accel/tcg: Improve setting of can_do_io at start of TB
Initialize can_do_io to true if this the TB has CF_LAST_IO and will consist of a single instruction. This avoids a set to 0 followed immediately by a set to 1. Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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@ -87,12 +87,12 @@ static TCGOp *gen_tb_start(DisasContextBase *db, uint32_t cflags)
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offsetof(ArchCPU, neg.icount_decr.u16.low) -
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offsetof(ArchCPU, env));
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/*
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* cpu->can_do_io is cleared automatically here at the beginning of
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* cpu->can_do_io is set automatically here at the beginning of
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* each translation block. The cost is minimal and only paid for
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* -icount, plus it would be very easy to forget doing it in the
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* translator.
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*/
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set_can_do_io(db, false);
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set_can_do_io(db, db->max_insns == 1 && (cflags & CF_LAST_IO));
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}
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return icount_start_insn;
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