https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121845
Bug ID: 121845
Summary: [Trunk] RISC-V rv64gcv: miscompile at -O0
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: xxs_chy at outlook dot com
Target Milestone: ---
Testcase:
#include <stdint.h>
#include <stdio.h>
typedef uint32_t a;
typedef uint64_t uint64;
uint64 b;
__attribute__((__vector_size__(4 * sizeof(a)))) a f = {504339, 7, 3};
uint64 *g = &b;
int32_t *c(uint8_t, int32_t *, uint32_t, uint32_t, int64_t);
int8_t d() {
int32_t e;
c(0, &e, 0, 0, 1);
return 0;
}
int32_t *c(uint8_t, int32_t *j, uint32_t, uint32_t, int64_t) {
f = __builtin_shufflevector(f, f, 0, 3, 2, 1);
*g = f[2];
return j;
}
int main() {
d();
printf("0x%016llx\n", b);
}
Command:
> riscv64-unknown-elf-gcc =march=rv64gcv -O0 -static reduced.c && qemu-riscv64
> 0x0000000000000000
> riscv64-unknown-elf-gcc =march=rv64gcv -O1/O2/O3 -static reduced.c &&
> qemu-riscv64
> 0x0000000000000003
The GCC version is after patching
https://gcc.gnu.org/cgit/gcc/commit/?id=e3d5e9f0c8c6f27bf59d321d5082be7b3bb39f8a.
Maybe related to some shuffle bugs before:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121780
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121742
