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| author | Eduard-Mihai Burtescu <eddyb@lyken.rs> | 2021-08-06 20:33:02 +0300 |
|---|---|---|
| committer | Eduard-Mihai Burtescu <eddyb@lyken.rs> | 2021-08-08 13:59:36 +0300 |
| commit | a1d014bdbc0159c6ed60e29dc0c3ef3110ff9776 (patch) | |
| tree | 41f372818dfbd78e9fead123f7b5b9b75813f6b4 /src/test/codegen/mem-replace-direct-memcpy.rs | |
| parent | 4c29cc8fd09889880880cb6081174c79744ab1b6 (diff) | |
| download | rust-a1d014bdbc0159c6ed60e29dc0c3ef3110ff9776.tar.gz rust-a1d014bdbc0159c6ed60e29dc0c3ef3110ff9776.zip | |
Avoid using the `copy_nonoverlapping` wrapper through `mem::replace`.
Diffstat (limited to 'src/test/codegen/mem-replace-direct-memcpy.rs')
| -rw-r--r-- | src/test/codegen/mem-replace-direct-memcpy.rs | 25 |
1 files changed, 25 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 00000000000..47f4fc27fd8 --- /dev/null +++ b/src/test/codegen/mem-replace-direct-memcpy.rs @@ -0,0 +1,25 @@ +// 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 + +#![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::{read,write}`. + +// CHECK-NOT: call void @llvm.memcpy +// CHECK: ; core::ptr::read +// CHECK-NOT: call void @llvm.memcpy +// CHECK: call void @llvm.memcpy.p0i8.p0i8.i{{.*}}(i8* align 1 %{{.*}}, i8* align 1 %src, i{{.*}} 1, i1 false) +// CHECK-NOT: call void @llvm.memcpy +// CHECK: ; core::ptr::write +// CHECK-NOT: call void @llvm.memcpy +// CHECK: call void @llvm.memcpy.p0i8.p0i8.i{{.*}}(i8* align 1 %dst, i8* align 1 %src, i{{.*}} 1, i1 false) +// CHECK-NOT: call void @llvm.memcpy |