On Mon, Jun 17, 2019 at 2:30 PM Luís Marques <luismarq...@lowrisc.org> wrote:
>
> On Thu, Jun 6, 2019 at 7:19 PM Denys Vlasenko <vda.li...@googlemail.com>
> wrote:
> > Can you experiment with LLVM and find a definition of SET_PTR_TO_GLOBALS()
> > which works for it?
>
> I did not find any correct solution for this other than disabling the
> optimization for Clang/LLVM.
Works for me with the following versions:
llvm-libs-8.0.0-7.fc31.x86_64
llvm-8.0.0-7.fc31.x86_64
clang-libs-8.0.0-3.fc31.x86_64
clang-8.0.0-3.fc31.x86_64
struct globals;
extern struct globals *const ptr_to_globals;
#define barrier() __asm__ __volatile__("":::"memory")
#define SET_PTR_TO_GLOBALS(x) do { \
(*(struct globals**)&ptr_to_globals) = (void*)(x); \
barrier(); \
} while (0)
void f(void *p)
{
SET_PTR_TO_GLOBALS(p);
}
$ clang -Os -Wall -S t.c
$ cat t.s
.text
.file "t.c"
.globl f # -- Begin function f
.type f,@function
f: # @f
.cfi_startproc
# %bb.0:
movq %rdi, ptr_to_globals(%rip)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ store to ptr_to_globals
#APP
#NO_APP
retq
.Lfunc_end0:
.size f, .Lfunc_end0-f
.cfi_endproc
# -- End function
.ident "clang version 8.0.0 (Fedora 8.0.0-3.fc31)"
.section ".note.GNU-stack","",@progbits
.addrsig
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