Auto merge of rust-lang#112718 - oli-obk:SIMD-destructure_mir_const, r=cjgillot

Make simd_shuffle_indices use valtrees

This removes the second-to-last user of the `destructure_mir_constant` query. So in a follow-up we can remove the query and just move the query provider function directly into pretty printing (which is the last user).

cc `@rust-lang/clippy` there's a small functional change, but I think it is correct?

Author: bors

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -870,13 +870,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         // promotes any complex rvalues to constants.
                         if i == 2 && intrinsic.as_str().starts_with("simd_shuffle") {
                             if let mir::Operand::Constant(constant) = arg {
-                                let c = self.eval_mir_constant(constant);
-                                let (llval, ty) = self.simd_shuffle_indices(
-                                    &bx,
-                                    constant.span,
-                                    self.monomorphize(constant.ty()),
-                                    c,
-                                );
+                                let (llval, ty) = self.simd_shuffle_indices(&bx, constant);
                                 return OperandRef {
                                     val: Immediate(llval),
                                     layout: bx.layout_of(ty),

compiler/rustc_codegen_ssa/src/mir/constant.rs

@@ -5,7 +5,6 @@ use rustc_middle::mir;
 use rustc_middle::mir::interpret::{ConstValue, ErrorHandled};
 use rustc_middle::ty::layout::HasTyCtxt;
 use rustc_middle::ty::{self, Ty};
-use rustc_span::source_map::Span;
 use rustc_target::abi::Abi;
 
 use super::FunctionCx;
@@ -59,22 +58,40 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         })
     }
 
+    /// This is a convenience helper for `simd_shuffle_indices`. It has the precondition
+    /// that the given `constant` is an `ConstantKind::Unevaluated` and must be convertible to
+    /// a `ValTree`. If you want a more general version of this, talk to `wg-const-eval` on zulip.
+    pub fn eval_unevaluated_mir_constant_to_valtree(
+        &self,
+        constant: &mir::Constant<'tcx>,
+    ) -> Result<Option<ty::ValTree<'tcx>>, ErrorHandled> {
+        let uv = match constant.literal {
+            mir::ConstantKind::Unevaluated(uv, _) => uv.shrink(),
+            other => span_bug!(constant.span, "{other:#?}"),
+        };
+        let uv = self.monomorphize(uv);
+        self.cx.tcx().const_eval_resolve_for_typeck(
+            ty::ParamEnv::reveal_all(),
+            uv,
+            Some(constant.span),
+        )
+    }
+
     /// process constant containing SIMD shuffle indices
     pub fn simd_shuffle_indices(
         &mut self,
         bx: &Bx,
-        span: Span,
-        ty: Ty<'tcx>,
-        constant: Result<ConstValue<'tcx>, ErrorHandled>,
+        constant: &mir::Constant<'tcx>,
     ) -> (Bx::Value, Ty<'tcx>) {
-        constant
+        let ty = self.monomorphize(constant.ty());
+        let val = self
+            .eval_unevaluated_mir_constant_to_valtree(constant)
+            .ok()
+            .flatten()
             .map(|val| {
                 let field_ty = ty.builtin_index().unwrap();
-                let c = mir::ConstantKind::from_value(val, ty);
-                let values: Vec<_> = bx
-                    .tcx()
-                    .destructure_mir_constant(ty::ParamEnv::reveal_all(), c)
-                    .fields
+                let values: Vec<_> = val
+                    .unwrap_branch()
                     .iter()
                     .map(|field| {
                         if let Some(prim) = field.try_to_scalar() {
@@ -88,15 +105,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         }
                     })
                     .collect();
-                let llval = bx.const_struct(&values, false);
-                (llval, c.ty())
+                bx.const_struct(&values, false)
             })
-            .unwrap_or_else(|_| {
-                bx.tcx().sess.emit_err(errors::ShuffleIndicesEvaluation { span });
+            .unwrap_or_else(|| {
+                bx.tcx().sess.emit_err(errors::ShuffleIndicesEvaluation { span: constant.span });
                 // We've errored, so we don't have to produce working code.
-                let ty = self.monomorphize(ty);
                 let llty = bx.backend_type(bx.layout_of(ty));
-                (bx.const_undef(llty), ty)
-            })
+                bx.const_undef(llty)
+            });
+        (val, ty)
     }
 }

