Index: llvm/trunk/test/TableGen/GlobalISelEmitter.td
===================================================================
--- llvm/trunk/test/TableGen/GlobalISelEmitter.td
+++ llvm/trunk/test/TableGen/GlobalISelEmitter.td
@@ -387,6 +387,42 @@
 def XORlike : I<(outs GPR32:$dst), (ins m1Z:$src2, GPR32:$src1),
                 [(set GPR32:$dst, (xor GPR32:$src1, -4))]>;
 
+//===- Test a simple pattern with multiple operands with defaults. --------===//
+//
+
+// CHECK-LABEL: if ([&]() {
+// CHECK-NEXT:    MachineInstr &MI0 = I;
+// CHECK-NEXT:    if (MI0.getNumOperands() < 3)
+// CHECK-NEXT:      return false;
+// CHECK-NEXT:    if ((MI0.getOpcode() == TargetOpcode::G_XOR) &&
+// CHECK-NEXT:        ((/* dst */ (MRI.getType(MI0.getOperand(0).getReg()) == (LLT::scalar(32))) &&
+// CHECK-NEXT:         ((&RBI.getRegBankFromRegClass(MyTarget::GPR32RegClass) == RBI.getRegBank(MI0.getOperand(0).getReg(), MRI, TRI))))) &&
+// CHECK-NEXT:        ((/* src1 */ (MRI.getType(MI0.getOperand(1).getReg()) == (LLT::scalar(32))) &&
+// CHECK-NEXT:         ((&RBI.getRegBankFromRegClass(MyTarget::GPR32RegClass) == RBI.getRegBank(MI0.getOperand(1).getReg(), MRI, TRI))))) &&
+// CHECK-NEXT:        ((/* Operand 2 */ (MRI.getType(MI0.getOperand(2).getReg()) == (LLT::scalar(32))) &&
+// CHECK-NEXT:        (isOperandImmEqual(MI0.getOperand(2), -5, MRI))))) {
+// CHECK-NEXT:      // (xor:i32 GPR32:i32:$src1, -5:i32) => (XORManyDefaults:i32 GPR32:i32:$src1)
+// CHECK-NEXT:      MachineInstrBuilder MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(MyTarget::XORManyDefaults));
+// CHECK-NEXT:      MIB.add(MI0.getOperand(0)/*dst*/);
+// CHECK-NEXT:      MIB.addImm(-1);
+// CHECK-NEXT:      MIB.addReg(MyTarget::R0);
+// CHECK-NEXT:      MIB.addReg(MyTarget::R0);
+// CHECK-NEXT:      MIB.add(MI0.getOperand(1)/*src1*/);
+// CHECK-NEXT:      for (const auto *FromMI : {&MI0, })
+// CHECK-NEXT:        for (const auto &MMO : FromMI->memoperands())
+// CHECK-NEXT:          MIB.addMemOperand(MMO);
+// CHECK-NEXT:      I.eraseFromParent();
+// CHECK-NEXT:      MachineInstr &NewI = *MIB;
+// CHECK-NEXT:      constrainSelectedInstRegOperands(NewI, TII, TRI, RBI);
+// CHECK-NEXT:      return true;
+// CHECK-NEXT:    }
+// CHECK-NEXT:    return false;
+// CHECK-NEXT:  }()) { return true; }
+
+// The -5 is just to distinguish it from the other cases.
+def XORManyDefaults : I<(outs GPR32:$dst), (ins m1Z:$src3, Z:$src2, GPR32:$src1),
+                        [(set GPR32:$dst, (xor GPR32:$src1, -5))]>;
+
 //===- Test a simple pattern with constant immediate operands. ------------===//
 //
 // This must precede the 3-register variants because constant immediates have
Index: llvm/trunk/utils/TableGen/GlobalISelEmitter.cpp
===================================================================
--- llvm/trunk/utils/TableGen/GlobalISelEmitter.cpp
+++ llvm/trunk/utils/TableGen/GlobalISelEmitter.cpp
@@ -1242,6 +1242,8 @@
   Error importExplicitUseRenderer(BuildMIAction &DstMIBuilder,
                                   TreePatternNode *DstChild,
                                   const InstructionMatcher &InsnMatcher) const;
+  Error importDefaultOperandRenderers(BuildMIAction &DstMIBuilder,
+                                      DagInit *DefaultOps) const;
   Error
   importImplicitDefRenderers(BuildMIAction &DstMIBuilder,
                              const std::vector<Record *> &ImplicitDefs) const;
@@ -1509,59 +1511,23 @@
     DstMIBuilder.addRenderer<CopyRenderer>(InsnMatcher, DstIOperand.Name);
   }
 
