Open
Description
If I change description = in config.toml, the Crate IDs change, which leads to different name mangling. In particular this means it's not possible to use PGO profiles produced by a compiler with one description to build a compiler with a different description. Is this intentional?
I'm not sure if v0 mangling actually has anything to do with this, but that's where it was convenient for me to insert the code to print IDs.
To see this, apply this patch:
From 705dac4190d0e1c67a848b5af4ba6fc51e3aaa56 Mon Sep 17 00:00:00 2001
From: Michael Benfield <mbenfield@google.com>
Date: Wed, 26 Oct 2022 01:11:29 +0000
Subject: [PATCH] print
---
compiler/rustc_symbol_mangling/src/v0.rs | 3 +++
1 file changed, 3 insertions(+)
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index ecfe6861e84..ee21131970f 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -739,6 +739,9 @@ fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
self.push_disambiguator(stable_crate_id.to_u64());
let name = self.tcx.crate_name(cnum);
+ if name.as_str().contains("rustc_serialize") {
+ println!("XXX {} : {:X}", name.as_str(), stable_crate_id.to_u64());
+ }
self.push_ident(name.as_str());
Ok(self)
}
--
and make these two files:
% cat configA.toml
[rust]
description = "A"
new-symbol-mangling = true
~/Code/rust3 [ mbenfield ]
% cat configB.toml
[rust]
description = "B"
new-symbol-mangling = true
then do
./x.py build --stage 2 --config configA.toml | grep XXX
and
./x.py build --stage 2 --config configB.toml | grep XXX
and you'll get different outputs.