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -92,7 +92,6 @@ pub(crate) fn try_destructure_mir_constant<'tcx>(
     param_env: ty::ParamEnv<'tcx>,
     val: mir::ConstantKind<'tcx>,
 ) -> InterpResult<'tcx, mir::DestructuredConstant<'tcx>> {
-    trace!("destructure_mir_constant: {:?}", val);
     let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, CanAccessStatics::No);
     let op = ecx.eval_mir_constant(&val, None, None)?;
 

compiler/rustc_middle/src/mir/interpret/queries.rs

@@ -95,11 +95,15 @@ impl<'tcx> TyCtxt<'tcx> {
                     // used generic parameters is a bug of evaluation, so checking for it
                     // here does feel somewhat sensible.
                     if !self.features().generic_const_exprs && ct.substs.has_non_region_param() {
-                        assert!(matches!(
-                            self.def_kind(ct.def),
-                            DefKind::InlineConst | DefKind::AnonConst
-                        ));
-                        let mir_body = self.mir_for_ctfe(ct.def);
+                        let def_kind = self.def_kind(instance.def_id());
+                        assert!(
+                            matches!(
+                                def_kind,
+                                DefKind::InlineConst | DefKind::AnonConst | DefKind::AssocConst
+                            ),
+                            "{cid:?} is {def_kind:?}",
+                        );
+                        let mir_body = self.mir_for_ctfe(instance.def_id());
                         if mir_body.is_polymorphic {
                             let Some(local_def_id) = ct.def.as_local() else { return };
                             self.struct_span_lint_hir(
@@ -239,15 +243,3 @@ impl<'tcx> TyCtxtEnsure<'tcx> {
         self.eval_to_allocation_raw(param_env.and(gid))
     }
 }
-
-impl<'tcx> TyCtxt<'tcx> {
-    /// Destructure a mir constant ADT or array into its variant index and its field values.
-    /// Panics if the destructuring fails, use `try_destructure_mir_constant` for fallible version.
-    pub fn destructure_mir_constant(
-        self,
-        param_env: ty::ParamEnv<'tcx>,
-        constant: mir::ConstantKind<'tcx>,
-    ) -> mir::DestructuredConstant<'tcx> {
-        self.try_destructure_mir_constant(param_env.and(constant)).unwrap()
-    }
-}

compiler/rustc_middle/src/mir/mod.rs

@@ -2581,10 +2581,9 @@ pub struct UnevaluatedConst<'tcx> {
 }
 
 impl<'tcx> UnevaluatedConst<'tcx> {
-    // FIXME: probably should get rid of this method. It's also wrong to
-    // shrink and then later expand a promoted.
     #[inline]
     pub fn shrink(self) -> ty::UnevaluatedConst<'tcx> {
+        assert_eq!(self.promoted, None);
         ty::UnevaluatedConst { def: self.def, substs: self.substs }
     }
 }

src/tools/clippy/clippy_lints/src/non_copy_const.rs

@@ -15,12 +15,14 @@ use rustc_hir::{
 };
 use rustc_hir_analysis::hir_ty_to_ty;
 use rustc_lint::{LateContext, LateLintPass, Lint};
-use rustc_middle::mir;
-use rustc_middle::mir::interpret::{ConstValue, ErrorHandled};
+use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::ty::adjustment::Adjust;
-use rustc_middle::ty::{self, Ty};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::{sym, InnerSpan, Span};
+use rustc_target::abi::VariantIdx;
+use rustc_middle::mir::interpret::EvalToValTreeResult;
+use rustc_middle::mir::interpret::GlobalId;
 
 // FIXME: this is a correctness problem but there's no suitable
 // warn-by-default category.
@@ -141,21 +143,35 @@ fn is_unfrozen<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
 
