diff --git a/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h b/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h
--- a/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h
+++ b/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h
@@ -30,19 +30,31 @@
 /// stored directly. For binary operations, e0 and e1 denote the index of the
 /// children tensor expressions.
 struct TensorExp {
-  TensorExp(Kind k, unsigned x, unsigned y, Value v)
-      : kind(k), e0(x), e1(y), val(v) {
-    assert((kind == Kind::kTensor && e0 != -1u && e1 == -1u && !val) ||
-           (kind == Kind::kInvariant && e0 == -1u && e1 == -1u && val) ||
-           (kind >= Kind::kMulF && e0 != -1u && e1 != -1u && !val));
+  TensorExp(Kind k, unsigned x, unsigned y, Value v) : kind(k), val(v) {
+    assert((kind == Kind::kTensor && x != -1u && y == -1u && !val) ||
+           (kind == Kind::kInvariant && x == -1u && y == -1u && val) ||
+           (kind >= Kind::kMulF && x != -1u && y != -1u && !val));
+    if (kind == Kind::kTensor) {
+      tensor = x;
+    } else if (kind >= Kind::kMulF) {
+      children.e0 = x;
+      children.e1 = y;
+    }
   }
 
   /// Tensor expression kind.
   Kind kind;
 
-  /// Indices of children expression(s).
-  unsigned e0;
-  unsigned e1;
+  union {
+    /// Expressions representing tensors simply have a tensor number.
+    unsigned tensor;
+
+    /// Binary operations hold the indices of their child expressions.
+    struct {
+      unsigned e0;
+      unsigned e1;
+    } children;
+  };
 
