[llvm-mca] Avoid repeated hash lookups (NFC) (#129656)

kazutakahirata · web-flow · commit c61c88862805 · 2025-03-04T00:08:51.000-08:00
diff --git a/llvm/tools/llvm-mca/CodeRegion.cpp b/llvm/tools/llvm-mca/CodeRegion.cpp
@@ -123,8 +123,8 @@ void InstrumentRegions::beginRegion(StringRef Description, SMLoc Loc,
     return;
   }
 
-  auto It = ActiveRegions.find(Description);
-  if (It != ActiveRegions.end()) {
+  auto [It, Inserted] = ActiveRegions.try_emplace(Description, Regions.size());
+  if (!Inserted) {
     const CodeRegion &R = *Regions[It->second];
     SM.PrintMessage(
         Loc, llvm::SourceMgr::DK_Error,
@@ -136,7 +136,6 @@ void InstrumentRegions::beginRegion(StringRef Description, SMLoc Loc,
     return;
   }
 
-  ActiveRegions[Description] = Regions.size();
   Regions.emplace_back(
       std::make_unique<InstrumentRegion>(Description, Loc, std::move(I)));
 }

Original file line number	Diff line number	Diff line change
`@@ -123,8 +123,8 @@ void InstrumentRegions::beginRegion(StringRef Description, SMLoc Loc,`
`123`	`123`	`return;`
`124`	`124`	`}`
`125`	`125`
`126`		`- auto It = ActiveRegions.find(Description);`
`127`		`- if (It != ActiveRegions.end()) {`
	`126`	`+ auto [It, Inserted] = ActiveRegions.try_emplace(Description, Regions.size());`
	`127`	`+ if (!Inserted) {`
`128`	`128`	`const CodeRegion &R = *Regions[It->second];`
`129`	`129`	`SM.PrintMessage(`
`130`	`130`	`Loc, llvm::SourceMgr::DK_Error,`
`@@ -136,7 +136,6 @@ void InstrumentRegions::beginRegion(StringRef Description, SMLoc Loc,`
`136`	`136`	`return;`
`137`	`137`	`}`
`138`	`138`
`139`		`- ActiveRegions[Description] = Regions.size();`
`140`	`139`	`Regions.emplace_back(`
`141`	`140`	`std::make_unique<InstrumentRegion>(Description, Loc, std::move(I)));`
`142`	`141`	`}`