xref: /llvm-project/llvm/test/Transforms/InstCombine/known-signbit-shift.ll (revision a2cf44b72cbf9361f37dd6f680502bb18070cba3)
1; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
2; RUN: opt < %s -passes=instcombine -S | FileCheck %s
3
4; Result of left shifting a non-negative integer
5; with nsw flag should also be non-negative
6define i1 @test_shift_nonnegative(i32 %a) {
7; CHECK-LABEL: @test_shift_nonnegative(
8; CHECK-NEXT:    ret i1 true
9;
10  %b = lshr i32 %a, 2
11  %shift = shl nsw i32 %b, 3
12  %cmp = icmp sge i32 %shift, 0
13  ret i1 %cmp
14}
15
16; Result of left shifting a negative integer with
17; nsw flag should also be negative
18define i1 @test_shift_negative(i32 %a, i32 %b) {
19; CHECK-LABEL: @test_shift_negative(
20; CHECK-NEXT:    ret i1 true
21;
22  %c = or i32 %a, -2147483648
23  %d = and i32 %b, 7
24  %shift = shl nsw i32 %c, %d
25  %cmp = icmp slt i32 %shift, 0
26  ret i1 %cmp
27}
28
29; If sign bit is a known zero, it cannot be a known one.
30; This test should not crash opt. The shift produces poison.
31define i32 @test_no_sign_bit_conflict1(i1 %b) {
32; CHECK-LABEL: @test_no_sign_bit_conflict1(
33; CHECK-NEXT:    ret i32 poison
34;
35  %sel = select i1 %b, i32 8193, i32 8192
36  %mul = shl nsw i32 %sel, 18
37  ret i32 %mul
38}
39
40; If sign bit is a known one, it cannot be a known zero.
41; This test should not crash opt. The shift produces poison.
42define i32 @test_no_sign_bit_conflict2(i1 %b) {
43; CHECK-LABEL: @test_no_sign_bit_conflict2(
44; CHECK-NEXT:    ret i32 poison
45;
46  %sel = select i1 %b, i32 -8193, i32 -8194
47  %mul = shl nsw i32 %sel, 18
48  ret i32 %mul
49}
50