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[PULL 01/60] target/riscv/vector_helper.c: skip set tail when vta is zer
From: |
Alistair Francis |
Subject: |
[PULL 01/60] target/riscv/vector_helper.c: skip set tail when vta is zero |
Date: |
Wed, 14 Jun 2023 11:19:18 +1000 |
From: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
The function is a no-op if 'vta' is zero but we're still doing a lot of
stuff in this function regardless. vext_set_elems_1s() will ignore every
single time (since vta is zero) and we just wasted time.
Skip it altogether in this case. Aside from the code simplification
there's a noticeable emulation performance gain by doing it. For a
regular C binary that does a vectors operation like this:
=======
#define SZ 10000000
int main ()
{
int *a = malloc (SZ * sizeof (int));
int *b = malloc (SZ * sizeof (int));
int *c = malloc (SZ * sizeof (int));
for (int i = 0; i < SZ; i++)
c[i] = a[i] + b[i];
return c[SZ - 1];
}
=======
Emulating it with qemu-riscv64 and RVV takes ~0.3 sec:
$ time ~/work/qemu/build/qemu-riscv64 \
-cpu rv64,debug=false,vext_spec=v1.0,v=true,vlen=128 ./foo.out
real 0m0.303s
user 0m0.281s
sys 0m0.023s
With this skip we take ~0.275 sec:
$ time ~/work/qemu/build/qemu-riscv64 \
-cpu rv64,debug=false,vext_spec=v1.0,v=true,vlen=128 ./foo.out
real 0m0.274s
user 0m0.252s
sys 0m0.019s
This performance gain adds up fast when executing heavy benchmarks like
SPEC.
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Message-Id: <20230427205708.246679-2-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
target/riscv/vector_helper.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
index f4d0438988..8e6c99e573 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -268,12 +268,17 @@ static void vext_set_tail_elems_1s(CPURISCVState *env,
target_ulong vl,
void *vd, uint32_t desc, uint32_t nf,
uint32_t esz, uint32_t max_elems)
{
- uint32_t total_elems = vext_get_total_elems(env, desc, esz);
- uint32_t vlenb = riscv_cpu_cfg(env)->vlen >> 3;
+ uint32_t total_elems, vlenb, registers_used;
uint32_t vta = vext_vta(desc);
- uint32_t registers_used;
int k;
+ if (vta == 0) {
+ return;
+ }
+
+ total_elems = vext_get_total_elems(env, desc, esz);
+ vlenb = riscv_cpu_cfg(env)->vlen >> 3;
+
for (k = 0; k < nf; ++k) {
vext_set_elems_1s(vd, vta, (k * max_elems + vl) * esz,
(k * max_elems + max_elems) * esz);
--
2.40.1
- [PULL 00/60] riscv-to-apply queue, Alistair Francis, 2023/06/13
- [PULL 01/60] target/riscv/vector_helper.c: skip set tail when vta is zero,
Alistair Francis <=
- [PULL 02/60] target/riscv: Move zc* out of the experimental properties, Alistair Francis, 2023/06/13
- [PULL 03/60] target/riscv/cpu.c: add riscv_cpu_validate_v(), Alistair Francis, 2023/06/13
- [PULL 04/60] target/riscv/cpu.c: remove set_vext_version(), Alistair Francis, 2023/06/13
- [PULL 05/60] target/riscv/cpu.c: remove set_priv_version(), Alistair Francis, 2023/06/13
- [PULL 06/60] target/riscv: add PRIV_VERSION_LATEST, Alistair Francis, 2023/06/13
- [PULL 07/60] target/riscv: Mask the implicitly enabled extensions in isa_string based on priv version, Alistair Francis, 2023/06/13
- [PULL 08/60] target/riscv: Update check for Zca/Zcf/Zcd, Alistair Francis, 2023/06/13
- [PULL 09/60] target/riscv/cpu.c: add priv_spec validate/disable_exts helpers, Alistair Francis, 2023/06/13
- [PULL 10/60] target/riscv/cpu.c: add riscv_cpu_validate_misa_mxl(), Alistair Francis, 2023/06/13
- [PULL 11/60] target/riscv/cpu.c: validate extensions before riscv_timer_init(), Alistair Francis, 2023/06/13