commit b2cd021dbbf3a9cb53838255db86df24b25c6610
author Devin Jeanpierre <jeanpierreda@google.com> Fri Oct 01 07:16:23 2021 +0000
committer Marcel Hlopko <hlopko@google.com> Fri Mar 25 21:54:27 2022 +0000
tree ab03d63e84528ae4a9d1d2e31ebae3f4c1213db1
parent c06204aa3b58263859b2a0b232e783ec8a1e4739

Add `is_trivial_abi` bit to Record IR.

Without a way to look up the Record for a given CcType/RsType, there is no way to make this influence code generation of actual calls which use this type. So this is currently unused.

However, this may be enough, by itself, to mark a type as trivially relocatable. A type with this bit can be passed through registers, which means that, by definition, its memory location doesn't matter, and it can be trivially relocated.

For example, see this godbolt link showing that marking a class as trivial_abi breaks it by causing it to get relocated!

https://godbolt.org/z/voMa5TPKq

PiperOrigin-RevId: 400123681

rs_bindings_from_cc/src_code_gen.rs

diff --git a/rs_bindings_from_cc/src_code_gen.rs b/rs_bindings_from_cc/src_code_gen.rs
index 6267238..74b3e6b 100644
--- a/rs_bindings_from_cc/src_code_gen.rs
+++ b/rs_bindings_from_cc/src_code_gen.rs
@@ -516,6 +516,7 @@
                 ],
                 size: 12,
                 alignment: 4,
+                is_trivial_abi: true,
             }],
             functions: vec![],
         };