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[mir-opt] Allow debuginfo to be generated for a constant or a Place

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Prior to this commit, debuginfo was always generated by mapping a name
to a Place. This has the side-effect that `SimplifyLocals` cannot remove
locals that are only used for debuginfo because their other uses have
been const-propagated.

To allow these locals to be removed, we now allow debuginfo to point to
a constant value. The `ConstProp` pass detects when debuginfo points to
a local with a known constant value and replaces it with the value. This
allows the later `SimplifyLocals` pass to remove the local.
This commit is contained in:
Wesley Wiser 2020-05-30 15:02:32 -04:00
parent b776d1c3e3
commit 01aec8d185
23 changed files with 406 additions and 127 deletions
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4
compiler/rustc_mir_build/src/build/matches/mod.rs
View file

@ -1992,7 +1992,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
self.var_debug_info.push(VarDebugInfo {
name,
source_info: debug_source_info,
place: for_arm_body.into(),
value: VarDebugInfoContents::Place(for_arm_body.into()),
});
let locals = if has_guard.0 {
let ref_for_guard = self.local_decls.push(LocalDecl::<'tcx> {
@ -2011,7 +2011,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
self.var_debug_info.push(VarDebugInfo {
name,
source_info: debug_source_info,
place: ref_for_guard.into(),
value: VarDebugInfoContents::Place(ref_for_guard.into()),
});
LocalsForNode::ForGuard { ref_for_guard, for_arm_body }
} else {

6
compiler/rustc_mir_build/src/build/mod.rs
View file

@ -796,7 +796,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
self.var_debug_info.push(VarDebugInfo {
name: ident.name,
source_info,
place: arg_local.into(),
value: VarDebugInfoContents::Place(arg_local.into()),
});
}
}
@ -860,10 +860,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
self.var_debug_info.push(VarDebugInfo {
name,
source_info: SourceInfo::outermost(tcx_hir.span(var_id)),
place: Place {
value: VarDebugInfoContents::Place(Place {
local: closure_env_arg,
projection: tcx.intern_place_elems(&projs),
},
}),
});
mutability