Ensure [rust] debuginfo-level-std doesn't change core's MIR

compiler/rustc_mir_transform/src/inline.rs

@@ -699,7 +699,17 @@ 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.debuginfo != DebugInfo::None {
+        if self
+            .tcx
+            .sess
+            .opts
+            .unstable_opts
+            .inline_mir_preserve_debug
+            .unwrap_or(self.tcx.sess.opts.debuginfo != DebugInfo::None)
+        {
+            // 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.
             caller_body.var_debug_info.append(&mut callee_body.var_debug_info);
         }
         caller_body.basic_blocks_mut().extend(callee_body.basic_blocks_mut().drain(..));

compiler/rustc_session/src/options.rs

@@ -1717,6 +1717,9 @@ options! {
         "enable MIR inlining (default: no)"),
     inline_mir_hint_threshold: Option<usize> = (None, parse_opt_number, [TRACKED],
         "inlining threshold for functions with inline hint (default: 100)"),
+    inline_mir_preserve_debug: Option<bool> = (None, parse_opt_bool, [TRACKED],
+        "when MIR inlining, whether to preserve debug info for callee variables \
+        (default: preserve for debuginfo != None, otherwise remove)"),
     inline_mir_threshold: Option<usize> = (None, parse_opt_number, [TRACKED],
         "a default MIR inlining threshold (default: 50)"),
     input_stats: bool = (false, parse_bool, [UNTRACKED],

src/bootstrap/src/core/builder.rs

@@ -2102,6 +2102,14 @@ impl<'a> Builder<'a> {
             // break when incremental compilation is enabled. So this overrides the "no inlining
             // during incremental builds" heuristic for the standard library.
             rustflags.arg("-Zinline-mir");
+
+            // always pass this after the next `#[cfg(bootstrap)]` update.
+            if compiler.stage != 0 {
+                // Similarly, we need to keep debug info for functions inlined into other std functions,
+                // even if we're not going to output debuginfo for the crate we're currently building,
+                // so that it'll be available when downstream consumers of std try to use it.
+                rustflags.arg("-Zinline-mir-preserve-debug");
+            }
         }
 
         if self.config.rustc_parallel

tests/mir-opt/inline/inline_coroutine.main.Inline.panic-abort.diff

@@ -16,6 +16,7 @@
 +     scope 3 (inlined Pin::<&mut {coroutine@$DIR/inline_coroutine.rs:19:5: 19:8}>::new) {
 +         debug pointer => _3;
 +         scope 4 (inlined Pin::<&mut {coroutine@$DIR/inline_coroutine.rs:19:5: 19:8}>::new_unchecked) {
++             debug pointer => _3;
 +         }
 +     }
 +     scope 5 (inlined g::{closure#0}) {

tests/mir-opt/inline/inline_coroutine.main.Inline.panic-unwind.diff

@@ -16,6 +16,7 @@
 +     scope 3 (inlined Pin::<&mut {coroutine@$DIR/inline_coroutine.rs:19:5: 19:8}>::new) {
 +         debug pointer => _3;
 +         scope 4 (inlined Pin::<&mut {coroutine@$DIR/inline_coroutine.rs:19:5: 19:8}>::new_unchecked) {
++             debug pointer => _3;
 +         }
 +     }
 +     scope 5 (inlined g::{closure#0}) {

tests/mir-opt/pre-codegen/checked_ops.checked_shl.PreCodegen.after.panic-abort.mir

@@ -13,11 +13,17 @@ fn checked_shl(_1: u32, _2: u32) -> Option<u32> {
             debug b => _5;
         }
         scope 3 (inlined core::num::<impl u32>::overflowing_shl) {
+            debug self => _1;
+            debug rhs => _2;
             let mut _4: u32;
             let mut _5: bool;
             scope 4 (inlined core::num::<impl u32>::wrapping_shl) {
+                debug self => _1;
+                debug rhs => _2;
                 let mut _3: u32;
                 scope 5 (inlined core::num::<impl u32>::unchecked_shl) {
+                    debug self => _1;
+                    debug rhs => _3;
                 }
             }
         }

tests/mir-opt/pre-codegen/checked_ops.checked_shl.PreCodegen.after.panic-unwind.mir

@@ -13,11 +13,17 @@ fn checked_shl(_1: u32, _2: u32) -> Option<u32> {
             debug b => _5;
         }
         scope 3 (inlined core::num::<impl u32>::overflowing_shl) {
+            debug self => _1;
+            debug rhs => _2;
             let mut _4: u32;
             let mut _5: bool;
             scope 4 (inlined core::num::<impl u32>::wrapping_shl) {
+                debug self => _1;
+                debug rhs => _2;
                 let mut _3: u32;
                 scope 5 (inlined core::num::<impl u32>::unchecked_shl) {
+                    debug self => _1;
+                    debug rhs => _3;
                 }
             }
         }

tests/mir-opt/pre-codegen/checked_ops.step_forward.PreCodegen.after.panic-abort.mir

