From 5e222393cff899512d12d47e49527f838cdc1b48 Mon Sep 17 00:00:00 2001
From: Roman Lebedev <lebedev.ri@gmail.com>
Date: Mon, 22 Jul 2019 22:08:45 +0000
Subject: [PATCH] [InstCombine][NFC] Tests for canonicalization of unsigned
 multiply overflow check

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@366748 91177308-0d34-0410-b5e6-96231b3b80d8
---
 ...mul-lack-of-overflow-check-via-mul-udiv.ll | 172 ++++++++++++++++++
 ...k-of-overflow-check-via-udiv-of-allones.ll | 107 +++++++++++
 ...nsigned-mul-overflow-check-via-mul-udiv.ll | 172 ++++++++++++++++++
 ...-mul-overflow-check-via-udiv-of-allones.ll | 105 +++++++++++
 4 files changed, 556 insertions(+)
 create mode 100644 test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-mul-udiv.ll
 create mode 100644 test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-udiv-of-allones.ll
 create mode 100644 test/Transforms/InstCombine/unsigned-mul-overflow-check-via-mul-udiv.ll
 create mode 100644 test/Transforms/InstCombine/unsigned-mul-overflow-check-via-udiv-of-allones.ll

diff --git a/test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-mul-udiv.ll b/test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-mul-udiv.ll
new file mode 100644
index 00000000000..11939f48c2b
--- /dev/null
+++ b/test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-mul-udiv.ll
@@ -0,0 +1,172 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+;   ((%x * %y) u/ %x) == %y
+; to
+;   @llvm.umul.with.overflow(%x, %y) + extractvalue + not
+
+define i1 @t0_basic(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0_basic(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  %t1 = udiv i8 %t0, %x
+  %r = icmp eq i8 %t1, %y
+  ret i1 %r
+}
+
+define <2 x i1> @t1_vec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t1_vec(
+; CHECK-NEXT:    [[T0:%.*]] = mul <2 x i8> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv <2 x i8> [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq <2 x i8> [[T1]], [[Y]]
+; CHECK-NEXT:    ret <2 x i1> [[R]]
+;
+  %t0 = mul <2 x i8> %x, %y
+  %t1 = udiv <2 x i8> %t0, %x
+  %r = icmp eq <2 x i8> %t1, %y
+  ret <2 x i1> %r
+}
+
+declare i8 @gen8()
+
+define i1 @t2_commutative(i8 %x) {
+; CHECK-LABEL: @t2_commutative(
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %y = call i8 @gen8()
+  %t0 = mul i8 %y, %x ; swapped
+  %t1 = udiv i8 %t0, %x
+  %r = icmp eq i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t3_commutative(i8 %x) {
+; CHECK-LABEL: @t3_commutative(
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %y = call i8 @gen8()
+  %t0 = mul i8 %y, %x ; swapped
+  %t1 = udiv i8 %t0, %x
+  %r = icmp eq i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t4_commutative(i8 %x) {
+; CHECK-LABEL: @t4_commutative(
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[Y]], [[T1]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %y = call i8 @gen8()
+  %t0 = mul i8 %y, %x ; swapped
+  %t1 = udiv i8 %t0, %x
+  %r = icmp eq i8 %y, %t1 ; swapped
+  ret i1 %r
+}
+
+; Extra-use tests
+
+declare void @use8(i8)
+
+define i1 @t5_extrause0(i8 %x, i8 %y) {
+; CHECK-LABEL: @t5_extrause0(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    call void @use8(i8 [[T0]])
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  call void @use8(i8 %t0)
+  %t1 = udiv i8 %t0, %x
+  %r = icmp eq i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t6_extrause1(i8 %x, i8 %y) {
+; CHECK-LABEL: @t6_extrause1(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    call void @use8(i8 [[T1]])
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  %t1 = udiv i8 %t0, %x
+  call void @use8(i8 %t1)
+  %r = icmp eq i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t7_extrause2(i8 %x, i8 %y) {
+; CHECK-LABEL: @t7_extrause2(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    call void @use8(i8 [[T0]])
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    call void @use8(i8 [[T1]])
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  call void @use8(i8 %t0)
+  %t1 = udiv i8 %t0, %x
+  call void @use8(i8 %t1)
+  %r = icmp eq i8 %t1, %y
+  ret i1 %r
+}
+
+; Negative tests
+
+define i1 @n8_different_x(i8 %x0, i8 %x1, i8 %y) {
+; CHECK-LABEL: @n8_different_x(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X0:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X1:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x0, %y
+  %t1 = udiv i8 %t0, %x1
+  %r = icmp eq i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @n9_different_y(i8 %x, i8 %y0, i8 %y1) {
+; CHECK-LABEL: @n9_different_y(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y0:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[T1]], [[Y1:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y0
+  %t1 = udiv i8 %t0, %x
+  %r = icmp eq i8 %t1, %y1
+  ret i1 %r
+}
+
+define i1 @n10_wrong_pred(i8 %x, i8 %y) {
+; CHECK-LABEL: @n10_wrong_pred(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ult i8 %t1, %y
