[llvm] [RISCV] Support Push/Pop with Xqci (PR #134191)

[Sam Elliott via llvm-commits]

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@@ -949,22 +964,32 @@ void RISCVFrameLowering::emitPrologue(MachineFunction &MF,
   }
 
   if (RVFI->useQCIInterrupt(MF)) {
+    // The function starts with `QC.C.MIENTER(.NEST)`, so the `(QC.)CM.PUSH(FP)`
+    // could only be the next instruction.
+    PossiblePush = std::next(PossiblePush);
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lenary wrote:

Happy to. I wasn't sure the idiomatic way to deal with iterators.

https://github.com/llvm/llvm-project/pull/134191