@@ -4,89 +4,12 @@ fn step_forward(_1: u16, _2: usize) -> u16 {
     debug x => _1;
     debug n => _2;
     let mut _0: u16;
-    scope 1 (inlined <u16 as Step>::forward) {
-        debug start => _1;
-        debug n => _2;
-        let mut _8: u16;
-        scope 2 {
-        }
-        scope 3 (inlined <u16 as Step>::forward_checked) {
-            scope 4 {
-                scope 6 (inlined core::num::<impl u16>::checked_add) {
-                    let mut _7: bool;
-                    scope 7 {
-                    }
-                    scope 8 (inlined core::num::<impl u16>::overflowing_add) {
-                        let mut _5: (u16, bool);
-                        let _6: bool;
-                        scope 9 {
-                        }
-                    }
-                }
-            }
-            scope 5 (inlined convert::num::ptr_try_from_impls::<impl TryFrom<usize> for u16>::try_from) {
-                let mut _3: bool;
-                let mut _4: u16;
-            }
-        }
-        scope 10 (inlined Option::<u16>::is_none) {
-            scope 11 (inlined Option::<u16>::is_some) {
-            }
-        }
-        scope 12 (inlined core::num::<impl u16>::wrapping_add) {
-        }
-    }
 
     bb0: {
-        StorageLive(_4);
+        _0 = <u16 as Step>::forward(move _1, move _2) -> [return: bb1, unwind unreachable];
-        StorageLive(_3);
-        _3 = Gt(_2, const 65535_usize);
-        switchInt(move _3) -> [0: bb1, otherwise: bb5];
     }
 
     bb1: {
-        _4 = _2 as u16 (IntToInt);
-        StorageDead(_3);
-        StorageLive(_6);
-        StorageLive(_5);
-        _5 = CheckedAdd(_1, _4);
-        _6 = (_5.1: bool);
-        StorageDead(_5);
-        StorageLive(_7);
-        _7 = unlikely(move _6) -> [return: bb2, unwind unreachable];
-    }
-
-    bb2: {
-        switchInt(move _7) -> [0: bb3, otherwise: bb4];
-    }
-
-    bb3: {
-        StorageDead(_7);
-        StorageDead(_6);
-        goto -> bb7;
-    }
-
-    bb4: {
-        StorageDead(_7);
-        StorageDead(_6);
-        goto -> bb6;
-    }
-
-    bb5: {
-        StorageDead(_3);
-        goto -> bb6;
-    }
-
-    bb6: {
-        assert(!const true, "attempt to compute `{} + {}`, which would overflow", const core::num::<impl u16>::MAX, const 1_u16) -> [success: bb7, unwind unreachable];
-    }
-
-    bb7: {
-        StorageLive(_8);
-        _8 = _2 as u16 (IntToInt);
-        _0 = Add(_1, _8);
-        StorageDead(_8);
-        StorageDead(_4);
         return;
     }
 }

tests/mir-opt/pre-codegen/checked_ops.step_forward.PreCodegen.after.panic-unwind.mir

@@ -4,89 +4,12 @@ fn step_forward(_1: u16, _2: usize) -> u16 {
     debug x => _1;
     debug n => _2;
     let mut _0: u16;
-    scope 1 (inlined <u16 as Step>::forward) {
-        debug start => _1;
-        debug n => _2;
-        let mut _8: u16;
-        scope 2 {
-        }
-        scope 3 (inlined <u16 as Step>::forward_checked) {
-            scope 4 {
-                scope 6 (inlined core::num::<impl u16>::checked_add) {
-                    let mut _7: bool;
-                    scope 7 {
-                    }
-                    scope 8 (inlined core::num::<impl u16>::overflowing_add) {
-                        let mut _5: (u16, bool);
-                        let _6: bool;
-                        scope 9 {
-                        }
-                    }
-                }
-            }
-            scope 5 (inlined convert::num::ptr_try_from_impls::<impl TryFrom<usize> for u16>::try_from) {
-                let mut _3: bool;
-                let mut _4: u16;
-            }
-        }
-        scope 10 (inlined Option::<u16>::is_none) {
-            scope 11 (inlined Option::<u16>::is_some) {
-            }
-        }
-        scope 12 (inlined core::num::<impl u16>::wrapping_add) {
-        }
-    }
 
     bb0: {
-        StorageLive(_4);
+        _0 = <u16 as Step>::forward(move _1, move _2) -> [return: bb1, unwind continue];
-        StorageLive(_3);
-        _3 = Gt(_2, const 65535_usize);
-        switchInt(move _3) -> [0: bb1, otherwise: bb5];
     }
 
     bb1: {
-        _4 = _2 as u16 (IntToInt);
-        StorageDead(_3);
-        StorageLive(_6);
-        StorageLive(_5);
-        _5 = CheckedAdd(_1, _4);
-        _6 = (_5.1: bool);
-        StorageDead(_5);
-        StorageLive(_7);
-        _7 = unlikely(move _6) -> [return: bb2, unwind unreachable];
-    }
-
-    bb2: {
-        switchInt(move _7) -> [0: bb3, otherwise: bb4];
-    }
-
-    bb3: {
-        StorageDead(_7);
-        StorageDead(_6);
-        goto -> bb7;
-    }
-
-    bb4: {
-        StorageDead(_7);
-        StorageDead(_6);
-        goto -> bb6;
-    }
-
-    bb5: {
-        StorageDead(_3);
-        goto -> bb6;
-    }
-
-    bb6: {
-        assert(!const true, "attempt to compute `{} + {}`, which would overflow", const core::num::<impl u16>::MAX, const 1_u16) -> [success: bb7, unwind continue];
-    }
-
-    bb7: {
-        StorageLive(_8);
-        _8 = _2 as u16 (IntToInt);
-        _0 = Add(_1, _8);
-        StorageDead(_8);
-        StorageDead(_4);
         return;
     }
 }