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Auto merge of #68665 - eddyb:debuginfo-early-create-var, r=nagisa

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codegen: create DIVariables ahead of using them with llvm.dbg.declare.

Instead of having `rustc_codegen_llvm` bundle creation of a `DIVariable` and `llvm.dbg.declare` into a single operation, they are now two separate methods, and the `DIVariable` is created earlier, specifically when `mir::VarDebugInfo`s are being partitioned into locals.

While this isn't currently needed, it's a prerequisite for #48300, which adds fragmented debuginfo, where one `mir::VarDebugInfo` has multiple parts of itself mapped to different `mir::Place`s.
For debuggers to see one composite variable instead of several ones with the same name, we need to create a single `DIVariable` and share it between multiple `llvm.dbg.declare` calls, which are likely pointing to different MIR locals.
That makes the `per_local_var_debug_info` partitioning a good spot to do this in, as we can create *exactly* one `DIVariable` per `mir::VarDebugInfo`, and refer to it as many things as needed.

I'm opening this PR separately because I want to test its perf impact in isolation (see https://github.com/rust-lang/rust/pull/48300#issuecomment-580121438).

r? @nagisa or @oli-obk cc @michaelwoerister @nikomatsakis
This commit is contained in:
bors 2020-02-03 13:06:44 +00:00
commit bdd946df3a
9 changed files with 209 additions and 94 deletions
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1
src/librustc_codegen_llvm/builder.rs
View file

@ -57,6 +57,7 @@ impl BackendTypes for Builder<'_, 'll, 'tcx> {
type Funclet = <CodegenCx<'ll, 'tcx> as BackendTypes>::Funclet;
type DIScope = <CodegenCx<'ll, 'tcx> as BackendTypes>::DIScope;
type DIVariable = <CodegenCx<'ll, 'tcx> as BackendTypes>::DIVariable;
}
impl ty::layout::HasDataLayout for Builder<'_, '_, '_> {

1
src/librustc_codegen_llvm/common.rs
View file

@ -91,6 +91,7 @@ impl BackendTypes for CodegenCx<'ll, 'tcx> {
type Funclet = Funclet<'ll>;
type DIScope = &'ll llvm::debuginfo::DIScope;
type DIVariable = &'ll llvm::debuginfo::DIVariable;
}
impl CodegenCx<'ll, 'tcx> {

