Auto merge of #94205 - Mark-Simulacrum:revert-93800, r=oli-obk

Revert #93800, fixing CI time regression

This reverts commit a240ccd (merge commit of #93800), reversing
changes made to 393fdc1.

This PR was likely responsible for a relatively large regression in
dist-x86_64-msvc-alt builder times, from approximately 1.7 to 2.8 hours,
bringing that builder into the pool of the slowest builders we currently have.

This seems to be limited to the alt builder due to needing parallel-compiler
enabled, likely leading to slow LLVM compilation for some reason. See some
investigation in [this Zulip stream](https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/msvc.28.3F.29.20builders.20running.20much.20slower).

cc `@lcnr` `@oli-obk` `@b-naber` (per original PRs review/author)

We can re-apply this PR once the regression is fixed, but it is sufficiently large that I don't think keeping this on master is viable in the meantime unless there's a very strong case to be made for it. Alternatively, we can disable that builder (it's not critical since it's an alt build), but that obviously carries its own costs.

compiler/rustc_middle/src/mir/mod.rs

@@ -2533,7 +2533,7 @@ pub enum ConstantKind<'tcx> {
 
 impl<'tcx> Constant<'tcx> {
     pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
-        match self.literal.try_to_scalar() {
+        match self.literal.const_for_ty()?.val().try_to_scalar() {
             Some(Scalar::Ptr(ptr, _size)) => match tcx.global_alloc(ptr.provenance) {
                 GlobalAlloc::Static(def_id) => {
                     assert!(!tcx.is_thread_local_static(def_id));

compiler/rustc_middle/src/mir/pretty.rs

@@ -17,8 +17,9 @@ use rustc_middle::mir::interpret::{
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::MirSource;
 use rustc_middle::mir::*;
-use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::ty::{self, TyCtxt, TypeFoldable, TypeVisitor};
 use rustc_target::abi::Size;
+use std::ops::ControlFlow;
 
 const INDENT: &str = "    ";
 /// Alignment for lining up comments following MIR statements
@@ -663,7 +664,6 @@ pub fn write_allocations<'tcx>(
     fn alloc_ids_from_alloc(alloc: &Allocation) -> impl DoubleEndedIterator<Item = AllocId> + '_ {
         alloc.relocations().values().map(|id| *id)
     }
-
     fn alloc_ids_from_const(val: ConstValue<'_>) -> impl Iterator<Item = AllocId> + '_ {
         match val {
             ConstValue::Scalar(interpret::Scalar::Ptr(ptr, _size)) => {
@@ -677,29 +677,17 @@ pub fn write_allocations<'tcx>(
             }
         }
     }
-
     struct CollectAllocIds(BTreeSet<AllocId>);
-
-    impl<'tcx> Visitor<'tcx> for CollectAllocIds {
-        fn visit_const(&mut self, c: ty::Const<'tcx>, _loc: Location) {
+    impl<'tcx> TypeVisitor<'tcx> for CollectAllocIds {
+        fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
             if let ty::ConstKind::Value(val) = c.val() {
                 self.0.extend(alloc_ids_from_const(val));
             }
-        }
-
-        fn visit_constant(&mut self, c: &Constant<'tcx>, loc: Location) {
-            match c.literal {
-                ConstantKind::Ty(c) => self.visit_const(c, loc),
-                ConstantKind::Val(val, _) => {
-                    self.0.extend(alloc_ids_from_const(val));
-                }
-            }
+            c.super_visit_with(self)
         }
     }
-
     let mut visitor = CollectAllocIds(Default::default());
-    visitor.visit_body(body);
-
+    body.visit_with(&mut visitor);
     // `seen` contains all seen allocations, including the ones we have *not* printed yet.
     // The protocol is to first `insert` into `seen`, and only if that returns `true`
     // then push to `todo`.

compiler/rustc_middle/src/thir.rs

@@ -17,7 +17,6 @@ use rustc_index::newtype_index;
 use rustc_index::vec::IndexVec;
 use rustc_middle::infer::canonical::Canonical;
 use rustc_middle::middle::region;
-use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{
     BinOp, BorrowKind, FakeReadCause, Field, Mutability, UnOp, UserTypeProjection,
 };
@@ -420,8 +419,7 @@ pub enum ExprKind<'tcx> {
     /// This is only distinguished from `Literal` so that we can register some
     /// info for diagnostics.
     StaticRef {
-        alloc_id: AllocId,
-        ty: Ty<'tcx>,
+        literal: Const<'tcx>,
         def_id: DefId,
     },
     /// Inline assembly, i.e. `asm!()`.

