bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Auto merge of #73210 - wesleywiser:consts_in_debuginfo, r=oli-obk

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

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:
bors 2020-12-15 08:46:00 +00:00
commit e99a89c7c0
16 changed files with 398 additions and 79 deletions
Download patch file Download diff file Expand all files Collapse all files

4
compiler/rustc_codegen_ssa/src/mir/constant.rs
View file

@ -11,7 +11,7 @@ use super::FunctionCx;
impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
pub fn eval_mir_constant_to_operand(
&mut self,
&self,
bx: &mut Bx,
constant: &mir::Constant<'tcx>,
) -> Result<OperandRef<'tcx, Bx::Value>, ErrorHandled> {
@ -21,7 +21,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}
pub fn eval_mir_constant(
&mut self,
&self,
constant: &mir::Constant<'tcx>,
) -> Result<ConstValue<'tcx>, ErrorHandled> {
match self.monomorphize(constant.literal).val {

105
compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
View file

@ -8,7 +8,7 @@ use rustc_span::symbol::{kw, Symbol};
use rustc_span::{BytePos, Span};
use rustc_target::abi::{LayoutOf, Size};
use super::operand::OperandValue;
use super::operand::{OperandRef, OperandValue};
use super::place::PlaceRef;
use super::{FunctionCx, LocalRef};
@ -116,6 +116,24 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
span
}
fn spill_operand_to_stack(
operand: &OperandRef<'tcx, Bx::Value>,
name: Option<String>,
bx: &mut Bx,
) -> PlaceRef<'tcx, Bx::Value> {
// "Spill" the value onto the stack, for debuginfo,
// without forcing non-debuginfo uses of the local
// to also load from the stack every single time.
// FIXME(#68817) use `llvm.dbg.value` instead,
// at least for the cases which LLVM handles correctly.
let spill_slot = PlaceRef::alloca(bx, operand.layout);
if let Some(name) = name {
bx.set_var_name(spill_slot.llval, &(name + ".dbg.spill"));
}
operand.val.store(bx, spill_slot);
spill_slot
}
/// Apply debuginfo and/or name, after creating the `alloca` for a local,
/// or initializing the local with an operand (whichever applies).
pub fn debug_introduce_local(&self, bx: &mut Bx, local: mir::Local) {
@ -226,17 +244,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
return;
}
// "Spill" the value onto the stack, for debuginfo,
// without forcing non-debuginfo uses of the local
// to also load from the stack every single time.
// FIXME(#68817) use `llvm.dbg.value` instead,
// at least for the cases which LLVM handles correctly.
let spill_slot = PlaceRef::alloca(bx, operand.layout);
if let Some(name) = name {
bx.set_var_name(spill_slot.llval, &(name + ".dbg.spill"));
}
operand.val.store(bx, spill_slot);
spill_slot
Self::spill_operand_to_stack(operand, name, bx)
}
LocalRef::Place(place) => *place,
@ -308,6 +316,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
/// Partition all `VarDebugInfo` in `self.mir`, by their base `Local`.
pub fn compute_per_local_var_debug_info(
&self,
bx: &mut Bx,
) -> Option<IndexVec<mir::Local, Vec<PerLocalVarDebugInfo<'tcx, Bx::DIVariable>>>> {
let full_debug_info = self.cx.sess().opts.debuginfo == DebugInfo::Full;
@ -322,31 +331,63 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
} else {
None
};
let dbg_var = dbg_scope_and_span.map(|(dbg_scope, _, span)| {
let place = var.place;
let var_ty = self.monomorphized_place_ty(place.as_ref());
let var_kind = if self.mir.local_kind(place.local) == mir::LocalKind::Arg
&& place.projection.is_empty()
&& var.source_info.scope == mir::OUTERMOST_SOURCE_SCOPE
{
let arg_index = place.local.index() - 1;
// FIXME(eddyb) shouldn't `ArgumentVariable` indices be
// offset in closures to account for the hidden environment?
// Also, is this `+ 1` needed at all?
VariableKind::ArgumentVariable(arg_index + 1)
} else {
VariableKind::LocalVariable
let dbg_var = dbg_scope_and_span.map(|(dbg_scope, _, span)| {
let (var_ty, var_kind) = match var.value {
mir::VarDebugInfoContents::Place(place) => {
let var_ty = self.monomorphized_place_ty(place.as_ref());
let var_kind = if self.mir.local_kind(place.local) == mir::LocalKind::Arg
&& place.projection.is_empty()
&& var.source_info.scope == mir::OUTERMOST_SOURCE_SCOPE
{
let arg_index = place.local.index() - 1;
// FIXME(eddyb) shouldn't `ArgumentVariable` indices be
// offset in closures to account for the hidden environment?
// Also, is this `+ 1` needed at all?
VariableKind::ArgumentVariable(arg_index + 1)
} else {
VariableKind::LocalVariable
};
(var_ty, var_kind)
}
mir::VarDebugInfoContents::Const(c) => {
let ty = self.monomorphize(c.literal.ty);
(ty, VariableKind::LocalVariable)
}
};
self.cx.create_dbg_var(var.name, var_ty, dbg_scope, var_kind, span)
});
per_local[var.place.local].push(PerLocalVarDebugInfo {
name: var.name,
source_info: var.source_info,
dbg_var,
projection: var.place.projection,
});
match var.value {
mir::VarDebugInfoContents::Place(place) => {
per_local[place.local].push(PerLocalVarDebugInfo {
name: var.name,
source_info: var.source_info,
dbg_var,
projection: place.projection,
});
}
mir::VarDebugInfoContents::Const(c) => {
if let Some(dbg_var) = dbg_var {
let dbg_loc = match self.dbg_loc(var.source_info) {
Some(dbg_loc) => dbg_loc,
None => continue,
};
if let Ok(operand) = self.eval_mir_constant_to_operand(bx, &c) {
let base = Self::spill_operand_to_stack(
&operand,
Some(var.name.to_string()),
bx,
);
bx.dbg_var_addr(dbg_var, dbg_loc, base.llval, Size::ZERO, &[]);
}
}
}
}
}
Some(per_local)
}

2
compiler/rustc_codegen_ssa/src/mir/mod.rs
View file

@ -186,7 +186,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
caller_location: None,
};
fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info();
fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info(&mut bx);
for const_ in &mir.required_consts {
if let Err(err) = fx.eval_mir_constant(const_) {