[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-ppc64le-linux-multistage` running on `ppc64le-clang-multistage-test` while building `llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/76/builds/8921

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'LLVM :: CodeGen/X86/vector-shuffle-combining-avx512bwvl.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/bin/llc < /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/X86/vector-shuffle-combining-avx512bwvl.ll -mtriple=i686-unknown -mattr=+avx512bw,+avx512vl | /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/bin/FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/X86/vector-shuffle-combining-avx512bwvl.ll --check-prefixes=CHECK,X86 # RUN: at line 2
+ /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/bin/llc -mtriple=i686-unknown -mattr=+avx512bw,+avx512vl
+ /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/bin/FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/X86/vector-shuffle-combining-avx512bwvl.ll --check-prefixes=CHECK,X86
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/X86/vector-shuffle-combining-avx512bwvl.ll:271:13: error: X86-NEXT: expected string not found in input
; X86-NEXT: xorl %edx, %edx
            ^
<stdin>:535:18: note: scanning from here
# %bb.0: # %entry
                 ^
<stdin>:536:2: note: possible intended match here
 xorl %eax, %eax
 ^

Input file: <stdin>
Check file: /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/X86/vector-shuffle-combining-avx512bwvl.ll

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

Input was:
<<<<<<
            .
            .
            .
          530:  .globl PR55050 # -- Begin function PR55050 
          531:  .p2align 4 
          532:  .type PR55050, at function 
          533: PR55050: # @PR55050 
          534:  .cfi_startproc 
          535: # %bb.0: # %entry 
next:271'0                      X error: no match found
          536:  xorl %eax, %eax 
next:271'0     ~~~~~~~~~~~~~~~~~
next:271'1      ?                possible intended match
          537:  testb %al, %al 
next:271'0     ~~~~~~~~~~~~~~~~
          538:  jne .LBB15_2 
next:271'0     ~~~~~~~~~~~~~~
          539: # %bb.1: # %if 
next:271'0     ~~~~~~~~~~~~~~~
          540:  xorl %eax, %eax 
next:271'0     ~~~~~~~~~~~~~~~~~
          541: .LBB15_2: # %exit 
next:271'0     ~~~~~~~~~~~~~~~~~~
            .
            .
...
Step 11 (ninja check 2) failure: stage 2 checked (failure)
******************** TEST 'LLVM :: CodeGen/VE/Vector/ticket-64420.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/llc < /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll -mtriple=ve -mattr=+vpu | /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll # RUN: at line 1
+ /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/llc -mtriple=ve -mattr=+vpu
+ /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/llc < /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll -mtriple=ve -mattr=-vpu | /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/FileCheck --check-prefix=SCALAR /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll # RUN: at line 2
+ /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/llc -mtriple=ve -mattr=-vpu
+ /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/bin/FileCheck --check-prefix=SCALAR /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/test/CodeGen/VE/Vector/ticket-64420.ll
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/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/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/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