On Wed, Feb 16, 2022 at 2:25 AM Richard Sandiford via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > atomic-inst-cas.c has code to skip __atomic_compare_exchange_n > calls for invalid memory orderings, but -Winvalid-memory-model > applies before the dead code is removed (which is the right > behaviour IMO). This patch therefore suppresses the warning > for this test.
It is a bit more complex than that, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104200#c3 for the reduced testcase. The undefined (invalid) arguments to __atomic_compare_exchange_n are only after constant propagation really which is not done at -O0, though the warning does it. So the warning does constant propagation of the arguments but not if it was conditionally executed. Most likely waccess should do a similar thing like it was done for the uninitialized warnings in https://gcc.gnu.org/pipermail/gcc-patches/2022-February/589983.html . Thanks, Andrew Pinski > > Tested on aarch64-linux-gnu & pushed. > > Richard > > > gcc/testsuite/ > * gcc.target/aarch64/atomic-inst-cas.c: Add > -Wno-invalid-memory-model. > --- > gcc/testsuite/gcc.target/aarch64/atomic-inst-cas.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/gcc/testsuite/gcc.target/aarch64/atomic-inst-cas.c > b/gcc/testsuite/gcc.target/aarch64/atomic-inst-cas.c > index f6f28922319..0b4533adade 100644 > --- a/gcc/testsuite/gcc.target/aarch64/atomic-inst-cas.c > +++ b/gcc/testsuite/gcc.target/aarch64/atomic-inst-cas.c > @@ -1,5 +1,7 @@ > /* { dg-do compile } */ > -/* { dg-options "-O2 -march=armv8-a+lse" } */ > +/* -Winvalid-memory-model warnings are issued before the dead invalid calls > + are removed. */ > +/* { dg-options "-O2 -march=armv8-a+lse -Wno-invalid-memory-model" } */ > > /* Test ARMv8.1-A CAS instruction. */ > > -- > 2.25.1
