[llvm] [AMDGPU] Avoid repeated hash lookups (NFC) (PR #127445)

[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/127445.diff


1 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp (+3-2) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp b/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp
index ac11526da0919..17f724c3173d9 100644
--- a/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp
+++ b/llvm/lib/Target/AMDGPU/R600OptimizeVectorRegisters.cpp
@@ -270,9 +270,10 @@ bool R600VectorRegMerger::tryMergeUsingCommonSlot(RegSeqInfo &RSI,
       MOE = RSI.Instr->operands_end(); MOp != MOE; ++MOp) {
     if (!MOp->isReg())
       continue;
-    if (PreviousRegSeqByReg[MOp->getReg()].empty())
+    auto &Insts = PreviousRegSeqByReg[MOp->getReg()];
+    if (Insts.empty())
       continue;
-    for (MachineInstr *MI : PreviousRegSeqByReg[MOp->getReg()]) {
+    for (MachineInstr *MI : Insts) {
       CompatibleRSI = PreviousRegSeq[MI];
       if (RSI == CompatibleRSI)
         continue;

``````````

</details>


https://github.com/llvm/llvm-project/pull/127445