compiler/rustc_middle/src/thir/visit.rs

@@ -123,7 +123,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
         }
         Closure { closure_id: _, substs: _, upvars: _, movability: _, fake_reads: _ } => {}
         Literal { literal, user_ty: _, const_id: _ } => visitor.visit_const(literal),
-        StaticRef { .. } => {}
+        StaticRef { literal, def_id: _ } => visitor.visit_const(literal),
         InlineAsm { ref operands, template: _, options: _, line_spans: _ } => {
             for op in &**operands {
                 use InlineAsmOperand::*;

compiler/rustc_mir_build/src/build/expr/as_constant.rs

@@ -1,7 +1,6 @@
 //! See docs in build/expr/mod.rs
 
 use crate::build::Builder;
-use rustc_middle::mir::interpret::{ConstValue, Scalar};
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty::CanonicalUserTypeAnnotation;
@@ -27,12 +26,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 assert_eq!(literal.ty(), ty);
                 Constant { span, user_ty, literal: literal.into() }
             }
-            ExprKind::StaticRef { alloc_id, ty, .. } => {
-                let const_val =
-                    ConstValue::Scalar(Scalar::from_pointer(alloc_id.into(), &this.tcx));
-                let literal = ConstantKind::Val(const_val, ty);
-
-                Constant { span, user_ty: None, literal }
+            ExprKind::StaticRef { literal, .. } => {
+                Constant { span, user_ty: None, literal: literal.into() }
             }
             ExprKind::ConstBlock { value } => {
                 Constant { span: span, user_ty: None, literal: value.into() }

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -8,6 +8,7 @@ use rustc_middle::hir::place::Place as HirPlace;
 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
 use rustc_middle::middle::region;
+use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::{BinOp, BorrowKind, Field, UnOp};
 use rustc_middle::thir::*;
 use rustc_middle::ty::adjustment::{
@@ -940,8 +941,15 @@ impl<'tcx> Cx<'tcx> {
                 let kind = if self.tcx.is_thread_local_static(id) {
                     ExprKind::ThreadLocalRef(id)
                 } else {
-                    let alloc_id = self.tcx.create_static_alloc(id);
-                    ExprKind::StaticRef { alloc_id, ty, def_id: id }
+                    let ptr = self.tcx.create_static_alloc(id);
+                    ExprKind::StaticRef {
+                        literal: ty::Const::from_scalar(
+                            self.tcx,
+                            Scalar::from_pointer(ptr.into(), &self.tcx),
+                            ty,
+                        ),
+                        def_id: id,
+                    }
                 };
                 ExprKind::Deref {
                     arg: self.thir.exprs.push(Expr { ty, temp_lifetime, span: expr.span, kind }),

src/test/mir-opt/const_allocation.main.ConstProp.after.32bit.mir

@@ -9,9 +9,12 @@ fn main() -> () {
         StorageLive(_1);                 // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
         StorageLive(_2);                 // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
         _2 = const {alloc1: &&[(Option<i32>, &[&str])]}; // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
+                                         // ty::Const
+                                         // + ty: &&[(std::option::Option<i32>, &[&str])]
+                                         // + val: Value(Scalar(alloc1))
                                          // mir::Constant
                                          // + span: $DIR/const_allocation.rs:8:5: 8:8
-                                         // + literal: Const { ty: &&[(Option<i32>, &[&str])], val: Value(Scalar(alloc1)) }
+                                         // + literal: Const { ty: &&[(std::option::Option<i32>, &[&str])], val: Value(Scalar(alloc1)) }
         _1 = (*_2);                      // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
         StorageDead(_2);                 // scope 0 at $DIR/const_allocation.rs:8:8: 8:9
         StorageDead(_1);                 // scope 0 at $DIR/const_allocation.rs:8:8: 8:9

src/test/mir-opt/const_allocation.main.ConstProp.after.64bit.mir

@@ -9,9 +9,12 @@ fn main() -> () {
         StorageLive(_1);                 // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
         StorageLive(_2);                 // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
         _2 = const {alloc1: &&[(Option<i32>, &[&str])]}; // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
+                                         // ty::Const
+                                         // + ty: &&[(std::option::Option<i32>, &[&str])]
+                                         // + val: Value(Scalar(alloc1))
                                          // mir::Constant
                                          // + span: $DIR/const_allocation.rs:8:5: 8:8
-                                         // + literal: Const { ty: &&[(Option<i32>, &[&str])], val: Value(Scalar(alloc1)) }
+                                         // + literal: Const { ty: &&[(std::option::Option<i32>, &[&str])], val: Value(Scalar(alloc1)) }
         _1 = (*_2);                      // scope 0 at $DIR/const_allocation.rs:8:5: 8:8
         StorageDead(_2);                 // scope 0 at $DIR/const_allocation.rs:8:8: 8:9
         StorageDead(_1);                 // scope 0 at $DIR/const_allocation.rs:8:8: 8:9

