[llvm] [SelectionDAG] Folding ZERO-EXTEND/SIGN_EXTEND poison to Poison value in getNode (PR #122741)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve2-vla-2stage` running on `linaro-g4-01` while building `llvm` at step 12 "ninja check 2".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/199/builds/2914

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

```
Step 12 (ninja check 2) failure: stage 2 checked (failure)
******************** TEST 'LLVM :: CodeGen/VE/Vector/ticket-64420.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/llc < /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll -mtriple=ve -mattr=+vpu | /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll # RUN: at line 1
+ /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/llc -mtriple=ve -mattr=+vpu
+ /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll
/home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/llc < /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll -mtriple=ve -mattr=-vpu | /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/FileCheck --check-prefix=SCALAR /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll # RUN: at line 2
+ /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/llc -mtriple=ve -mattr=-vpu
+ /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage2/bin/FileCheck --check-prefix=SCALAR /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll
/home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll:23:16: error: SCALAR-NEXT: is not on the line after the previous match
; SCALAR-NEXT: st %s1, 8(, %s0)
               ^
<stdin>:11:2: note: 'next' match was here
 st %s1, 8(, %s0)
 ^
<stdin>:9:9: note: previous match ended here
# %bb.1: # %bb7
        ^
<stdin>:10:1: note: non-matching line after previous match is here
 or %s1, 0, (0)1
^

Input file: <stdin>
Check file: /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll

-dump-input=help explains the following input dump.

Input was:
<<<<<<
         .
         .
         .
         6: func: # @func 
         7: # %bb.0: # %start 
         8:  brne.w 0, %s0, .LBB0_2 
         9: # %bb.1: # %bb7 
        10:  or %s1, 0, (0)1 
        11:  st %s1, 8(, %s0) 
next:23      !~~~~~~~~~~~~~~~  error: match on wrong line
        12:  st %s1, (, %s0) 
        13:  b.l.t (, %s10) 
        14: .LBB0_2: # %panic3 
        15: .Lfunc_end0: 
        16:  .size func, .Lfunc_end0-func 
        17:  # -- End function 
        18:  .section ".note.GNU-stack","", at progbits 
>>>>>>

...

```

</details>

https://github.com/llvm/llvm-project/pull/122741