target/riscv: add 'vlenb' field in cpu->cfg

Our usage of 'vlenb' is overwhelming superior than the use of 'vlen'.
We're using 'vlenb' most of the time, having to do 'vlen >> 3' or
'vlen / 8' in every instance.

In hindsight we would be better if the 'vlenb' property  was introduced
instead of 'vlen'. That's not what happened, and now we can't easily get
rid of it due to user scripts all around. What we can do, however, is to
change our internal representation to use 'vlenb'.

Add a 'vlenb' field in cpu->cfg. It'll be set via the existing 'vlen'
property, i.e. setting 'vlen' will also set 'vlenb'.

We'll replace all 'vlen >> 3' code to use 'vlenb' directly. Start with
the single instance we have in target/riscv/cpu.c.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240122161107.26737-2-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -852,7 +852,7 @@ static void riscv_cpu_dump_state(CPUState *cs, FILE *f, int flags)
                              csr_ops[csrno].name, val);
             }
         }
-        uint16_t vlenb = cpu->cfg.vlen >> 3;
+        uint16_t vlenb = cpu->cfg.vlenb;
 
         for (i = 0; i < 32; i++) {
             qemu_fprintf(f, " %-8s ", riscv_rvv_regnames[i]);
@@ -1325,6 +1325,7 @@ static void riscv_cpu_init(Object *obj)
     /* Default values for non-bool cpu properties */
     cpu->cfg.pmu_mask = MAKE_64BIT_MASK(3, 16);
     cpu->cfg.vlen = 128;
+    cpu->cfg.vlenb = 128 >> 3;
     cpu->cfg.elen = 64;
     cpu->cfg.cbom_blocksize = 64;
     cpu->cfg.cbop_blocksize = 64;
@@ -1824,6 +1825,7 @@ static void prop_vlen_set(Object *obj, Visitor *v, const char *name,
 
     cpu_option_add_user_setting(name, value);
     cpu->cfg.vlen = value;
+    cpu->cfg.vlenb = value >> 3;
 }
 
 static void prop_vlen_get(Object *obj, Visitor *v, const char *name,

target/riscv/cpu_cfg.h

@@ -140,6 +140,7 @@ struct RISCVCPUConfig {
 
     uint32_t pmu_mask;
     uint16_t vlen;
+    uint16_t vlenb;
     uint16_t elen;
     uint16_t cbom_blocksize;
     uint16_t cbop_blocksize;