[llvm] [AVR] Set mayLoad/mayStore flags of some load/store instructions (PR #172986)

[Ben Shi via llvm-commits]

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@@ -984,20 +986,23 @@ let canFoldAsLoad = 1, isReMaterializable = 1 in {
   // The pseudo expansion pass trivially expands this into LDDWRdPtrQ.
   //
   // This instruction may be removed once PR13375 is fixed.
-  let mayLoad = 1, hasSideEffects = 0 in
+  let hasSideEffects = 0 in
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benshi001 wrote:

I will do `hasSideEffects = 0/1` later, and just pushed a new commit with other fixes for your comments, you are appreciated to have a check.

https://github.com/llvm/llvm-project/pull/172986