[llvm] [X86] lowerShuffleAsBroadcast - use LoadSDNode::getBasePtr instead of raw getOperand() call. NFC. (PR #139747)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-key-instructions` running on `sie-linux-worker5` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/208/builds/1148

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: tools/llvm-exegesis/RISCV/rvv/filter.test' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
/home/buildbot/buildbot-root/llvm-ki/build/bin/llvm-exegesis -mtriple=riscv64 -mcpu=sifive-x280 -benchmark-phase=assemble-measured-code --mode=inverse_throughput --opcode-name=PseudoVNCLIPU_WX_M1_MASK     --riscv-filter-config='vtype = {VXRM: rod, AVL: VLMAX, SEW: e(8|16), Policy: ta/mu}' --max-configs-per-opcode=1000 --min-instructions=10 | /home/buildbot/buildbot-root/llvm-ki/build/bin/FileCheck /home/buildbot/buildbot-root/llvm-ki/llvm-project/llvm/test/tools/llvm-exegesis/RISCV/rvv/filter.test # RUN: at line 1
+ /home/buildbot/buildbot-root/llvm-ki/build/bin/llvm-exegesis -mtriple=riscv64 -mcpu=sifive-x280 -benchmark-phase=assemble-measured-code --mode=inverse_throughput --opcode-name=PseudoVNCLIPU_WX_M1_MASK '--riscv-filter-config=vtype = {VXRM: rod, AVL: VLMAX, SEW: e(8|16), Policy: ta/mu}' --max-configs-per-opcode=1000 --min-instructions=10
+ /home/buildbot/buildbot-root/llvm-ki/build/bin/FileCheck /home/buildbot/buildbot-root/llvm-ki/llvm-project/llvm/test/tools/llvm-exegesis/RISCV/rvv/filter.test
PseudoVNCLIPU_WX_M1_MASK: Failed to produce any snippet via: instruction has tied variables, avoiding Read-After-Write issue, picking random def and use registers not aliasing each other, for uses, one unique register for each position
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/buildbot/buildbot-root/llvm-ki/build/bin/FileCheck /home/buildbot/buildbot-root/llvm-ki/llvm-project/llvm/test/tools/llvm-exegesis/RISCV/rvv/filter.test

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/139747