure: stage 1 checked (failure)
...
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/llvm/config.py:520: note: using ld64.lld: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/ld64.lld
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/llvm/config.py:520: note: using wasm-ld: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/wasm-ld
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/discovery.py:276: warning: input '/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/interception/Unit' contained no tests
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/discovery.py:276: warning: input '/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/Unit' contained no tests
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/llvm/config.py:520: note: using ld.lld: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/ld.lld
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/llvm/config.py:520: note: using lld-link: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/lld-link
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/llvm/config.py:520: note: using ld64.lld: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/ld64.lld
llvm-lit: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/utils/lit/lit/llvm/config.py:520: note: using wasm-ld: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/wasm-ld
-- Testing: 97613 tests, 64 workers --
UNRESOLVED: Flang :: Driver/slp-vectorize.ll (1 of 97613)
******************** TEST 'Flang :: Driver/slp-vectorize.ll' FAILED ********************
Test has no 'RUN:' line
********************
PASS: LLVM :: CodeGen/RISCV/rvv/expandload.ll (2 of 97613)
PASS: libFuzzer-aarch64-default-Linux :: swap-cmp.test (3 of 97613)
PASS: UBSan-AddressSanitizer-aarch64 :: TestCases/ImplicitConversion/signed-integer-truncation-ignorelist.c (4 of 97613)
PASS: Clang :: CodeGen/X86/avx2-builtins.c (5 of 97613)
PASS: LLVM :: CodeGen/AMDGPU/llvm.amdgcn.permlane.ll (6 of 97613)
PASS: UBSan-AddressSanitizer-aarch64 :: TestCases/ImplicitConversion/unsigned-integer-truncation-ignorelist.c (7 of 97613)
PASS: Clang :: OpenMP/target_simd_codegen_registration.cpp (8 of 97613)
PASS: Clang :: OpenMP/target_teams_distribute_codegen_registration.cpp (9 of 97613)
PASS: Clang :: Headers/arm-neon-header.c (10 of 97613)
PASS: Clang :: OpenMP/target_parallel_for_codegen_registration.cpp (11 of 97613)
PASS: UBSan-ThreadSanitizer-aarch64 :: TestCases/ImplicitConversion/signed-integer-truncation-ignorelist.c (12 of 97613)
PASS: Clang :: Driver/x86-target-features.c (13 of 97613)
PASS: Clang :: CodeGen/X86/rot-intrinsics.c (14 of 97613)
PASS: Clang :: OpenMP/target_teams_distribute_simd_codegen_registration.cpp (15 of 97613)
PASS: libFuzzer-aarch64-default-Linux :: value-profile-cmp.test (16 of 97613)
PASS: Clang :: OpenMP/target_parallel_for_simd_codegen_registration.cpp (17 of 97613)
PASS: Clang :: Driver/clang_f_opts.c (18 of 97613)
PASS: UBSan-ThreadSanitizer-aarch64 :: TestCases/ImplicitConversion/unsigned-integer-truncation-ignorelist.c (19 of 97613)
PASS: Clang :: CodeGen/X86/sse2-builtins.c (20 of 97613)
PASS: libFuzzer-aarch64-default-Linux :: large.test (21 of 97613)
PASS: Clang :: Analysis/runtime-regression.c (22 of 97613)
PASS: libFuzzer-aarch64-default-Linux :: msan.test (23 of 97613)
PASS: Clang :: CodeGen/X86/avx-builtins.c (24 of 97613)
PASS: Clang :: Driver/linux-ld.c (25 of 97613)
PASS: ThreadSanitizer-aarch64 :: signal_thread.cpp (26 of 97613)
PASS: SanitizerCommon-lsan-aarch64-Linux :: Linux/signal_segv_handler.cpp (27 of 97613)
PASS: LLVM :: CodeGen/ARM/build-attributes.ll (28 of 97613)
PASS: HWAddressSanitizer-aarch64 :: TestCases/Linux/create-thread-stress.cpp (29 of 97613)
PASS: SanitizerCommon-hwasan-aarch64-Linux :: Linux/signal_segv_handler.cpp (30 of 97613)
PASS: ThreadSanitizer-aarch64 :: deadlock_detector_stress_test.cpp (31 of 97613)
PASS: SanitizerCommon-tsan-aarch64-Linux :: Linux/signal_segv_handler.cpp (32 of 97613)
PASS: LLVM :: CodeGen/AMDGPU/sched-group-barrier-pipeline-solver.mir (33 of 97613)
PASS: Clang :: OpenMP/target_teams_distribute_parallel_for_simd_codegen_registration.cpp (34 of 97613)
PASS: SanitizerCommon-msan-aarch64-Linux :: Linux/signal_segv_handler.cpp (35 of 97613)
PASS: SanitizerCommon-asan-aarch64-Linux :: Linux/signal_segv_handler.cpp (36 of 97613)
PASS: Clang :: Preprocessor/predefined-arch-macros.c (37 of 97613)

```

</details>

https://github.com/llvm/llvm-project/pull/131974