86
src/librustc_codegen_llvm/debuginfo/mod.rs
View file

@ -11,7 +11,7 @@ use self::utils::{create_DIArray, is_node_local_to_unit, span_start, DIB};
use crate::llvm;
use crate::llvm::debuginfo::{
DIArray, DIBuilder, DIFile, DIFlags, DILexicalBlock, DISPFlags, DIScope, DIType,
DIArray, DIBuilder, DIFile, DIFlags, DILexicalBlock, DISPFlags, DIScope, DIType, DIVariable,
};
use rustc::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc::ty::subst::{GenericArgKind, SubstsRef};
@ -143,33 +143,23 @@ pub fn finalize(cx: &CodegenCx<'_, '_>) {
};
}
impl DebugInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
fn declare_local(
impl DebugInfoBuilderMethods for Builder<'a, 'll, 'tcx> {
// FIXME(eddyb) find a common convention for all of the debuginfo-related
// names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
fn dbg_var_addr(
&mut self,
dbg_context: &FunctionDebugContext<&'ll DIScope>,
variable_name: ast::Name,
variable_type: Ty<'tcx>,
dbg_var: &'ll DIVariable,
scope_metadata: &'ll DIScope,
variable_alloca: Self::Value,
direct_offset: Size,
indirect_offsets: &[Size],
variable_kind: VariableKind,
span: Span,
) {
assert!(!dbg_context.source_locations_enabled);
let cx = self.cx();
let file = span_start(cx, span).file;
let file_metadata = file_metadata(cx, &file.name, dbg_context.defining_crate);
let loc = span_start(cx, span);
let type_metadata = type_metadata(cx, variable_type, span);
let (argument_index, dwarf_tag) = match variable_kind {
ArgumentVariable(index) => (index as c_uint, DW_TAG_arg_variable),
LocalVariable => (0, DW_TAG_auto_variable),
};
let align = cx.align_of(variable_type);
// Convert the direct and indirect offsets to address ops.
let op_deref = || unsafe { llvm::LLVMRustDIBuilderCreateOpDeref() };
@ -188,32 +178,19 @@ impl DebugInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
}
}
let name = SmallCStr::new(&variable_name.as_str());
let metadata = unsafe {
llvm::LLVMRustDIBuilderCreateVariable(
DIB(cx),
dwarf_tag,
scope_metadata,
name.as_ptr(),
file_metadata,
loc.line as c_uint,
type_metadata,
cx.sess().opts.optimize != config::OptLevel::No,
DIFlags::FlagZero,
argument_index,
align.bytes() as u32,
)
};
// FIXME(eddyb) maybe this information could be extracted from `var`,
// to avoid having to pass it down in both places?
source_loc::set_debug_location(
self,
InternalDebugLocation::new(scope_metadata, loc.line, loc.col.to_usize()),
);
unsafe {
let debug_loc = llvm::LLVMGetCurrentDebugLocation(self.llbuilder);
// FIXME(eddyb) replace `llvm.dbg.declare` with `llvm.dbg.addr`.
let instr = llvm::LLVMRustDIBuilderInsertDeclareAtEnd(
DIB(cx),
variable_alloca,
metadata,
dbg_var,
addr_ops.as_ptr(),
addr_ops.len() as c_uint,
debug_loc,
@ -313,7 +290,8 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
// Get the linkage_name, which is just the symbol name
let linkage_name = mangled_name_of_instance(self, instance);
let scope_line = span_start(self, span).line;
// FIXME(eddyb) does this need to be separate from `loc.line` for some reason?
let scope_line = loc.line;
let function_name = CString::new(name).unwrap();
let linkage_name = SmallCStr::new(&linkage_name.name.as_str());
@ -558,4 +536,44 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
fn debuginfo_finalize(&self) {
finalize(self)
}
// FIXME(eddyb) find a common convention for all of the debuginfo-related
// names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
fn create_dbg_var(
&self,
dbg_context: &FunctionDebugContext<&'ll DIScope>,
variable_name: ast::Name,
variable_type: Ty<'tcx>,
scope_metadata: &'ll DIScope,
variable_kind: VariableKind,
span: Span,
) -> &'ll DIVariable {
let loc = span_start(self, span);
let file_metadata = file_metadata(self, &loc.file.name, dbg_context.defining_crate);
let type_metadata = type_metadata(self, variable_type, span);
let (argument_index, dwarf_tag) = match variable_kind {
ArgumentVariable(index) => (index as c_uint, DW_TAG_arg_variable),
LocalVariable => (0, DW_TAG_auto_variable),
};
let align = self.align_of(variable_type);
let name = SmallCStr::new(&variable_name.as_str());
unsafe {
llvm::LLVMRustDIBuilderCreateVariable(
DIB(self),
dwarf_tag,
scope_metadata,
name.as_ptr(),
file_metadata,
loc.line as c_uint,
type_metadata,
self.sess().opts.optimize != config::OptLevel::No,
DIFlags::FlagZero,
argument_index,
align.bytes() as u32,
)
}
}
}

