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accel/tcg: Improve setting of can_do_io at start of TB

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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>
(cherry picked from commit a2f99d484c)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Richard Henderson 2023-09-14 08:26:47 -07:00 committed by Michael Tokarev
parent a98097d3a9
commit 6c2e2e4f77
1 changed files with 2 additions and 2 deletions
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accel/tcg/translator.c
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@ -87,12 +87,12 @@ static TCGOp *gen_tb_start(DisasContextBase *db, uint32_t cflags)
offsetof(ArchCPU, neg.icount_decr.u16.low) -
offsetof(ArchCPU, env));
/*
* cpu->can_do_io is cleared automatically here at the beginning of
* cpu->can_do_io is set automatically here at the beginning of
* each translation block. The cost is minimal and only paid for
* -icount, plus it would be very easy to forget doing it in the
* translator.
*/
set_can_do_io(db, false);
set_can_do_io(db, db->max_insns == 1 && (cflags & CF_LAST_IO));
}
return icount_start_insn;