rust/tests/codegen/issues/issue-37945.rs

// compile-flags: -O -Zmerge-functions=disabled
// ignore-32bit LLVM has a bug with them
// ignore-debug

// Check that LLVM understands that `Iter` pointer is not null. Issue #37945.

#![crate_type = "lib"]

use std::slice::Iter;

#[no_mangle]
pub fn is_empty_1(xs: Iter<f32>) -> bool {
// CHECK-LABEL: @is_empty_1(
// CHECK-NEXT:  start:
// CHECK-NEXT:    [[A:%.*]] = icmp ne {{i32\*|ptr}} {{%xs.0|%xs.1}}, null
// CHECK-NEXT:    tail call void @llvm.assume(i1 [[A]])
// The order between %xs.0 and %xs.1 on the next line doesn't matter
// and different LLVM versions produce different order.
// CHECK-NEXT:    [[B:%.*]] = icmp eq {{i32\*|ptr}} {{%xs.0, %xs.1|%xs.1, %xs.0}}
// CHECK-NEXT:    ret i1 [[B:%.*]]
    {xs}.next().is_none()
}

#[no_mangle]
pub fn is_empty_2(xs: Iter<f32>) -> bool {
// CHECK-LABEL: @is_empty_2
// CHECK-NEXT:  start:
// CHECK-NEXT:    [[C:%.*]] = icmp ne {{i32\*|ptr}} {{%xs.0|%xs.1}}, null
// CHECK-NEXT:    tail call void @llvm.assume(i1 [[C]])
// The order between %xs.0 and %xs.1 on the next line doesn't matter
// and different LLVM versions produce different order.
// CHECK-NEXT:    [[D:%.*]] = icmp eq {{i32\*|ptr}} {{%xs.0, %xs.1|%xs.1, %xs.0}}
// CHECK-NEXT:    ret i1 [[D:%.*]]
    xs.map(|&x| x).next().is_none()
}