Add checks to make sure we don't create bogus extend nodes, and fix a bug

where we were doing exactly that which was causing failures on x86 and
alpha.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26284 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -665,6 +665,9 @@ SDOperand DAGCombiner::visitADD(SDNode *N) {
   // fold (A+(B-A)) -> B
   if (N1.getOpcode() == ISD::SUB && N0 == N1.getOperand(1))
     return N1.getOperand(0);
+  // 
+  if (SimplifyDemandedBits(SDOperand(N, 0)))
+    return SDOperand();
   return SDOperand();
 }
 
@@ -2297,13 +2300,16 @@ SDOperand DAGCombiner::SimplifySelectCC(SDOperand N0, SDOperand N1,
     // Get a SetCC of the condition
     // FIXME: Should probably make sure that setcc is legal if we ever have a
     // target where it isn't.
-    SDOperand Temp, SCC = DAG.getSetCC(TLI.getSetCCResultTy(), N0, N1, CC);
+    SDOperand Temp, SCC;
-    WorkList.push_back(SCC.Val);
     // cast from setcc result type to select result type
-    if (AfterLegalize)
+    if (AfterLegalize) {
+      SCC  = DAG.getSetCC(TLI.getSetCCResultTy(), N0, N1, CC);
       Temp = DAG.getZeroExtendInReg(SCC, N2.getValueType());
-    else
+    } else {
+      SCC  = DAG.getSetCC(MVT::i1, N0, N1, CC);
       Temp = DAG.getNode(ISD::ZERO_EXTEND, N2.getValueType(), SCC);
+    }
+    WorkList.push_back(SCC.Val);
     WorkList.push_back(Temp.Val);
     // shl setcc result by log2 n2c
     return DAG.getNode(ISD::SHL, N2.getValueType(), Temp,

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -1047,22 +1047,26 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
     return Operand;         // Factor of one node?  No factor.
   case ISD::SIGN_EXTEND:
     if (Operand.getValueType() == VT) return Operand;   // noop extension
+    assert(Operand.getValueType() < VT && "Invalid sext node, dst < src!");
     if (OpOpcode == ISD::SIGN_EXTEND || OpOpcode == ISD::ZERO_EXTEND)
       return getNode(OpOpcode, VT, Operand.Val->getOperand(0));
     break;
   case ISD::ZERO_EXTEND:
     if (Operand.getValueType() == VT) return Operand;   // noop extension
+    assert(Operand.getValueType() < VT && "Invalid zext node, dst < src!");
     if (OpOpcode == ISD::ZERO_EXTEND)   // (zext (zext x)) -> (zext x)
       return getNode(ISD::ZERO_EXTEND, VT, Operand.Val->getOperand(0));
     break;
   case ISD::ANY_EXTEND:
     if (Operand.getValueType() == VT) return Operand;   // noop extension
+    assert(Operand.getValueType() < VT && "Invalid anyext node, dst < src!");
     if (OpOpcode == ISD::ZERO_EXTEND || OpOpcode == ISD::SIGN_EXTEND)
       // (ext (zext x)) -> (zext x)  and  (ext (sext x)) -> (sext x)
       return getNode(OpOpcode, VT, Operand.Val->getOperand(0));
     break;
   case ISD::TRUNCATE:
     if (Operand.getValueType() == VT) return Operand;   // noop truncate
+    assert(Operand.getValueType() > VT && "Invalid truncate node, src < dst!");
     if (OpOpcode == ISD::TRUNCATE)
       return getNode(ISD::TRUNCATE, VT, Operand.Val->getOperand(0));
     else if (OpOpcode == ISD::ZERO_EXTEND || OpOpcode == ISD::SIGN_EXTEND ||