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ssa: implement #[collapse_debuginfo]

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Debuginfo line information for macro invocations are collapsed by
default - line information are replaced by the line of the outermost
expansion site. Using `-Zdebug-macros` disables this behaviour.

When the `collapse_debuginfo` feature is enabled, the default behaviour
is reversed so that debuginfo is not collapsed by default. In addition,
the `#[collapse_debuginfo]` attribute is available and can be applied to
macro definitions which will then have their line information collapsed.

Signed-off-by: David Wood <david.wood@huawei.com>
This commit is contained in:
David Wood 2022-07-21 16:19:22 +01:00
parent 2991a7c715
commit 38958aa8bd
20 changed files with 699 additions and 35 deletions
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8
compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
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@ -3,7 +3,7 @@ use rustc_index::vec::IndexVec;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::mir;
use rustc_middle::ty;
use rustc_middle::ty::layout::LayoutOf;
use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
use rustc_session::config::DebugInfo;
use rustc_span::symbol::{kw, Symbol};
use rustc_span::{BytePos, Span};
@ -93,15 +93,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}
/// In order to have a good line stepping behavior in debugger, we overwrite debug
/// locations of macro expansions with that of the outermost expansion site
/// (unless the crate is being compiled with `-Z debug-macros`).
/// locations of macro expansions with that of the outermost expansion site (when the macro is
/// annotated with `#[collapse_debuginfo]` or when `-Zdebug-macros` is provided).
fn adjust_span_for_debugging(&self, mut span: Span) -> Span {
// Bail out if debug info emission is not enabled.
if self.debug_context.is_none() {
return span;
}
if span.from_expansion() && !self.cx.sess().opts.unstable_opts.debug_macros {
if self.cx.tcx().should_collapse_debuginfo(span) {
// Walk up the macro expansion chain until we reach a non-expanded span.
// We also stop at the function body level because no line stepping can occur
// at the level above that.