Auto merge of #138190 - cuviper:beta-next, r=cuviper

[beta] backports

- Don't infer attributes of virtual calls based on the function body #137669
- Revert "store ScalarPair via memset when one side is undef and the other side can be memset" #137894

r? cuviper

Author: bors

Diff for: compiler/rustc_codegen_gcc/src/common.rs

@@ -64,11 +64,6 @@ impl<'gcc, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         if type_is_pointer(typ) { self.context.new_null(typ) } else { self.const_int(typ, 0) }
     }
 
-    fn is_undef(&self, _val: RValue<'gcc>) -> bool {
-        // FIXME: actually check for undef
-        false
-    }
-
     fn const_undef(&self, typ: Type<'gcc>) -> RValue<'gcc> {
         let local = self.current_func.borrow().expect("func").new_local(None, typ, "undefined");
         if typ.is_struct().is_some() {

Diff for: compiler/rustc_codegen_llvm/src/common.rs

@@ -126,10 +126,6 @@ impl<'ll, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         unsafe { llvm::LLVMGetUndef(t) }
     }
 
-    fn is_undef(&self, v: &'ll Value) -> bool {
-        unsafe { llvm::LLVMIsUndef(v) == True }
-    }
-
     fn const_poison(&self, t: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMGetPoison(t) }
     }

Diff for: compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1035,7 +1035,6 @@ unsafe extern "C" {
     pub(crate) fn LLVMMetadataTypeInContext(C: &Context) -> &Type;
 
     // Operations on all values
-    pub(crate) fn LLVMIsUndef(Val: &Value) -> Bool;
     pub(crate) fn LLVMTypeOf(Val: &Value) -> &Type;
     pub(crate) fn LLVMGetValueName2(Val: &Value, Length: *mut size_t) -> *const c_char;
     pub(crate) fn LLVMSetValueName2(Val: &Value, Name: *const c_char, NameLen: size_t);

Diff for: compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -204,30 +204,14 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
         let alloc_align = alloc.inner().align;
         assert!(alloc_align >= layout.align.abi);
 
-        // Returns `None` when the value is partially undefined or any byte of it has provenance.
-        // Otherwise returns the value or (if the entire value is undef) returns an undef.
         let read_scalar = |start, size, s: abi::Scalar, ty| {
-            let range = alloc_range(start, size);
             match alloc.0.read_scalar(
                 bx,
-                range,
+                alloc_range(start, size),
                 /*read_provenance*/ matches!(s.primitive(), abi::Primitive::Pointer(_)),
             ) {
-                Ok(val) => Some(bx.scalar_to_backend(val, s, ty)),
-                Err(_) => {
-                    // We may have failed due to partial provenance or unexpected provenance,
-                    // continue down the normal code path if so.
-                    if alloc.0.provenance().range_empty(range, &bx.tcx())
-                        // Since `read_scalar` failed, but there were no relocations involved, the
-                        // bytes must be partially or fully uninitialized. Thus we can now unwrap the
-                        // information about the range of uninit bytes and check if it's the full range.
-                        && alloc.0.init_mask().is_range_initialized(range).unwrap_err() == range
-                    {
-                        Some(bx.const_undef(ty))
-                    } else {
-                        None
-                    }
-                }
+                Ok(val) => bx.scalar_to_backend(val, s, ty),
+                Err(_) => bx.const_poison(ty),
             }
         };
 
