Rollup merge of rust-lang#122290 - RalfJung:mir-printing, r=compiler-errors

MIR printing: print the path of uneval'd const Currently it just prints `const _` which makes it impossible to say which constant is being referred to. Also refer to promoteds in a consistent way; previously MIR printing would do ``` promoted[0] in C1: &Option<Cell<i32>> = { // ... } ``` Now that should be ``` const C1::promoted[0]: &Option<Cell<i32>> = { // ... } ``` We don't seem to have a test for that so I tried it by hand, it seems to work: ``` const main::promoted[12]: &[&str; 3] = { let mut _0: &[&str; 3]; let mut _1: [&str; 3]; let mut _2: &str; let mut _3: &str; let mut _4: &str; let mut _5: &str; bb0: { _3 = const "b"; _2 = &(*_3); _5 = const "c"; _4 = &(*_5); _1 = [const "a", move _2, move _4]; _0 = &_1; return; } } ```

Author: matthiaskrgr

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -67,7 +67,7 @@ fn eval_body_using_ecx<'mir, 'tcx>(
  trace!(
  "eval_body_using_ecx: pushing stack frame for global: {}{}",
  with_no_trimmed_paths!(ecx.tcx.def_path_str(cid.instance.def_id())),
- cid.promoted.map_or_else(String::new, |p| format!("::promoted[{p:?}]"))
+ cid.promoted.map_or_else(String::new, |p| format!("::{p:?}"))
  );
 
  ecx.push_stack_frame(

compiler/rustc_middle/src/mir/consts.rs

@@ -7,6 +7,7 @@ use rustc_target::abi::{HasDataLayout, Size};
 
 use crate::mir::interpret::{alloc_range, AllocId, ConstAllocation, ErrorHandled, Scalar};
 use crate::mir::{pretty_print_const_value, Promoted};
+use crate::ty::print::with_no_trimmed_paths;
 use crate::ty::GenericArgsRef;
 use crate::ty::ScalarInt;
 use crate::ty::{self, print::pretty_print_const, Ty, TyCtxt};
@@ -489,9 +490,18 @@ impl<'tcx> Display for Const<'tcx> {
  Const::Ty(c) => pretty_print_const(c, fmt, true),
  Const::Val(val, ty) => pretty_print_const_value(val, ty, fmt),
  // FIXME(valtrees): Correctly print mir constants.
- Const::Unevaluated(..) => {
- fmt.write_str("_")?;
- Ok(())
+ Const::Unevaluated(c, _ty) => {
+ ty::tls::with(move |tcx| {
+ let c = tcx.lift(c).unwrap();
+ // Matches `GlobalId` printing.
+ let instance =
+ with_no_trimmed_paths!(tcx.def_path_str_with_args(c.def, c.args));
+ write!(fmt, "{instance}")?;
+ if let Some(promoted) = c.promoted {
+ write!(fmt, "::{promoted:?}")?;
+ }
+ Ok(())
+ })
  }
  }
  }

compiler/rustc_middle/src/mir/pretty.rs

@@ -496,7 +496,7 @@ fn write_mir_sig(tcx: TyCtxt<'_>, body: &Body<'_>, w: &mut dyn io::Write) -> io:
  _ => tcx.is_closure_like(def_id),
  };
  match (kind, body.source.promoted) {
- (_, Some(i)) => write!(w, "{i:?} in ")?,
+ (_, Some(_)) => write!(w, "const ")?, // promoteds are the closest to consts
  (DefKind::Const | DefKind::AssocConst, _) => write!(w, "const ")?,
  (DefKind::Static(hir::Mutability::Not), _) => write!(w, "static ")?,
  (DefKind::Static(hir::Mutability::Mut), _) => write!(w, "static mut ")?,
@@ -509,6 +509,9 @@ fn write_mir_sig(tcx: TyCtxt<'_>, body: &Body<'_>, w: &mut dyn io::Write) -> io:
  // see notes on #41697 elsewhere
  write!(w, "{}", tcx.def_path_str(def_id))?
  }
+ if let Some(p) = body.source.promoted {
+ write!(w, "::{p:?}")?;
+ }
 
  if body.source.promoted.is_none() && is_function {
  write!(w, "(")?;

tests/mir-opt/building/custom/consts.consts.built.after.mir

@@ -10,9 +10,9 @@ fn consts() -> () {
 
  bb0: {
  _1 = const 5_u8;
- _2 = const _;
+ _2 = const consts::<C>::{constant#0};
  _3 = const C;
- _4 = const _;
+ _4 = const D;
  _5 = consts::<10>;
  return;
  }

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

@@ -1,6 +1,6 @@
 // MIR for `BAR::promoted[0]` after SimplifyCfg-elaborate-drops
 
-promoted[0] in BAR: &[&i32; 1] = {
+const BAR::promoted[0]: &[&i32; 1] = {
  let mut _0: &[&i32; 1];
  let mut _1: [&i32; 1];
  let mut _2: &i32;

tests/mir-opt/const_promotion_extern_static.BAR.PromoteTemps.diff

@@ -20,7 +20,7 @@
 - _4 = &(*_5);
 - _3 = [move _4];
 - _2 = &_3;
-+ _6 = const _;
++ _6 = const BAR::promoted[0];
 + _2 = &(*_6);
  _1 = move _2 as &[&i32] (PointerCoercion(Unsize));
 - StorageDead(_4);

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

@@ -1,6 +1,6 @@
 // MIR for `FOO::promoted[0]` after SimplifyCfg-elaborate-drops
 
-promoted[0] in FOO: &[&i32; 1] = {
+const FOO::promoted[0]: &[&i32; 1] = {
  let mut _0: &[&i32; 1];
  let mut _1: [&i32; 1];
  let mut _2: &i32;

tests/mir-opt/const_promotion_extern_static.FOO.PromoteTemps.diff

@@ -22,7 +22,7 @@
 - _4 = &(*_5);
 - _3 = [move _4];
 - _2 = &_3;
-+ _6 = const _;
++ _6 = const FOO::promoted[0];
 + _2 = &(*_6);
  _1 = move _2 as &[&i32] (PointerCoercion(Unsize));
 - StorageDead(_4);

tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-abort.diff

@@ -25,7 +25,7 @@
  StorageLive(_1);
  StorageLive(_2);
  StorageLive(_3);
- _9 = const _;
+ _9 = const main::promoted[0];
  _3 = &(*_9);
  _2 = &raw const (*_3);
  _1 = move _2 as *const [i32] (PointerCoercion(Unsize));

tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-unwind.diff

@@ -25,7 +25,7 @@
  StorageLive(_1);
  StorageLive(_2);
  StorageLive(_3);
- _9 = const _;
+ _9 = const main::promoted[0];
  _3 = &(*_9);
  _2 = &raw const (*_3);
  _1 = move _2 as *const [i32] (PointerCoercion(Unsize));