Only preserve DebugInfo in DeadStoreElimination if requested.

compiler/rustc_mir_transform/src/dead_store_elimination.rs

@@ -12,6 +12,7 @@
 //!     will still not cause any further changes.
 //!
 
+use crate::simplify::preserve_debug_even_if_never_generated;
 use crate::util::is_within_packed;
 use rustc_middle::bug;
 use rustc_middle::mir::visit::Visitor;
@@ -32,10 +33,16 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 
     // If the user requests complete debuginfo, mark the locals that appear in it as live, so
     // we don't remove assignements to them.
-    let mut always_live = debuginfo_locals(body);
-    always_live.union(&borrowed_locals);
-
-    let mut live = MaybeTransitiveLiveLocals::new(&always_live)
+    let mut always_live;
+    let always_live = if preserve_debug_even_if_never_generated(tcx) {
+        always_live = debuginfo_locals(body);
+        always_live.union(&borrowed_locals);
+        &always_live
+    } else {
+        &borrowed_locals
+    };
+
+    let mut live = MaybeTransitiveLiveLocals::new(always_live)
         .into_engine(tcx, body)
         .iterate_to_fixpoint()
         .into_results_cursor(body);

compiler/rustc_mir_transform/src/inline.rs

@@ -12,14 +12,14 @@ use rustc_middle::mir::visit::*;
 use rustc_middle::mir::*;
 use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, Instance, InstanceKind, ParamEnv, Ty, TyCtxt, TypeFlags};
-use rustc_session::config::{DebugInfo, OptLevel};
+use rustc_session::config::OptLevel;
 use rustc_span::source_map::Spanned;
 use rustc_span::sym;
 use rustc_target::abi::FieldIdx;
 use rustc_target::spec::abi::Abi;
 
 use crate::cost_checker::CostChecker;
-use crate::simplify::simplify_cfg;
+use crate::simplify::{preserve_debug_even_if_never_generated, simplify_cfg};
 use crate::util;
 use crate::validate::validate_types;
 use std::iter;
@@ -719,14 +719,7 @@ impl<'tcx> Inliner<'tcx> {
         // Insert all of the (mapped) parts of the callee body into the caller.
         caller_body.local_decls.extend(callee_body.drain_vars_and_temps());
         caller_body.source_scopes.extend(&mut callee_body.source_scopes.drain(..));
-        if self
-            .tcx
-            .sess
-            .opts
-            .unstable_opts
-            .inline_mir_preserve_debug
-            .unwrap_or(self.tcx.sess.opts.debuginfo != DebugInfo::None)
-        {
+        if preserve_debug_even_if_never_generated(self.tcx) {
             // Note that we need to preserve these in the standard library so that
             // people working on rust can build with or without debuginfo while
             // still getting consistent results from the mir-opt tests.

compiler/rustc_mir_transform/src/lib.rs

@@ -597,7 +597,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &gvn::GVN,
             &simplify::SimplifyLocals::AfterGVN,
             &dataflow_const_prop::DataflowConstProp,
-            &single_use_consts::SingleUseConsts,
+            &single_use_consts::SingleUseConsts::Initial,
             &o1(simplify_branches::SimplifyConstCondition::AfterConstProp),
             &jump_threading::JumpThreading,
             &early_otherwise_branch::EarlyOtherwiseBranch,
@@ -607,6 +607,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &o1(remove_noop_landing_pads::RemoveNoopLandingPads),
             &o1(simplify::SimplifyCfg::Final),
             &copy_prop::CopyProp,
+            &single_use_consts::SingleUseConsts::Final,
             &dead_store_elimination::DeadStoreElimination::Final,
             &nrvo::RenameReturnPlace,
             &simplify::SimplifyLocals::Final,

compiler/rustc_mir_transform/src/simplify.rs

@@ -31,6 +31,7 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
+use rustc_session::config::DebugInfo;
 use smallvec::SmallVec;
 
 pub enum SimplifyCfg {
@@ -581,3 +582,12 @@ impl<'tcx> MutVisitor<'tcx> for LocalUpdater<'tcx> {
         *l = self.map[*l].unwrap();
     }
 }
+
+pub(crate) fn preserve_debug_even_if_never_generated(tcx: TyCtxt<'_>) -> bool {
+    tcx.sess.opts.unstable_opts.inline_mir_preserve_debug.unwrap_or_else(|| {
+        match tcx.sess.opts.debuginfo {
+            DebugInfo::None | DebugInfo::LineDirectivesOnly | DebugInfo::LineTablesOnly => false,
+            DebugInfo::Limited | DebugInfo::Full => true,
+        }
+    })
+}

