Fix a bug in RegsForValue::getCopyToRegs() that causes cyclical scheduling units. If it's creating multiple CopyToReg nodes that are "flagged" together, it should not create a TokenFactor for it's chain outputs:
c1, f1 = CopyToReg
c2, f2 = CopyToReg
c3 = TokenFactor c1, c2
...
= user c3, ..., f2
Now that the two CopyToReg's and the user are "flagged" together. They effectively forms a single scheduling unit. The TokenFactor is now both an operand and a successor of the Flagged nodes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50376 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 496051f..2d65a33 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -3455,8 +3455,18 @@
Chains[i] = Part.getValue(0);
}
- if (NumRegs == 1)
- Chain = Chains[0];
+ if (NumRegs == 1 || Flag)
+ // If NumRegs > 1 && Flag is used then the use of the last CopyToReg is
+ // flagged to it. That is the CopyToReg nodes and the user are considered
+ // a single scheduling unit. If we create a TokenFactor and return it as
+ // chain, then the TokenFactor is both a predecessor (operand) of the
+ // user as well as a successor (the TF operands are flagged to the user).
+ // c1, f1 = CopyToReg
+ // c2, f2 = CopyToReg
+ // c3 = TokenFactor c1, c2
+ // ...
+ // = op c3, ..., f2
+ Chain = Chains[NumRegs-1];
else
Chain = DAG.getNode(ISD::TokenFactor, MVT::Other, &Chains[0], NumRegs);
}