[llvm-commits] [llvm] r50376 - /llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

[Evan Cheng]

Author: evancheng
Date: Mon Apr 28 17:07:13 2008
New Revision: 50376

URL: http://llvm.org/viewvc/llvm-project?rev=50376&view=rev
Log:
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.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp?rev=50376&r1=50375&r2=50376&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp Mon Apr 28 17:07:13 2008
@@ -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);
 }