158
src/librustc_codegen_ssa/mir/debuginfo.rs
View file

@ -1,12 +1,12 @@
use crate::traits::*;
use rustc::mir;
use rustc::session::config::DebugInfo;
use rustc::ty;
use rustc::ty::layout::{LayoutOf, Size};
use rustc::ty::TyCtxt;
use rustc_hir::def_id::CrateNum;
use rustc_index::vec::IndexVec;
use rustc_span::symbol::kw;
use rustc_span::symbol::{kw, Symbol};
use rustc_span::{BytePos, Span};
use super::OperandValue;
@ -24,6 +24,19 @@ pub enum VariableKind {
LocalVariable,
}
/// Like `mir::VarDebugInfo`, but within a `mir::Local`.
#[derive(Copy, Clone)]
pub struct PerLocalVarDebugInfo<'tcx, D> {
pub name: Symbol,
pub source_info: mir::SourceInfo,
/// `DIVariable` returned by `create_dbg_var`.
pub dbg_var: Option<D>,
/// `.place.projection` from `mir::VarDebugInfo`.
pub projection: &'tcx ty::List<mir::PlaceElem<'tcx>>,
}
#[derive(Clone, Copy, Debug)]
pub struct DebugScope<D> {
pub scope_metadata: Option<D>,
@ -103,6 +116,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
// FIXME(eddyb) use `llvm.dbg.value` (which would work for operands),
// not just `llvm.dbg.declare` (which requires `alloca`).
pub fn debug_introduce_local(&self, bx: &mut Bx, local: mir::Local) {
let full_debug_info = bx.sess().opts.debuginfo == DebugInfo::Full;
// FIXME(eddyb) maybe name the return place as `_0` or `return`?
if local == mir::RETURN_PLACE {
return;
@ -112,35 +127,63 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
Some(per_local) => &per_local[local],
None => return,
};
let whole_local_var = vars.iter().copied().find(|var| var.place.projection.is_empty());
let has_proj = || vars.iter().any(|var| !var.place.projection.is_empty());
let whole_local_var = vars.iter().find(|var| var.projection.is_empty()).copied();
let has_proj = || vars.iter().any(|var| !var.projection.is_empty());
let (fallback_var, kind) = if self.mir.local_kind(local) == mir::LocalKind::Arg {
let fallback_var = if self.mir.local_kind(local) == mir::LocalKind::Arg {
let arg_index = local.index() - 1;
// Add debuginfo even to unnamed arguments.
// FIXME(eddyb) is this really needed?
let var = if arg_index == 0 && has_proj() {
if arg_index == 0 && has_proj() {
// Hide closure environments from debuginfo.
// FIXME(eddyb) shouldn't `ArgumentVariable` indices
// be offset to account for the hidden environment?
None
} else if whole_local_var.is_some() {
// No need to make up anything, there is a `mir::VarDebugInfo`
// covering the whole local.
// FIXME(eddyb) take `whole_local_var.source_info.scope` into
// account, just in case it doesn't use `ArgumentVariable`
// (after #67586 gets fixed).
None
} else {
Some(mir::VarDebugInfo {
name: kw::Invalid,
source_info: self.mir.local_decls[local].source_info,
place: local.into(),
})
let name = kw::Invalid;
let decl = &self.mir.local_decls[local];
let (scope, span) = if full_debug_info {
self.debug_loc(decl.source_info)
} else {
(None, decl.source_info.span)
};
(var, VariableKind::ArgumentVariable(arg_index + 1))
let dbg_var = scope.map(|scope| {
// FIXME(eddyb) is this `+ 1` needed at all?
let kind = VariableKind::ArgumentVariable(arg_index + 1);
self.cx.create_dbg_var(
self.debug_context.as_ref().unwrap(),
name,
self.monomorphize(&decl.ty),
scope,
kind,
span,
)
});
Some(PerLocalVarDebugInfo {
name,
source_info: decl.source_info,
dbg_var,
projection: ty::List::empty(),
})
}
} else {
(None, VariableKind::LocalVariable)
None
};