-  // Figure out which operands need defaults inserted. Operands that subclass
-  // OperandWithDefaultOps are considered from left to right until we have
-  // enough operands to render the instruction.
-  SmallSet<unsigned, 2> DefaultOperands;
-  unsigned DstINumUses = DstI.Operands.size() - DstI.Operands.NumDefs;
-  unsigned NumDefaultOperands = 0;
-  for (unsigned I = 0; I < DstINumUses &&
-                       DstINumUses > Dst->getNumChildren() + NumDefaultOperands;
-       ++I) {
-    const auto &DstIOperand = DstI.Operands[DstI.Operands.NumDefs + I];
-    if (DstIOperand.Rec->isSubClassOf("OperandWithDefaultOps")) {
-      DefaultOperands.insert(I);
-      NumDefaultOperands +=
-          DstIOperand.Rec->getValueAsDag("DefaultOps")->getNumArgs();
-    }
-  }
-  if (DstINumUses > Dst->getNumChildren() + DefaultOperands.size())
-    return failedImport("Insufficient operands supplied and default ops "
-                        "couldn't make up the shortfall");
-  if (DstINumUses < Dst->getNumChildren() + DefaultOperands.size())
-    return failedImport("Too many operands supplied");
-
   // Render the explicit uses.
   unsigned Child = 0;
+  unsigned DstINumUses = DstI.Operands.size() - DstI.Operands.NumDefs;
+  unsigned NumDefaultOps = 0;
   for (unsigned I = 0; I != DstINumUses; ++I) {
-    // If we need to insert default ops here, then do so.
-    if (DefaultOperands.count(I)) {
-      const auto &DstIOperand = DstI.Operands[DstI.Operands.NumDefs + I];
+    const auto &DstIOperand = DstI.Operands[DstI.Operands.NumDefs + I];
 
+    // If the operand has default values, introduce them now.
+    // FIXME: Until we have a decent test case that dictates we should do
+    // otherwise, we're going to assume that operands with default values cannot
+    // be specified in the patterns. Therefore, adding them will not cause us to
+    // end up with too many rendered operands.
+    if (DstIOperand.Rec->isSubClassOf("OperandWithDefaultOps")) {
       DagInit *DefaultOps = DstIOperand.Rec->getValueAsDag("DefaultOps");
-      for (const auto *DefaultOp : DefaultOps->args()) {
-        // Look through ValueType operators.
-        if (const DagInit *DefaultDagOp = dyn_cast<DagInit>(DefaultOp)) {
-          if (const DefInit *DefaultDagOperator =
-                  dyn_cast<DefInit>(DefaultDagOp->getOperator())) {
-            if (DefaultDagOperator->getDef()->isSubClassOf("ValueType"))
-              DefaultOp = DefaultDagOp->getArg(0);
-          }
-        }
-
-        if (const DefInit *DefaultDefOp = dyn_cast<DefInit>(DefaultOp)) {
-          DstMIBuilder.addRenderer<AddRegisterRenderer>(DefaultDefOp->getDef());
-          continue;
-        }
-
-        if (const IntInit *DefaultIntOp = dyn_cast<IntInit>(DefaultOp)) {
-          DstMIBuilder.addRenderer<ImmRenderer>(DefaultIntOp->getValue());
-          continue;
-        }
-
-        return failedImport("Could not add default op");
-      }
-
+      if (auto Error = importDefaultOperandRenderers(DstMIBuilder, DefaultOps))
+        return std::move(Error);
+      ++NumDefaultOps;
       continue;
     }
 
@@ -1571,9 +1537,44 @@
     ++Child;
   }
 
+  if (NumDefaultOps + Dst->getNumChildren() != DstINumUses)
+    return failedImport("Expected " + std::to_string(DstINumUses) +
+                        " used operands but found " +
+                        std::to_string(Dst->getNumChildren()) +
+                        " explicit ones and " + std::to_string(NumDefaultOps) +
+                        " default ones");
+
   return DstMIBuilder;
 }
 
+Error GlobalISelEmitter::importDefaultOperandRenderers(
+    BuildMIAction &DstMIBuilder, DagInit *DefaultOps) const {
+  for (const auto *DefaultOp : DefaultOps->args()) {
+    // Look through ValueType operators.
+    if (const DagInit *DefaultDagOp = dyn_cast<DagInit>(DefaultOp)) {
+      if (const DefInit *DefaultDagOperator =
+              dyn_cast<DefInit>(DefaultDagOp->getOperator())) {
+        if (DefaultDagOperator->getDef()->isSubClassOf("ValueType"))
+          DefaultOp = DefaultDagOp->getArg(0);
+      }
+    }
+
+    if (const DefInit *DefaultDefOp = dyn_cast<DefInit>(DefaultOp)) {
+      DstMIBuilder.addRenderer<AddRegisterRenderer>(DefaultDefOp->getDef());
+      continue;
+    }
+
+    if (const IntInit *DefaultIntOp = dyn_cast<IntInit>(DefaultOp)) {
+      DstMIBuilder.addRenderer<ImmRenderer>(DefaultIntOp->getValue());
+      continue;
+    }
+
+    return failedImport("Could not add default op");
+  }
+
+  return Error::success();
+}
+
 Error GlobalISelEmitter::importImplicitDefRenderers(
     BuildMIAction &DstMIBuilder,
     const std::vector<Record *> &ImplicitDefs) const {