[PATCH] D58911: DAG: Don't try to cluster loads with tied inputs

[Matt Arsenault via Phabricator via llvm-commits]

arsenm marked an inline comment as done.
arsenm added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:251
+      const SDNode *B = O2SMap[OffsetB];
+      if (A->isOperandOf(B))
+        return true;
----------------
rampitec wrote:
> There is unlikely but possible case neither is operand of another but depend through a third instruction.
> Also what would happen if:
> 
> A: load i16 [base]
> B: load i16 [base + 2]
> C: load i8 [base + 1]
> 
> I guess normal sorting will tell A < C < B. With your change: B < A, A < C, C < B. That creates an impossible sort order.
It turns out this is already broken even if clustering is disabled. Fixing this requires another patch to rewrite the patterns


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https://reviews.llvm.org/D58911