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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/125632.diff


1 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp (+2-2) 


``````````diff
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;

``````````

</details>


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