[CodeGen] Avoid repeated hash lookups (NFC) (#129190)

kazutakahirata · web-flow · commit 44b9f5eeab63 · 2025-02-27T23:01:35.000-08:00
diff --git a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
@@ -600,12 +600,12 @@ class MemLocFragmentFill {
         break;
     }
 
-    auto CurrentLiveInEntry = LiveIn.find(&BB);
     // If there's no LiveIn entry for the block yet, add it.
-    if (CurrentLiveInEntry == LiveIn.end()) {
+    auto [CurrentLiveInEntry, Inserted] = LiveIn.try_emplace(&BB);
+    if (Inserted) {
       LLVM_DEBUG(dbgs() << "change=true (first) on meet on " << BB.getName()
                         << "\n");
-      LiveIn[&BB] = std::move(BBLiveIn);
+      CurrentLiveInEntry->second = std::move(BBLiveIn);
       return /*Changed=*/true;
     }
 

Original file line number	Diff line number	Diff line change
`@@ -600,12 +600,12 @@ class MemLocFragmentFill {`
`600`	`600`	`break;`
`601`	`601`	`}`
`602`	`602`
`603`		`- auto CurrentLiveInEntry = LiveIn.find(&BB);`
`604`	`603`	`// If there's no LiveIn entry for the block yet, add it.`
`605`		`- if (CurrentLiveInEntry == LiveIn.end()) {`
	`604`	`+ auto [CurrentLiveInEntry, Inserted] = LiveIn.try_emplace(&BB);`
	`605`	`+ if (Inserted) {`
`606`	`606`	`LLVM_DEBUG(dbgs() << "change=true (first) on meet on " << BB.getName()`
`607`	`607`	`<< "\n");`
`608`		`- LiveIn[&BB] = std::move(BBLiveIn);`
	`608`	`+ CurrentLiveInEntry->second = std::move(BBLiveIn);`
`609`	`609`	`return /Changed=/true;`
`610`	`610`	`}`
`611`	`611`