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target/riscv: rvv-1.0: take fractional LMUL into vector max elements calculation 

Update vext_get_vlmax() and MAXSZ() to take fractional LMUL into
calculation for RVV 1.0.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20211210075704.23951-27-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Frank Chang 2021-12-10 15:56:12 +08:00 committed by Alistair Francis
parent 5a9f8e1552
commit a689a82b7f
3 changed files with 42 additions and 13 deletions
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27
target/riscv/cpu.h
View File

@ -430,18 +430,27 @@ static inline RISCVMXL riscv_cpu_mxl(CPURISCVState *env)
#endif
/*
* A simplification for VLMAX
* = (1 << LMUL) * VLEN / (8 * (1 << SEW))
* = (VLEN << LMUL) / (8 << SEW)
* = (VLEN << LMUL) >> (SEW + 3)
* = VLEN >> (SEW + 3 - LMUL)
* Encode LMUL to lmul as follows:
* LMUL vlmul lmul
* 1 000 0
* 2 001 1
* 4 010 2
* 8 011 3
* - 100 -
* 1/8 101 -3
* 1/4 110 -2
* 1/2 111 -1
*
* then, we can calculate VLMAX = vlen >> (vsew + 3 - lmul)
* e.g. vlen = 256 bits, SEW = 16, LMUL = 1/8
* => VLMAX = vlen >> (1 + 3 - (-3))
* = 256 >> 7
* = 2
*/
static inline uint32_t vext_get_vlmax(RISCVCPU *cpu, target_ulong vtype)
{
uint8_t sew, lmul;
sew = FIELD_EX64(vtype, VTYPE, VSEW);
lmul = FIELD_EX64(vtype, VTYPE, VLMUL);
uint8_t sew = FIELD_EX64(vtype, VTYPE, VSEW);
int8_t lmul = sextract32(FIELD_EX64(vtype, VTYPE, VLMUL), 0, 3);
return cpu->cfg.vlen >> (sew + 3 - lmul);
}

16
target/riscv/cpu_helper.c
View File

@ -75,12 +75,22 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
*cs_base = 0;
if (riscv_has_ext(env, RVV)) {
/*
* If env->vl equals to VLMAX, we can use generic vector operation
* expanders (GVEC) to accerlate the vector operations.
* However, as LMUL could be a fractional number. The maximum
* vector size can be operated might be less than 8 bytes,
* which is not supported by GVEC. So we set vl_eq_vlmax flag to true
* only when maxsz >= 8 bytes.
*/
uint32_t vlmax = vext_get_vlmax(env_archcpu(env), env->vtype);
bool vl_eq_vlmax = (env->vstart == 0) && (vlmax == env->vl);
uint32_t sew = FIELD_EX64(env->vtype, VTYPE, VSEW);
uint32_t maxsz = vlmax << sew;
bool vl_eq_vlmax = (env->vstart == 0) && (vlmax == env->vl) &&
(maxsz >= 8);
flags = FIELD_DP32(flags, TB_FLAGS, VILL,
FIELD_EX64(env->vtype, VTYPE, VILL));
flags = FIELD_DP32(flags, TB_FLAGS, SEW,
FIELD_EX64(env->vtype, VTYPE, VSEW));
flags = FIELD_DP32(flags, TB_FLAGS, SEW, sew);
flags = FIELD_DP32(flags, TB_FLAGS, LMUL,
FIELD_EX64(env->vtype, VTYPE, VLMUL));
flags = FIELD_DP32(flags, TB_FLAGS, VL_EQ_VLMAX, vl_eq_vlmax);

12
target/riscv/insn_trans/trans_rvv.c.inc
View File

@ -1049,7 +1049,17 @@ GEN_LDST_WHOLE_TRANS(vs8r_v, 8, true)
/*
*** Vector Integer Arithmetic Instructions
*/
#define MAXSZ(s) (s->vlen >> (3 - s->lmul))
/*
* MAXSZ returns the maximum vector size can be operated in bytes,
* which is used in GVEC IR when vl_eq_vlmax flag is set to true
* to accerlate vector operation.
*/
static inline uint32_t MAXSZ(DisasContext *s)
{
int scale = s->lmul - 3;
return scale < 0 ? s->vlen >> -scale : s->vlen << scale;
}
static bool opivv_check(DisasContext *s, arg_rmrr *a)
{