[Pkg-rust-maintainers] Bug#917192: rustc: Please include patch to fix C ABI on sparc64

[John Paul Adrian Glaubitz]

Source: rustc
Version: 1.31.0+dfsg1-2
Severity: normal
Tags: upstream patch
User: debian-sparc at lists.debian.org
Usertags: sparc64

Hi!

The Rust compiler misses some special handling for empty structs in
the C ABI. This was discovered today by Michael Karcher who has
written a patch to address the issue, it's already sent upstream [1].

I'm attaching the patch. With the patches from #916818, #917000
and #917191, the testsuite failures on sparc64 drop to 9 for me.

> [1] https://github.com/rust-lang/rust/pull/57085

--
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz at debian.org
`. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913
-------------- next part --------------
>From 970747edb47795a1012929ea468c2b75f087b289 Mon Sep 17 00:00:00 2001
From: Michael Karcher <github at mkarcher.dialup.fu-berlin.de>
Date: Sun, 23 Dec 2018 20:33:52 +0100
Subject: [PATCH] librustc_codegen_llvm: Don't eliminate empty structs in C ABI
 on linux-sparc64

This is in accordance with the SPARC Compliance Definition 4.2.1,
Page 3P-12. It says that structs of up to 8 bytes (which applies
to empty structs as well) are to be passed in one register.
---
 src/librustc_codegen_llvm/abi.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/librustc_codegen_llvm/abi.rs b/src/librustc_codegen_llvm/abi.rs
index b8954dee79..c083137f08 100644
--- a/src/librustc_codegen_llvm/abi.rs
+++ b/src/librustc_codegen_llvm/abi.rs
@@ -456,6 +456,9 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
         let linux_s390x = target.target_os == "linux"
                        && target.arch == "s390x"
                        && target.target_env == "gnu";
+        let linux_sparc64 = target.target_os == "linux"
+                       && target.arch == "sparc64"
+                       && target.target_env == "gnu";
         let rust_abi = match sig.abi {
             RustIntrinsic | PlatformIntrinsic | Rust | RustCall => true,
             _ => false
@@ -526,8 +529,9 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
             if arg.layout.is_zst() {
                 // For some forsaken reason, x86_64-pc-windows-gnu
                 // doesn't ignore zero-sized struct arguments.
-                // The same is true for s390x-unknown-linux-gnu.
-                if is_return || rust_abi || (!win_x64_gnu && !linux_s390x) {
+                // The same is true for s390x-unknown-linux-gnu
+                // and sparc64-unknown-linux-gnu.
+                if is_return || rust_abi || (!win_x64_gnu && !linux_s390x && !linux_sparc64) {
                     arg.mode = PassMode::Ignore;
                 }
             }
-- 
2.20.1