diff --git a/llvm/test/Transforms/InstCombine/add-mask-neg.ll b/llvm/test/Transforms/InstCombine/add-mask-neg.ll
new file mode 100644
index 0000000000000..7a7d4216e3bd7
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/add-mask-neg.ll
@@ -0,0 +1,121 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S -passes=instcombine | FileCheck %s
+
+;
+; TODO: Canonicalize ((X & -X) - 1) --> (~X & (X - 1))
+;
+
+define i32 @dec_mask_neg_i32(i32 %X) {
+; CHECK-LABEL: @dec_mask_neg_i32(
+; CHECK-NEXT:    [[NEG:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and i32 [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add i32 [[MASK]], -1
+; CHECK-NEXT:    ret i32 [[DEC]]
+;
+  %neg = sub i32 0, %X
+  %mask = and i32 %neg, %X
+  %dec = add i32 %mask, -1
+  ret i32 %dec
+}
+
+define i32 @dec_mask_commute_neg_i32(i32 %X) {
+; CHECK-LABEL: @dec_mask_commute_neg_i32(
+; CHECK-NEXT:    [[NEG:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and i32 [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add i32 [[MASK]], -1
+; CHECK-NEXT:    ret i32 [[DEC]]
+;
+  %neg = sub i32 0, %X
+  %mask = and i32 %X, %neg
+  %dec = add i32 %mask, -1
+  ret i32 %dec
+}
+
+define i32 @dec_commute_mask_neg_i32(i32 %X) {
+; CHECK-LABEL: @dec_commute_mask_neg_i32(
+; CHECK-NEXT:    [[NEG:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and i32 [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add i32 [[MASK]], -1
+; CHECK-NEXT:    ret i32 [[DEC]]
+;
+  %neg = sub i32 0, %X
+  %mask = and i32 %neg, %X
+  %dec = add i32 -1, %mask
+  ret i32 %dec
+}
+
+define i32 @dec_mask_neg_multiuse_i32(i32 %X) {
+; CHECK-LABEL: @dec_mask_neg_multiuse_i32(
+; CHECK-NEXT:    [[NEG:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and i32 [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add i32 [[MASK]], -1
+; CHECK-NEXT:    call void @use(i32 [[NEG]])
+; CHECK-NEXT:    ret i32 [[DEC]]
+;
+  %neg = sub i32 0, %X
+  %mask = and i32 %neg, %X
+  %dec = add i32 %mask, -1
+  call void @use(i32 %neg)
+  ret i32 %dec
+}
+
+define i32 @dec_mask_multiuse_neg_i32(i32 %X) {
+; CHECK-LABEL: @dec_mask_multiuse_neg_i32(
+; CHECK-NEXT:    [[NEG:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and i32 [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add i32 [[MASK]], -1
+; CHECK-NEXT:    call void @use(i32 [[MASK]])
+; CHECK-NEXT:    ret i32 [[DEC]]
+;
+  %neg = sub i32 0, %X
+  %mask = and i32 %neg, %X
+  %dec = add i32 %mask, -1
+  call void @use(i32 %mask)
+  ret i32 %dec
+}
+
+define <2 x i32> @dec_mask_neg_v2i32(<2 x i32> %X) {
+; CHECK-LABEL: @dec_mask_neg_v2i32(
+; CHECK-NEXT:    [[NEG:%.*]] = sub <2 x i32> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and <2 x i32> [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add <2 x i32> [[MASK]], <i32 -1, i32 -1>
+; CHECK-NEXT:    ret <2 x i32> [[DEC]]
+;
+  %neg = sub <2 x i32> zeroinitializer, %X
+  %mask = and <2 x i32> %neg, %X
+  %dec = add <2 x i32> %mask, <i32 -1, i32 -1>
+  ret <2 x i32> %dec
+}
+
+define <2 x i32> @dec_mask_neg_v2i32_undef(<2 x i32> %X) {
+; CHECK-LABEL: @dec_mask_neg_v2i32_undef(
+; CHECK-NEXT:    [[NEG:%.*]] = sub <2 x i32> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and <2 x i32> [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add <2 x i32> [[MASK]], <i32 -1, i32 undef>
+; CHECK-NEXT:    ret <2 x i32> [[DEC]]
+;
+  %neg = sub <2 x i32> zeroinitializer, %X
+  %mask = and <2 x i32> %neg, %X
+  %dec = add <2 x i32> %mask, <i32 -1, i32 undef>
+  ret <2 x i32> %dec
+}
+
+define <2 x i32> @dec_mask_multiuse_neg_multiuse_v2i32(<2 x i32> %X) {
+; CHECK-LABEL: @dec_mask_multiuse_neg_multiuse_v2i32(
+; CHECK-NEXT:    [[NEG:%.*]] = sub <2 x i32> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT:    [[MASK:%.*]] = and <2 x i32> [[NEG]], [[X]]
+; CHECK-NEXT:    [[DEC:%.*]] = add <2 x i32> [[MASK]], <i32 -1, i32 -1>
+; CHECK-NEXT:    call void @usev(<2 x i32> [[NEG]])
+; CHECK-NEXT:    call void @usev(<2 x i32> [[MASK]])
+; CHECK-NEXT:    ret <2 x i32> [[DEC]]
+;
+  %neg = sub <2 x i32> zeroinitializer, %X
+  %mask = and <2 x i32> %neg, %X
+  %dec = add <2 x i32> %mask, <i32 -1, i32 -1>
+  call void @usev(<2 x i32> %neg)
+  call void @usev(<2 x i32> %mask)
+  ret <2 x i32> %dec
+}
+
+declare void @use(i32)
+declare void @usev(<2 x i32>)