https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127553
Bug ID: 127553
Summary: RISC-V: RVV builtin calls are not rejected when
building without RVV and the call can be optimized
away
Product: gcc
Version: 16.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: bunk at stusta dot de
Target Milestone: ---
A CMake test of the snappy package in Debian wrongly reported RVV 1.0 support
due to:
$ cat test.cc
#include <riscv_vector.h>
#include <stdint.h>
#include <stddef.h>
int main() {
uint8_t val = 3, dup[8];
size_t vl = __riscv_vsetvl_e8m1(8);
vuint8m1_t v = __riscv_vmv_v_x_u8m1(val, vl);
return 0;
}
$ g++ -march=rv64gc -c -Wall test.cc
test.cc: In function 'int main()':
test.cc:5:22: warning: unused variable 'dup' [-Wunused-variable]
5 | uint8_t val = 3, dup[8];
| ^~~
test.cc:7:16: warning: unused variable 'v' [-Wunused-variable]
7 | vuint8m1_t v = __riscv_vmv_v_x_u8m1(val, vl);
| ^
test.cc:6:36: error: built-in function '__riscv_vsetvl_e8m1(8)' requires the
'v' ISA extension
6 | size_t vl = __riscv_vsetvl_e8m1(8);
| ~~~~~~~~~~~~~~~~~~~^~~
test.cc:7:40: error: this operation requires the RVV ISA extension
7 | vuint8m1_t v = __riscv_vmv_v_x_u8m1(val, vl);
| ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~
test.cc:7:40: note: you can enable RVV using the command-line option '-march',
or by using the 'target' attribute or pragma
test.cc:7:40: error: built-in function '__riscv_vmv_v_x_u8m1(val, vl)' requires
the 'v' ISA extension
$ g++ -march=rv64gc -c -Wall -O2 test.cc
test.cc: In function 'int main()':
test.cc:5:22: warning: unused variable 'dup' [-Wunused-variable]
5 | uint8_t val = 3, dup[8];
| ^~~
test.cc:7:16: warning: unused variable 'v' [-Wunused-variable]
7 | vuint8m1_t v = __riscv_vmv_v_x_u8m1(val, vl);
| ^
$
Seen with GCC 16, 15 and 14 (RVV 1.0 support was added in GCC 14).
