[llvm] [GVNSink] Avoid repeated hash lookups (NFC) (PR #113023)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `premerge-monolithic-linux` running on `premerge-linux-1` while building `llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/12373

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

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
...
PASS: Clang :: OpenMP/master_taskloop_lastprivate_messages.cpp (11801 of 95252)
PASS: LLVM :: CodeGen/X86/combine-sub-usat.ll (11802 of 95252)
PASS: LLVM :: CodeGen/AMDGPU/GlobalISel/legalize-ushlsat.mir (11803 of 95252)
PASS: Clang :: Sema/attr-guard_nocf.c (11804 of 95252)
PASS: LLVM :: CodeGen/AMDGPU/GlobalISel/llvm.amdgcn.udot4.ll (11805 of 95252)
PASS: LLVM :: CodeGen/Thumb2/mve-vcmpfz.ll (11806 of 95252)
PASS: Clang :: CodeGen/RISCV/rvv-intrinsics-autogenerated/non-policy/overloaded/bfloat16/vlsseg8e16.c (11807 of 95252)
PASS: Clang :: CodeGen/RISCV/rvv-intrinsics-autogenerated/policy/non-overloaded/vlseg6e8ff.c (11808 of 95252)
PASS: LLVM :: CodeGen/AArch64/ptrauth-indirectbr.ll (11809 of 95252)
TIMEOUT: Clangd Unit Tests :: ./ClangdTests/13/79 (11810 of 95252)
******************** TEST 'Clangd Unit Tests :: ./ClangdTests/13/79' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/build/buildbot/premerge-monolithic-linux/build/tools/clang/tools/extra/clangd/unittests/./ClangdTests-Clangd Unit Tests-3986539-13-79.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=79 GTEST_SHARD_INDEX=13 /build/buildbot/premerge-monolithic-linux/build/tools/clang/tools/extra/clangd/unittests/./ClangdTests
--

Note: This is test shard 14 of 79.
[==========] Running 16 tests from 15 test suites.
[----------] Global test environment set-up.
[----------] 1 test from BackgroundIndexTest
[ RUN      ] BackgroundIndexTest.MainFileRefs
Enqueueing 1 commands for indexing
Failed to load shard: /clangd-test/root/A.cc
Indexing /clangd-test/root/A.cc (digest:=2BC243980BABC53C)
Indexed /clangd-test/root/A.cc (2 symbols, 3 refs, 2 files)
BackgroundIndex: building version 1 when background indexer is idle
BackgroundIndex: serving version 1 (25872 bytes)
Dex query tree: true
[       OK ] BackgroundIndexTest.MainFileRefs (17 ms)
[----------] 1 test from BackgroundIndexTest (17 ms total)

[----------] 2 tests from CompletionTest
[ RUN      ] CompletionTest.ScopedWithFilter
Built preamble of size 214412 for file /clangd-test/foo.cpp version null in 0.02 seconds
Ignored diagnostic. /clangd-test/foo.cpp:2:22:use of undeclared identifier 'ns'
Code complete: fuzzyFind({
  "AnyScope": false,
  "Limit": null,
  "PreferredTypes": [],
  "ProximityPaths": [
    "/clangd-test/foo.cpp"
  ],
  "Query": "x",
  "RestrictForCodeCompletion": true,
  "Scopes": [
    "ns::"
  ]
})
Code complete: sema context Symbol, query scopes [ns::] (AnyScope=false), expected type <none>

```

</details>

https://github.com/llvm/llvm-project/pull/113023