let local_ref = &self.locals[local];
if !bx.sess().fewer_names() {
let name = match whole_local_var.or(fallback_var.as_ref()) {
let name = match whole_local_var.or(fallback_var) {
Some(var) if var.name != kw::Invalid => var.name.to_string(),
_ => format!("{:?}", local),
};
@ -163,7 +206,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}
}
if bx.sess().opts.debuginfo != DebugInfo::Full {
if !full_debug_info {
return;
}
@ -178,11 +221,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
_ => return,
};
let vars = vars.iter().copied().chain(if whole_local_var.is_none() {
fallback_var.as_ref()
} else {
None
});
let vars = vars.iter().copied().chain(fallback_var);
for var in vars {
let mut layout = base.layout;
@ -190,10 +229,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
// FIXME(eddyb) use smallvec here.
let mut indirect_offsets = vec![];
let kind =
if var.place.projection.is_empty() { kind } else { VariableKind::LocalVariable };
for elem in &var.place.projection[..] {
for elem in &var.projection[..] {
match *elem {
mir::ProjectionElem::Deref => {
indirect_offsets.push(Size::ZERO);
@ -202,7 +238,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
.ty
.builtin_deref(true)
.unwrap_or_else(|| {
span_bug!(var.source_info.span, "cannot deref `{}`", layout.ty,)
span_bug!(var.source_info.span, "cannot deref `{}`", layout.ty)
})
.ty,
);
@ -219,27 +255,27 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
_ => span_bug!(
var.source_info.span,
"unsupported var debuginfo place `{:?}`",
var.place,
mir::Place { local, projection: var.projection },
),
}
}
let (scope, span) = self.debug_loc(var.source_info);
if let Some(scope) = scope {
bx.declare_local(
if let Some(dbg_var) = var.dbg_var {
bx.dbg_var_addr(
debug_context,
var.name,
layout.ty,
dbg_var,
scope,
base.llval,
direct_offset,
&indirect_offsets,
kind,
span,
);
}
}
}
}
pub fn debug_introduce_locals(&self, bx: &mut Bx) {
if bx.sess().opts.debuginfo == DebugInfo::Full || !bx.sess().fewer_names() {
@ -248,20 +284,60 @@ 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,
) -> Option<IndexVec<mir::Local, Vec<PerLocalVarDebugInfo<'tcx, Bx::DIVariable>>>> {
let full_debug_info = self.cx.sess().opts.debuginfo == DebugInfo::Full;
if !(full_debug_info || !self.cx.sess().fewer_names()) {
return None;
}
/// Partition all `VarDebuginfo` in `body`, by their base `Local`.
pub fn per_local_var_debug_info(
tcx: TyCtxt<'tcx>,
body: &'a mir::Body<'tcx>,
) -> Option<IndexVec<mir::Local, Vec<&'a mir::VarDebugInfo<'tcx>>>> {
if tcx.sess.opts.debuginfo == DebugInfo::Full || !tcx.sess.fewer_names() {
let mut per_local = IndexVec::from_elem(vec![], &body.local_decls);
for var in &body.var_debug_info {
per_local[var.place.local].push(var);
let mut per_local = IndexVec::from_elem(vec![], &self.mir.local_decls);
for var in &self.mir.var_debug_info {
let (scope, span) = if full_debug_info {
self.debug_loc(var.source_info)
} else {
(None, var.source_info.span)
};
let dbg_var = scope.map(|scope| {
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()
{
// FIXME(eddyb, #67586) take `var.source_info.scope` into
// account to avoid using `ArgumentVariable` more than once
// per argument local.
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
};
self.cx.create_dbg_var(
self.debug_context.as_ref().unwrap(),
var.name,
var_ty,
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,
});
}
Some(per_local)
} else {
None
}
}

