Hi Jin Ma,
This situation is the same on x86. When using -O0, the lpad instruction
is merely a redundant instruction and does not affect the execution result.
This is the ASM result for x86, and there is also an endbr64 in foo().
https://godbolt.org/z/M1fTendE3
On Wed, Mar 12, 2025 at 5:44 PM Jin Ma <ji...@linux.alibaba.com> wrote:
> Hi, Monk Chiang
>
> I noticed that at -O0, static functions are emitting lpad instructions,
> whereas
> they do not at -O2. I'm not sure if this is expected behavior.
>
> Upon further investigation, I found that c_node->only_called_directly_p()
> returns
> false, which is caused by force_output being set to 1. Tracing back, I
> encountered
> the following patch[1] and PR25961[2], which set force_output to 1 for
> static
> functions at -O0, while it is 0 at -O2.
>
> Do you have any comments on this?
>
>
> Example code:
>
> int cc = 333;
> extern int aa;
>
> __attribute__((noinline))
> static void
> foo(void)
> {
> cc = aa;
> }
> int main(void)
>
> {
> foo();
> return 0;
> }
>
> [1] https://gcc.gnu.org/legacy-ml/gcc-patches/2006-05/msg00315.html
> [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24561
>
