[llvm] [InstCombine] Canonicalize non-i8 gep of mul to i8 (PR #96606)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-ubuntu-fast` running on `sie-linux-worker` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/926

Here is the relevant piece of the build log for the reference:
```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang-Unit :: Analysis/FlowSensitive/./ClangAnalysisFlowSensitiveTests/35/42' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/unittests/Analysis/FlowSensitive/./ClangAnalysisFlowSensitiveTests-Clang-Unit-1429860-35-42.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=42 GTEST_SHARD_INDEX=35 /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/unittests/Analysis/FlowSensitive/./ClangAnalysisFlowSensitiveTests
--

Script:
--
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/unittests/Analysis/FlowSensitive/./ClangAnalysisFlowSensitiveTests --gtest_filter=TransferTest.StructModeledFieldsInTypeid
--
input.cc:20:7: error: use of typeid requires -frtti
   20 |       typeid(*s.NonPoly);
      |       ^
input.cc:21:7: error: use of typeid requires -frtti
   21 |       typeid(*s.Poly);
      |       ^
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp:92: Failure
Value of: llvm::detail::TakeError(checkDataflowWithNoopAnalysis(Code, VerifyResults, Options, Std, TargetFun))
Expected: succeeded
  Actual: failed  (Invalid argument Source file has syntax or type errors, they were printed to the test log)


/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp:92
Value of: llvm::detail::TakeError(checkDataflowWithNoopAnalysis(Code, VerifyResults, Options, Std, TargetFun))
Expected: succeeded
  Actual: failed  (Invalid argument Source file has syntax or type errors, they were printed to the test log)



********************


```

https://github.com/llvm/llvm-project/pull/96606