diff --git a/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td b/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
--- a/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
+++ b/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
@@ -319,6 +319,20 @@
       CPred<"(getScalarOrElementWidth($0) - getScalarOrElementWidth($1)) == "
               "*getIntOrSplatIntValue($2)">]>>;
 
+// trunci(extsi(x)) -> extsi(x), when only the sign-extension bits are truncated
+def TruncIExtSIToExtSI :
+    Pat<(Arith_TruncIOp:$tr (Arith_ExtSIOp:$ext $x)),
+        (Arith_ExtSIOp $x),
+        [(ValueWiderThan $ext, $tr),
+         (ValueWiderThan $tr, $x)]>;
+
+// trunci(extui(x)) -> extui(x), when only the zero-extension bits are truncated
+def TruncIExtUIToExtUI :
+    Pat<(Arith_TruncIOp:$tr (Arith_ExtUIOp:$ext $x)),
+        (Arith_ExtUIOp $x),
+        [(ValueWiderThan $ext, $tr),
+         (ValueWiderThan $tr, $x)]>;
+
 // trunci(shrsi(x, c)) -> trunci(shrui(x, c))
 def TruncIShrSIToTrunciShrUI :
     Pat<(Arith_TruncIOp:$tr
diff --git a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
--- a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
+++ b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
@@ -1290,8 +1290,9 @@
 
 void arith::TruncIOp::getCanonicalizationPatterns(RewritePatternSet &patterns,
                                                   MLIRContext *context) {
-  patterns.add<TruncIShrSIToTrunciShrUI, TruncIShrUIMulIToMulSIExtended,
-               TruncIShrUIMulIToMulUIExtended>(context);
+  patterns.add<TruncIExtSIToExtSI, TruncIExtUIToExtUI, TruncIShrSIToTrunciShrUI,
+               TruncIShrUIMulIToMulSIExtended, TruncIShrUIMulIToMulUIExtended>(
+      context);
 }
 
 LogicalResult arith::TruncIOp::verify() {
diff --git a/mlir/test/Dialect/Arith/canonicalize.mlir b/mlir/test/Dialect/Arith/canonicalize.mlir
--- a/mlir/test/Dialect/Arith/canonicalize.mlir
+++ b/mlir/test/Dialect/Arith/canonicalize.mlir
@@ -629,6 +629,16 @@
   return %trunci : i16
 }
 
+// CHECK-LABEL: @truncExtui3
+//       CHECK:  %[[ARG0:.+]]: i8
+//       CHECK:  %[[CST:.*]] = arith.extui %[[ARG0:.+]] : i8 to i16
+//       CHECK:   return  %[[CST:.*]] : i16
+func.func @truncExtui3(%arg0: i8) -> i16 {
+  %extui = arith.extui %arg0 : i8 to i32
+  %trunci = arith.trunci %extui : i32 to i16
+  return %trunci : i16
+}
+
 // CHECK-LABEL: @truncExtuiVector
 //       CHECK:  %[[ARG0:.+]]: vector<2xi32>
 //       CHECK:  %[[CST:.*]] = arith.trunci %[[ARG0:.+]] : vector<2xi32> to vector<2xi16>
@@ -658,6 +668,16 @@
   return %trunci : i16
 }
 
+// CHECK-LABEL: @truncExtsi3
+//       CHECK:  %[[ARG0:.+]]: i8
+//       CHECK:  %[[CST:.*]] = arith.extsi %[[ARG0:.+]] : i8 to i16
+//       CHECK:   return  %[[CST:.*]] : i16
+func.func @truncExtsi3(%arg0: i8) -> i16 {
+  %extsi = arith.extsi %arg0 : i8 to i32
+  %trunci = arith.trunci %extsi : i32 to i16
+  return %trunci : i16
+}
+
 // CHECK-LABEL: @truncExtsiVector
 //       CHECK:  %[[ARG0:.+]]: vector<2xi32>
 //       CHECK:  %[[CST:.*]] = arith.trunci %[[ARG0:.+]] : vector<2xi32> to vector<2xi16>
diff --git a/mlir/test/Transforms/canonicalize.mlir b/mlir/test/Transforms/canonicalize.mlir
--- a/mlir/test/Transforms/canonicalize.mlir
+++ b/mlir/test/Transforms/canonicalize.mlir
@@ -1107,14 +1107,10 @@
 
 // -----
 
-// TODO Canonicalize this into:
-//   arith.extui %arg0 : i1 to i2
-
-// CHECK-LABEL: func @do_not_fold_trunci
+// CHECK-LABEL: func @fold_trunci
 // CHECK-SAME:    (%[[ARG0:[0-9a-z]*]]: i1)
-func.func @do_not_fold_trunci(%arg0: i1) -> i2 attributes {} {
-  // CHECK-NEXT: arith.extui %[[ARG0]] : i1 to i8
-  // CHECK-NEXT: %[[RES:[0-9a-z]*]] = arith.trunci %{{.*}} : i8 to i2
+func.func @fold_trunci(%arg0: i1) -> i2 attributes {} {
+  // CHECK-NEXT: %[[RES:[0-9a-z]*]] = arith.extui %[[ARG0]] : i1 to i2
   // CHECK-NEXT: return %[[RES]] : i2
   %0 = arith.extui %arg0 : i1 to i8
   %1 = arith.trunci %0 : i8 to i2
@@ -1123,11 +1119,10 @@
 
 // -----
 
-// CHECK-LABEL: func @do_not_fold_trunci_vector
+// CHECK-LABEL: func @fold_trunci_vector
 // CHECK-SAME:    (%[[ARG0:[0-9a-z]*]]: vector<4xi1>)
-func.func @do_not_fold_trunci_vector(%arg0: vector<4xi1>) -> vector<4xi2> attributes {} {
-  // CHECK-NEXT: arith.extui %[[ARG0]] : vector<4xi1> to vector<4xi8>
-  // CHECK-NEXT: %[[RES:[0-9a-z]*]] = arith.trunci %{{.*}} : vector<4xi8> to vector<4xi2>
+func.func @fold_trunci_vector(%arg0: vector<4xi1>) -> vector<4xi2> attributes {} {
+  // CHECK-NEXT: %[[RES:[0-9a-z]*]] = arith.extui %[[ARG0]] : vector<4xi1> to vector<4xi2>
   // CHECK-NEXT: return %[[RES]] : vector<4xi2>
   %0 = arith.extui %arg0 : vector<4xi1> to vector<4xi8>
   %1 = arith.trunci %0 : vector<4xi8> to vector<4xi2>