[gcc r11-8281] libstdc++: Add workaround for ia32 floating atomics miscompilations [PR100184]

Jakub Jelinek jakub@gcc.gnu.org
Thu Apr 22 13:10:54 GMT 2021


https://gcc.gnu.org/g:a21f3b38c3b9a5c28c79be37b040e7d06d827d76

commit r11-8281-ga21f3b38c3b9a5c28c79be37b040e7d06d827d76
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Apr 22 15:08:21 2021 +0200

    libstdc++: Add workaround for ia32 floating atomics miscompilations [PR100184]
    
    gcc on ia32 miscompiles various atomics involving floating point,
    unfortunately I'm afraid it is too late to fix that for 11.1 and
    as I'm quite lost on it, it might take a while for 12 too
    (disabling all the 8 peephole2s would be easiest, but then we'd
    run into optimization regressions).
    
    While 1.cc just FAILs, with dejagnu 1.6.1 wait_notify.cc hangs the
    make check even after the timeout fires.  The following patch therefore
    xfails the former and skips the latter.
    
    Tested on x86_64-linux where
    make check RUNTESTFLAGS='conformance.exp=atomic_float/*.cc'
    is still
                    === libstdc++ Summary ===
    
     # of expected passes            8
    and on i686-linux, where it is now
                    === libstdc++ Summary ===
    
     # of expected passes            5
     # of expected failures          1
     # of unsupported tests          1
    
    2021-04-22  Jakub Jelinek  <jakub@redhat.com>
    
            PR target/100182
            * testsuite/29_atomics/atomic_float/1.cc: Add dg-xfail-run-if for
            ia32.
            * testsuite/29_atomics/atomic_float/wait_notify.cc: Add dg-skip-if for
            ia32.
    
    (cherry picked from commit 0f4588141fcbe4e0f1fa12776b47200870f6c621)

Diff:
---
 libstdc++-v3/testsuite/29_atomics/atomic_float/1.cc           | 1 +
 libstdc++-v3/testsuite/29_atomics/atomic_float/wait_notify.cc | 1 +
 2 files changed, 2 insertions(+)

diff --git a/libstdc++-v3/testsuite/29_atomics/atomic_float/1.cc b/libstdc++-v3/testsuite/29_atomics/atomic_float/1.cc
index b2008368a95..797d3b7ecbe 100644
--- a/libstdc++-v3/testsuite/29_atomics/atomic_float/1.cc
+++ b/libstdc++-v3/testsuite/29_atomics/atomic_float/1.cc
@@ -18,6 +18,7 @@
 // { dg-add-options ieee }
 // { dg-options "-std=gnu++2a" }
 // { dg-do run { target c++2a } }
+// { dg-xfail-run-if "PR100182" { ia32 } }
 
 #include <atomic>
 #include <testsuite_hooks.h>
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic_float/wait_notify.cc b/libstdc++-v3/testsuite/29_atomics/atomic_float/wait_notify.cc
index 01768da290b..e0ff34dbf24 100644
--- a/libstdc++-v3/testsuite/29_atomics/atomic_float/wait_notify.cc
+++ b/libstdc++-v3/testsuite/29_atomics/atomic_float/wait_notify.cc
@@ -2,6 +2,7 @@
 // { dg-do run { target c++2a } }
 // { dg-require-gthreads "" }
 // { dg-additional-options "-pthread" { target pthread } }
+// { dg-skip-if "PR100182" { ia32 } }
 // { dg-add-options libatomic }
 
 // Copyright (C) 2020-2021 Free Software Foundation, Inc.


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