13
src/librustc_codegen_ssa/mir/mod.rs
View file

@ -11,7 +11,7 @@ use rustc_index::bit_set::BitSet;
use rustc_index::vec::IndexVec;
use self::analyze::CleanupKind;
use self::debuginfo::FunctionDebugContext;
use self::debuginfo::{FunctionDebugContext, PerLocalVarDebugInfo};
use self::place::PlaceRef;
use rustc::mir::traversal;
@ -74,9 +74,10 @@ pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
/// notably `expect`.
locals: IndexVec<mir::Local, LocalRef<'tcx, Bx::Value>>,
/// All `VarDebuginfo` from the MIR body, partitioned by `Local`.
/// This is `None` if no variable debuginfo/names are needed.
per_local_var_debug_info: Option<IndexVec<mir::Local, Vec<&'tcx mir::VarDebugInfo<'tcx>>>>,
/// All `VarDebugInfo` from the MIR body, partitioned by `Local`.
/// This is `None` if no var`#[non_exhaustive]`iable debuginfo/names are needed.
per_local_var_debug_info:
Option<IndexVec<mir::Local, Vec<PerLocalVarDebugInfo<'tcx, Bx::DIVariable>>>>,
/// Caller location propagated if this function has `#[track_caller]`.
caller_location: Option<OperandRef<'tcx, Bx::Value>>,
@ -178,10 +179,12 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
funclets,
locals: IndexVec::new(),
debug_context,
per_local_var_debug_info: debuginfo::per_local_var_debug_info(cx.tcx(), mir_body),
per_local_var_debug_info: None,
caller_location: None,
};
fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info();
let memory_locals = analyze::non_ssa_locals(&fx);
// Allocate variable and temp allocas

3
src/librustc_codegen_ssa/traits/backend.rs
View file

@ -21,7 +21,10 @@ pub trait BackendTypes {
type Type: CodegenObject;
type Funclet;
// FIXME(eddyb) find a common convention for all of the debuginfo-related
// names (choose between `Dbg`, `Debug`, `DebugInfo`, `DI` etc.).
type DIScope: Copy;
type DIVariable: Copy;
}
pub trait Backend<'tcx>:

2
src/librustc_codegen_ssa/traits/builder.rs
View file

@ -28,7 +28,7 @@ pub enum OverflowOp {
pub trait BuilderMethods<'a, 'tcx>:
HasCodegen<'tcx>
+ DebugInfoBuilderMethods<'tcx>
+ DebugInfoBuilderMethods
+ ArgAbiMethods<'tcx>
+ AbiBuilderMethods<'tcx>
+ IntrinsicCallMethods<'tcx>

22
src/librustc_codegen_ssa/traits/debuginfo.rs
View file

@ -30,20 +30,32 @@ pub trait DebugInfoMethods<'tcx>: BackendTypes {
defining_crate: CrateNum,
) -> Self::DIScope;
fn debuginfo_finalize(&self);
}
pub trait DebugInfoBuilderMethods<'tcx>: BackendTypes {
fn declare_local(
&mut self,
// FIXME(eddyb) find a common convention for all of the debuginfo-related
// names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
fn create_dbg_var(
&self,
dbg_context: &FunctionDebugContext<Self::DIScope>,
variable_name: Name,
variable_type: Ty<'tcx>,
scope_metadata: Self::DIScope,
variable_kind: VariableKind,
span: Span,
) -> Self::DIVariable;
}
pub trait DebugInfoBuilderMethods: BackendTypes {
// FIXME(eddyb) find a common convention for all of the debuginfo-related
// names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
fn dbg_var_addr(
&mut self,
dbg_context: &FunctionDebugContext<Self::DIScope>,
dbg_var: Self::DIVariable,
scope_metadata: Self::DIScope,
variable_alloca: Self::Value,
direct_offset: Size,
// NB: each offset implies a deref (i.e. they're steps in a pointer chain).
indirect_offsets: &[Size],
variable_kind: VariableKind,
span: Span,
);
fn set_source_location(

1
src/librustc_codegen_ssa/traits/mod.rs
View file

@ -93,5 +93,6 @@ pub trait HasCodegen<'tcx>:
Type = Self::Type,
Funclet = Self::Funclet,
DIScope = Self::DIScope,
DIVariable = Self::DIVariable,
>;
}