https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111153
Bug ID: 111153
Summary: RISC-V: Incorrect Vector cost model for reduction
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: ---
Consider this following case:
#include <stdint.h>
#define DEF_REDUC_PLUS(TYPE) \
TYPE __attribute__ ((noinline, noclone)) \
reduc_plus_##TYPE (TYPE * __restrict a, int n) \
{ \
TYPE r = 0; \
for (int i = 0; i < n; ++i) \
r += a[i]; \
return r; \
}
#define TEST_PLUS(T) \
T (int32_t) \
TEST_PLUS (DEF_REDUC_PLUS)
-O3 --param=riscv-autovec-preference=scalable:
reduc_plus_int32_t:
ble a1,zero,.L8
addiw a5,a1,-1
li a4,4
addi sp,sp,-16
mv a2,a0
sext.w a3,a1
bleu a5,a4,.L9
srliw a4,a3,2
slli a4,a4,4
mv a5,a0
add a4,a4,a0
vsetivli zero,4,e32,m1,ta,ma
vmv.v.i v1,0
vse32.v v1,0(sp)
.L4:
vle32.v v1,0(a5)
vle32.v v2,0(sp)
addi a5,a5,16
vadd.vv v1,v2,v1
vse32.v v1,0(sp)
bne a4,a5,.L4
ld a5,0(sp)
lw a4,0(sp)
andi a1,a1,-4
srai a5,a5,32
addw a5,a4,a5
lw a4,8(sp)
addw a5,a5,a4
ld a4,8(sp)
srai a4,a4,32
addw a0,a5,a4
beq a3,a1,.L15
.L3:
subw a3,a3,a1
slli a5,a1,32
slli a3,a3,32
srli a3,a3,32
srli a5,a5,30
add a2,a2,a5
vsetvli a5,a3,e8,mf4,tu,mu
vsetvli a4,zero,e32,m1,ta,ma
sub a1,a3,a5
vmv.v.i v1,0
vsetvli zero,a3,e32,m1,tu,ma
vle32.v v2,0(a2)
vmv.v.v v1,v2
bne a3,a5,.L21
.L7:
vsetvli a4,zero,e32,m1,ta,ma
vmv.s.x v2,zero
vredsum.vs v1,v1,v2
vmv.x.s a5,v1
addw a0,a0,a5
.L15:
addi sp,sp,16
jr ra
.L21:
slli a5,a5,2
add a2,a2,a5
vsetvli zero,a1,e32,m1,tu,ma
vle32.v v2,0(a2)
vadd.vv v1,v1,v2
j .L7
.L8:
li a0,0
ret
.L9:
li a1,0
li a0,0
j .L3
-O3 --param=riscv-autovec-preference=scalable -fno-vect-cost-model:
reduc_plus_int32_t:
ble a1,zero,.L4
vsetvli a3,zero,e32,m1,ta,ma
vmv.v.i v1,0
.L3:
vsetvli a5,a1,e32,m1,tu,ma
slli a4,a5,2
sub a1,a1,a5
vle32.v v2,0(a0)
add a0,a0,a4
vadd.vv v1,v2,v1
bne a1,zero,.L3
vsetvli a3,zero,e32,m1,ta,ma
vmv.s.x v2,zero
vredsum.vs v1,v1,v2
vmv.x.s a0,v1
ret
.L4:
li a0,0
ret
The current vector cost model generates inferiors codegen.
