[PATCH] D112323: GlobalISel/Utils: Use incoming regbank while constraining the superclasses

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

It's not accurate to say it would lead to incorrect codegen, we would just prefer to pick the classes beforehand rather than let the allocator decide until it needs to split live ranges



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Comment at: llvm/lib/CodeGen/GlobalISel/Utils.cpp:117
+  // not be overriden.
+  if (MRI.getRegBankOrNull(Reg) && RegClass) {
+    const TargetRegisterClass *RC =
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I'm not sure there's any case where this shoudl be called where MRI.getRegBankOrNull(Reg) can be null?


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Comment at: llvm/lib/CodeGen/GlobalISel/Utils.cpp:122
+               TRI.getCommonSubClass(RegClass, RC) == RC))
+      RegClass = RC;
+  }
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I would expect this to just directly assign getCommonSubClass's result without the comparison


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112323/new/

https://reviews.llvm.org/D112323