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author | Peter Maydell <peter.maydell@linaro.org> | 2021-07-25 18:44:05 +0100 |
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committer | Richard Henderson <richard.henderson@linaro.org> | 2021-07-26 06:56:03 -1000 |
commit | c8cf47a946200239826e58abc203dcaa4fdbb30c (patch) | |
tree | 056644e66875fa1c5eaea710427a61abd34726b0 | |
parent | df3a2de51a07089a4a729fe1f792f658df9dade4 (diff) | |
download | qemu-c8cf47a946200239826e58abc203dcaa4fdbb30c.zip qemu-c8cf47a946200239826e58abc203dcaa4fdbb30c.tar.gz qemu-c8cf47a946200239826e58abc203dcaa4fdbb30c.tar.bz2 |
accel/tcg: Remove unnecessary check on icount_extra in cpu_loop_exec_tb()
In cpu_loop_exec_tb(), we decide whether to look for a TB with
exactly insns_left instructions in it using the condition
(!cpu->icount_extra && insns_left > 0 && insns_left < tb->icount)
The check for icount_extra == 0 is unnecessary, because we just set
insns_left = MIN(0xffff, cpu->icount_budget);
icount_extra = icount_budget - insns_left;
and so icount_extra can only be non-zero if icount_budget > 0xffff
and insns_left == 0xffff. But in that case insns_left >= tb->icount
because 0xffff is much larger than TCG_MAX_INSNS, so the condition
will be false anyway.
Remove the unnecessary check, and instead assert:
* that we are only going to execute a partial TB here if the
icount budget has run out (ie icount_extra == 0)
* that the number of insns we're going to execute does fit into
the CF_COUNT_MASK
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210725174405.24568-3-peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
-rw-r--r-- | accel/tcg/cpu-exec.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 6e8dc29..5aa42fb 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -843,7 +843,9 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb, * 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) { + if (insns_left > 0 && insns_left < tb->icount) { + assert(insns_left <= CF_COUNT_MASK); + assert(cpu->icount_extra == 0); cpu->cflags_next_tb = (tb->cflags & ~CF_COUNT_MASK) | insns_left; } #endif |