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author | bors <bors@rust-lang.org> | 2023-05-14 05:31:10 +0000 |
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committer | bors <bors@rust-lang.org> | 2023-05-14 05:31:10 +0000 |
commit | bc888958c9e1fdde09791f15d3421bdc3b6d7d29 (patch) | |
tree | 7c58f002e19288e067a691a56b09cb71d7b3ad29 /compiler/rustc_middle | |
parent | ad6ab11234ae885913229f6de2c4465bdc0d76f3 (diff) | |
parent | 8fb888dfaa1618838a288c41a8dc8ad24d1dadd5 (diff) | |
download | rust-bc888958c9e1fdde09791f15d3421bdc3b6d7d29.tar.gz |
Auto merge of #111440 - cjgillot:refprop-debuginfo, r=oli-obk
Allow MIR debuginfo to point to a variable's address
MIR optimizations currently do not to operate on borrowed locals.
When enabling #106285, many borrows will be left as-is because they are used in debuginfo. This pass allows to replace this pattern directly in MIR debuginfo:
```rust
a => _1
_1 = &raw? mut? _2
```
becomes
```rust
a => &_2
// No statement to borrow _2.
```
This pass is implemented as a drive-by in ReferencePropagation MIR pass.
This transformation allows following following MIR opts to treat _2 as an unborrowed local, and optimize it as such, even in builds with debuginfo.
In codegen, when encountering `a => &..&_2`, we create a list of allocas:
```llvm
store ptr %_2.dbg.spill, ptr %a.ref0.dbg.spill
store ptr %a.ref0.dbg.spill, ptr %a.ref1.dbg.spill
...
call void `@llvm.dbg.declare(metadata` ptr %a.ref{n}.dbg.spill, /* ... */)
```
Caveat: this transformation looses the exact type, we do not differentiate `a` as a immutable, mutable reference or a raw pointer. Everything is declared to `*mut` to codegen. I'm not convinced this is a blocker.
Diffstat (limited to 'compiler/rustc_middle')
-rw-r--r-- | compiler/rustc_middle/src/mir/mod.rs | 45 | ||||
-rw-r--r-- | compiler/rustc_middle/src/mir/pretty.rs | 9 | ||||
-rw-r--r-- | compiler/rustc_middle/src/mir/visit.rs | 1 | ||||
-rw-r--r-- | compiler/rustc_middle/src/ty/structural_impls.rs | 1 |
4 files changed, 40 insertions, 16 deletions
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs index 55991facd89..6b0401a4c9b 100644 --- a/compiler/rustc_middle/src/mir/mod.rs +++ b/compiler/rustc_middle/src/mir/mod.rs @@ -1111,6 +1111,10 @@ pub struct VarDebugInfo<'tcx> { /// originated from (starting from 1). Note, if MIR inlining is enabled, then this is the /// argument number in the original function before it was inlined. pub argument_index: Option<u16>, + + /// The data represents `name` dereferenced `references` times, + /// and not the direct value. + pub references: u8, } /////////////////////////////////////////////////////////////////////////// @@ -1550,8 +1554,11 @@ impl<V, T> ProjectionElem<V, T> { /// Returns `true` if this is accepted inside `VarDebugInfoContents::Place`. pub fn can_use_in_debuginfo(&self) -> bool { match self { - Self::Deref | Self::Downcast(_, _) | Self::Field(_, _) => true, - Self::ConstantIndex { .. } + Self::ConstantIndex { from_end: false, .. } + | Self::Deref + | Self::Downcast(_, _) + | Self::Field(_, _) => true, + Self::ConstantIndex { from_end: true, .. } | Self::Index(_) | Self::OpaqueCast(_) | Self::Subslice { .. } => false, @@ -1639,18 +1646,7 @@ impl<'tcx> Place<'tcx> { return self; } - let mut v: Vec<PlaceElem<'tcx>>; - - let new_projections = if self.projection.is_empty() { - more_projections - } else { - v = Vec::with_capacity(self.projection.len() + more_projections.len()); - v.extend(self.projection); - v.extend(more_projections); - &v - }; - - Place { local: self.local, projection: tcx.mk_place_elems(new_projections) } + self.as_ref().project_deeper(more_projections, tcx) } } @@ -1721,6 +1717,27 @@ impl<'tcx> PlaceRef<'tcx> { (base, *proj) }) } + + /// Generates a new place by appending `more_projections` to the existing ones + /// and interning the result. + pub fn project_deeper( + self, + more_projections: &[PlaceElem<'tcx>], + tcx: TyCtxt<'tcx>, + ) -> Place<'tcx> { + let mut v: Vec<PlaceElem<'tcx>>; + + let new_projections = if self.projection.is_empty() { + more_projections + } else { + v = Vec::with_capacity(self.projection.len() + more_projections.len()); + v.extend(self.projection); + v.extend(more_projections); + &v + }; + + Place { local: self.local, projection: tcx.mk_place_elems(new_projections) } + } } impl Debug for Place<'_> { diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs index fa8a339631e..62c3d8cf239 100644 --- a/compiler/rustc_middle/src/mir/pretty.rs +++ b/compiler/rustc_middle/src/mir/pretty.rs @@ -551,8 +551,13 @@ fn write_scope_tree( } let indented_debug_info = format!( - "{0:1$}debug {2} => {3:?};", - INDENT, indent, var_debug_info.name, var_debug_info.value, + "{0:1$}debug {2} => {3:&<4$}{5:?};", + INDENT, + indent, + var_debug_info.name, + "", + var_debug_info.references as usize, + var_debug_info.value, ); writeln!( diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs index d7a7fdebda6..596dd80bf48 100644 --- a/compiler/rustc_middle/src/mir/visit.rs +++ b/compiler/rustc_middle/src/mir/visit.rs @@ -842,6 +842,7 @@ macro_rules! make_mir_visitor { source_info, value, argument_index: _, + references: _, } = var_debug_info; self.visit_source_info(source_info); diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs index 29a3bc8bb97..e73208b877f 100644 --- a/compiler/rustc_middle/src/ty/structural_impls.rs +++ b/compiler/rustc_middle/src/ty/structural_impls.rs @@ -204,6 +204,7 @@ CloneLiftImpls! { (), bool, usize, + u8, u16, u32, u64, |