diff options
Diffstat (limited to 'src/test/codegen/mem-replace-direct-memcpy.rs')
| -rw-r--r-- | src/test/codegen/mem-replace-direct-memcpy.rs | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/src/test/codegen/mem-replace-direct-memcpy.rs b/src/test/codegen/mem-replace-direct-memcpy.rs new file mode 100644 index 000000000..8095d309f --- /dev/null +++ b/src/test/codegen/mem-replace-direct-memcpy.rs @@ -0,0 +1,35 @@ +// ignore-test + +// WHY IS THIS TEST BEING IGNORED: +// +// This test depends on characteristics of how the stdlib was compiled, +// namely that sufficient inlining occurred to ensure that the call to +// `std::mem::replace` boils down to just two calls of `llvm.memcpy`. +// +// But the MIR inlining policy is in flux as of 1.64-beta, and the intermittent +// breakage of this test that results is causing problems for people trying to +// do development. + +// 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 + +#![crate_type = "lib"] + +pub fn replace_byte(dst: &mut u8, src: u8) -> u8 { + 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 two direct calls we want, from `ptr::replace`. + +// CHECK-NOT: call void @llvm.memcpy +// CHECK: ; core::mem::replace +// CHECK-NOT: call void @llvm.memcpy +// CHECK: call void @llvm.memcpy.{{.+}}({{i8\*|ptr}} align 1 %{{.*}}, {{i8\*|ptr}} align 1 %dest, i{{.*}} 1, i1 false) +// CHECK-NOT: call void @llvm.memcpy +// CHECK: call void @llvm.memcpy.{{.+}}({{i8\*|ptr}} align 1 %dest, {{i8\*|ptr}} align 1 %src{{.*}}, i{{.*}} 1, i1 false) +// CHECK-NOT: call void @llvm.memcpy |