[CodeGen] Avoid repeated map lookups (NFC) (llvm#127025)

kazutakahirata · web-flow · commit e7bf6a4e042f · 2025-02-13T09:11:17.000-08:00
diff --git a/llvm/lib/CodeGen/LiveStacks.cpp b/llvm/lib/CodeGen/LiveStacks.cpp
@@ -62,8 +62,8 @@ LiveStacks::getOrCreateInterval(int Slot, const TargetRegisterClass *RC) {
     S2RCMap.insert(std::make_pair(Slot, RC));
   } else {
     // Use the largest common subclass register class.
-    const TargetRegisterClass *OldRC = S2RCMap[Slot];
-    S2RCMap[Slot] = TRI->getCommonSubClass(OldRC, RC);
+    const TargetRegisterClass *&OldRC = S2RCMap[Slot];
+    OldRC = TRI->getCommonSubClass(OldRC, RC);
   }
   return I->second;
 }

Original file line number	Diff line number	Diff line change
`@@ -62,8 +62,8 @@ LiveStacks::getOrCreateInterval(int Slot, const TargetRegisterClass *RC) {`
`62`	`62`	`S2RCMap.insert(std::make_pair(Slot, RC));`
`63`	`63`	`} else {`
`64`	`64`	`// Use the largest common subclass register class.`
`65`		`- const TargetRegisterClass *OldRC = S2RCMap[Slot];`
`66`		`- S2RCMap[Slot] = TRI->getCommonSubClass(OldRC, RC);`
	`65`	`+ const TargetRegisterClass *&OldRC = S2RCMap[Slot];`
	`66`	`+ OldRC = TRI->getCommonSubClass(OldRC, RC);`
`67`	`67`	`}`
`68`	`68`	`return I->second;`
`69`	`69`	`}`