+  ret i1 %r
+}
diff --git a/test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-udiv-of-allones.ll b/test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-udiv-of-allones.ll
new file mode 100644
index 00000000000..2865dfafd51
--- /dev/null
+++ b/test/Transforms/InstCombine/unsigned-mul-lack-of-overflow-check-via-udiv-of-allones.ll
@@ -0,0 +1,107 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+;   (-1 u/ %x) u>= %y
+; to
+;   @llvm.umul.with.overflow(%x, %y) + extractvalue + not
+
+define i1 @t0_basic(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0_basic(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %r = icmp uge i8 %t0, %y
+  ret i1 %r
+}
+
+define <2 x i1> @t1_vec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t1_vec(
+; CHECK-NEXT:    [[T0:%.*]] = udiv <2 x i8> <i8 -1, i8 -1>, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp uge <2 x i8> [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret <2 x i1> [[R]]
+;
+  %t0 = udiv <2 x i8> <i8 -1, i8 -1>, %x
+  %r = icmp uge <2 x i8> %t0, %y
+  ret <2 x i1> %r
+}
+
+define <3 x i1> @t2_vec_undef(<3 x i8> %x, <3 x i8> %y) {
+; CHECK-LABEL: @t2_vec_undef(
+; CHECK-NEXT:    [[T0:%.*]] = udiv <3 x i8> <i8 -1, i8 undef, i8 -1>, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp uge <3 x i8> [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret <3 x i1> [[R]]
+;
+  %t0 = udiv <3 x i8> <i8 -1, i8 undef, i8 -1>, %x
+  %r = icmp uge <3 x i8> %t0, %y
+  ret <3 x i1> %r
+}
+
+declare i8 @gen8()
+
+define i1 @t3_commutative(i8 %x) {
+; CHECK-LABEL: @t3_commutative(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[Y]], [[T0]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %y = call i8 @gen8()
+  %r = icmp ult i8 %y, %t0 ; swapped
+  ret i1 %r
+}
+
+; Negative tests
+
+declare void @use8(i8)
+
+define i1 @n4_extrause(i8 %x, i8 %y) {
+; CHECK-LABEL: @n4_extrause(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    call void @use8(i8 [[T0]])
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  call void @use8(i8 %t0)
+  %r = icmp uge i8 %t0, %y
+  ret i1 %r
+}
+
+define i1 @n5_not_negone(i8 %x, i8 %y) {
+; CHECK-LABEL: @n5_not_negone(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -2, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -2, %x ; not -1
+  %r = icmp uge i8 %t0, %y
+  ret i1 %r
+}
+
+define i1 @n6_wrong_pred0(i8 %x, i8 %y) {
+; CHECK-LABEL: @n6_wrong_pred0(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ule i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %r = icmp ule i8 %t0, %y
+  ret i1 %r
+}
+
+define i1 @n6_wrong_pred1(i8 %x) {
+; CHECK-LABEL: @n6_wrong_pred1(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i8 [[Y]], [[T0]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %y = call i8 @gen8()
+  %r = icmp ugt i8 %y, %t0 ; swapped
+  ret i1 %r
+}
diff --git a/test/Transforms/InstCombine/unsigned-mul-overflow-check-via-mul-udiv.ll b/test/Transforms/InstCombine/unsigned-mul-overflow-check-via-mul-udiv.ll
new file mode 100644
index 00000000000..d6447a77d15
--- /dev/null
+++ b/test/Transforms/InstCombine/unsigned-mul-overflow-check-via-mul-udiv.ll
@@ -0,0 +1,172 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+;   ((%x * %y) u/ %x) != %y
+; to
+;   @llvm.umul.with.overflow(%x, %y) + extractvalue
+
+define i1 @t0_basic(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0_basic(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ne i8 %t1, %y
+  ret i1 %r
+}
+
+define <2 x i1> @t1_vec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t1_vec(
+; CHECK-NEXT:    [[T0:%.*]] = mul <2 x i8> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv <2 x i8> [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne <2 x i8> [[T1]], [[Y]]
+; CHECK-NEXT:    ret <2 x i1> [[R]]
+;
+  %t0 = mul <2 x i8> %x, %y
+  %t1 = udiv <2 x i8> %t0, %x
+  %r = icmp ne <2 x i8> %t1, %y
+  ret <2 x i1> %r
+}
+
+declare i8 @gen8()
+
+define i1 @t2_commutative(i8 %x) {
+; CHECK-LABEL: @t2_commutative(
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %y = call i8 @gen8()
+  %t0 = mul i8 %y, %x ; swapped
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ne i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t3_commutative(i8 %x) {
+; CHECK-LABEL: @t3_commutative(
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %y = call i8 @gen8()
+  %t0 = mul i8 %y, %x ; swapped
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ne i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t4_commutative(i8 %x) {
+; CHECK-LABEL: @t4_commutative(
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[Y]], [[T1]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %y = call i8 @gen8()
+  %t0 = mul i8 %y, %x ; swapped
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ne i8 %y, %t1 ; swapped
+  ret i1 %r
+}
+
+; Extra-use tests
+
+declare void @use8(i8)
+
+define i1 @t5_extrause0(i8 %x, i8 %y) {
