diff --git a/Sources/LLVM/IRBuilder.swift b/Sources/LLVM/IRBuilder.swift
index a1a0a44d..9211360a 100644
--- a/Sources/LLVM/IRBuilder.swift
+++ b/Sources/LLVM/IRBuilder.swift
@@ -501,7 +501,7 @@ public class IRBuilder {
       case .noSignedWrap:
         return LLVMBuildNSWSub(llvm, lhsVal, rhsVal, name)
       case .noUnsignedWrap:
-        return LLVMBuildNSWSub(llvm, lhsVal, rhsVal, name)
+        return LLVMBuildNUWSub(llvm, lhsVal, rhsVal, name)
       case .default:
         return LLVMBuildSub(llvm, lhsVal, rhsVal, name)
       }
diff --git a/Tests/LLVMTests/IRBuilderSpec.swift b/Tests/LLVMTests/IRBuilderSpec.swift
index 891c6be2..5fb50979 100644
--- a/Tests/LLVMTests/IRBuilderSpec.swift
+++ b/Tests/LLVMTests/IRBuilderSpec.swift
@@ -4,21 +4,142 @@ import Foundation
 
 class IRBuilderSpec : XCTestCase {
   func testIRBuilder() {
-    XCTAssert(fileCheckOutput(of: .stderr) {
-      // CHECK: ; ModuleID = 'IRBuilderTest'
-      // CHECK-NEXT: source_filename = "IRBuilderTest"
+    XCTAssert(fileCheckOutput(of: .stderr, withPrefixes: ["IRBUILDER"]) {
+      // IRBUILDER: ; ModuleID = 'IRBuilderTest'
+      // IRBUILDER-NEXT: source_filename = "IRBuilderTest"
       let module = Module(name: "IRBuilderTest")
       let builder = IRBuilder(module: module)
-      // CHECK: define void @main() {
+      // IRBUILDER: define void @main() {
       let main = builder.addFunction("main",
                                      type: FunctionType(argTypes: [],
                                                         returnType: VoidType()))
-      // CHECK-NEXT: entry:
+      // IRBUILDER-NEXT: entry:
       let entry = main.appendBasicBlock(named: "entry")
       builder.positionAtEnd(of: entry)
-      // CHECK-NEXT: ret void
+      // IRBUILDER-NEXT: ret void
       builder.buildRetVoid()
-      // CHECK-NEXT: }
+      // IRBUILDER-NEXT: }
+      module.dump()
+    })
+
+    // MARK: Arithmetic Instructions
+
+    XCTAssert(fileCheckOutput(of: .stderr, withPrefixes: ["IRBUILDERARITH"]) {
+      // IRBUILDERARITH: ; ModuleID = 'IRBuilderTest'
+      // IRBUILDERARITH-NEXT: source_filename = "IRBuilderTest"
+      let module = Module(name: "IRBuilderTest")
+      let builder = IRBuilder(module: module)
+
+      // IRBUILDERARITH: @a = global i32 1
+      // IRBUILDERARITH-NEXT: @b = global i32 1
+      var g1 = builder.addGlobal("a", type: IntType.int32)
+      g1.initializer = Int32(1)
+      var g2 = builder.addGlobal("b", type: IntType.int32)
+      g2.initializer = Int32(1)
+
+      // IRBUILDERARITH: define void @main() {
+      let main = builder.addFunction("main",
+                                     type: FunctionType(argTypes: [],
+                                                        returnType: VoidType()))
+      // IRBUILDERARITH-NEXT: entry:
+      let entry = main.appendBasicBlock(named: "entry")
+      builder.positionAtEnd(of: entry)
+
+      // IRBUILDERARITH-NEXT: %0 = load i32, i32* @a
+      let vg1 = builder.buildLoad(g1)
+      // IRBUILDERARITH-NEXT: %1 = load i32, i32* @b
+      let vg2 = builder.buildLoad(g2)
+
+      // IRBUILDERARITH-NEXT: %2 = add i32 %0, %1
+      _ = builder.buildAdd(vg1, vg2)
+      // IRBUILDERARITH-NEXT: %3 = sub i32 %0, %1
+      _ = builder.buildSub(vg1, vg2)
+      // IRBUILDERARITH-NEXT: %4 = mul i32 %0, %1
+      _ = builder.buildMul(vg1, vg2)
+      // IRBUILDERARITH-NEXT: %5 = sdiv i32 %0, %1
+      _ = builder.buildDiv(vg1, vg2, signed: true)
+      // IRBUILDERARITH-NEXT: %6 = udiv i32 %0, %1
+      _ = builder.buildDiv(vg1, vg2, signed: false)
+
