[llvm] [CodeGen] Avoid repeated hash lookups (NFC) (PR #128300)

[Kazu Hirata via llvm-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/128300

None

>From ff8a93ba0f826da9eea465b780e2996641fc851f Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Fri, 21 Feb 2025 11:23:16 -0800
Subject: [PATCH] [CodeGen] Avoid repeated hash lookups (NFC)

---
 llvm/lib/CodeGen/InlineSpiller.cpp | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
index 3834a6d7a355e..919dca112b69f 100644
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -1545,24 +1545,21 @@ void HoistSpillHelper::runHoistSpills(
     for (MachineDomTreeNode *Child : (*RIt)->children()) {
       if (!SpillsInSubTreeMap.contains(Child))
         continue;
-      // The stmt "SpillsInSubTree = SpillsInSubTreeMap[*RIt].first" below
+      // The stmt "auto &[...] = SpillsInSubTreeMap[*RIt]" below
       // should be placed before getting the begin and end iterators of
       // SpillsInSubTreeMap[Child].first, or else the iterators may be
       // invalidated when SpillsInSubTreeMap[*RIt] is seen the first time
       // and the map grows and then the original buckets in the map are moved.
-      SmallPtrSet<MachineDomTreeNode *, 16> &SpillsInSubTree =
-          SpillsInSubTreeMap[*RIt].first;
-      BlockFrequency &SubTreeCost = SpillsInSubTreeMap[*RIt].second;
-      SubTreeCost += SpillsInSubTreeMap[Child].second;
-      auto BI = SpillsInSubTreeMap[Child].first.begin();
-      auto EI = SpillsInSubTreeMap[Child].first.end();
+      auto &[SpillsInSubTree, SubTreeCost] = SpillsInSubTreeMap[*RIt];
+      auto ChildIt = SpillsInSubTreeMap.find(Child);
+      SubTreeCost += ChildIt->second.second;
+      auto BI = ChildIt->second.first.begin();
+      auto EI = ChildIt->second.first.end();
       SpillsInSubTree.insert(BI, EI);
-      SpillsInSubTreeMap.erase(Child);
+      SpillsInSubTreeMap.erase(ChildIt);
     }
 
-    SmallPtrSet<MachineDomTreeNode *, 16> &SpillsInSubTree =
-          SpillsInSubTreeMap[*RIt].first;
-    BlockFrequency &SubTreeCost = SpillsInSubTreeMap[*RIt].second;
+    auto &[SpillsInSubTree, SubTreeCost] = SpillsInSubTreeMap[*RIt];
     // No spills in subtree, simply continue.
     if (SpillsInSubTree.empty())
       continue;