[llvm] [AMDGPU] Prevent cyclic behaviour in SIFoldOperands (PR #82099)

[via llvm-commits]

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@@ -772,7 +773,7 @@ void SIFoldOperands::foldOperand(
   if (UseMI->isRegSequence()) {
     Register RegSeqDstReg = UseMI->getOperand(0).getReg();
     unsigned RegSeqDstSubReg = UseMI->getOperand(UseOpIdx + 1).getImm();
-
+    static std::unordered_set<MachineInstr *> seenMI;
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choikwa wrote:

not sure if function static var is better here or removing const qualifiers from several member functions

https://github.com/llvm/llvm-project/pull/82099