rust/tests/codegen/zst-offset.rs
Erik Desjardins 8ebd307d2a use GEP inbounds for ZST and DST field offsets
For the former, it's fine for `inbounds` offsets to be one-past-the-end,
so it's okay even if the ZST is the last field in the layout:

> The base pointer has an in bounds address of an allocated object,
> which means that it points into an allocated object, or to its end.

https://llvm.org/docs/LangRef.html#getelementptr-instruction

For the latter, even DST fields must always be inside the layout
(or to its end for ZSTs), so using inbounds is also fine there.
2024-03-04 09:32:33 -05:00

44 lines
1.2 KiB
Rust

//@ compile-flags: -C no-prepopulate-passes -Copt-level=0
#![crate_type = "lib"]
#![feature(repr_simd)]
// Hack to get the correct size for the length part in slices
// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
#[no_mangle]
pub fn helper(_: usize) {
}
// Check that we correctly generate a GEP for a ZST that is not included in Scalar layout
// CHECK-LABEL: @scalar_layout
#[no_mangle]
pub fn scalar_layout(s: &(u64, ())) {
// CHECK: getelementptr inbounds i8, {{.+}}, [[USIZE]] 8
let x = &s.1;
witness(&x); // keep variable in an alloca
}
// Check that we correctly generate a GEP for a ZST that is not included in ScalarPair layout
// CHECK-LABEL: @scalarpair_layout
#[no_mangle]
pub fn scalarpair_layout(s: &(u64, u32, ())) {
// CHECK: getelementptr inbounds i8, {{.+}}, [[USIZE]] 12
let x = &s.2;
witness(&x); // keep variable in an alloca
}
#[repr(simd)]
pub struct U64x4(u64, u64, u64, u64);
// Check that we correctly generate a GEP for a ZST that is not included in Vector layout
// CHECK-LABEL: @vector_layout
#[no_mangle]
pub fn vector_layout(s: &(U64x4, ())) {
// CHECK: getelementptr inbounds i8, {{.+}}, [[USIZE]] 32
let x = &s.1;
witness(&x); // keep variable in an alloca
}
#[inline(never)]
fn witness(_: &impl Sized) {}