[llvm] [AMDGPU] Avoid repeated hash lookups (NFC) (PR #125632)

[Kazu Hirata via llvm-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/125632

None

>From 9895fb9863286e64d9da412d94534bad9fce5df9 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Mon, 3 Feb 2025 16:39:17 -0800
Subject: [PATCH] [AMDGPU] Avoid repeated hash lookups (NFC)

---
 llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp b/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp
index a20319ea4f9d35..ac11526da0919c 100644
--- a/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp
+++ b/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp
@@ -287,10 +287,10 @@ bool R600VectorRegMerger::tryMergeUsingFreeSlot(RegSeqInfo &RSI,
     RegSeqInfo &CompatibleRSI,
     std::vector<std::pair<unsigned, unsigned>> &RemapChan) {
   unsigned NeededUndefs = 4 - RSI.UndefReg.size();
-  if (PreviousRegSeqByUndefCount[NeededUndefs].empty())
-    return false;
   std::vector<MachineInstr *> &MIs =
       PreviousRegSeqByUndefCount[NeededUndefs];
+  if (MIs.empty())
+    return false;
   CompatibleRSI = PreviousRegSeq[MIs.back()];
   tryMergeVector(&CompatibleRSI, &RSI, RemapChan);
   return true;