 fn is_value_unfrozen_raw<'tcx>(
     cx: &LateContext<'tcx>,
-    result: Result<ConstValue<'tcx>, ErrorHandled>,
+    result: Result<Option<ty::ValTree<'tcx>>, ErrorHandled>,
     ty: Ty<'tcx>,
 ) -> bool {
-    fn inner<'tcx>(cx: &LateContext<'tcx>, val: mir::ConstantKind<'tcx>) -> bool {
-        match val.ty().kind() {
+    fn inner<'tcx>(cx: &LateContext<'tcx>, val: ty::ValTree<'tcx>, ty: Ty<'tcx>) -> bool {
+        match *ty.kind() {
             // the fact that we have to dig into every structs to search enums
             // leads us to the point checking `UnsafeCell` directly is the only option.
             ty::Adt(ty_def, ..) if ty_def.is_unsafe_cell() => true,
             // As of 2022-09-08 miri doesn't track which union field is active so there's no safe way to check the
             // contained value.
             ty::Adt(def, ..) if def.is_union() => false,
-            ty::Array(..) | ty::Adt(..) | ty::Tuple(..) => {
-                let val = cx.tcx.destructure_mir_constant(cx.param_env, val);
-                val.fields.iter().any(|field| inner(cx, *field))
+            ty::Array(ty, _)  => {
+                val.unwrap_branch().iter().any(|field| inner(cx, *field, ty))
             },
+            ty::Adt(def, _) if def.is_union() => false,
+            ty::Adt(def, substs) if def.is_enum() => {
+                let (&variant_index, fields) = val.unwrap_branch().split_first().unwrap();
+                let variant_index =
+                    VariantIdx::from_u32(variant_index.unwrap_leaf().try_to_u32().ok().unwrap());
+                fields.iter().copied().zip(
+                    def.variants()[variant_index]
+                        .fields
+                        .iter()
+                        .map(|field| field.ty(cx.tcx, substs))).any(|(field, ty)| inner(cx, field, ty))
+            }
+            ty::Adt(def, substs) => {
+                val.unwrap_branch().iter().zip(def.non_enum_variant().fields.iter().map(|field| field.ty(cx.tcx, substs))).any(|(field, ty)| inner(cx, *field, ty))
+            }
+            ty::Tuple(tys) => val.unwrap_branch().iter().zip(tys).any(|(field, ty)| inner(cx, *field, ty)),
             _ => false,
         }
     }
@@ -184,24 +200,44 @@ fn is_value_unfrozen_raw<'tcx>(
             // I chose this way because unfrozen enums as assoc consts are rare (or, hopefully, none).
             err == ErrorHandled::TooGeneric
         },
-        |val| inner(cx, mir::ConstantKind::from_value(val, ty)),
+        |val| val.map_or(true, |val| inner(cx, val, ty)),
     )
 }
 
 fn is_value_unfrozen_poly<'tcx>(cx: &LateContext<'tcx>, body_id: BodyId, ty: Ty<'tcx>) -> bool {
-    let result = cx.tcx.const_eval_poly(body_id.hir_id.owner.to_def_id());
+    let def_id = body_id.hir_id.owner.to_def_id();
+    let substs = ty::InternalSubsts::identity_for_item(cx.tcx, def_id);
+    let instance = ty::Instance::new(def_id, substs);
+    let cid = rustc_middle::mir::interpret::GlobalId { instance, promoted: None };
+    let param_env = cx.tcx.param_env(def_id).with_reveal_all_normalized(cx.tcx);
+    let result = cx.tcx.const_eval_global_id_for_typeck(param_env, cid, None);
     is_value_unfrozen_raw(cx, result, ty)
 }
 
 fn is_value_unfrozen_expr<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId, def_id: DefId, ty: Ty<'tcx>) -> bool {
     let substs = cx.typeck_results().node_substs(hir_id);
 
-    let result = cx
-        .tcx
-        .const_eval_resolve(cx.param_env, mir::UnevaluatedConst::new(def_id, substs), None);
+    let result = const_eval_resolve(cx.tcx, cx.param_env, ty::UnevaluatedConst::new(def_id, substs), None);
     is_value_unfrozen_raw(cx, result, ty)
 }
 
+
+pub fn const_eval_resolve<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    ct: ty::UnevaluatedConst<'tcx>,
+    span: Option<Span>,
+) -> EvalToValTreeResult<'tcx> {
+    match ty::Instance::resolve(tcx, param_env, ct.def, ct.substs) {
+        Ok(Some(instance)) => {
+            let cid = GlobalId { instance, promoted: None };
+            tcx.const_eval_global_id_for_typeck(param_env, cid, span)
+        }
+        Ok(None) => Err(ErrorHandled::TooGeneric),
+        Err(err) => Err(ErrorHandled::Reported(err.into())),
+    }
+}
+
 #[derive(Copy, Clone)]
 enum Source {
     Item { item: Span },

src/tools/clippy/tests/ui/crashes/ice-9445.stderr

@@ -0,0 +1,12 @@
+error: a `const` item should never be interior mutable
+  --> $DIR/ice-9445.rs:1:1
+   |
+LL | const UNINIT: core::mem::MaybeUninit<core::cell::Cell<&'static ()>> = core::mem::MaybeUninit::uninit();
+   | -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   | |
+   | make this a static item (maybe with lazy_static)
+   |
+   = note: `-D clippy::declare-interior-mutable-const` implied by `-D warnings`
+
+error: aborting due to previous error
+