[PATCH] musl: always use 'lib' directory for all x86_64 ABIs [PR90077]

[Sergei Trofimovich]

From: Sergei Trofimovich <siarheit@google.com>

musl library intentionally does not support glibc-style multilib layout
and usually assumes --libdir=lib (Gentoo and Alpine Linux both use it).

Before the change --disable-multilib x86_64-gentoo-linux-musl returned:

    $ gcc -print-multi-os-directory
    ../lib64
    $ gcc -print-multi-os-directory -m32
    ../lib32
    $ gcc -print-multi-os-directory -mx32
    ../libx32

After the change the layout is always the same:

    $ gcc -print-multi-os-directory
    ../lib
    $ gcc -print-multi-os-directory -m32
    ../lib
    $ gcc -print-multi-os-directory -mx32
    ../lib

The discrepancy was noticed in meson build system which uses
-print-multi-os-directory to find out target directory.

Debian's multi-arch setup should not change.

	PR target/90077

gcc/ChangeLog

	* gcc/config.gcc: Specal case musl to t-linux64-musl.

	* gcc/config/i386/t-linux64-musl: New file based on t-linux64
	that pins MULTILIB_OSDIRNAMES to lib.
---
 gcc/config.gcc                 | 10 ++++++++--
 gcc/config/i386/t-linux64-musl | 28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)
 create mode 100644 gcc/config/i386/t-linux64-musl

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 0230bb88861..a87a59c9403 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1923,7 +1923,10 @@ i[34567]86-*-linux* | i[34567]86-*-kfreebsd*-gnu | i[34567]86-*-gnu* | i[34567]8
 		if test x$enable_targets = xall; then
 			tm_file="${tm_file} i386/x86-64.h i386/gnu-user-common.h i386/gnu-user64.h i386/linux-common.h i386/linux64.h"
 			tm_defines="${tm_defines} TARGET_BI_ARCH=1"
-			tmake_file="${tmake_file} i386/t-linux64"
+			case $target in
+				*-*-*musl*) tmake_file="${tmake_file} i386/t-linux64-musl";;
+				*) tmake_file="${tmake_file} i386/t-linux64";;
+			esac
 			x86_multilibs="${with_multilib_list}"
 			if test "$x86_multilibs" = "default"; then
 				x86_multilibs="m64,m32"
@@ -1983,7 +1986,10 @@ x86_64-*-linux* | x86_64-*-kfreebsd*-gnu)
 		tm_file="${tm_file} kfreebsd-gnu.h i386/kfreebsd-gnu64.h"
 		;;
 	esac
-	tmake_file="${tmake_file} i386/t-linux64"
+	case $target in
+		*-*-*musl*) tmake_file="${tmake_file} i386/t-linux64-musl";;
+		*) tmake_file="${tmake_file} i386/t-linux64";;
+	esac
 	x86_multilibs="${with_multilib_list}"
 	if test "$x86_multilibs" = "default"; then
 		case ${with_abi} in
diff --git a/gcc/config/i386/t-linux64-musl b/gcc/config/i386/t-linux64-musl
new file mode 100644
index 00000000000..58e23c3c7dc
--- /dev/null
+++ b/gcc/config/i386/t-linux64-musl
@@ -0,0 +1,28 @@
+# Copyright (C) 2002-2021 Free Software Foundation, Inc.
+#
+# This file is part of GCC.
+#
+# GCC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GCC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+# musl explicitly does not support lib/lib32/lib64 layouts and always
+# uses lib layout. On debian full arch suffix is used. Thus we populate
+# all the m32/m64/mx32 with the same lib and apply multiarch suffix.
+
+comma=,
+MULTILIB_OPTIONS    = $(subst $(comma),/,$(TM_MULTILIB_CONFIG))
+MULTILIB_DIRNAMES   = $(patsubst m%, %, $(subst /, ,$(MULTILIB_OPTIONS)))
+MULTILIB_OSDIRNAMES = m64=../lib$(call if_multiarch,:x86_64-linux-gnu)
+MULTILIB_OSDIRNAMES+= m32=../lib$(call if_multiarch,:i386-linux-gnu)
+MULTILIB_OSDIRNAMES+= mx32=../lib$(call if_multiarch,:x86_64-linux-gnux32)
-- 
2.32.0