[llvm] [NFC][CodeGen] Optimize hash table lookups in MachineBlockHashInfo (PR #192823)

[Vitaly Buka via llvm-commits]

https://github.com/vitalybuka created https://github.com/llvm/llvm-project/pull/192823

None

>From 5bde512e3cf9f762d2d1d8cb233613fa934e6826 Mon Sep 17 00:00:00 2001
From: Vitaly Buka <vitalybuka at google.com>
Date: Sat, 18 Apr 2026 21:44:24 -0700
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.7
---
 llvm/lib/CodeGen/MachineBlockHashInfo.cpp | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/CodeGen/MachineBlockHashInfo.cpp b/llvm/lib/CodeGen/MachineBlockHashInfo.cpp
index 73dfc7c62a95c..f2f73f63bcc0c 100644
--- a/llvm/lib/CodeGen/MachineBlockHashInfo.cpp
+++ b/llvm/lib/CodeGen/MachineBlockHashInfo.cpp
@@ -66,18 +66,19 @@ bool MachineBlockHashInfo::runOnMachineFunction(MachineFunction &F) {
   uint16_t Offset = 0;
   // Initialize hash components
   for (const MachineBasicBlock &MBB : F) {
+    auto &HashInfo = HashInfos[&MBB];
     // offset of the machine basic block
-    HashInfos[&MBB].Offset = Offset;
-    Offset += MBB.size();
+    HashInfo.Offset = Offset + MBB.size();
     // Hashing opcodes
-    HashInfos[&MBB].OpcodeHash = hashBlock(MBB, /*HashOperands=*/false);
+    HashInfo.OpcodeHash = hashBlock(MBB, /*HashOperands=*/false);
     // Hash complete instructions
-    HashInfos[&MBB].InstrHash = hashBlock(MBB, /*HashOperands=*/true);
+    HashInfo.InstrHash = hashBlock(MBB, /*HashOperands=*/true);
   }
 
   // Initialize neighbor hash
   for (const MachineBasicBlock &MBB : F) {
-    uint64_t Hash = HashInfos[&MBB].OpcodeHash;
+    auto &HashInfo = HashInfos[&MBB];
+    uint64_t Hash = HashInfo.OpcodeHash;
     // Append hashes of successors
     for (const MachineBasicBlock *SuccMBB : MBB.successors()) {
       uint64_t SuccHash = HashInfos[SuccMBB].OpcodeHash;
@@ -88,7 +89,7 @@ bool MachineBlockHashInfo::runOnMachineFunction(MachineFunction &F) {
       uint64_t PredHash = HashInfos[PredMBB].OpcodeHash;
       Hash = hashing::detail::hash_16_bytes(Hash, PredHash);
     }
-    HashInfos[&MBB].NeighborHash = Hash;
+    HashInfo.NeighborHash = Hash;
   }
 
   // Assign hashes