   /// Direct link to IR for an invariant. During code generation,
   /// field is used to cache "hoisted" loop invariant tensor loads.
diff --git a/mlir/lib/Dialect/SparseTensor/Transforms/Sparsification.cpp b/mlir/lib/Dialect/SparseTensor/Transforms/Sparsification.cpp
--- a/mlir/lib/Dialect/SparseTensor/Transforms/Sparsification.cpp
+++ b/mlir/lib/Dialect/SparseTensor/Transforms/Sparsification.cpp
@@ -259,11 +259,11 @@
 static unsigned isConjunction(Merger &merger, unsigned tensor, unsigned exp) {
   switch (merger.exp(exp).kind) {
   case Kind::kTensor:
-    return merger.exp(exp).e0 == tensor;
+    return merger.exp(exp).tensor == tensor;
   case Kind::kMulF:
   case Kind::kMulI:
-    return isConjunction(merger, tensor, merger.exp(exp).e0) ||
-           isConjunction(merger, tensor, merger.exp(exp).e1);
+    return isConjunction(merger, tensor, merger.exp(exp).children.e0) ||
+           isConjunction(merger, tensor, merger.exp(exp).children.e1);
   default:
     return false;
   }
@@ -500,7 +500,7 @@
   }
   // Actual load.
   SmallVector<Value, 4> args;
-  OpOperand *t = op.getInputAndOutputOperands()[merger.exp(exp).e0];
+  OpOperand *t = op.getInputAndOutputOperands()[merger.exp(exp).tensor];
   unsigned tensor = t->getOperandNumber();
   auto map = op.getTiedIndexingMap(t);
   auto enc = getSparseTensorEncoding(t->get().getType());
@@ -673,8 +673,8 @@
     return genTensorLoad(merger, codegen, rewriter, op, exp);
   else if (merger.exp(exp).kind == Kind::kInvariant)
     return genInvariantValue(merger, codegen, rewriter, exp);
-  Value v0 = genExp(merger, codegen, rewriter, op, merger.exp(exp).e0);
-  Value v1 = genExp(merger, codegen, rewriter, op, merger.exp(exp).e1);
+  Value v0 = genExp(merger, codegen, rewriter, op, merger.exp(exp).children.e0);
+  Value v1 = genExp(merger, codegen, rewriter, op, merger.exp(exp).children.e1);
   switch (merger.exp(exp).kind) {
   case Kind::kTensor:
   case Kind::kInvariant:
@@ -698,7 +698,7 @@
   if (merger.exp(exp).kind == Kind::kTensor) {
     // Inspect tensor indices.
     bool atLevel = ldx == -1u;
-    OpOperand *t = op.getInputAndOutputOperands()[merger.exp(exp).e0];
+    OpOperand *t = op.getInputAndOutputOperands()[merger.exp(exp).tensor];
     auto map = op.getTiedIndexingMap(t);
     auto enc = getSparseTensorEncoding(t->get().getType());
     for (unsigned d = 0, rank = map.getNumResults(); d < rank; d++) {
@@ -720,8 +720,8 @@
     // Traverse into the binary operations. Note that we only hoist
     // tensor loads, since subsequent MLIR/LLVM passes know how to
     // deal with all other kinds of derived loop invariants.
-    unsigned e0 = merger.exp(exp).e0;
-    unsigned e1 = merger.exp(exp).e1;
+    unsigned e0 = merger.exp(exp).children.e0;
+    unsigned e1 = merger.exp(exp).children.e1;
     genInvariants(merger, codegen, rewriter, op, e0, ldx, hoist);
     genInvariants(merger, codegen, rewriter, op, e1, ldx, hoist);
   }
diff --git a/mlir/lib/Dialect/SparseTensor/Utils/Merger.cpp b/mlir/lib/Dialect/SparseTensor/Utils/Merger.cpp
--- a/mlir/lib/Dialect/SparseTensor/Utils/Merger.cpp
+++ b/mlir/lib/Dialect/SparseTensor/Utils/Merger.cpp
@@ -68,7 +68,7 @@
     if (p0 != p1) {
       // Is this a straightforward copy?
       unsigned e = latPoints[p1].exp;
-      if (exp(e).kind == Kind::kTensor && exp(e).e0 == outTensor)
+      if (exp(e).kind == Kind::kTensor && exp(e).tensor == outTensor)
         continue;
       // Conjunction already covered?
       for (unsigned p2 : latSets[s]) {
@@ -144,12 +144,12 @@
     // set to the undefined index in that dimension. An invariant expression
     // is set to a synthetic tensor with undefined indices only.
     unsigned s = addSet();
-    unsigned t = kind == Kind::kTensor ? exp(e).e0 : syntheticTensor;
+    unsigned t = kind == Kind::kTensor ? exp(e).tensor : syntheticTensor;
     set(s).push_back(addLat(t, idx, e));
     return s;
   }
-  unsigned s0 = buildLattices(exp(e).e0, idx);
-  unsigned s1 = buildLattices(exp(e).e1, idx);
+  unsigned s0 = buildLattices(exp(e).children.e0, idx);
+  unsigned s1 = buildLattices(exp(e).children.e1, idx);
   switch (kind) {
   case Kind::kTensor:
   case Kind::kInvariant:
@@ -173,7 +173,7 @@
 void Merger::dumpExp(unsigned e) const {
   switch (tensorExps[e].kind) {
   case Kind::kTensor:
-    llvm::dbgs() << "tensor_" << tensorExps[e].e0;
+    llvm::dbgs() << "tensor_" << tensorExps[e].tensor;
     break;
   case Kind::kInvariant:
     llvm::dbgs() << "invariant";
@@ -181,17 +181,17 @@
   default:
   case Kind::kMulI:
     llvm::dbgs() << "(";
-    dumpExp(tensorExps[e].e0);
+    dumpExp(tensorExps[e].children.e0);
     llvm::dbgs() << " * ";
-    dumpExp(tensorExps[e].e1);
+    dumpExp(tensorExps[e].children.e1);
     llvm::dbgs() << ")";
     break;
   case Kind::kAddF:
   case Kind::kAddI:
     llvm::dbgs() << "(";
-    dumpExp(tensorExps[e].e0);
+    dumpExp(tensorExps[e].children.e0);
     llvm::dbgs() << " + ";
-    dumpExp(tensorExps[e].e1);
+    dumpExp(tensorExps[e].children.e1);
     llvm::dbgs() << ")";
     break;
   }