[llvm] r214574 - [SDAG] MorphNodeTo recursively deletes dead operands of the old

[Chandler Carruth]

Author: chandlerc
Date: Fri Aug  1 17:09:43 2014
New Revision: 214574

URL: http://llvm.org/viewvc/llvm-project?rev=214574&view=rev
Log:
[SDAG] MorphNodeTo recursively deletes dead operands of the old
fromulation of the node, which isn't really the desired behavior from
within the combiner or legalizer, but is necessary within ISel. I've
added a hopefully helpful comment and fixed the only two places where
this took place.

Yet another step toward the combiner and legalizer not needing to use
update listeners with virtual calls to manage the worklists behind
legalization and combining.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/trunk/lib/Target/Mips/MipsSEISelLowering.cpp
    llvm/trunk/lib/Target/R600/SIISelLowering.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=214574&r1=214573&r2=214574&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Fri Aug  1 17:09:43 2014
@@ -5467,6 +5467,10 @@ SDNode *SelectionDAG::UpdadeSDLocOnMerge
 /// node, and because it doesn't require CSE recalculation for any of
 /// the node's users.
 ///
+/// However, note that MorphNodeTo recursively deletes dead nodes from the DAG.
+/// As a consequence it isn't appropriate to use from within the DAG combiner or
+/// the legalizer which maintain worklists that would need to be updated when
+/// deleting things.
 SDNode *SelectionDAG::MorphNodeTo(SDNode *N, unsigned Opc,
                                   SDVTList VTs, ArrayRef<SDValue> Ops) {
   unsigned NumOps = Ops.size();

Modified: llvm/trunk/lib/Target/Mips/MipsSEISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/MipsSEISelLowering.cpp?rev=214574&r1=214573&r2=214574&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Mips/MipsSEISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/Mips/MipsSEISelLowering.cpp Fri Aug  1 17:09:43 2014
@@ -578,10 +578,9 @@ static SDValue performANDCombine(SDNode
     if ((Op0Opcode == MipsISD::VEXTRACT_ZEXT_ELT && Log2 >= ExtendTySize) ||
         Log2 == ExtendTySize) {
       SDValue Ops[] = { Op0->getOperand(0), Op0->getOperand(1), Op0Op2 };
-      DAG.MorphNodeTo(Op0.getNode(), MipsISD::VEXTRACT_ZEXT_ELT,
-                      Op0->getVTList(),
-                      makeArrayRef(Ops, Op0->getNumOperands()));
-      return Op0;
+      return DAG.getNode(MipsISD::VEXTRACT_ZEXT_ELT, SDLoc(Op0),
+                         Op0->getVTList(),
+                         makeArrayRef(Ops, Op0->getNumOperands()));
     }
   }
 
@@ -923,10 +922,9 @@ static SDValue performSRACombine(SDNode
            TotalBits <= 32)) {
         SDValue Ops[] = { Op0Op0->getOperand(0), Op0Op0->getOperand(1),
                           Op0Op0->getOperand(2) };
-        DAG.MorphNodeTo(Op0Op0.getNode(), MipsISD::VEXTRACT_SEXT_ELT,
-                        Op0Op0->getVTList(),
-                        makeArrayRef(Ops, Op0Op0->getNumOperands()));
-        return Op0Op0;
+        return DAG.getNode(MipsISD::VEXTRACT_SEXT_ELT, SDLoc(Op0Op0),
+                           Op0Op0->getVTList(),
+                           makeArrayRef(Ops, Op0Op0->getNumOperands()));
       }
     }
   }

Modified: llvm/trunk/lib/Target/R600/SIISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/R600/SIISelLowering.cpp?rev=214574&r1=214573&r2=214574&view=diff
==============================================================================
--- llvm/trunk/lib/Target/R600/SIISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/R600/SIISelLowering.cpp Fri Aug  1 17:09:43 2014
@@ -774,7 +774,9 @@ SDValue SITargetLowering::LowerBRCOND(SD
       BR->getOperand(0),
       BRCOND.getOperand(2)
     };
-    DAG.MorphNodeTo(BR, ISD::BR, BR->getVTList(), Ops);
+    SDValue NewBR = DAG.getNode(ISD::BR, DL, BR->getVTList(), Ops);
+    DAG.ReplaceAllUsesWith(BR, NewBR.getNode());
+    BR = NewBR.getNode();
   }
 
   SDValue Chain = SDValue(Result, Result->getNumValues() - 1);