+      // IRBUILDERARITH-NEXT: %7 = add nsw i32 %0, %1
+      _ = builder.buildAdd(vg1, vg2, overflowBehavior: .noSignedWrap)
+      // IRBUILDERARITH-NEXT: %8 = sub nsw i32 %0, %1
+      _ = builder.buildSub(vg1, vg2, overflowBehavior: .noSignedWrap)
+      // IRBUILDERARITH-NEXT: %9 = mul nsw i32 %0, %1
+      _ = builder.buildMul(vg1, vg2, overflowBehavior: .noSignedWrap)
+
+      // IRBUILDERARITH-NEXT: %10 = add nuw i32 %0, %1
+      _ = builder.buildAdd(vg1, vg2, overflowBehavior: .noUnsignedWrap)
+      // IRBUILDERARITH-NEXT: %11 = sub nuw i32 %0, %1
+      _ = builder.buildSub(vg1, vg2, overflowBehavior: .noUnsignedWrap)
+      // IRBUILDERARITH-NEXT: %12 = mul nuw i32 %0, %1
+      _ = builder.buildMul(vg1, vg2, overflowBehavior: .noUnsignedWrap)
+
+      // IRBUILDERARITH-NEXT: %13 = sub i32 0, %0
+      _ = builder.buildNeg(vg1, overflowBehavior: .default)
+      // IRBUILDERARITH-NEXT: %14 = sub nuw i32 0, %0
+      _ = builder.buildNeg(vg1, overflowBehavior: .noUnsignedWrap)
+      // IRBUILDERARITH-NEXT: %15 = sub nsw i32 0, %0
+      _ = builder.buildNeg(vg1, overflowBehavior: .noSignedWrap)
+
+
+      // IRBUILDERARITH-NEXT: ret void
+      builder.buildRetVoid()
+      // IRBUILDERARITH-NEXT: }
+      module.dump()
+    })
+
+    // MARK: Integer comparisons
+    XCTAssert(fileCheckOutput(of: .stderr, withPrefixes: ["IRBUILDERCMP"]) {
+      // IRBUILDERCMP: ; ModuleID = 'IRBuilderTest'
+      // IRBUILDERCMP-NEXT: source_filename = "IRBuilderTest"
+      let module = Module(name: "IRBuilderTest")
+      let builder = IRBuilder(module: module)
+
+      // IRBUILDERCMP: @a = global i32 1
+      // IRBUILDERCMP-NEXT: @b = global i32 1
+      var g1 = builder.addGlobal("a", type: IntType.int32)
+      g1.initializer = Int32(1)
+      var g2 = builder.addGlobal("b", type: IntType.int32)
+      g2.initializer = Int32(1)
+
+      // IRBUILDERCMP: define void @main() {
+      let main = builder.addFunction("main",
+                                     type: FunctionType(argTypes: [],
+                                                        returnType: VoidType()))
+      // IRBUILDERCMP-NEXT: entry:
+      let entry = main.appendBasicBlock(named: "entry")
+      builder.positionAtEnd(of: entry)
+
+      // IRBUILDERCMP-NEXT: %0 = load i32, i32* @a
+      let vg1 = builder.buildLoad(g1)
+      // IRBUILDERCMP-NEXT: %1 = load i32, i32* @b
+      let vg2 = builder.buildLoad(g2)
+
+      // IRBUILDERCMP-NEXT: %2 = icmp eq i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .eq)
+      // IRBUILDERCMP-NEXT: %3 = icmp ne i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .ne)
+      // IRBUILDERCMP-NEXT: %4 = icmp ugt i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .ugt)
+      // IRBUILDERCMP-NEXT: %5 = icmp uge i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .uge)
+      // IRBUILDERCMP-NEXT: %6 = icmp ult i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .ult)
+      // IRBUILDERCMP-NEXT: %7 = icmp ule i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .ule)
+      // IRBUILDERCMP-NEXT: %8 = icmp sgt i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .sgt)
+      // IRBUILDERCMP-NEXT: %9 = icmp sge i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .sge)
+      // IRBUILDERCMP-NEXT: %10 = icmp slt i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .slt)
+      // IRBUILDERCMP-NEXT: %11 = icmp sle i32 %0, %1
+      _ = builder.buildICmp(vg1, vg2, .sle)
+
+      // IRBUILDERCMP-NEXT: ret void
+      builder.buildRetVoid()
+      // IRBUILDERCMP-NEXT: }
       module.dump()
     })
   }