compiler/rustc_mir_transform/src/single_use_consts.rs

@@ -18,13 +18,23 @@ use rustc_middle::ty::TyCtxt;
 ///
 /// It also removes *never*-used constants, since it had all the information
 /// needed to do that too, including updating the debug info.
-pub struct SingleUseConsts;
+pub enum SingleUseConsts {
+    Initial,
+    Final,
+}
 
 impl<'tcx> MirPass<'tcx> for SingleUseConsts {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
         sess.mir_opt_level() > 0
     }
 
+    fn name(&self) -> &'static str {
+        match self {
+            SingleUseConsts::Initial => "SingleUseConsts-initial",
+            SingleUseConsts::Final => "SingleUseConsts-final",
+        }
+    }
+
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let mut finder = SingleUseConstsFinder {
             ineligible_locals: BitSet::new_empty(body.local_decls.len()),

tests/codegen/slice-ref-equality.rs

@@ -1,4 +1,4 @@
-//@ compile-flags: -O -Zmerge-functions=disabled
+//@ compile-flags: -O -Zmerge-functions=disabled -Cdebuginfo=0
 #![crate_type = "lib"]
 
 use std::num::NonZero;

tests/crashes/101962.rs

@@ -1,4 +1,5 @@
 //@ known-bug: #101962
+//@ compile-flags: -Cdebuginfo=2
 
 #![feature(core_intrinsics)]
 

tests/crashes/79409.rs

@@ -1,4 +1,5 @@
 //@ known-bug: #79409
+//@ compile-flags: -Cdebuginfo=2
 
 #![feature(extern_types)]
 #![feature(unsized_locals)]

tests/incremental/hashes/enum_constructors.rs

@@ -318,9 +318,9 @@ pub fn change_constructor_variant_c_like() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,optimized_mir")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes,optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail6")]
 pub fn change_constructor_variant_c_like() {
     let _x = Clike::C;

tests/incremental/hashes/for_loops.rs

@@ -28,9 +28,9 @@ pub fn change_loop_body() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail6")]
 pub fn change_loop_body() {
     let mut _x = 0;
@@ -180,7 +180,7 @@ pub fn add_loop_label_to_break() {
 #[cfg(not(any(cfail1,cfail4)))]
 #[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail6")]
 pub fn add_loop_label_to_break() {
     let mut _x = 0;

tests/incremental/hashes/let_expressions.rs

@@ -91,7 +91,7 @@ pub fn change_mutability_of_slot() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,typeck")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,typeck,optimized_mir")]
 #[rustc_clean(cfg="cfail3")]
 #[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes,typeck,optimized_mir")]
 #[rustc_clean(cfg="cfail6")]
@@ -176,7 +176,7 @@ pub fn change_mutability_of_binding_in_pattern() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,typeck")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,typeck,optimized_mir")]
 #[rustc_clean(cfg="cfail3")]
 #[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes,typeck,optimized_mir")]
 #[rustc_clean(cfg="cfail6")]
@@ -193,9 +193,9 @@ pub fn add_initializer() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,typeck,optimized_mir")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,typeck")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes,typeck,optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes,typeck")]
 #[rustc_clean(cfg="cfail6")]
 pub fn add_initializer() {
     let _x: i16 = 3i16;
@@ -210,9 +210,9 @@ pub fn change_initializer() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail6")]
 pub fn change_initializer() {
     let _x = 5u16;

tests/incremental/hashes/loop_expressions.rs

@@ -28,9 +28,9 @@ pub fn change_loop_body() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail6")]
 pub fn change_loop_body() {
     let mut _x = 0;

tests/incremental/hashes/match_expressions.rs

@@ -227,7 +227,7 @@ pub fn change_mutability_of_binding_in_pattern(x: u32) -> u32 {
 
