[llvm] [MemCpyOpt] Fix the invalid code modification for GEP (PR #68479)

[Kai Yan via llvm-commits]

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@@ -1062,19 +1066,25 @@ bool MemCpyOptPass::performCallSlotOptzn(Instruction *cpyLoad,
   // If necessary, perform additional analysis.
   if (isModOrRefSet(MR))
     MR = BAA.callCapturesBefore(C, DestWithSrcSize, DT);
-  if (isModOrRefSet(MR))
+  if (isModOrRefSet(MR)) {
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kaiyan96 wrote:

RAII is a good idea. I have changed my implementation to an InstructionPositionGuard.

https://github.com/llvm/llvm-project/pull/68479