[llvm] [CodeGen] Use DenseMap::operator[] (NFC) (PR #108489)

[Kazu Hirata via llvm-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/108489

Once we modernize CopyInfo with default member initializations,

  Copies.insert({Unit, ...})

becomes equivalent to:

  Copies.try_emplace(Unit)

which we can simplify further down to Copies[Unit].


>From 853f97ee1fa1ba00e6343dda78b3eab24afcf0c4 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Thu, 12 Sep 2024 21:32:33 -0700
Subject: [PATCH] [CodeGen] Use DenseMap::operator[] (NFC)

Once we modernize CopyInfo with default member initializations,

  Copies.insert({Unit, ...})

becomes equivalent to:

  Copies.try_emplace(Unit)

which we can simplify further down to Copies[Unit].
---
 llvm/lib/CodeGen/MachineCopyPropagation.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
index fab36f4858e093..8bcc437cbfb865 100644
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -108,9 +108,10 @@ static std::optional<DestSourcePair> isCopyInstr(const MachineInstr &MI,
 
 class CopyTracker {
   struct CopyInfo {
-    MachineInstr *MI, *LastSeenUseInCopy;
+    MachineInstr *MI = nullptr;
+    MachineInstr *LastSeenUseInCopy = nullptr;
     SmallVector<MCRegister, 4> DefRegs;
-    bool Avail;
+    bool Avail = false;
   };
 
   DenseMap<MCRegUnit, CopyInfo> Copies;
@@ -240,8 +241,7 @@ class CopyTracker {
     // Remember source that's copied to Def. Once it's clobbered, then
     // it's no longer available for copy propagation.
     for (MCRegUnit Unit : TRI.regunits(Src)) {
-      auto I = Copies.insert({Unit, {nullptr, nullptr, {}, false}});
-      auto &Copy = I.first->second;
+      auto &Copy = Copies[Unit];
       if (!is_contained(Copy.DefRegs, Def))
         Copy.DefRegs.push_back(Def);
       Copy.LastSeenUseInCopy = MI;