On Dec 15, 2023, Richard Biener <richard.guent...@gmail.com> wrote:
> I think __noipa__ is more complete and will make the libgcc functions appear
> as black boxes to callers.
I was hesitant to use __noipa__ because I thought it might disable
relevant optimizations even when not using LTO, but it is likely safer
in the long run to use it, so I've added it, thanks.
> OK your or this way.
Here's what I'm checking in shortly. Regstrapped on x86_64-linux-gnu.
strub: avoid lto inlining
The strub builtins are not suited for cross-unit inlining, they should
only be inlined by the builtin expanders, if at all. While testing on
sparc64, it occurred to me that, if libgcc was built with LTO enabled,
lto1 might inline them, and that would likely break things. So, make
sure they're clearly marked as not inlinable.
for libgcc/ChangeLog
* strub.c (ATTRIBUTE_NOINLINE): New.
(ATTRIBUTE_STRUB_CALLABLE): Add it.
(__strub_dummy_force_no_leaf): Drop it.
---
libgcc/strub.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/libgcc/strub.c b/libgcc/strub.c
index b0f990d9deebb..3b7cc26b3d8f0 100644
--- a/libgcc/strub.c
+++ b/libgcc/strub.c
@@ -36,7 +36,12 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If
not, see
# define TOPS <
#endif
-#define ATTRIBUTE_STRUB_CALLABLE __attribute__ ((__strub__ ("callable")))
+/* Make sure these builtins won't be inlined, even with LTO. */
+#define ATTRIBUTE_NOINLINE \
+ __attribute__ ((__noinline__, __noclone__, __noipa__))
+
+#define ATTRIBUTE_STRUB_CALLABLE \
+ __attribute__ ((__strub__ ("callable"))) ATTRIBUTE_NOINLINE
/* Enter a stack scrubbing context, initializing the watermark to the caller's
stack address. */
@@ -72,7 +77,6 @@ __strub_update (void **watermark)
/* Dummy function, called to force the caller to not be a leaf function, so
that it can't use the red zone. */
static void ATTRIBUTE_STRUB_CALLABLE
-__attribute__ ((__noinline__, __noipa__))
__strub_dummy_force_no_leaf (void)
{
}
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
More tolerance and less prejudice are key for inclusion and diversity
Excluding neuro-others for not behaving ""normal"" is *not* inclusive
