diff --git a/llvm/include/llvm/IR/IRBuilder.h b/llvm/include/llvm/IR/IRBuilder.h
--- a/llvm/include/llvm/IR/IRBuilder.h
+++ b/llvm/include/llvm/IR/IRBuilder.h
@@ -940,6 +940,11 @@
     return CreateBinaryIntrinsic(Intrinsic::maximum, LHS, RHS, nullptr, Name);
   }
 
+  /// Create call to the usub_sat intrinsic.
+  CallInst *CreateUSubSat(Value *LHS, Value *RHS, const Twine &Name = "") {
+    return CreateBinaryIntrinsic(Intrinsic::usub_sat, LHS, RHS, nullptr, Name);
+  }
+
   /// Create a call to the arithmetic_fence intrinsic.
   CallInst *CreateArithmeticFence(Value *Val, Type *DstType,
                                   const Twine &Name = "") {
diff --git a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
--- a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -1276,10 +1276,7 @@
       DestSize = Builder.CreateZExt(DestSize, SrcSize->getType());
   }
 
-  Value *Ule = Builder.CreateICmpULE(DestSize, SrcSize);
-  Value *SizeDiff = Builder.CreateSub(DestSize, SrcSize);
-  Value *MemsetLen = Builder.CreateSelect(
-      Ule, ConstantInt::getNullValue(DestSize->getType()), SizeDiff);
+  Value *MemsetLen = Builder.CreateUSubSat(DestSize, SrcSize, "memset.len");
   unsigned DestAS = Dest->getType()->getPointerAddressSpace();
   Instruction *NewMemSet = Builder.CreateMemSet(
       Builder.CreateGEP(
diff --git a/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll b/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
--- a/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
+++ b/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
@@ -7,11 +7,9 @@
 
 define void @test_constant(i64 %src_size, ptr %dst, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_constant(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr @C, i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -22,11 +20,9 @@
 
 define void @test(ptr %src, i64 %src_size, ptr noalias %dst, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -38,11 +34,9 @@
 define void @test_different_types_i32_i64(ptr noalias %dst, ptr %src, i32 %dst_size, i64 %src_size, i8 %c) {
 ; CHECK-LABEL: @test_different_types_i32_i64(
 ; CHECK-NEXT:    [[TMP1:%.*]] = zext i32 [[DST_SIZE:%.*]] to i64
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp ule i64 [[TMP1]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP3:%.*]] = sub i64 [[TMP1]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP4:%.*]] = select i1 [[TMP2]], i64 0, i64 [[TMP3]]
-; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP5]], i8 [[C:%.*]], i64 [[TMP4]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[TMP1]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP2]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -54,11 +48,9 @@
 define void @test_different_types_i128_i32(ptr noalias %dst, ptr %src, i128 %dst_size, i32 %src_size, i8 %c) {
 ; CHECK-LABEL: @test_different_types_i128_i32(
 ; CHECK-NEXT:    [[TMP1:%.*]] = zext i32 [[SRC_SIZE:%.*]] to i128
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp ule i128 [[DST_SIZE:%.*]], [[TMP1]]
-; CHECK-NEXT:    [[TMP3:%.*]] = sub i128 [[DST_SIZE]], [[TMP1]]
-; CHECK-NEXT:    [[TMP4:%.*]] = select i1 [[TMP2]], i128 0, i128 [[TMP3]]
-; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr i8, ptr [[DST:%.*]], i128 [[TMP1]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i128(ptr align 1 [[TMP5]], i8 [[C:%.*]], i128 [[TMP4]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i128 @llvm.usub.sat.i128(i128 [[DST_SIZE:%.*]], i128 [[TMP1]])
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr i8, ptr [[DST:%.*]], i128 [[TMP1]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i128(ptr align 1 [[TMP2]], i8 [[C:%.*]], i128 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i32(ptr [[DST]], ptr [[SRC:%.*]], i32 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -70,11 +62,9 @@
 define void @test_different_types_i32_i128(ptr noalias %dst, ptr %src, i32 %dst_size, i128 %src_size, i8 %c) {
 ; CHECK-LABEL: @test_different_types_i32_i128(
 ; CHECK-NEXT:    [[TMP1:%.*]] = zext i32 [[DST_SIZE:%.*]] to i128
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp ule i128 [[TMP1]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP3:%.*]] = sub i128 [[TMP1]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP4:%.*]] = select i1 [[TMP2]], i128 0, i128 [[TMP3]]
-; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr i8, ptr [[DST:%.*]], i128 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i128(ptr align 1 [[TMP5]], i8 [[C:%.*]], i128 [[TMP4]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i128 @llvm.usub.sat.i128(i128 [[TMP1]], i128 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr i8, ptr [[DST:%.*]], i128 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i128(ptr align 1 [[TMP2]], i8 [[C:%.*]], i128 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i128(ptr [[DST]], ptr [[SRC:%.*]], i128 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -86,11 +76,9 @@
 define void @test_different_types_i64_i32(ptr noalias %dst, ptr %src, i64 %dst_size, i32 %src_size, i8 %c) {
 ; CHECK-LABEL: @test_different_types_i64_i32(
 ; CHECK-NEXT:    [[TMP1:%.*]] = zext i32 [[SRC_SIZE:%.*]] to i64
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[TMP1]]
-; CHECK-NEXT:    [[TMP3:%.*]] = sub i64 [[DST_SIZE]], [[TMP1]]
-; CHECK-NEXT:    [[TMP4:%.*]] = select i1 [[TMP2]], i64 0, i64 [[TMP3]]
-; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[TMP1]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP5]], i8 [[C:%.*]], i64 [[TMP4]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[TMP1]])
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[TMP1]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP2]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i32(ptr [[DST]], ptr [[SRC:%.*]], i32 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -101,11 +89,9 @@
 
