[llvm] [SimplifyCFG] Don't separate a load/store from its gep during sinking (PR #102318)

[Eli Friedman via llvm-commits]

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@@ -2335,6 +2345,10 @@ static bool sinkCommonCodeFromPredecessors(BasicBlock *BB,
               return InstructionsToSink.contains(V);
             })) {
           ++NumPHIInsts;
+          // Do not separate a load/store from the gep producing the address.
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efriedma-quic wrote:

If I'm following correctly, this is preventing the fold in cases where the GEP would likely fold into the load/store instruction, and the GEP itself won't sink?  That probably makes sense, given the GEP is very likely to fold into the load/store, and it's hard to analyze PHIs.

Maybe expand the comment here a bit.

https://github.com/llvm/llvm-project/pull/102318