--- /dev/null
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+; x - ((x / y) * y)
+; to
+; x % y
+
+; Also,
+; ((x / y) * y)
+; can then be simplified to
+; x - (x % y)
+
+declare void @use8(i8)
+declare void @use2xi8(<2 x i8>)
+
+define i8 @t0_basic(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0_basic(
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = sdiv i8 %x, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+define <2 x i8> @t1_vector(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t1_vector(
+; CHECK-NEXT: [[DIV:%.*]] = sdiv <2 x i8> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use2xi8(<2 x i8> [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul <2 x i8> [[DIV]], [[Y]]
+; CHECK-NEXT: [[REM:%.*]] = sub <2 x i8> [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret <2 x i8> [[REM]]
+;
+ %div = sdiv <2 x i8> %x, %y
+ call void @use2xi8(<2 x i8> %div)
+ %roundXdownToMultipleOfY = mul <2 x i8> %div, %y
+ %rem = sub <2 x i8> %x, %roundXdownToMultipleOfY
+ ret <2 x i8> %rem
+}
+
+; Extra use
+
+define i8 @t4_extrause(i8 %x, i8 %y) {
+; CHECK-LABEL: @t4_extrause(
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y]]
+; CHECK-NEXT: call void @use8(i8 [[ROUNDXDOWNTOMULTIPLEOFY]])
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = sdiv i8 %x, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y
+ call void @use8(i8 %roundXdownToMultipleOfY)
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+; Commutativity
+
+declare i8 @gen8()
+
+define i8 @t5_commutative(i8 %x) {
+; CHECK-LABEL: @t5_commutative(
+; CHECK-NEXT: [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i8 [[X:%.*]], [[Y]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[Y]], [[DIV]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %y = call i8 @gen8()
+ %div = sdiv i8 %x, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %y, %div ; swapped
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+; Negative tests
+
+define i8 @n6_different_x(i8 %x0, i8 %x1, i8 %y) {
+; CHECK-LABEL: @n6_different_x(
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i8 [[X0:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X1:%.*]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = sdiv i8 %x0, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y
+ %rem = sub i8 %x1, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+define i8 @n6_different_y(i8 %x, i8 %y0, i8 %y1) {
+; CHECK-LABEL: @n6_different_y(
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i8 [[X:%.*]], [[Y0:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y1:%.*]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = sdiv i8 %x, %y0
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y1
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
--- /dev/null
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+; x - ((x / y) * y)
+; to
+; x % y
+
+; Also,
+; ((x / y) * y)
+; can then be simplified to
+; x - (x % y)
+
+declare void @use8(i8)
+declare void @use2xi8(<2 x i8>)
+
+define i8 @t0_basic(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0_basic(
+; CHECK-NEXT: [[DIV:%.*]] = udiv i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = udiv i8 %x, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+define <2 x i8> @t1_vector(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t1_vector(
+; CHECK-NEXT: [[DIV:%.*]] = udiv <2 x i8> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use2xi8(<2 x i8> [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul <2 x i8> [[DIV]], [[Y]]
+; CHECK-NEXT: [[REM:%.*]] = sub <2 x i8> [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret <2 x i8> [[REM]]
+;
+ %div = udiv <2 x i8> %x, %y
+ call void @use2xi8(<2 x i8> %div)
+ %roundXdownToMultipleOfY = mul <2 x i8> %div, %y
+ %rem = sub <2 x i8> %x, %roundXdownToMultipleOfY
+ ret <2 x i8> %rem
+}
+
+; Extra use
+
+define i8 @t4_extrause(i8 %x, i8 %y) {
+; CHECK-LABEL: @t4_extrause(
+; CHECK-NEXT: [[DIV:%.*]] = udiv i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y]]
+; CHECK-NEXT: call void @use8(i8 [[ROUNDXDOWNTOMULTIPLEOFY]])
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = udiv i8 %x, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y
+ call void @use8(i8 %roundXdownToMultipleOfY)
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+; Commutativity
+
+declare i8 @gen8()
+
+define i8 @t5_commutative(i8 %x) {
+; CHECK-LABEL: @t5_commutative(
+; CHECK-NEXT: [[Y:%.*]] = call i8 @gen8()
+; CHECK-NEXT: [[DIV:%.*]] = udiv i8 [[X:%.*]], [[Y]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[Y]], [[DIV]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %y = call i8 @gen8()
+ %div = udiv i8 %x, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %y, %div ; swapped
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+; Negative tests
+
+define i8 @n6_different_x(i8 %x0, i8 %x1, i8 %y) {
+; CHECK-LABEL: @n6_different_x(
+; CHECK-NEXT: [[DIV:%.*]] = udiv i8 [[X0:%.*]], [[Y:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X1:%.*]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = udiv i8 %x0, %y
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y
+ %rem = sub i8 %x1, %roundXdownToMultipleOfY
+ ret i8 %rem
+}
+
+define i8 @n6_different_y(i8 %x, i8 %y0, i8 %y1) {
+; CHECK-LABEL: @n6_different_y(
+; CHECK-NEXT: [[DIV:%.*]] = udiv i8 [[X:%.*]], [[Y0:%.*]]
+; CHECK-NEXT: call void @use8(i8 [[DIV]])
+; CHECK-NEXT: [[ROUNDXDOWNTOMULTIPLEOFY:%.*]] = mul i8 [[DIV]], [[Y1:%.*]]
+; CHECK-NEXT: [[REM:%.*]] = sub i8 [[X]], [[ROUNDXDOWNTOMULTIPLEOFY]]
+; CHECK-NEXT: ret i8 [[REM]]
+;
+ %div = udiv i8 %x, %y0
+ call void @use8(i8 %div)
+ %roundXdownToMultipleOfY = mul i8 %div, %y1
+ %rem = sub i8 %x, %roundXdownToMultipleOfY
+ ret i8 %rem
+}