 define void @test_align_same(ptr %src, ptr noalias %dst, i64 %dst_size) {
 ; CHECK-LABEL: @test_align_same(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], 80
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], 80
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 80
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 8 [[TMP4]], i8 0, i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 80)
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 80
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 8 [[TMP1]], i8 0, i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 80, i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -116,11 +102,9 @@
 
 define void @test_align_min(ptr %src, ptr noalias %dst, i64 %dst_size) {
 ; CHECK-LABEL: @test_align_min(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], 36
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], 36
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 36
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 4 [[TMP4]], i8 0, i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 36)
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 36
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 4 [[TMP1]], i8 0, i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 36, i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -131,11 +115,9 @@
 
 define void @test_align_memcpy(ptr %src, ptr noalias %dst, i64 %dst_size) {
 ; CHECK-LABEL: @test_align_memcpy(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], 80
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], 80
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 80
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 8 [[TMP4]], i8 0, i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 80)
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 80
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 8 [[TMP1]], i8 0, i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[DST]], ptr align 8 [[SRC:%.*]], i64 80, i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -146,12 +128,10 @@
 
 define void @test_non_i8_dst_type(ptr %src, i64 %src_size, ptr noalias %dst_pi64, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_non_i8_dst_type(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST_PI64:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST_PI64:%.*]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST_PI64:%.*]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST_PI64]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
   call void @llvm.memset.p0.i64(ptr %dst_pi64, i8 %c, i64 %dst_size, i1 false)
@@ -207,7 +187,7 @@
 define void @test_throwing_call(ptr %src, i64 %src_size, ptr noalias %dst, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_throwing_call(
 ; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr [[DST:%.*]], i8 [[C:%.*]], i64 [[DST_SIZE:%.*]], i1 false)
-; CHECK-NEXT:    call void @call() #[[ATTR2:[0-9]+]]
+; CHECK-NEXT:    call void @call() #[[ATTR3:[0-9]+]]
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 [[SRC_SIZE:%.*]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -220,12 +200,10 @@
 define void @test_throwing_call_alloca(ptr %src, i64 %src_size, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_throwing_call_alloca(
 ; CHECK-NEXT:    [[DST:%.*]] = alloca i8, align 1
-; CHECK-NEXT:    call void @call() #[[ATTR2]]
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    call void @call() #[[ATTR3]]
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -288,11 +266,9 @@
 ; CHECK-LABEL: @test_must_alias_different_size(
 ; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 16
 ; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr i8, ptr [[DST]], i64 16
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[GEP2]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[GEP2]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[GEP2]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -305,11 +281,9 @@
 
 define void @test_weird_element_type(ptr %src, i64 %src_size, ptr noalias %dst, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_weird_element_type(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP5]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -320,11 +294,9 @@
 
 define void @test_addrspace(ptr addrspace(1) %src, i64 %src_size, ptr addrspace(1) noalias %dst, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_addrspace(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr addrspace(1) [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p1.i64(ptr addrspace(1) align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr addrspace(1) [[DST:%.*]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p1.i64(ptr addrspace(1) align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p1.p1.i64(ptr addrspace(1) [[DST]], ptr addrspace(1) [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/Transforms/MemCpyOpt/opaque-ptr.ll b/llvm/test/Transforms/MemCpyOpt/opaque-ptr.ll
--- a/llvm/test/Transforms/MemCpyOpt/opaque-ptr.ll
+++ b/llvm/test/Transforms/MemCpyOpt/opaque-ptr.ll
@@ -3,11 +3,9 @@
 
 define void @test_memset_memcpy(ptr %src, i64 %src_size, ptr noalias %dst, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_memset_memcpy(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[MEMSET_LEN:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[DST_SIZE:%.*]], i64 [[SRC_SIZE:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP1]], i8 [[C:%.*]], i64 [[MEMSET_LEN]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;