[llvm] [LiveDebugValues] Avoid repeated hash lookups (NFC) (PR #108484)

[Kazu Hirata via llvm-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/108484

None

>From 332c9228efae35c9b4ac6ac66025aca9a2cc99aa Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Thu, 12 Sep 2024 01:04:53 -0700
Subject: [PATCH] [LiveDebugValues] Avoid repeated hash lookups (NFC)

---
 llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
index a69dbbbbdab3cd..a73a3aa59403b3 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -2231,11 +2231,9 @@ void InstrRefBasedLDV::accumulateFragmentMap(MachineInstr &MI) {
   // If this is the first sighting of this variable, then we are guaranteed
   // there are currently no overlapping fragments either. Initialize the set
   // of seen fragments, record no overlaps for the current one, and return.
-  auto SeenIt = SeenFragments.find(MIVar.getVariable());
-  if (SeenIt == SeenFragments.end()) {
-    SmallSet<FragmentInfo, 4> OneFragment;
-    OneFragment.insert(ThisFragment);
-    SeenFragments.insert({MIVar.getVariable(), OneFragment});
+  auto [SeenIt, Inserted] = SeenFragments.try_emplace(MIVar.getVariable());
+  if (Inserted) {
+    SeenIt->second.insert(ThisFragment);
 
     OverlapFragments.insert({{MIVar.getVariable(), ThisFragment}, {}});
     return;