+; CHECK-LABEL: @t5_extrause0(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    call void @use8(i8 [[T0]])
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  call void @use8(i8 %t0)
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ne i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t6_extrause1(i8 %x, i8 %y) {
+; CHECK-LABEL: @t6_extrause1(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    call void @use8(i8 [[T1]])
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  %t1 = udiv i8 %t0, %x
+  call void @use8(i8 %t1)
+  %r = icmp ne i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @t7_extrause2(i8 %x, i8 %y) {
+; CHECK-LABEL: @t7_extrause2(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    call void @use8(i8 [[T0]])
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    call void @use8(i8 [[T1]])
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  call void @use8(i8 %t0)
+  %t1 = udiv i8 %t0, %x
+  call void @use8(i8 %t1)
+  %r = icmp ne i8 %t1, %y
+  ret i1 %r
+}
+
+; Negative tests
+
+define i1 @n8_different_x(i8 %x0, i8 %x1, i8 %y) {
+; CHECK-LABEL: @n8_different_x(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X0:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X1:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x0, %y
+  %t1 = udiv i8 %t0, %x1
+  %r = icmp ne i8 %t1, %y
+  ret i1 %r
+}
+
+define i1 @n9_different_y(i8 %x, i8 %y0, i8 %y1) {
+; CHECK-LABEL: @n9_different_y(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y0:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[T1]], [[Y1:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y0
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ne i8 %t1, %y1
+  ret i1 %r
+}
+
+define i1 @n10_wrong_pred(i8 %x, i8 %y) {
+; CHECK-LABEL: @n10_wrong_pred(
+; CHECK-NEXT:    [[T0:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[T1:%.*]] = udiv i8 [[T0]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i8 [[T1]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = mul i8 %x, %y
+  %t1 = udiv i8 %t0, %x
+  %r = icmp ugt i8 %t1, %y
+  ret i1 %r
+}
diff --git a/test/Transforms/InstCombine/unsigned-mul-overflow-check-via-udiv-of-allones.ll b/test/Transforms/InstCombine/unsigned-mul-overflow-check-via-udiv-of-allones.ll
new file mode 100644
index 00000000000..d66f5f7c40a
--- /dev/null
+++ b/test/Transforms/InstCombine/unsigned-mul-overflow-check-via-udiv-of-allones.ll
@@ -0,0 +1,105 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+;   (-1 u/ %x) u< %y
+; to
+;   @llvm.umul.with.overflow(%x, %y) + extractvalue
+
+define i1 @t0_basic(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0_basic(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %r = icmp ult i8 %t0, %y
+  ret i1 %r
+}
+
+define <2 x i1> @t1_vec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t1_vec(
+; CHECK-NEXT:    [[T0:%.*]] = udiv <2 x i8> <i8 -1, i8 -1>, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ult <2 x i8> [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret <2 x i1> [[R]]
+;
+  %t0 = udiv <2 x i8> <i8 -1, i8 -1>, %x
+  %r = icmp ult <2 x i8> %t0, %y
+  ret <2 x i1> %r
+}
+
+define <3 x i1> @t2_vec_undef(<3 x i8> %x, <3 x i8> %y) {
+; CHECK-LABEL: @t2_vec_undef(
+; CHECK-NEXT:    [[T0:%.*]] = udiv <3 x i8> <i8 -1, i8 undef, i8 -1>, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ult <3 x i8> [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret <3 x i1> [[R]]
+;
+  %t0 = udiv <3 x i8> <i8 -1, i8 undef, i8 -1>, %x
+  %r = icmp ult <3 x i8> %t0, %y
+  ret <3 x i1> %r
+}
+
+declare i8 @gen8()
+
+define i1 @t3_commutative(i8 %x) {
+; CHECK-LABEL: @t3_commutative(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i8 [[Y]], [[T0]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %y = call i8 @gen8()
+  %r = icmp uge i8 %y, %t0 ; swapped
+  ret i1 %r
+}
+
+; Negative tests
+
+declare void @use8(i8)
+
+define i1 @n4_extrause(i8 %x, i8 %y) {
+; CHECK-LABEL: @n4_extrause(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    call void @use8(i8 [[T0]])
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  call void @use8(i8 %t0)
+  %r = icmp ult i8 %t0, %y
+  ret i1 %r
+}
+
+define i1 @n5_not_negone(i8 %x, i8 %y) {
+; CHECK-LABEL: @n5_not_negone(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -2, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -2, %x ; not -1
+  %r = icmp ult i8 %t0, %y
+  ret i1 %r
+}
+
+define i1 @n6_wrong_pred0(i8 %x, i8 %y) {
+; CHECK-LABEL: @n6_wrong_pred0(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ule i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %r = icmp ule i8 %t0, %y
+  ret i1 %r
+}
+
+define i1 @n6_wrong_pred1(i8 %x, i8 %y) {
+; CHECK-LABEL: @n6_wrong_pred1(
+; CHECK-NEXT:    [[T0:%.*]] = udiv i8 -1, [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i8 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = udiv i8 -1, %x
+  %r = icmp ugt i8 %t0, %y
+  ret i1 %r
+}
-- 
2.40.0