[llvm] [GlobalIsel] Combine freeze (PR #93239)

[Thorsten Schütt via llvm-commits]

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@@ -265,11 +265,13 @@ bool CombinerHelper::matchFreezeOfSingleMaybePoisonOperand(
     }
   }
 
+  Observer.changingInstr(*OrigDef);
   cast<GenericMachineInstr>(OrigDef)->dropPoisonGeneratingFlags();
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tschuett wrote:

In Instcombine, the change is *above* the returns.
https://github.com/llvm/llvm-project/blob/cb7995a1308c1bef396f9a2b2b14472cbdcca755/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp#L4428
We could move the change into both `MatchInfo` s.

https://github.com/llvm/llvm-project/pull/93239