@@ -238,14 +222,16 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
         // check that walks over the type of `mplace` to make sure it is truly correct to treat this
         // like a `Scalar` (or `ScalarPair`).
         match layout.backend_repr {
-            BackendRepr::Scalar(s) => {
+            BackendRepr::Scalar(s @ abi::Scalar::Initialized { .. }) => {
                 let size = s.size(bx);
                 assert_eq!(size, layout.size, "abi::Scalar size does not match layout size");
-                if let Some(val) = read_scalar(offset, size, s, bx.immediate_backend_type(layout)) {
-                    return OperandRef { val: OperandValue::Immediate(val), layout };
-                }
+                let val = read_scalar(offset, size, s, bx.immediate_backend_type(layout));
+                OperandRef { val: OperandValue::Immediate(val), layout }
             }
-            BackendRepr::ScalarPair(a, b) => {
+            BackendRepr::ScalarPair(
+                a @ abi::Scalar::Initialized { .. },
+                b @ abi::Scalar::Initialized { .. },
+            ) => {
                 let (a_size, b_size) = (a.size(bx), b.size(bx));
                 let b_offset = (offset + a_size).align_to(b.align(bx).abi);
                 assert!(b_offset.bytes() > 0);
@@ -261,21 +247,20 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
                     b,
                     bx.scalar_pair_element_backend_type(layout, 1, true),
                 );
-                if let (Some(a_val), Some(b_val)) = (a_val, b_val) {
-                    return OperandRef { val: OperandValue::Pair(a_val, b_val), layout };
-                }
+                OperandRef { val: OperandValue::Pair(a_val, b_val), layout }
+            }
+            _ if layout.is_zst() => OperandRef::zero_sized(layout),
+            _ => {
+                // Neither a scalar nor scalar pair. Load from a place
+                // FIXME: should we cache `const_data_from_alloc` to avoid repeating this for the
+                // same `ConstAllocation`?
+                let init = bx.const_data_from_alloc(alloc);
+                let base_addr = bx.static_addr_of(init, alloc_align, None);
+
+                let llval = bx.const_ptr_byte_offset(base_addr, offset);
+                bx.load_operand(PlaceRef::new_sized(llval, layout))
             }
-            _ if layout.is_zst() => return OperandRef::zero_sized(layout),
-            _ => {}
         }
-        // Neither a scalar nor scalar pair. Load from a place
-        // FIXME: should we cache `const_data_from_alloc` to avoid repeating this for the
-        // same `ConstAllocation`?
-        let init = bx.const_data_from_alloc(alloc);
-        let base_addr = bx.static_addr_of(init, alloc_align, None);
-
-        let llval = bx.const_ptr_byte_offset(base_addr, offset);
-        bx.load_operand(PlaceRef::new_sized(llval, layout))
     }
 
     /// Asserts that this operand refers to a scalar and returns

Diff for: compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -8,7 +8,7 @@ use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_middle::{bug, mir, span_bug};
 use rustc_session::config::OptLevel;
 use rustc_span::{DUMMY_SP, Span};
-use tracing::{debug, instrument, trace};
+use tracing::{debug, instrument};
 
 use super::operand::{OperandRef, OperandValue};
 use super::place::PlaceRef;
@@ -93,8 +93,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     return;
                 }
 
-                // If `v` is an integer constant whose value is just a single byte repeated N times,
-                // emit a `memset` filling the entire `dest` with that byte.
                 let try_init_all_same = |bx: &mut Bx, v| {
                     let start = dest.val.llval;
                     let size = bx.const_usize(dest.layout.size.bytes());
@@ -119,33 +117,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     false
                 };
 
-                trace!(?cg_elem.val);
                 match cg_elem.val {
                     OperandValue::Immediate(v) => {
                         if try_init_all_same(bx, v) {
                             return;
                         }
                     }
-                    OperandValue::Pair(a, b) => {
-                        let a_is_undef = bx.cx().is_undef(a);
-                        match (a_is_undef, bx.cx().is_undef(b)) {
-                            // Can happen for uninit unions
-                            (true, true) => {
-                                // FIXME: can we produce better output here?
-                            }
-                            (false, true) | (true, false) => {
-                                let val = if a_is_undef { b } else { a };
-                                if try_init_all_same(bx, val) {
-                                    return;
-                                }
-                            }
-                            (false, false) => {
-                                // FIXME: if both are the same value, use try_init_all_same
-                            }
-                        }
-                    }
-                    OperandValue::ZeroSized => unreachable!("checked above"),
-                    OperandValue::Ref(..) => {}
+                    _ => (),
                 }
 
