[llvm] [SLP][REVEC] Fix false assumption of the source for castToScalarTyElem. (PR #99424)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/2111

Here is the relevant piece of the build log for the reference:
```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: Transforms/SLPVectorizer/revec-fix-99411.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 2: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/opt -mtriple x86_64-unknown-linux-gnu -passes=slp-vectorizer -S /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll | /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll
+ /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll
+ /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/opt -mtriple x86_64-unknown-linux-gnu -passes=slp-vectorizer -S /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll
/Users/buildbot/buildbot-root/aarch64-darwin/build/bin/opt: warning: failed to infer data layout: unable to get target for 'x86_64-unknown-linux-gnu', see --version and --triple.
/Users/buildbot/buildbot-root/aarch64-darwin/build/bin/opt: WARNING: failed to create target machine for 'x86_64-unknown-linux-gnu': unable to get target for 'x86_64-unknown-linux-gnu', see --version and --triple.
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll:7:15: error: CHECK-NEXT: expected string not found in input
; CHECK-NEXT: store <2 x i64> zeroinitializer, ptr null, align 8
              ^
<stdin>:6:7: note: scanning from here
entry:
      ^
<stdin>:7:19: note: possible intended match here
 %0 = extractelement <1 x i64> zeroinitializer, i64 0
                  ^

Input file: <stdin>
Check file: /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll

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

Input was:
<<<<<<
           1: ; ModuleID = '/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll' 
           2: source_filename = "/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/test/Transforms/SLPVectorizer/revec-fix-99411.ll" 
           3: target triple = "x86_64-unknown-linux-gnu" 
           4:  
           5: define void  at e() { 
label:5'0                 ^~~
label:5'1                 ^~~
           6: entry: 
next:6        ^~~~~~
next:7'0            X error: no match found
           7:  %0 = extractelement <1 x i64> zeroinitializer, i64 0 
next:7'0      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
next:7'1                        ?                                    possible intended match
           8:  %bf.value = and i64 %0, 0 
next:7'0      ~~~~~~~~~~~~~~~~~~~~~~~~~~~
           9:  %bf.set = or i64 0, %bf.value 
next:7'0      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          10:  store i64 %bf.set, ptr getelementptr inbounds (i8, ptr null, i64 8), align 8 
next:7'0      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          11:  %bf.value2 = and i64 0, 0 
next:7'0      ~~~~~~~~~~~~~~~~~~~~~~~~~~~
          12:  %bf.set4 = or i64 0, %bf.value2 
next:7'0      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...

```

https://github.com/llvm/llvm-project/pull/99424