From 7093903ba7a71c1d30e817daa41a4328dc6a8db2 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Mon, 4 Sep 2023 15:32:07 +0200 Subject: [PATCH] read_via_copy: don't prematurely optimize away the read --- .../src/lower_intrinsics.rs | 23 +++++++++---------- ...inhabited.LowerIntrinsics.panic-abort.diff | 1 + ...nhabited.LowerIntrinsics.panic-unwind.diff | 1 + tests/ui/consts/const-eval/ub-uninhabit.rs | 16 +++++++++++++ .../ui/consts/const-eval/ub-uninhabit.stderr | 14 +++++++---- 5 files changed, 39 insertions(+), 16 deletions(-) diff --git a/compiler/rustc_mir_transform/src/lower_intrinsics.rs b/compiler/rustc_mir_transform/src/lower_intrinsics.rs index fc36c6e4124a6..a8dc91ca43969 100644 --- a/compiler/rustc_mir_transform/src/lower_intrinsics.rs +++ b/compiler/rustc_mir_transform/src/lower_intrinsics.rs @@ -176,23 +176,22 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics { } else { span_bug!(terminator.source_info.span, "Only passing a local is supported"); }; + // Add new statement at the end of the block that does the read, and patch + // up the terminator. + block.statements.push(Statement { + source_info: terminator.source_info, + kind: StatementKind::Assign(Box::new(( + *destination, + Rvalue::Use(Operand::Copy(derefed_place)), + ))), + }); terminator.kind = match *target { None => { // No target means this read something uninhabited, - // so it must be unreachable, and we don't need to - // preserve the assignment either. + // so it must be unreachable. TerminatorKind::Unreachable } - Some(target) => { - block.statements.push(Statement { - source_info: terminator.source_info, - kind: StatementKind::Assign(Box::new(( - *destination, - Rvalue::Use(Operand::Copy(derefed_place)), - ))), - }); - TerminatorKind::Goto { target } - } + Some(target) => TerminatorKind::Goto { target }, } } sym::write_via_move => { diff --git a/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-abort.diff b/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-abort.diff index 95a4a83d66386..b2cf3cc1ccac5 100644 --- a/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-abort.diff +++ b/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-abort.diff @@ -12,6 +12,7 @@ StorageLive(_2); _2 = &raw const (*_1); - _0 = read_via_copy::(move _2) -> unwind unreachable; ++ _0 = (*_2); + unreachable; } } diff --git a/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-unwind.diff b/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-unwind.diff index 95a4a83d66386..b2cf3cc1ccac5 100644 --- a/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-unwind.diff +++ b/tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.panic-unwind.diff @@ -12,6 +12,7 @@ StorageLive(_2); _2 = &raw const (*_1); - _0 = read_via_copy::(move _2) -> unwind unreachable; ++ _0 = (*_2); + unreachable; } } diff --git a/tests/ui/consts/const-eval/ub-uninhabit.rs b/tests/ui/consts/const-eval/ub-uninhabit.rs index 10edae437ee74..01600f545ae03 100644 --- a/tests/ui/consts/const-eval/ub-uninhabit.rs +++ b/tests/ui/consts/const-eval/ub-uninhabit.rs @@ -1,7 +1,10 @@ // Strip out raw byte dumps to make comparison platform-independent: // normalize-stderr-test "(the raw bytes of the constant) \(size: [0-9]*, align: [0-9]*\)" -> "$1 (size: $$SIZE, align: $$ALIGN)" // normalize-stderr-test "([0-9a-f][0-9a-f] |╾─*a(lloc)?[0-9]+(\+[a-z0-9]+)?─*╼ )+ *│.*" -> "HEX_DUMP" +#![feature(core_intrinsics)] +#![feature(never_type)] +use std::intrinsics; use std::mem; #[derive(Copy, Clone)] @@ -15,11 +18,24 @@ union MaybeUninit { const BAD_BAD_BAD: Bar = unsafe { MaybeUninit { uninit: () }.init }; //~^ ERROR evaluation of constant value failed +//~| constructing invalid value const BAD_BAD_REF: &Bar = unsafe { mem::transmute(1usize) }; //~^ ERROR it is undefined behavior to use this value +//~| constructing invalid value const BAD_BAD_ARRAY: [Bar; 1] = unsafe { MaybeUninit { uninit: () }.init }; //~^ ERROR evaluation of constant value failed +//~| constructing invalid value + + +const READ_NEVER: () = unsafe { + let mem = [0u32; 8]; + let ptr = mem.as_ptr().cast::(); + let _val = intrinsics::read_via_copy(ptr); + //~^ ERROR evaluation of constant value failed + //~| constructing invalid value +}; + fn main() {} diff --git a/tests/ui/consts/const-eval/ub-uninhabit.stderr b/tests/ui/consts/const-eval/ub-uninhabit.stderr index f1ad0f04d3dbe..d26f4e03666e9 100644 --- a/tests/ui/consts/const-eval/ub-uninhabit.stderr +++ b/tests/ui/consts/const-eval/ub-uninhabit.stderr @@ -1,11 +1,11 @@ error[E0080]: evaluation of constant value failed - --> $DIR/ub-uninhabit.rs:16:35 + --> $DIR/ub-uninhabit.rs:19:35 | LL | const BAD_BAD_BAD: Bar = unsafe { MaybeUninit { uninit: () }.init }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered a value of uninhabited type `Bar` error[E0080]: it is undefined behavior to use this value - --> $DIR/ub-uninhabit.rs:19:1 + --> $DIR/ub-uninhabit.rs:23:1 | LL | const BAD_BAD_REF: &Bar = unsafe { mem::transmute(1usize) }; | ^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered a reference pointing to uninhabited type Bar @@ -16,11 +16,17 @@ LL | const BAD_BAD_REF: &Bar = unsafe { mem::transmute(1usize) }; } error[E0080]: evaluation of constant value failed - --> $DIR/ub-uninhabit.rs:22:42 + --> $DIR/ub-uninhabit.rs:27:42 | LL | const BAD_BAD_ARRAY: [Bar; 1] = unsafe { MaybeUninit { uninit: () }.init }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at [0]: encountered a value of uninhabited type `Bar` -error: aborting due to 3 previous errors +error[E0080]: evaluation of constant value failed + --> $DIR/ub-uninhabit.rs:35:16 + | +LL | let _val = intrinsics::read_via_copy(ptr); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered a value of the never type `!` + +error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0080`.