commit 474238bbfa194ef8f46ee8b3e8d91258885ceb63
author Kazu Hirata <kazu@google.com> Sat Mar 08 00:20:53 2025 -0800
committer GitHub <noreply@github.com> Sat Mar 08 00:20:53 2025 -0800
tree 6273d89885f2f5a4dfb9210ca649980e632bdcb3
parent e85e44ca9cca70990a0b6a96a11014f2ac56aca5

[CodeGen] Avoid repeated hash lookups (NFC) (#130388)

llvm/lib/CodeGen/RegisterBankInfo.cpp

diff --git a/llvm/lib/CodeGen/RegisterBankInfo.cpp b/llvm/lib/CodeGen/RegisterBankInfo.cpp
index a0061ec..eaef139 100644
--- a/llvm/lib/CodeGen/RegisterBankInfo.cpp
+++ b/llvm/lib/CodeGen/RegisterBankInfo.cpp
@@ -282,13 +282,13 @@
   ++NumPartialMappingsAccessed;
 
   hash_code Hash = hashPartialMapping(StartIdx, Length, &RegBank);
-  const auto &It = MapOfPartialMappings.find(Hash);
-  if (It != MapOfPartialMappings.end())
+  auto [It, Inserted] = MapOfPartialMappings.try_emplace(Hash);
+  if (!Inserted)
     return *It->second;
 
   ++NumPartialMappingsCreated;
 
-  auto &PartMapping = MapOfPartialMappings[Hash];
+  auto &PartMapping = It->second;
   PartMapping = std::make_unique<PartialMapping>(StartIdx, Length, RegBank);
   return *PartMapping;
 }
@@ -316,13 +316,13 @@
   ++NumValueMappingsAccessed;
 
   hash_code Hash = hashValueMapping(BreakDown, NumBreakDowns);
-  const auto &It = MapOfValueMappings.find(Hash);
-  if (It != MapOfValueMappings.end())
+  auto [It, Inserted] = MapOfValueMappings.try_emplace(Hash);
+  if (!Inserted)
     return *It->second;
 
   ++NumValueMappingsCreated;
 
-  auto &ValMapping = MapOfValueMappings[Hash];
+  auto &ValMapping = It->second;
   ValMapping = std::make_unique<ValueMapping>(BreakDown, NumBreakDowns);
   return *ValMapping;
 }
@@ -390,13 +390,13 @@
 
   hash_code Hash =
       hashInstructionMapping(ID, Cost, OperandsMapping, NumOperands);
-  const auto &It = MapOfInstructionMappings.find(Hash);
-  if (It != MapOfInstructionMappings.end())
+  auto [It, Inserted] = MapOfInstructionMappings.try_emplace(Hash);
+  if (!Inserted)
     return *It->second;
 
   ++NumInstructionMappingsCreated;
 
-  auto &InstrMapping = MapOfInstructionMappings[Hash];
+  auto &InstrMapping = It->second;
   InstrMapping = std::make_unique<InstructionMapping>(
       ID, Cost, OperandsMapping, NumOperands);
   return *InstrMapping;