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accel/tcg: actually cache our partial icount TB 

When we exit a block under icount with instructions left to execute we
might need a shorter than normal block to take us to the next
deterministic event. Instead of creating a throwaway block on demand
we use the existing compile flags mechanism to ensure we fetch (or
compile and fetch) a block with exactly the number of instructions we
need.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210213130325.14781-17-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2021-02-13 13:03:18 +00:00
parent 4c134d07b9
commit bc662a3351
1 changed files with 9 additions and 8 deletions
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17
accel/tcg/cpu-exec.c
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@ -730,16 +730,17 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
/* Ensure global icount has gone forward */
icount_update(cpu);
/* Refill decrementer and continue execution. */
insns_left = MIN(0xffff, cpu->icount_budget);
insns_left = MIN(CF_COUNT_MASK, cpu->icount_budget);
cpu_neg(cpu)->icount_decr.u16.low = insns_left;
cpu->icount_extra = cpu->icount_budget - insns_left;
if (!cpu->icount_extra && insns_left < tb->icount) {
/* Execute any remaining instructions, then let the main loop
* handle the next event.
*/
if (insns_left > 0) {
cpu_exec_nocache(cpu, insns_left, tb, false);
}
/*
* If the next tb has more instructions than we have left to
* execute we need to ensure we find/generate a TB with exactly
* insns_left instructions in it.
*/
if (!cpu->icount_extra && insns_left > 0 && insns_left < tb->icount) {
cpu->cflags_next_tb = (tb->cflags & ~CF_COUNT_MASK) | insns_left;
}
#endif
}