| // 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` 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(%Big) |
| // 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 |
