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Create a single source scope for promoteds

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A promoted inherits all scopes from the parent body.  At the same time,
almost all statements and terminators inside the promoted body so far
refer only to one of those scopes: the outermost one.

Instead of inheriting all scopes, inherit only a single scope
corresponding to the location of the promoted, making sure that there
are no references to other scopes.
This commit is contained in:
Tomasz Miąsko 2020-10-14 00:00:00 +00:00
parent 5565241f65
commit db54752082
2 changed files with 14 additions and 5 deletions
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17
compiler/rustc_mir/src/transform/promote_consts.rs
View File

@ -124,6 +124,15 @@ fn forces_explicit_promotion(&self) -> bool {
Candidate::Argument { .. } | Candidate::InlineAsm { .. } => true,
}
}
fn source_info(&self, body: &Body<'_>) -> SourceInfo {
match self {
Candidate::Ref(location) | Candidate::Repeat(location) => *body.source_info(*location),
Candidate::Argument { bb, .. } | Candidate::InlineAsm { bb, .. } => {
*body.source_info(body.terminator_loc(*bb))
}
}
}
}
fn args_required_const(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Vec<usize>> {
@ -953,6 +962,7 @@ fn promote_temp(&mut self, temp: Local) -> Local {
from_hir_call,
fn_span,
},
source_info: SourceInfo::outermost(terminator.source_info.span),
..terminator
};
}
@ -1163,12 +1173,13 @@ pub fn promote_candidates<'tcx>(
// Declare return place local so that `mir::Body::new` doesn't complain.
let initial_locals = iter::once(LocalDecl::new(tcx.types.never, body.span)).collect();
let mut scope = body.source_scopes[candidate.source_info(body).scope].clone();
scope.parent_scope = None;
let mut promoted = Body::new(
body.source, // `promoted` gets filled in below
IndexVec::new(),
// FIXME: maybe try to filter this to avoid blowing up
// memory usage?
body.source_scopes.clone(),
IndexVec::from_elem_n(scope, 1),
initial_locals,
IndexVec::new(),
0,

2
src/test/mir-opt/const_promotion_extern_static.FOO-promoted[0].ConstProp.after.mir
View File

@ -5,8 +5,6 @@ promoted[0] in FOO: &[&i32; 1] = {
let mut _1: [&i32; 1]; // in scope 0 at $DIR/const-promotion-extern-static.rs:13:31: 13:46
let mut _2: &i32; // in scope 0 at $DIR/const-promotion-extern-static.rs:13:32: 13:45
let mut _3: &i32; // in scope 0 at $DIR/const-promotion-extern-static.rs:13:42: 13:43
scope 1 {
}
bb0: {
_3 = const {alloc2: &i32}; // scope 0 at $DIR/const-promotion-extern-static.rs:13:42: 13:43