[Utils] Avoid repeated hash lookups (NFC)

kazutakahirata · kazutakahirata · commit 3768547ee612 · 2025-03-08T20:09:01.000-08:00
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6883,9 +6883,10 @@ static bool switchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
     for (const auto &I : Results) {
       PHINode *PHI = I.first;
       Constant *Value = I.second;
-      if (!ResultLists.count(PHI))
+      auto [It, Inserted] = ResultLists.try_emplace(PHI);
+      if (Inserted)
         PHIs.push_back(PHI);
-      ResultLists[PHI].push_back(std::make_pair(CaseVal, Value));
+      It->second.push_back(std::make_pair(CaseVal, Value));
     }
   }
 

Original file line number	Diff line number	Diff line change
`@@ -6883,9 +6883,10 @@ static bool switchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,`
`6883`	`6883`	`for (const auto &I : Results) {`
`6884`	`6884`	`PHINode *PHI = I.first;`
`6885`	`6885`	`Constant *Value = I.second;`
`6886`		`- if (!ResultLists.count(PHI))`
	`6886`	`+ auto [It, Inserted] = ResultLists.try_emplace(PHI);`
	`6887`	`+ if (Inserted)`
`6887`	`6888`	`PHIs.push_back(PHI);`
`6888`		`- ResultLists[PHI].push_back(std::make_pair(CaseVal, Value));`
	`6889`	`+ It->second.push_back(std::make_pair(CaseVal, Value));`
`6889`	`6890`	`}`
`6890`	`6891`	`}`
`6891`	`6892`