Index: mlir/lib/Dialect/Arith/IR/ArithOps.cpp
===================================================================
--- mlir/lib/Dialect/Arith/IR/ArithOps.cpp
+++ mlir/lib/Dialect/Arith/IR/ArithOps.cpp
@@ -1243,15 +1243,35 @@
 //===----------------------------------------------------------------------===//
 // TruncIOp
 //===----------------------------------------------------------------------===//
+template <typename ValType, typename Op1, typename Op2>
+static std::pair<unsigned, unsigned> getOpOfBitWith(Op1 op1, Op2 op2) {
+  Type op1Type = getElementTypeOrSelf(op1.getIn().getType());
+  Type op2Type = getElementTypeOrSelf(op2.getType());
+  unsigned op1BitWith = op1Type.cast<IntegerType>().getWidth();
+  unsigned op2BitWith = op2Type.cast<IntegerType>().getWidth();
+  return std::make_pair(op1BitWith, op2BitWith);
+}
 
 OpFoldResult arith::TruncIOp::fold(ArrayRef<Attribute> operands) {
-  assert(operands.size() == 1 && "unary operation takes one operand");
-
-  // trunci(zexti(a)) -> a
-  // trunci(sexti(a)) -> a
   if (matchPattern(getOperand(), m_Op<arith::ExtUIOp>()) ||
-      matchPattern(getOperand(), m_Op<arith::ExtSIOp>()))
+      matchPattern(getOperand(), m_Op<arith::ExtSIOp>())) {
+    // trunci(zexti(a)) -> trunci(a)
+    // trunci(sexti(a)) -> trunci(a)
+    std::pair<unsigned, unsigned> bitWith;
+    if (arith::ExtUIOp zextOp = getIn().getDefiningOp<arith::ExtUIOp>()) {
+      bitWith = getOpOfBitWith<IntegerType>(zextOp, *this);
+    } else {
+      bitWith = getOpOfBitWith<IntegerType>(
+          getIn().getDefiningOp<arith::ExtSIOp>(), *this);
+    }
+    if (bitWith.first > bitWith.second) {
+      setOperand(getOperand().getDefiningOp()->getOperand(0));
+      return getResult();
+    }
+    // trunci(zexti(a)) -> a
+    // trunci(sexti(a)) -> a
     return getOperand().getDefiningOp()->getOperand(0);
+  }
 
   // trunci(trunci(a)) -> trunci(a))
   if (matchPattern(getOperand(), m_Op<arith::TruncIOp>())) {
Index: mlir/test/Dialect/Arith/canonicalize.mlir
===================================================================
--- mlir/test/Dialect/Arith/canonicalize.mlir
+++ mlir/test/Dialect/Arith/canonicalize.mlir
@@ -429,6 +429,16 @@
   return %trunci : i32
 }
 
+// CHECK-LABEL: @truncExtui
+//       CHECK:  %[[ARG0:.+]]: i32
+//       CHECK:  %[[CST:.*]] = arith.trunci %[[ARG0:.+]] : i32 to i16
+//       CHECK:   return  %[[CST:.*]]
+func.func @truncExtuiToTrunci(%arg0: i32) -> i16 {
+  %extui = arith.extui %arg0 : i32 to i64
+  %trunci = arith.trunci %extui : i64 to i16
+  return %trunci : i16
+}
+
 // CHECK-LABEL: @truncExtsi
 //       CHECK-NOT:  trunci
 //       CHECK:   return  %arg0
@@ -438,6 +448,16 @@
   return %trunci : i32
 }
 
+// CHECK-LABEL: @truncExtsiToTrunc
+//       CHECK:  %[[ARG0:.+]]: i32
+//       CHECK:  %[[CST:.*]] = arith.trunci %[[ARG0:.+]] : i32 to i16
+//       CHECK:   return  %[[CST:.*]]
+func.func @truncExtsiToTrunc(%arg0: i32) -> i16 {
+  %extsi = arith.extsi %arg0 : i32 to i64
+  %trunci = arith.trunci %extsi : i64 to i16
+  return %trunci : i16
+}
+
 // CHECK-LABEL: @truncConstantSplat
 //       CHECK:   %[[cres:.+]] = arith.constant dense<-2> : vector<4xi8>
 //       CHECK:   return %[[cres]]