[llvm] [CodeGen] Avoid repeated hash lookups (NFC) (PR #123557)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-regalloc

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/123557.diff


1 Files Affected:

- (modified) llvm/lib/CodeGen/MachineCopyPropagation.cpp (+4-4) 


``````````diff
diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
index 0afd73d8ecdccb..d44b064dcb4b2e 100644
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -127,11 +127,11 @@ class CopyTracker {
   BitVector &getPreservedRegUnits(const MachineOperand &RegMaskOp,
                                   const TargetRegisterInfo &TRI) {
     const uint32_t *RegMask = RegMaskOp.getRegMask();
-    auto Existing = RegMaskToPreservedRegUnits.find(RegMask);
-    if (Existing != RegMaskToPreservedRegUnits.end()) {
-      return Existing->second;
+    auto [It, Inserted] = RegMaskToPreservedRegUnits.try_emplace(RegMask);
+    if (!Inserted) {
+      return It->second;
     } else {
-      BitVector &PreservedRegUnits = RegMaskToPreservedRegUnits[RegMask];
+      BitVector &PreservedRegUnits = It->second;
 
       PreservedRegUnits.resize(TRI.getNumRegUnits());
       for (unsigned SafeReg = 0, E = TRI.getNumRegs(); SafeReg < E; ++SafeReg)

``````````

</details>


https://github.com/llvm/llvm-project/pull/123557