src/test/mir-opt/const_allocation2.main.ConstProp.after.32bit.mir

@@ -9,9 +9,12 @@ fn main() -> () {
         StorageLive(_1);                 // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
         StorageLive(_2);                 // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
         _2 = const {alloc1: &&[(Option<i32>, &[&u8])]}; // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
+                                         // ty::Const
+                                         // + ty: &&[(std::option::Option<i32>, &[&u8])]
+                                         // + val: Value(Scalar(alloc1))
                                          // mir::Constant
                                          // + span: $DIR/const_allocation2.rs:5:5: 5:8
-                                         // + literal: Const { ty: &&[(Option<i32>, &[&u8])], val: Value(Scalar(alloc1)) }
+                                         // + literal: Const { ty: &&[(std::option::Option<i32>, &[&u8])], val: Value(Scalar(alloc1)) }
         _1 = (*_2);                      // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
         StorageDead(_2);                 // scope 0 at $DIR/const_allocation2.rs:5:8: 5:9
         StorageDead(_1);                 // scope 0 at $DIR/const_allocation2.rs:5:8: 5:9

src/test/mir-opt/const_allocation2.main.ConstProp.after.64bit.mir

@@ -9,9 +9,12 @@ fn main() -> () {
         StorageLive(_1);                 // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
         StorageLive(_2);                 // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
         _2 = const {alloc1: &&[(Option<i32>, &[&u8])]}; // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
+                                         // ty::Const
+                                         // + ty: &&[(std::option::Option<i32>, &[&u8])]
+                                         // + val: Value(Scalar(alloc1))
                                          // mir::Constant
                                          // + span: $DIR/const_allocation2.rs:5:5: 5:8
-                                         // + literal: Const { ty: &&[(Option<i32>, &[&u8])], val: Value(Scalar(alloc1)) }
+                                         // + literal: Const { ty: &&[(std::option::Option<i32>, &[&u8])], val: Value(Scalar(alloc1)) }
         _1 = (*_2);                      // scope 0 at $DIR/const_allocation2.rs:5:5: 5:8
         StorageDead(_2);                 // scope 0 at $DIR/const_allocation2.rs:5:8: 5:9
         StorageDead(_1);                 // scope 0 at $DIR/const_allocation2.rs:5:8: 5:9

src/test/mir-opt/const_allocation3.main.ConstProp.after.32bit.mir

@@ -9,6 +9,9 @@ fn main() -> () {
         StorageLive(_1);                 // scope 0 at $DIR/const_allocation3.rs:5:5: 5:8
         StorageLive(_2);                 // scope 0 at $DIR/const_allocation3.rs:5:5: 5:8
         _2 = const {alloc1: &&Packed};   // scope 0 at $DIR/const_allocation3.rs:5:5: 5:8
+                                         // ty::Const
+                                         // + ty: &&Packed
+                                         // + val: Value(Scalar(alloc1))
                                          // mir::Constant
                                          // + span: $DIR/const_allocation3.rs:5:5: 5:8
                                          // + literal: Const { ty: &&Packed, val: Value(Scalar(alloc1)) }

src/test/mir-opt/const_allocation3.main.ConstProp.after.64bit.mir

@@ -9,6 +9,9 @@ fn main() -> () {
         StorageLive(_1);                 // scope 0 at $DIR/const_allocation3.rs:5:5: 5:8
         StorageLive(_2);                 // scope 0 at $DIR/const_allocation3.rs:5:5: 5:8
         _2 = const {alloc1: &&Packed};   // scope 0 at $DIR/const_allocation3.rs:5:5: 5:8
+                                         // ty::Const
+                                         // + ty: &&Packed
+                                         // + val: Value(Scalar(alloc1))
                                          // mir::Constant
                                          // + span: $DIR/const_allocation3.rs:5:5: 5:8
                                          // + literal: Const { ty: &&Packed, val: Value(Scalar(alloc1)) }

src/test/mir-opt/const_promotion_extern_static.BAR-promoted[0].SimplifyCfg-elaborate-drops.after.mir

