Index: mlir/lib/Dialect/Arith/IR/ArithOps.cpp
===================================================================
--- mlir/lib/Dialect/Arith/IR/ArithOps.cpp
+++ mlir/lib/Dialect/Arith/IR/ArithOps.cpp
@@ -1245,13 +1245,29 @@
 //===----------------------------------------------------------------------===//
 
 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)
+    int64_t srcBitWith;
+    int64_t dstBitWith;
+    if (arith::ExtUIOp zextOp = getIn().getDefiningOp<arith::ExtUIOp>()) {
+      srcBitWith = getScalarOrElementWidth(zextOp.getIn().getType());
+      dstBitWith = getScalarOrElementWidth(getType());
+    } else {
+      srcBitWith = getScalarOrElementWidth(
+          getIn().getDefiningOp<arith::ExtSIOp>().getIn().getType());
+      dstBitWith = getScalarOrElementWidth(getType());
+    }
+    if (srcBitWith > dstBitWith) {
+      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: @truncExtuiToTrunci
+//       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: @truncExtsiToTrunci
+//       CHECK:  %[[ARG0:.+]]: i32
+//       CHECK:  %[[CST:.*]] = arith.trunci %[[ARG0:.+]] : i32 to i16
+//       CHECK:   return  %[[CST:.*]]
+func.func @truncExtsiToTrunci(%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]]