On 03/24/2010 10:07 AM, Richard Henderson wrote:
> struct CPUSmallCommonState
> {
> // most of the stuff from CPU_COMMON.
> // sorted for some thought of padding elimination. ;-)
> };
>
> struct CPULargeCommonState
> {
> CPUTLBEntry tlb_table[NB_MMU_MODES][CPU_TLB_SIZE];
> target_phys_addr_t iotlb[NB_MMU_MODES][CPU_TLB_SIZE];
> struct TranslationBlock *tb_jmp_cache[TB_JMP_CACHE_SIZE];
> jmp_buf jmp_env;
> };
...
> Now. If you're compiling a file for which cpu-specific code is ok:
>
> register CPUXYZLargeState *env __asm__(AREG0);
> #define ENV_SMALL_COMMON_STATE (&env->s.common_s)
> #define ENV_LARGE_COMMON_STATE (&env->common_l)
>
> If you're compiling a file which is supposed to be independant of cpu:
>
> register CPUSmallCommonState *env __asm__(AREG0);
> #define ENV_SMALL_COMMON_STATE (env)
> #define ENV_LARGE_COMMON_STATE ((CPULargeCommonState *)((char *)env +
> cpu_large_state_offset))
On 03/24/2010 11:00 AM, Blue Swirl wrote:
> One trick is to define a fixed offset (about half CPUState size) and
> make env point to CPUState + offset. Then the negative part of the
> offset space can be used efficiently. But this just doubles the space
> that can be accessed fast, so it's not a big win.
A good idea. We can eliminate the cpu_large_state_offset from above via:
struct CPUSmallCommonState
{
// most of the stuff from CPU_COMMON.
} __attribute__((aligned));
struct CPUXYZPrivateState
{
// all the cpu-specific stuff
};
struct CPUXYZSmallState
{
CPUXYZPrivateState p;
CPUSmallCommonState s;
};
struct CPUXYZAllState
{
CPUXYZSmallState s;
CPULargeCommonState l; // ARG0 register points here.
};
register void *biased_env __asm__(AREG0);
static inline CPUXYZPrivateState *get_env_cpu_private(void)
{
return &((CPUXYZSmallState *)biased_env - 1)->p;
}
static inline CPUSmallCommonState *get_env_common_small(void)
{
return (CPUSmallCommonState *)biased_env - 1;
}
static inline CPULargeCommonState *get_env_common_large(void)
{
return (CPULargeCommonState *)biased_env;
}
r~
