[PATCH] D72961: In early-ifconversion check that the operands of a PHI share a common regclass with the destination regclass.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

What is the restriction on the register classes of PHI operands, if they don't have to have to be same register class as the result?  I don't see any relevant documentation, or checks in MachineVerifier::checkPHIOps().



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Comment at: llvm/lib/CodeGen/EarlyIfConversion.cpp:522
+    // We need to make sure the register classes have a common subclass
+    // to avoid cross-class copies.
+    const TargetRegisterClass *DstRC =
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Not sure why we want to avoid a cross-class copy here; won't we generate a cross-class copy anyway in PHIElimination?


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https://reviews.llvm.org/D72961