https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112713
Bug ID: 112713
Summary: RISC-V: Trunk GCC regression on VSETVL PASS comparing
with GCC-13
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: juzhe.zhong at rivai dot ai
Target Milestone: ---
https://godbolt.org/z/qePhcxd5z
#include "riscv_vector.h"
size_t
foo (char const *buf, size_t len)
{
size_t sum = 0;
size_t vl = __riscv_vsetvlmax_e8m8();
size_t step = vl * 4;
const char *it = buf, *end = buf + len;
for(; it + step <= end; ) {
it += vl;
vint8m8_t v3 = __riscv_vle8_v_i8m8((void*)it, vl); it += vl;
vbool1_t m3 = __riscv_vmsgt_vx_i8m8_b1(v3, -65, vl);
sum += __riscv_vcpop_m_b1(m3, vl);
}
return sum;
}
GCC-14 ASM:
foo:
vsetvli a4,zero,e8,m8,ta,ma
slli a5,a4,2
add a1,a0,a1
add a5,a0,a5
bltu a1,a5,.L4
slli a6,a4,1
add a5,a0,a4
add t1,a6,a4
li a0,0
li a7,-65
vsetvli zero,zero,e8,m8,ta,ma ----------> redundant
.L3:
vle8.v v8,0(a5)
add a5,a5,a6
add a3,t1,a5
vmsgt.vx v8,v8,a7
vcpop.m a2,v8
add a0,a0,a2
bgeu a1,a3,.L3
ret
.L4:
li a0,0
ret
GCC-13 ASM:
foo:
vsetvli a4,zero,e8,m8,ta,ma
slli a5,a4,2
add a1,a0,a1
add a5,a0,a5
bltu a1,a5,.L4
slli a6,a4,1
add a5,a0,a4
add t1,a6,a4
li a0,0
li a7,-65
.L3:
vle8.v v8,0(a5)
add a5,a5,a6
add a3,t1,a5
vmsgt.vx v24,v8,a7
vcpop.m a2,v24
add a0,a0,a2
bgeu a1,a3,.L3
ret
.L4:
li a0,0
ret
Trunk GCC-14 has a regression that cause a redundant vsetvl.
Such regression need to be fixed and I will take a look at it.
