[gcc r12-7582] [nvptx] Add multilib mptx=3.1

[Tom de Vries <vries@gcc.gnu.org>]

https://gcc.gnu.org/g:975e7ade35095839b4dd2cc0f2b303bd63950db9

commit r12-7582-g975e7ade35095839b4dd2cc0f2b303bd63950db9
Author: Tom de Vries <tdevries@suse.de>
Date:   Tue Mar 8 09:25:39 2022 +0100

    [nvptx] Add multilib mptx=3.1
    
    With commit 5b5e456f018 ("[nvptx] Build libraries with mptx=3.1") the
    intention was that the ptx isa version for all libraries was switched back to
    3.1 using MULTILIB_EXTRA_OPTS, without changing the default 6.0.
    
    Further testing revealed that this is not the case, and some libs were still
    build with 6.0.
    
    Fix this by introducing an mptx=3.1 multilib.
    
    Adding a multilib should be avoided if possible, because it adds build time.
    But I think it's a reasonable trade-off.  With --disable-multilib, the default
    lib with misa=sm_30 and mptx=6.0 should be usable in most scenarios.  With
    --enable-multilib, we can enable older drivers, as well as generate code
    similar to how that was done in previous gcc releases, which is very useful.
    
    Tested on nvptx.
    
    gcc/ChangeLog:
    
    2022-03-07  Tom de Vries  <tdevries@suse.de>
    
            * config/nvptx/t-nvptx (MULTILIB_EXTRA_OPTS): Move mptx=3.1 ...
            (MULTILIB_OPTIONS): ... here.

Diff:
---
 gcc/config/nvptx/t-nvptx | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/gcc/config/nvptx/t-nvptx b/gcc/config/nvptx/t-nvptx
index a4a5341bb24..b63c4a5a39d 100644
--- a/gcc/config/nvptx/t-nvptx
+++ b/gcc/config/nvptx/t-nvptx
@@ -30,6 +30,4 @@ s-nvptx-gen-opt: $(srcdir)/config/nvptx/nvptx-sm.def
 	  tmp-nvptx-gen.opt $(srcdir)/config/nvptx/nvptx-gen.opt
 	$(STAMP) s-nvptx-gen-opt
 
-MULTILIB_OPTIONS = mgomp
-
-MULTILIB_EXTRA_OPTS = mptx=3.1
+MULTILIB_OPTIONS = mgomp mptx=3.1