1 files changed, 55 insertions, 0 deletions
diff --git a/llvm/test/Analysis/ValueTracking/known-signbit-shift.ll b/llvm/test/Analysis/ValueTracking/known-signbit-shift.ll
new file mode 100644
index 00000000000..bf984cb7474
--- /dev/null
+++ b/llvm/test/Analysis/ValueTracking/known-signbit-shift.ll
@@ -0,0 +1,55 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; Result of left shifting a non-negative integer
+; with nsw flag should also be non-negative
+define i1 @test_shift_nonnegative(i32 %a) {
+; CHECK-LABEL: @test_shift_nonnegative(
+; CHECK-NEXT:    ret i1 true
+;
+  %b = lshr i32 %a, 2
+  %shift = shl nsw i32 %b, 3
+  %cmp = icmp sge i32 %shift, 0
+  ret i1 %cmp
+}
+
+; Result of left shifting a negative integer with
+; nsw flag should also be negative
+define i1 @test_shift_negative(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_shift_negative(
+; CHECK-NEXT:    ret i1 true
+;
+  %c = or i32 %a, -2147483648
+  %d = and i32 %b, 7
+  %shift = shl nsw i32 %c, %d
+  %cmp = icmp slt i32 %shift, 0
+  ret i1 %cmp
+}
+
+; If sign bit is a known zero, it cannot be a known one.
+; This test should not crash opt.
+define i32 @test_no_sign_bit_conflict1(i1 %b) {
+; CHECK-LABEL: @test_no_sign_bit_conflict1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 %b, i32 -2147221504, i32 -2147483648
+; CHECK-NEXT:    ret i32 [[SEL]]
+;
+entry:
+  %sel = select i1 %b, i32 8193, i32 8192
+  %mul = shl nsw i32 %sel, 18
+  ret i32 %mul
+}
+
+; If sign bit is a known one, it cannot be a known zero.
+; This test should not crash opt.
+define i32 @test_no_sign_bit_conflict2(i1 %b) {
+; CHECK-LABEL: @test_no_sign_bit_conflict2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 %b, i32 2147221504, i32 2146959360
+; CHECK-NEXT:    ret i32 [[SEL]]
+;
+entry:
+  %sel = select i1 %b, i32 -8193, i32 -8194
+  %mul = shl nsw i32 %sel, 18
+  ret i32 %mul
+}