[IPO] Avoid repeated hash lookups (NFC)

[kazutakahirata]

No description provided.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Kazu Hirata (kazutakahirata)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/130389.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/IPO/GlobalDCE.cpp (+4-7)

diff --git a/llvm/lib/Transforms/IPO/GlobalDCE.cpp b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
index eca36fb31cea0..250c0443cb4af 100644
--- a/llvm/lib/Transforms/IPO/GlobalDCE.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
@@ -67,16 +67,13 @@ void GlobalDCEPass::ComputeDependencies(Value *V,
     Deps.insert(GV);
   } else if (auto *CE = dyn_cast<Constant>(V)) {
     // Avoid walking the whole tree of a big ConstantExprs multiple times.
-    auto Where = ConstantDependenciesCache.find(CE);
-    if (Where != ConstantDependenciesCache.end()) {
-      auto const &K = Where->second;
-      Deps.insert(K.begin(), K.end());
-    } else {
-      SmallPtrSetImpl<GlobalValue *> &LocalDeps = ConstantDependenciesCache[CE];
+    auto [Where, Inserted] = ConstantDependenciesCache.try_emplace(CE);
+    SmallPtrSetImpl<GlobalValue *> &LocalDeps = Where->second;
+    if (Inserted) {
       for (User *CEUser : CE->users())
         ComputeDependencies(CEUser, LocalDeps);
-      Deps.insert(LocalDeps.begin(), LocalDeps.end());
     }
+    Deps.insert(LocalDeps.begin(), LocalDeps.end());
   }
 }
 

[llvm-ci]

LLVM Buildbot has detected a new failure on builder llvm-clang-x86_64-win-fast running on as-builder-3 while building llvm at step 7 "test-build-unified-tree-check-llvm-unit".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/2/builds/18771

Here is the relevant piece of the build log for the reference

Step 7 (test-build-unified-tree-check-llvm-unit) failure: test (failure)
******************** TEST 'LLVM-Unit :: Support/./SupportTests.exe/49/86' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:C:\buildbot\as-builder-3\llvm-clang-x86_64-win-fast\build\unittests\Support\.\SupportTests.exe-LLVM-Unit-1072-49-86.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=86 GTEST_SHARD_INDEX=49 C:\buildbot\as-builder-3\llvm-clang-x86_64-win-fast\build\unittests\Support\.\SupportTests.exe
--

Script:
--
C:\buildbot\as-builder-3\llvm-clang-x86_64-win-fast\build\unittests\Support\.\SupportTests.exe --gtest_filter=Caching.NoCommit
--
C:\buildbot\as-builder-3\llvm-clang-x86_64-win-fast\llvm-project\llvm\unittests\Support\Caching.cpp(142): error: Value of: AddStream
  Actual: false
Expected: true


C:\buildbot\as-builder-3\llvm-clang-x86_64-win-fast\llvm-project\llvm\unittests\Support\Caching.cpp:142
Value of: AddStream
  Actual: false
Expected: true



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