@@ -8,6 +8,9 @@ promoted[0] in BAR: &[&i32; 1] = {
 
     bb0: {
         _3 = const {alloc1: &i32};       // scope 0 at $DIR/const-promotion-extern-static.rs:9:33: 9:34
+                                         // ty::Const
+                                         // + ty: &i32
+                                         // + val: Value(Scalar(alloc1))
                                          // mir::Constant
                                          // + span: $DIR/const-promotion-extern-static.rs:9:33: 9:34
                                          // + literal: Const { ty: &i32, val: Value(Scalar(alloc1)) }

src/test/mir-opt/const_promotion_extern_static.BAR.PromoteTemps.diff

@@ -18,7 +18,9 @@
 -         StorageLive(_5);                 // scope 0 at $DIR/const-promotion-extern-static.rs:9:33: 9:34
 -         _5 = const {alloc1: &i32};       // scope 0 at $DIR/const-promotion-extern-static.rs:9:33: 9:34
 +         _6 = const BAR::promoted[0];     // scope 0 at $DIR/const-promotion-extern-static.rs:9:31: 9:44
-+                                          // ty::Const
+                                           // ty::Const
+-                                          // + ty: &i32
+-                                          // + val: Value(Scalar(alloc1))
 +                                          // + ty: &[&i32; 1]
 +                                          // + val: Unevaluated(BAR, [], Some(promoted[0]))
                                            // mir::Constant

src/test/mir-opt/const_promotion_extern_static.FOO-promoted[0].SimplifyCfg-elaborate-drops.after.mir

@@ -8,6 +8,9 @@ promoted[0] in FOO: &[&i32; 1] = {
 
     bb0: {
         _3 = const {alloc3: *const i32}; // scope 0 at $DIR/const-promotion-extern-static.rs:13:42: 13:43
+                                         // ty::Const
+                                         // + ty: *const i32
+                                         // + val: Value(Scalar(alloc3))
                                          // mir::Constant
                                          // + span: $DIR/const-promotion-extern-static.rs:13:42: 13:43
                                          // + literal: Const { ty: *const i32, val: Value(Scalar(alloc3)) }

src/test/mir-opt/const_promotion_extern_static.FOO.PromoteTemps.diff

@@ -20,7 +20,9 @@
 -         StorageLive(_5);                 // scope 1 at $DIR/const-promotion-extern-static.rs:13:42: 13:43
 -         _5 = const {alloc3: *const i32}; // scope 1 at $DIR/const-promotion-extern-static.rs:13:42: 13:43
 +         _6 = const FOO::promoted[0];     // scope 0 at $DIR/const-promotion-extern-static.rs:13:31: 13:55
-+                                          // ty::Const
+                                           // ty::Const
+-                                          // + ty: *const i32
+-                                          // + val: Value(Scalar(alloc3))
 +                                          // + ty: &[&i32; 1]
 +                                          // + val: Unevaluated(FOO, [], Some(promoted[0]))
                                            // mir::Constant

src/test/mir-opt/const_prop/mutable_variable_no_prop.main.ConstProp.diff

@@ -24,6 +24,9 @@
           StorageLive(_3);                 // scope 2 at $DIR/mutable_variable_no_prop.rs:9:13: 9:19
           StorageLive(_4);                 // scope 2 at $DIR/mutable_variable_no_prop.rs:9:13: 9:19
           _4 = const {alloc1: *mut u32};   // scope 2 at $DIR/mutable_variable_no_prop.rs:9:13: 9:19
+                                           // ty::Const
+                                           // + ty: *mut u32
+                                           // + val: Value(Scalar(alloc1))
                                            // mir::Constant
                                            // + span: $DIR/mutable_variable_no_prop.rs:9:13: 9:19
                                            // + literal: Const { ty: *mut u32, val: Value(Scalar(alloc1)) }

src/test/mir-opt/const_prop/read_immutable_static.main.ConstProp.diff

@@ -17,6 +17,9 @@
           StorageLive(_2);                 // scope 0 at $DIR/read_immutable_static.rs:7:13: 7:16
           StorageLive(_3);                 // scope 0 at $DIR/read_immutable_static.rs:7:13: 7:16
           _3 = const {alloc1: &u8};        // scope 0 at $DIR/read_immutable_static.rs:7:13: 7:16
+                                           // ty::Const
+                                           // + ty: &u8
+                                           // + val: Value(Scalar(alloc1))
                                            // mir::Constant
                                            // + span: $DIR/read_immutable_static.rs:7:13: 7:16
                                            // + literal: Const { ty: &u8, val: Value(Scalar(alloc1)) }
@@ -25,6 +28,9 @@
           StorageLive(_4);                 // scope 0 at $DIR/read_immutable_static.rs:7:19: 7:22
           StorageLive(_5);                 // scope 0 at $DIR/read_immutable_static.rs:7:19: 7:22
           _5 = const {alloc1: &u8};        // scope 0 at $DIR/read_immutable_static.rs:7:19: 7:22
+                                           // ty::Const
+                                           // + ty: &u8
+                                           // + val: Value(Scalar(alloc1))
                                            // mir::Constant
                                            // + span: $DIR/read_immutable_static.rs:7:19: 7:22
                                            // + literal: Const { ty: &u8, val: Value(Scalar(alloc1)) }