target/riscv/vector_helper.c: fix 'vmvr_v' memcpy endianess

vmvr_v isn't handling the case where the host might be big endian and
the bytes to be copied aren't sequential.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Fixes: f714361 ("target/riscv: rvv-1.0: implement vstart CSR")
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240314175704.478276-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/vector_helper.c

@@ -5075,9 +5075,17 @@ void HELPER(vmvr_v)(void *vd, void *vs2, CPURISCVState *env, uint32_t desc)
     uint32_t startb = env->vstart * sewb;
     uint32_t i = startb;
 
+    if (HOST_BIG_ENDIAN && i % 8 != 0) {
+        uint32_t j = ROUND_UP(i, 8);
+        memcpy((uint8_t *)vd + H1(j - 1),
+               (uint8_t *)vs2 + H1(j - 1),
+               j - i);
+        i = j;
+    }
+
     memcpy((uint8_t *)vd + H1(i),
            (uint8_t *)vs2 + H1(i),
-           maxsz - startb);
+           maxsz - i);
 
     env->vstart = 0;
 }