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target-arm: A64: Avoid duplicate exit_tb(0) in non-linked goto_tb

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If gen_goto_tb() decides not to link the two TBs, then the
fallback path generates unnecessary code:
 * if singlestep is enabled then we generate unreachable code
   after the gen_exception_internal(EXCP_DEBUG)
 * if singlestep is disabled then we will generate exit_tb(0)
   twice, once in gen_goto_tb() and once coming out of the
   main loop with is_jmp set to DISAS_JUMP

Correct these deficiencies by only emitting exit_tb() in the
non-singlestep case, in which case we can use DISAS_TB_JUMP
to suppress the main-loop exit_tb().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
This commit is contained in:
Peter Maydell 2014-08-19 18:56:26 +01:00
parent 3a2982038a
commit cc9c1ed14e
1 changed files with 3 additions and 2 deletions
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5
target-arm/translate-a64.c
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@ -234,9 +234,10 @@ static inline void gen_goto_tb(DisasContext *s, int n, uint64_t dest)
gen_a64_set_pc_im(dest);
if (s->singlestep_enabled) {
gen_exception_internal(EXCP_DEBUG);
} else {
tcg_gen_exit_tb(0);
s->is_jmp = DISAS_TB_JUMP;
}
tcg_gen_exit_tb(0);
s->is_jmp = DISAS_JUMP;
}
}