--- /dev/null
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+; Given:
+; sub %y, (xor %x, -1)
+; Transform it to:
+; add (add %x, %y), 1
+
+;------------------------------------------------------------------------------;
+; Scalar tests
+;------------------------------------------------------------------------------;
+
+define i32 @p0_scalar(i32 %x, i32 %y) {
+; CHECK-LABEL: @p0_scalar(
+; CHECK-NEXT: [[T0:%.*]] = xor i32 [[X:%.*]], -1
+; CHECK-NEXT: [[T1:%.*]] = sub i32 [[Y:%.*]], [[T0]]
+; CHECK-NEXT: ret i32 [[T1]]
+;
+ %t0 = xor i32 %x, -1
+ %t1 = sub i32 %y, %t0
+ ret i32 %t1
+}
+
+;------------------------------------------------------------------------------;
+; Vector tests
+;------------------------------------------------------------------------------;
+
+define <4 x i32> @p1_vector_splat(<4 x i32> %x, <4 x i32> %y) {
+; CHECK-LABEL: @p1_vector_splat(
+; CHECK-NEXT: [[T0:%.*]] = xor <4 x i32> [[X:%.*]], <i32 -1, i32 -1, i32 -1, i32 -1>
+; CHECK-NEXT: [[T1:%.*]] = sub <4 x i32> [[Y:%.*]], [[T0]]
+; CHECK-NEXT: ret <4 x i32> [[T1]]
+;
+ %t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 -1, i32 -1>
+ %t1 = sub <4 x i32> %y, %t0
+ ret <4 x i32> %t1
+}
+
+define <4 x i32> @p2_vector_undef(<4 x i32> %x, <4 x i32> %y) {
+; CHECK-LABEL: @p2_vector_undef(
+; CHECK-NEXT: [[T0:%.*]] = xor <4 x i32> [[X:%.*]], <i32 -1, i32 -1, i32 undef, i32 -1>
+; CHECK-NEXT: [[T1:%.*]] = sub <4 x i32> [[Y:%.*]], [[T0]]
+; CHECK-NEXT: ret <4 x i32> [[T1]]
+;
+ %t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 undef, i32 -1>
+ %t1 = sub <4 x i32> %y, %t0
+ ret <4 x i32> %t1
+}
+
+;------------------------------------------------------------------------------;
+; One-use test
+;------------------------------------------------------------------------------;
+
+declare void @use32(i32)
+
+define i32 @p3_oneuse(i32 %x, i32 %y) {
+; CHECK-LABEL: @p3_oneuse(
+; CHECK-NEXT: [[T0:%.*]] = xor i32 [[X:%.*]], -1
+; CHECK-NEXT: call void @use32(i32 [[T0]])
+; CHECK-NEXT: [[T1:%.*]] = sub i32 [[Y:%.*]], [[T0]]
+; CHECK-NEXT: ret i32 [[T1]]
+;
+ %t0 = xor i32 %x, -1
+ call void @use32(i32 %t0)
+ %t1 = sub i32 %y, %t0
+ ret i32 %t1
+}
+
+;------------------------------------------------------------------------------;
+; Basic negative tests
+;------------------------------------------------------------------------------;
+
+; The `sub` (and the fold) is not commutative.
+define i32 @n4(i32 %x, i32 %y) {
+; CHECK-LABEL: @n4(
+; CHECK-NEXT: [[T0:%.*]] = xor i32 [[X:%.*]], -1
+; CHECK-NEXT: [[T1:%.*]] = sub i32 [[T0]], [[Y:%.*]]
+; CHECK-NEXT: ret i32 [[T1]]
+;
+ %t0 = xor i32 %x, -1
+ %t1 = sub i32 %t0, %y ; swapped
+ ret i32 %t1
+}
+
+define i32 @n5_is_not_not(i32 %x, i32 %y) {
+; CHECK-LABEL: @n5_is_not_not(
+; CHECK-NEXT: [[T0:%.*]] = xor i32 [[X:%.*]], 2147483647
+; CHECK-NEXT: [[T1:%.*]] = sub i32 [[Y:%.*]], [[T0]]
+; CHECK-NEXT: ret i32 [[T1]]
+;
+ %t0 = xor i32 %x, 2147483647 ; not -1
+ %t1 = sub i32 %y, %t0
+ ret i32 %t1
+}