                 let count = self

Diff for: compiler/rustc_codegen_ssa/src/traits/consts.rs

@@ -9,7 +9,6 @@ pub trait ConstCodegenMethods<'tcx>: BackendTypes {
     /// Generate an uninitialized value (matching uninitialized memory in MIR).
     /// Whether memory is initialized or not is tracked byte-for-byte.
     fn const_undef(&self, t: Self::Type) -> Self::Value;
-    fn is_undef(&self, v: Self::Value) -> bool;
     /// Generate a fake value. Poison always affects the entire value, even if just a single byte is
     /// poison. This can only be used in codepaths that are already UB, i.e., UB-free Rust code
     /// (including code that e.g. copies uninit memory with `MaybeUninit`) can never encounter a

Diff for: compiler/rustc_middle/src/mir/interpret/allocation.rs

@@ -222,7 +222,7 @@ impl AllocError {
 }
 
 /// The information that makes up a memory access: offset and size.
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone)]
 pub struct AllocRange {
     pub start: Size,
     pub size: Size,

Diff for: compiler/rustc_middle/src/ty/instance.rs

@@ -111,8 +111,9 @@ pub enum InstanceKind<'tcx> {
 
     /// Dynamic dispatch to `<dyn Trait as Trait>::fn`.
     ///
-    /// This `InstanceKind` does not have callable MIR. Calls to `Virtual` instances must be
-    /// codegen'd as virtual calls through the vtable.
+    /// This `InstanceKind` may have a callable MIR as the default implementation.
+    /// Calls to `Virtual` instances must be codegen'd as virtual calls through the vtable.
+    /// *This means we might not know exactly what is being called.*
     ///
     /// If this is reified to a `fn` pointer, a `ReifyShim` is used (see `ReifyShim` above for more
     /// details on that).

Diff for: compiler/rustc_ty_utils/src/abi.rs

@@ -309,15 +309,11 @@ fn fn_abi_of_fn_ptr<'tcx>(
     query: ty::PseudoCanonicalInput<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> {
     let ty::PseudoCanonicalInput { typing_env, value: (sig, extra_args) } = query;
-
-    let cx = LayoutCx::new(tcx, typing_env);
     fn_abi_new_uncached(
-        &cx,
+        &LayoutCx::new(tcx, typing_env),
         tcx.instantiate_bound_regions_with_erased(sig),
         extra_args,
         None,
-        None,
-        false,
     )
 }
 
@@ -326,19 +322,11 @@ fn fn_abi_of_instance<'tcx>(
     query: ty::PseudoCanonicalInput<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> {
     let ty::PseudoCanonicalInput { typing_env, value: (instance, extra_args) } = query;
-
-    let sig = fn_sig_for_fn_abi(tcx, instance, typing_env);
-
-    let caller_location =
-        instance.def.requires_caller_location(tcx).then(|| tcx.caller_location_ty());
-
     fn_abi_new_uncached(
         &LayoutCx::new(tcx, typing_env),
-        sig,
+        fn_sig_for_fn_abi(tcx, instance, typing_env),
         extra_args,
-        caller_location,
-        Some(instance.def_id()),
-        matches!(instance.def, ty::InstanceKind::Virtual(..)),
+        Some(instance),
     )
 }
 
@@ -549,19 +537,25 @@ fn fn_abi_sanity_check<'tcx>(
     fn_arg_sanity_check(cx, fn_abi, spec_abi, &fn_abi.ret);
 }
 
