[InstCombine][NFC] Tests for 'unsigned sub overflow' check

----------------------------------------
Name: unsigned sub, overflow, v0
  %sub = sub i8 %x, %y
  %ov = icmp ugt i8 %sub, %x
=>
  %agg = usub_overflow i8 %x, %y
  %sub = extractvalue {i8, i1} %agg, 0
  %ov = extractvalue {i8, i1} %agg, 1

Done: 1
Optimization is correct!

----------------------------------------
Name: unsigned sub, no overflow, v0
  %sub = sub i8 %x, %y
  %ov = icmp ule i8 %sub, %x
=>
  %agg = usub_overflow i8 %x, %y
  %sub = extractvalue {i8, i1} %agg, 0
  %not.ov = extractvalue {i8, i1} %agg, 1
  %ov = xor %not.ov, -1

Done: 1
Optimization is correct!

llvm-svn: 371099

1 files changed, 155 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/unsigned-sub-overflow-check.ll b/llvm/test/Transforms/InstCombine/unsigned-sub-overflow-check.ll
new file mode 100644
index 00000000000..e51e36ff1c7
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/unsigned-sub-overflow-check.ll
@@ -0,0 +1,155 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+;   (%x - %y) u> %x
+; to
+;   @llvm.sub.with.overflow(%x, %y) + extractvalue
+
+define i1 @t0_basic(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0_basic(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp ugt i8 %t0, %x
+  ret i1 %r
+}
+
+define <2 x i1> @t1_vec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t1_vec(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult <2 x i8> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    ret <2 x i1> [[R]]
+;
+  %t0 = sub <2 x i8> %x, %y
+  %r = icmp ugt <2 x i8> %t0, %x
+  ret <2 x i1> %r
+}
+
+; Commutativity
+
+define i1 @t2_commutative(i8 %x, i8 %y) {
+; CHECK-LABEL: @t2_commutative(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp ult i8 %x, %t0 ; swapped
+  ret i1 %r
+}
+
+; Extra-use tests
+
+declare void @use8(i8)
+
+define i1 @t3_extrause0(i8 %x, i8 %y) {
+; CHECK-LABEL: @t3_extrause0(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    call void @use8(i8 [[T0]])
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[X]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  call void @use8(i8 %t0)
+  %r = icmp ugt i8 %t0, %x
+  ret i1 %r
+}
+
+; Negative tests
+
+define i1 @n4_not_commutative(i8 %x, i8 %y) {
+; CHECK-LABEL: @n4_not_commutative(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i8 [[T0]], [[Y]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp ugt i8 %t0, %y ; can't check against %y.
+  ret i1 %r
+}
+
+define i1 @n5_wrong_pred0(i8 %x, i8 %y) {
+; CHECK-LABEL: @n5_wrong_pred0(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i8 [[T0]], [[X]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp uge i8 %t0, %x
+  ret i1 %r
+}
+
+define i1 @n6_wrong_pred1(i8 %x, i8 %y) {
+; CHECK-LABEL: @n6_wrong_pred1(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[T0]], [[X]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp ult i8 %t0, %x
+  ret i1 %r
+}
+
+define i1 @n7_wrong_pred2(i8 %x, i8 %y) {
+; CHECK-LABEL: @n7_wrong_pred2(
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[Y:%.*]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp eq i8 %t0, %x
+  ret i1 %r
+}
+
+define i1 @n8_wrong_pred3(i8 %x, i8 %y) {
+; CHECK-LABEL: @n8_wrong_pred3(
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[Y:%.*]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp ne i8 %t0, %x
+  ret i1 %r
+}
+
+define i1 @n9_wrong_pred4(i8 %x, i8 %y) {
+; CHECK-LABEL: @n9_wrong_pred4(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp slt i8 [[T0]], [[X]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp slt i8 %t0, %x
+  ret i1 %r
+}
+
+define i1 @n10_wrong_pred5(i8 %x, i8 %y) {
+; CHECK-LABEL: @n10_wrong_pred5(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp sle i8 [[T0]], [[X]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp sle i8 %t0, %x
+  ret i1 %r
+}
+
+define i1 @n11_wrong_pred6(i8 %x, i8 %y) {
+; CHECK-LABEL: @n11_wrong_pred6(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp sgt i8 [[T0]], [[X]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp sgt i8 %t0, %x
+  ret i1 %r
+}
+
+define i1 @n12_wrong_pred7(i8 %x, i8 %y) {
+; CHECK-LABEL: @n12_wrong_pred7(
+; CHECK-NEXT:    [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp sge i8 [[T0]], [[X]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %t0 = sub i8 %x, %y
+  %r = icmp sge i8 %t0, %x
+  ret i1 %r
+}