[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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214574 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index b9a0f44990f2734d5e7f3a886c8a58b7c784a5d3..a69a11941ca37387a57afa30a53d7ca1985df514 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5467,6 +5467,10 @@ SDNode *SelectionDAG::UpdadeSDLocOnMergedSDNode(SDNode *N, SDLoc OLoc) {
 /// 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();

diff --git a/lib/Target/Mips/MipsSEISelLowering.cpp b/lib/Target/Mips/MipsSEISelLowering.cpp
index 16b414e885659daa55af596d8db8656293cc0d06..515b8ac87c6d906f127170989738f5f894fe5b8a 100644 (file)
--- a/lib/Target/Mips/MipsSEISelLowering.cpp
+++ b/lib/Target/Mips/MipsSEISelLowering.cpp
@@ -578,10 +578,9 @@ static SDValue performANDCombine(SDNode *N, SelectionDAG &DAG,
     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 *N, SelectionDAG &DAG,
            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()));
       }
     }
   }

diff --git a/lib/Target/R600/SIISelLowering.cpp b/lib/Target/R600/SIISelLowering.cpp
index dc26a82e19d1521a359561130ea2e92a1baf2525..36afe5792a3f09ee91605560348bf5b7f3b3418a 100644 (file)
--- a/lib/Target/R600/SIISelLowering.cpp
+++ b/lib/Target/R600/SIISelLowering.cpp
@@ -774,7 +774,9 @@ SDValue SITargetLowering::LowerBRCOND(SDValue BRCOND,
       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);