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Don't lookup span position when the span hasn't changed

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This improves performance of FunctionDebugContext::define by ~60%

Fixes #807
This commit is contained in:
bjorn3 2020-03-14 15:18:04 +01:00
parent 660b5c33e7
commit efe3d84ce4
1 changed files with 10 additions and 1 deletions
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11
src/debuginfo/line_info.rs
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@ -123,8 +123,17 @@ impl<'a, 'tcx> FunctionDebugContext<'a, 'tcx> {
let line_strings = &mut self.debug_context.dwarf.line_strings;
let function_span = self.mir.span;
let mut last_span = None;
let mut last_file = None;
let mut create_row_for_span = |line_program: &mut LineProgram, span: Span| {
if let Some(last_span) = last_span {
if span == last_span {
line_program.generate_row();
return;
}
}
last_span = Some(span);
// Based on https://github.com/rust-lang/rust/blob/e369d87b015a84653343032833d65d0545fd3f26/src/librustc_codegen_ssa/mir/mod.rs#L116-L131
// 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
@ -150,7 +159,7 @@ impl<'a, 'tcx> FunctionDebugContext<'a, 'tcx> {
// line_program_add_file is very slow.
// Optimize for the common case of the current file not being changed.
let current_file_changed = if let Some(last_file) = &mut last_file {
let current_file_changed = if let Some(last_file) = &last_file {
// If the allocations are not equal, then the files may still be equal, but that
// is not a problem, as this is just an optimization.
!Lrc::ptr_eq(last_file, &file)