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| author | bors <bors@rust-lang.org> | 2023-03-15 11:44:12 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2023-03-15 11:44:12 +0000 |
| commit | e4b9f86054c581d931f8bad0c87523c53e1e8e3f (patch) | |
| tree | 0282c090692c6fd05dad0bfe0a6c0094344e267d /tests/codegen/mem-replace-direct-memcpy.rs | |
| parent | 992d154f3a84cc8abcefcf6e6cf3698e4821b506 (diff) | |
| parent | dfc3377954f9e03172fed57ca890141006a0d82e (diff) | |
| download | rust-e4b9f86054c581d931f8bad0c87523c53e1e8e3f.tar.gz rust-e4b9f86054c581d931f8bad0c87523c53e1e8e3f.zip | |
Auto merge of #109035 - scottmcm:ptr-read-should-know-undef, r=WaffleLapkin,JakobDegen
Ensure `ptr::read` gets all the same LLVM `load` metadata that dereferencing does I was looking into `array::IntoIter` optimization, and noticed that it wasn't annotating the loads with `noundef` for simple things like `array::IntoIter<i32, N>`. Trying to narrow it down, it seems that was because `MaybeUninit::assume_init_read` isn't marking the load as initialized (<https://rust.godbolt.org/z/Mxd8TPTnv>), which is unfortunate since that's basically its reason to exist. The root cause is that `ptr::read` is currently implemented via the *untyped* `copy_nonoverlapping`, and thus the `load` doesn't get any type-aware metadata: no `noundef`, no `!range`. This PR solves that by lowering `ptr::read(p)` to `copy *p` in MIR, for which the backends already do the right thing. Fortuitiously, this also improves the IR we give to LLVM for things like `mem::replace`, and fixes a couple of long-standing bugs where `ptr::read` on `Copy` types was worse than `*`ing them. Zulip conversation: <https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Move.20array.3A.3AIntoIter.20to.20ManuallyDrop/near/341189936> cc `@erikdesjardins` `@JakobDegen` `@workingjubilee` `@the8472` Fixes #106369 Fixes #73258
Diffstat (limited to 'tests/codegen/mem-replace-direct-memcpy.rs')
| -rw-r--r-- | tests/codegen/mem-replace-direct-memcpy.rs | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/tests/codegen/mem-replace-direct-memcpy.rs b/tests/codegen/mem-replace-direct-memcpy.rs index e8bbf0e1bbd..83babab4f84 100644 --- a/tests/codegen/mem-replace-direct-memcpy.rs +++ b/tests/codegen/mem-replace-direct-memcpy.rs @@ -13,12 +13,21 @@ pub fn replace_byte(dst: &mut u8, src: u8) -> u8 { } // 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`. +// the entire output, are the 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 %{{.*}}, i{{.*}} 1, i1 false) -// CHECK-NOT: call void @llvm.memcpy -// CHECK: call void @llvm.memcpy.{{.+}}({{i8\*|ptr}} align 1 %{{.*}}, {{i8\*|ptr}} align 1 %{{.*}}, i{{.*}} 1, i1 false) + +// For a small type, we expect one each of `load`/`store`/`memcpy` instead +// CHECK-LABEL: define internal noundef i8 @{{.+}}mem{{.+}}replace + // CHECK-NOT: alloca + // CHECK: alloca i8 + // CHECK-NOT: alloca + // CHECK-NOT: call void @llvm.memcpy + // CHECK: load i8 + // CHECK-NOT: call void @llvm.memcpy + // CHECK: store i8 + // CHECK-NOT: call void @llvm.memcpy + // CHECK: call void @llvm.memcpy.{{.+}}({{i8\*|ptr}} align 1 %{{.*}}, {{i8\*|ptr}} align 1 %{{.*}}, i{{.*}} 1, i1 false) + // CHECK-NOT: call void @llvm.memcpy + // CHECK-NOT: call void @llvm.memcpy |