https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108132
Bug ID: 108132
Summary: Wrong instruction scheduling around function call with
longjmp on aarch64 at O2
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: qinzhao at gcc dot gnu.org
Target Milestone: ---
The error only happens on aarch64 (fine on X86).
The following testing case:
[opc@qinzhao-aarch64-ol8]$ cat t.c
#include <stdio.h>
#include <setjmp.h>
#include <stdbool.h>
jmp_buf ex_buf__;
int f(int x)
{
int arr[] = {1,2,6,8,9,10};
int lo=0;
int hi=5;
while(lo<=hi) {
int mid=(lo+hi)/2;
if(arr[mid]==x) {
longjmp(ex_buf__, 1);
} else if(arr[mid]<x) {
lo=mid+1;
} else if(arr[mid]>x) {
hi=mid-1;
}
}
return -1;
}
int
main(int argc, char** argv)
{
int a=2;
bool b=false;
do {
if( !setjmp(ex_buf__) ){
a=f(a);
b=true;
} else {
printf("a : %d\n",a);
printf("Got Exception!\n");
}
} while(0);
if(b) {
printf("b is true!\n");
}
return 0;
}
when compiled with the latest upstream gcc13 on aarch64 with -O2, the variable
"b" was set to true, which is wrong.
when disable insn scheduling by adding -fno-schedule-insns, the issue gone:
[opc@qinzhao-aarch64-ol8]$ /home/opc/Install/latest/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/home/opc/Install/latest/bin/gcc
COLLECT_LTO_WRAPPER=/home/opc/Install/latest/libexec/gcc/aarch64-unknown-linux-gnu/13.0.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: ../latest_gcc/configure --prefix=/home/opc/Install/latest
--enable-languages=c,c++ --disable-bootstrap
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 13.0.0 20221215 (experimental) (GCC)
[opc@qinzhao-aarch64-ol8]$ /home/opc/Install/latest/bin/gcc -O2 t.c
[opc@qinzhao-aarch64-ol8]$ ./a.out
a : 2
Got Exception!
b is true!
[opc@qinzhao-aarch64-ol8]$ /home/opc/Install/latest/bin/gcc -O2
-fno-schedule-insns t.c
[opc@qinzhao-aarch64-ol8]$ ./a.out
a : 2
Got Exception!
[opc@qinzhao-aarch64-ol8]$