 // Ignore optimized_mir in cfail2, the only change to optimized MIR is a span.
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,typeck")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes,optimized_mir,typeck")]
 #[rustc_clean(cfg="cfail3")]
 #[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes,optimized_mir,typeck")]
 #[rustc_clean(cfg="cfail6")]

tests/incremental/hashes/while_loops.rs

@@ -28,9 +28,9 @@ pub fn change_loop_body() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail6")]
 pub fn change_loop_body() {
     let mut _x = 0;
@@ -53,9 +53,9 @@ pub fn change_loop_condition() {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes, optimized_mir")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail6")]
 pub fn change_loop_condition() {
     let mut _x = 0;
@@ -211,7 +211,7 @@ pub fn change_continue_label() {
 #[cfg(not(any(cfail1,cfail4)))]
 #[rustc_clean(cfg="cfail2", except="opt_hir_owner_nodes")]
 #[rustc_clean(cfg="cfail3")]
-#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes")]
+#[rustc_clean(cfg="cfail5", except="opt_hir_owner_nodes, optimized_mir")]
 #[rustc_clean(cfg="cfail6")]
 pub fn change_continue_label() {
     let mut _x = 0;

tests/mir-opt/const_debuginfo.main.SingleUseConsts.diff → tests/mir-opt/const_debuginfo.main.SingleUseConsts-final.diff

@@ -1,5 +1,5 @@
-- // MIR for `main` before SingleUseConsts
-+ // MIR for `main` after SingleUseConsts
+- // MIR for `main` before SingleUseConsts-final
++ // MIR for `main` after SingleUseConsts-final
 
   fn main() -> () {
       let mut _0: ();

tests/mir-opt/const_debuginfo.rs

@@ -1,4 +1,4 @@
-//@ test-mir-pass: SingleUseConsts
+//@ test-mir-pass: SingleUseConsts-final
 //@ compile-flags: -C overflow-checks=no -Zmir-enable-passes=+GVN -Zdump-mir-exclude-alloc-bytes
 
 #![allow(unused)]
@@ -8,7 +8,7 @@ struct Point {
     y: u32,
 }
 
-// EMIT_MIR const_debuginfo.main.SingleUseConsts.diff
+// EMIT_MIR const_debuginfo.main.SingleUseConsts-final.diff
 fn main() {
     // CHECK-LABEL: fn main(
     // CHECK: debug x => const 1_u8;

tests/mir-opt/dead-store-elimination/cycle.cycle.DeadStoreElimination-initial.diff

@@ -2,31 +2,70 @@
 + // MIR for `cycle` after DeadStoreElimination-initial
 
   fn cycle(_1: i32, _2: i32, _3: i32) -> () {
+      debug x => _1;
+      debug y => _2;
+      debug z => _3;
       let mut _0: ();
-      let mut _4: bool;
-      let mut _5: i32;
+      let mut _4: ();
+      let mut _5: bool;
+      let _6: i32;
+      let mut _7: i32;
+      let mut _8: i32;
+      let mut _9: i32;
+      let mut _10: !;
+      let _11: ();
+      let mut _12: !;
+      scope 1 {
+          debug temp => _6;
+      }
 
       bb0: {
-          _4 = cond() -> [return: bb1, unwind continue];
+          goto -> bb1;
       }
 
       bb1: {
-          switchInt(_4) -> [1: bb2, otherwise: bb3];
+          StorageLive(_5);
+          _5 = cond() -> [return: bb2, unwind continue];
       }
 
       bb2: {
--         _5 = _3;
--         _3 = _2;
--         _2 = _1;
--         _1 = _5;
+          switchInt(move _5) -> [0: bb4, otherwise: bb3];
+      }
+
+      bb3: {
+          StorageLive(_6);
+-         _6 = _3;
++         nop;
+          StorageLive(_7);
+-         _7 = _2;
+-         _3 = move _7;
 +         nop;
 +         nop;
+          StorageDead(_7);
+          StorageLive(_8);
+-         _8 = _1;
+-         _2 = move _8;
 +         nop;
 +         nop;
-          _4 = cond() -> [return: bb1, unwind continue];
+          StorageDead(_8);
+          StorageLive(_9);
+-         _9 = _6;
+-         _1 = move _9;
++         nop;
++         nop;
+          StorageDead(_9);
+-         _4 = const ();
++         nop;
+          StorageDead(_6);
+          StorageDead(_5);
+          goto -> bb1;
       }
 
-      bb3: {
+      bb4: {
+          StorageLive(_11);
+          _0 = const ();
+          StorageDead(_11);
+          StorageDead(_5);
           return;
       }
   }