[gcc(refs/users/aoliva/heads/testme)] [rs6000] add os-missing-powerpc64.h for powerpc-elf

[Alexandre Oliva]

https://gcc.gnu.org/g:75d9c92dc38d4915530ffb0a335ae0ea745501af

commit 75d9c92dc38d4915530ffb0a335ae0ea745501af
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Tue Mar 10 04:18:15 2026 -0300

    [rs6000] add os-missing-powerpc64.h for powerpc-elf
    
    Disable the implicit enabling of -mpowerpc64 upon
    -mcpu=<ppc64-supporting>, instead of assuming the embedded operating
    system can save and restore all 64 bits of registers, which has ABI
    implications.  Compiling with -mpowerpc64 explicitly restores current
    behavior, in case the operating system can indeed deal with this
    unusual scenario.
    
    
    for  gcc/ChangeLog
    
            * config/rs6000/os-missing-powerpc64.h: New.
            * config.gcc <powerpc-*-elf*>: Add it.

Diff:
---
 gcc/config.gcc                           |  2 +-
 gcc/config/rs6000/os-missing-powerpc64.h | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 35958b17009c..d57fdb5cb614 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -3107,7 +3107,7 @@ powerpc-*-eabisim*)
 	use_gcc_stdint=wrap
 	;;
 powerpc-*-elf*)
-	tm_file="${tm_file} elfos.h gnu-user.h freebsd-spec.h newlib-stdint.h rs6000/sysv4.h"
+	tm_file="${tm_file} elfos.h gnu-user.h freebsd-spec.h newlib-stdint.h rs6000/sysv4.h rs6000/os-missing-powerpc64.h"
 	extra_options="${extra_options} rs6000/sysv4.opt"
 	tmake_file="rs6000/t-fprules rs6000/t-ppcgas rs6000/t-ppccomm"
 	;;
diff --git a/gcc/config/rs6000/os-missing-powerpc64.h b/gcc/config/rs6000/os-missing-powerpc64.h
new file mode 100644
index 000000000000..0e9fd34868da
--- /dev/null
+++ b/gcc/config/rs6000/os-missing-powerpc64.h
@@ -0,0 +1,28 @@
+/* Adjust for operating systems without 64-bit support.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+   Contributed by Richard Kenner (kenner@vlsi1.ultra.nyu.edu)
+
+   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.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This setting arranges for the compiler to *not* enable -mpowerpc64
+   implicitly when a 64-bit CPU is selected while building in 32-bit mode.  */
+#define OS_MISSING_POWERPC64 !TARGET_64BIT