From 6ef39e69eac42e1cc86ec8eeb1b85c6b3a8784fa Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Thu, 2 May 2019 20:34:26 +1000
Subject: [PATCH] Avoid repeated interning of static strings.
`file_metadata_raw` interns the strings `"<unknown>"` and `""` very
frequently. This commit avoids that, which reduces the number of symbols
interned significantly and reduces instruction counts by up to 0.5% on
some workloads.
---
.../debuginfo/metadata.rs | 22 +++++++++++--------
src/librustc_codegen_llvm/debuginfo/mod.rs | 2 +-
2 files changed, 14 insertions(+), 10 deletions(-)
diff --git a/src/librustc_codegen_llvm/debuginfo/metadata.rs b/src/librustc_codegen_llvm/debuginfo/metadata.rs
index 765992fd2b70e..0d67865d71708 100644
--- a/src/librustc_codegen_llvm/debuginfo/metadata.rs
+++ b/src/librustc_codegen_llvm/debuginfo/metadata.rs
@@ -784,26 +784,30 @@ pub fn file_metadata(cx: &CodegenCx<'ll, '_>,
file_name,
defining_crate);
- let directory = if defining_crate == LOCAL_CRATE {
- &cx.sess().working_dir.0
+ let file_name = &file_name.to_string();
+ let file_name_symbol = Symbol::intern(file_name);
+ if defining_crate == LOCAL_CRATE {
+ let directory = &cx.sess().working_dir.0.to_string_lossy();
+ file_metadata_raw(cx, file_name, Some(file_name_symbol),
+ directory, Some(Symbol::intern(directory)))
} else {
// If the path comes from an upstream crate we assume it has been made
// independent of the compiler's working directory one way or another.
- Path::new("")
- };
-
- file_metadata_raw(cx, &file_name.to_string(), &directory.to_string_lossy())
+ file_metadata_raw(cx, file_name, Some(file_name_symbol), "", None)
+ }
}
pub fn unknown_file_metadata(cx: &CodegenCx<'ll, '_>) -> &'ll DIFile {
- file_metadata_raw(cx, "<unknown>", "")
+ file_metadata_raw(cx, "<unknown>", None, "", None)
}
fn file_metadata_raw(cx: &CodegenCx<'ll, '_>,
file_name: &str,
- directory: &str)
+ file_name_symbol: Option<Symbol>,
+ directory: &str,
+ directory_symbol: Option<Symbol>)
-> &'ll DIFile {
- let key = (Symbol::intern(file_name), Symbol::intern(directory));
+ let key = (file_name_symbol, directory_symbol);
if let Some(file_metadata) = debug_context(cx).created_files.borrow().get(&key) {
return *file_metadata;
diff --git a/src/librustc_codegen_llvm/debuginfo/mod.rs b/src/librustc_codegen_llvm/debuginfo/mod.rs
index 2154ac9b1d259..f3070a03b4ed5 100644
--- a/src/librustc_codegen_llvm/debuginfo/mod.rs
+++ b/src/librustc_codegen_llvm/debuginfo/mod.rs
@@ -63,7 +63,7 @@ pub struct CrateDebugContext<'a, 'tcx> {
llcontext: &'a llvm::Context,
llmod: &'a llvm::Module,
builder: &'a mut DIBuilder<'a>,
- created_files: RefCell<FxHashMap<(Symbol, Symbol), &'a DIFile>>,
+ created_files: RefCell<FxHashMap<(Option<Symbol>, Option<Symbol>), &'a DIFile>>,
created_enum_disr_types: RefCell<FxHashMap<(DefId, layout::Primitive), &'a DIType>>,
type_map: RefCell<TypeMap<'a, 'tcx>>,