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: the debug assertions get in the way
|
|
|
|
#![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` has it down to just the two essential ones.
|
|
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 two `memcpy`s
|
|
// CHECK-LABEL: define internal void @{{.+}}mem{{.+}}replace{{.+}}sret(%Big)
|
|
// CHECK-NOT: alloca
|
|
// CHECK-NOT: call void @llvm.memcpy
|
|
// CHECK: call void @llvm.memcpy.{{.+}}({{i8\*|ptr}} align 8 %0, {{i8\*|ptr}} align 8 %dest, i{{.*}} 56, i1 false)
|
|
// CHECK-NOT: call void @llvm.memcpy
|
|
// CHECK: call void @llvm.memcpy.{{.+}}({{i8\*|ptr}} align 8 %dest, {{i8\*|ptr}} align 8 %src, i{{.*}} 56, i1 false)
|
|
// CHECK-NOT: call void @llvm.memcpy
|
|
|
|
// CHECK-NOT: call void @llvm.memcpy
|