[SelectionDAG] Avoid repeated hash lookups (NFC) (llvm#131266)

kazutakahirata · web-flow · commit 8d333e167503 · 2025-03-14T07:21:34.000-07:00
diff --git a/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
@@ -889,7 +889,8 @@ SDValue SelectionDAGBuilder::LowerAsSTATEPOINT(
     }
 
     // Handle multiple gc.relocates of the same input efficiently.
-    if (VirtRegs.count(SD))
+    auto [VRegIt, Inserted] = VirtRegs.try_emplace(SD);
+    if (!Inserted)
       continue;
 
     auto *RetTy = Relocate->getType();
@@ -900,7 +901,7 @@ SDValue SelectionDAGBuilder::LowerAsSTATEPOINT(
     RFV.getCopyToRegs(Relocated, DAG, getCurSDLoc(), Chain, nullptr);
     PendingExports.push_back(Chain);
 
-    VirtRegs[SD] = Reg;
+    VRegIt->second = Reg;
   }
 
   // Record for later use how each relocation was lowered.  This is needed to

Original file line number	Diff line number	Diff line change
`@@ -889,7 +889,8 @@ SDValue SelectionDAGBuilder::LowerAsSTATEPOINT(`
`889`	`889`	`}`
`890`	`890`
`891`	`891`	`// Handle multiple gc.relocates of the same input efficiently.`
`892`		`- if (VirtRegs.count(SD))`
	`892`	`+ auto [VRegIt, Inserted] = VirtRegs.try_emplace(SD);`
	`893`	`+ if (!Inserted)`
`893`	`894`	`continue;`
`894`	`895`
`895`	`896`	`auto *RetTy = Relocate->getType();`
`@@ -900,7 +901,7 @@ SDValue SelectionDAGBuilder::LowerAsSTATEPOINT(`
`900`	`901`	`RFV.getCopyToRegs(Relocated, DAG, getCurSDLoc(), Chain, nullptr);`
`901`	`902`	`PendingExports.push_back(Chain);`
`902`	`903`
`903`		`- VirtRegs[SD] = Reg;`
	`904`	`+ VRegIt->second = Reg;`
`904`	`905`	`}`
`905`	`906`
`906`	`907`	`// Record for later use how each relocation was lowered. This is needed to`