mirror of
https://github.com/rust-lang/rust.git
synced 2025-10-31 13:04:42 +00:00
35 lines
1.4 KiB
Rust
35 lines
1.4 KiB
Rust
// This test ensures that `mem::replace::<T>` only ever calls `@llvm.memcpy`
|
|
// with `size_of::<T>()` as the size, and never goes through any wrapper that
|
|
// may e.g. multiply `size_of::<T>()` with a variable "count" (which is only
|
|
// known to be `1` after inlining).
|
|
|
|
//@ compile-flags: -C no-prepopulate-passes -Zinline-mir=no
|
|
//@ ignore-debug: precondition checks in ptr::read make them a bad candidate for MIR inlining
|
|
//@ needs-deterministic-layouts
|
|
|
|
#![crate_type = "lib"]
|
|
|
|
#[repr(C, align(8))]
|
|
pub struct Big([u64; 7]);
|
|
pub fn replace_big(dst: &mut Big, src: Big) -> Big {
|
|
// Back in 1.68, this emitted six `memcpy`s.
|
|
// `read_via_copy` in 1.69 got that down to three.
|
|
// `write_via_move` and nvro get this down to the essential two.
|
|
std::mem::replace(dst, src)
|
|
}
|
|
|
|
// NOTE(eddyb) the `CHECK-NOT`s ensure that the only calls of `@llvm.memcpy` in
|
|
// the entire output, are the direct calls we want, from `ptr::replace`.
|
|
|
|
// CHECK-NOT: call void @llvm.memcpy
|
|
|
|
// For a large type, we expect exactly three `memcpy`s
|
|
// CHECK-LABEL: define internal void @{{.+}}mem{{.+}}replace{{.+}}sret([56 x i8])
|
|
// CHECK-NOT: call void @llvm.memcpy
|
|
// CHECK: call void @llvm.memcpy.{{.+}}(ptr align 8 %result, ptr align 8 %dest, i{{.*}} 56, i1 false)
|
|
// CHECK-NOT: call void @llvm.memcpy
|
|
// CHECK: call void @llvm.memcpy.{{.+}}(ptr align 8 %dest, ptr align 8 %src, i{{.*}} 56, i1 false)
|
|
// CHECK-NOT: call void @llvm.memcpy
|
|
|
|
// CHECK-NOT: call void @llvm.memcpy
|