-// FIXME(eddyb) perhaps group the signature/type-containing (or all of them?)
-// arguments of this method, into a separate `struct`.
-#[tracing::instrument(level = "debug", skip(cx, caller_location, fn_def_id, force_thin_self_ptr))]
+#[tracing::instrument(level = "debug", skip(cx, instance))]
 fn fn_abi_new_uncached<'tcx>(
     cx: &LayoutCx<'tcx>,
     sig: ty::FnSig<'tcx>,
     extra_args: &[Ty<'tcx>],
-    caller_location: Option<Ty<'tcx>>,
-    fn_def_id: Option<DefId>,
-    // FIXME(eddyb) replace this with something typed, like an `enum`.
-    force_thin_self_ptr: bool,
+    instance: Option<ty::Instance<'tcx>>,
 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> {
     let tcx = cx.tcx();
+    let (caller_location, determined_fn_def_id, is_virtual_call) = if let Some(instance) = instance
+    {
+        let is_virtual_call = matches!(instance.def, ty::InstanceKind::Virtual(..));
+        (
+            instance.def.requires_caller_location(tcx).then(|| tcx.caller_location_ty()),
+            if is_virtual_call { None } else { Some(instance.def_id()) },
+            is_virtual_call,
+        )
+    } else {
+        (None, None, false)
+    };
     let sig = tcx.normalize_erasing_regions(cx.typing_env, sig);
 
     let conv = conv_from_spec_abi(cx.tcx(), sig.abi, sig.c_variadic);
@@ -570,16 +564,11 @@ fn fn_abi_new_uncached<'tcx>(
     let extra_args = if sig.abi == ExternAbi::RustCall {
         assert!(!sig.c_variadic && extra_args.is_empty());
 
-        if let Some(input) = sig.inputs().last() {
-            if let ty::Tuple(tupled_arguments) = input.kind() {
-                inputs = &sig.inputs()[0..sig.inputs().len() - 1];
-                tupled_arguments
-            } else {
-                bug!(
-                    "argument to function with \"rust-call\" ABI \
-                        is not a tuple"
-                );
-            }
+        if let Some(input) = sig.inputs().last()
+            && let ty::Tuple(tupled_arguments) = input.kind()
+        {
+            inputs = &sig.inputs()[0..sig.inputs().len() - 1];
+            tupled_arguments
         } else {
             bug!(
                 "argument to function with \"rust-call\" ABI \
@@ -592,7 +581,7 @@ fn fn_abi_new_uncached<'tcx>(
     };
 
     let is_drop_in_place =
-        fn_def_id.is_some_and(|def_id| tcx.is_lang_item(def_id, LangItem::DropInPlace));
+        determined_fn_def_id.is_some_and(|def_id| tcx.is_lang_item(def_id, LangItem::DropInPlace));
 
     let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, &'tcx FnAbiError<'tcx>> {
         let span = tracing::debug_span!("arg_of");
@@ -605,7 +594,7 @@ fn fn_abi_new_uncached<'tcx>(
         });
 
         let layout = cx.layout_of(ty).map_err(|err| &*tcx.arena.alloc(FnAbiError::Layout(*err)))?;
-        let layout = if force_thin_self_ptr && arg_idx == Some(0) {
+        let layout = if is_virtual_call && arg_idx == Some(0) {
             // Don't pass the vtable, it's not an argument of the virtual fn.
             // Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait`
             // or `&/&mut dyn Trait` because this is special-cased elsewhere in codegen
@@ -648,9 +637,22 @@ fn fn_abi_new_uncached<'tcx>(
         c_variadic: sig.c_variadic,
         fixed_count: inputs.len() as u32,
         conv,
-        can_unwind: fn_can_unwind(cx.tcx(), fn_def_id, sig.abi),
+        can_unwind: fn_can_unwind(
+            tcx,
+            // Since `#[rustc_nounwind]` can change unwinding, we cannot infer unwinding by `fn_def_id` for a virtual call.
+            determined_fn_def_id,
+            sig.abi,
+        ),
     };
-    fn_abi_adjust_for_abi(cx, &mut fn_abi, sig.abi, fn_def_id);
+    fn_abi_adjust_for_abi(
+        cx,
+        &mut fn_abi,
+        sig.abi,
+        // If this is a virtual call, we cannot pass the `fn_def_id`, as it might call other
+        // functions from vtable. Internally, `deduced_param_attrs` attempts to infer attributes by
+        // visit the function body.
+        determined_fn_def_id,
+    );
     debug!("fn_abi_new_uncached = {:?}", fn_abi);
     fn_abi_sanity_check(cx, &fn_abi, sig.abi);
     Ok(tcx.arena.alloc(fn_abi))