From 521d0c4a30083dd447fcf397e8b1de278acb81af Mon Sep 17 00:00:00 2001 From: bjorn3 <17426603+bjorn3@users.noreply.github.com> Date: Fri, 21 Mar 2025 12:30:25 +0000 Subject: [PATCH] Cache current_dll_path output Computing the current dll path is somewhat expensive relative to other work when compiling `fn main() {}` as `dladdr` needs to iterate over the symbol table of librustc_driver.so until it finds a match. --- compiler/rustc_session/src/filesearch.rs | 122 ++++++++++++----------- 1 file changed, 66 insertions(+), 56 deletions(-) diff --git a/compiler/rustc_session/src/filesearch.rs b/compiler/rustc_session/src/filesearch.rs index 50f09c57107e6..bdeca91eb64a4 100644 --- a/compiler/rustc_session/src/filesearch.rs +++ b/compiler/rustc_session/src/filesearch.rs @@ -60,66 +60,76 @@ pub fn make_target_bin_path(sysroot: &Path, target_triple: &str) -> PathBuf { #[cfg(unix)] fn current_dll_path() -> Result { - use std::ffi::{CStr, OsStr}; - use std::os::unix::prelude::*; - - #[cfg(not(target_os = "aix"))] - unsafe { - let addr = current_dll_path as usize as *mut _; - let mut info = std::mem::zeroed(); - if libc::dladdr(addr, &mut info) == 0 { - return Err("dladdr failed".into()); - } - if info.dli_fname.is_null() { - return Err("dladdr returned null pointer".into()); - } - let bytes = CStr::from_ptr(info.dli_fname).to_bytes(); - let os = OsStr::from_bytes(bytes); - Ok(PathBuf::from(os)) - } - - #[cfg(target_os = "aix")] - unsafe { - // On AIX, the symbol `current_dll_path` references a function descriptor. - // A function descriptor is consisted of (See https://reviews.llvm.org/D62532) - // * The address of the entry point of the function. - // * The TOC base address for the function. - // * The environment pointer. - // The function descriptor is in the data section. - let addr = current_dll_path as u64; - let mut buffer = vec![std::mem::zeroed::(); 64]; - loop { - if libc::loadquery( - libc::L_GETINFO, - buffer.as_mut_ptr() as *mut u8, - (size_of::() * buffer.len()) as u32, - ) >= 0 - { - break; - } else { - if std::io::Error::last_os_error().raw_os_error().unwrap() != libc::ENOMEM { - return Err("loadquery failed".into()); + use std::sync::OnceLock; + + // This is somewhat expensive relative to other work when compiling `fn main() {}` as `dladdr` + // needs to iterate over the symbol table of librustc_driver.so until it finds a match. + // As such cache this to avoid recomputing if we try to get the sysroot in multiple places. + static CURRENT_DLL_PATH: OnceLock> = OnceLock::new(); + CURRENT_DLL_PATH + .get_or_init(|| { + use std::ffi::{CStr, OsStr}; + use std::os::unix::prelude::*; + + #[cfg(not(target_os = "aix"))] + unsafe { + let addr = current_dll_path as usize as *mut _; + let mut info = std::mem::zeroed(); + if libc::dladdr(addr, &mut info) == 0 { + return Err("dladdr failed".into()); } - buffer.resize(buffer.len() * 2, std::mem::zeroed::()); - } - } - let mut current = buffer.as_mut_ptr() as *mut libc::ld_info; - loop { - let data_base = (*current).ldinfo_dataorg as u64; - let data_end = data_base + (*current).ldinfo_datasize; - if (data_base..data_end).contains(&addr) { - let bytes = CStr::from_ptr(&(*current).ldinfo_filename[0]).to_bytes(); + if info.dli_fname.is_null() { + return Err("dladdr returned null pointer".into()); + } + let bytes = CStr::from_ptr(info.dli_fname).to_bytes(); let os = OsStr::from_bytes(bytes); - return Ok(PathBuf::from(os)); + Ok(PathBuf::from(os)) } - if (*current).ldinfo_next == 0 { - break; + + #[cfg(target_os = "aix")] + unsafe { + // On AIX, the symbol `current_dll_path` references a function descriptor. + // A function descriptor is consisted of (See https://reviews.llvm.org/D62532) + // * The address of the entry point of the function. + // * The TOC base address for the function. + // * The environment pointer. + // The function descriptor is in the data section. + let addr = current_dll_path as u64; + let mut buffer = vec![std::mem::zeroed::(); 64]; + loop { + if libc::loadquery( + libc::L_GETINFO, + buffer.as_mut_ptr() as *mut u8, + (size_of::() * buffer.len()) as u32, + ) >= 0 + { + break; + } else { + if std::io::Error::last_os_error().raw_os_error().unwrap() != libc::ENOMEM { + return Err("loadquery failed".into()); + } + buffer.resize(buffer.len() * 2, std::mem::zeroed::()); + } + } + let mut current = buffer.as_mut_ptr() as *mut libc::ld_info; + loop { + let data_base = (*current).ldinfo_dataorg as u64; + let data_end = data_base + (*current).ldinfo_datasize; + if (data_base..data_end).contains(&addr) { + let bytes = CStr::from_ptr(&(*current).ldinfo_filename[0]).to_bytes(); + let os = OsStr::from_bytes(bytes); + return Ok(PathBuf::from(os)); + } + if (*current).ldinfo_next == 0 { + break; + } + current = (current as *mut i8).offset((*current).ldinfo_next as isize) + as *mut libc::ld_info; + } + return Err(format!("current dll's address {} is not in the load map", addr)); } - current = - (current as *mut i8).offset((*current).ldinfo_next as isize) as *mut libc::ld_info; - } - return Err(format!("current dll's address {} is not in the load map", addr)); - } + }) + .clone() } #[cfg(windows)]