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[PULL for-6.1 02/12] accel/tcg: Remove unnecessary check on icount_extra
From: |
Richard Henderson |
Subject: |
[PULL for-6.1 02/12] accel/tcg: Remove unnecessary check on icount_extra in cpu_loop_exec_tb() |
Date: |
Mon, 26 Jul 2021 11:47:19 -1000 |
From: Peter Maydell <peter.maydell@linaro.org>
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>
---
accel/tcg/cpu-exec.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 6e8dc29119..5aa42fbff3 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
--
2.25.1
- [PULL for-6.1 00/12] tcg and misc patch queue, Richard Henderson, 2021/07/26
- [PULL for-6.1 02/12] accel/tcg: Remove unnecessary check on icount_extra in cpu_loop_exec_tb(),
Richard Henderson <=
- [PULL for-6.1 01/12] accel/tcg: Don't use CF_COUNT_MASK as the max value of icount_decr.u16.low, Richard Henderson, 2021/07/26
- [PULL for-6.1 03/12] bitops.h: revert db1ffc32dd ("qemu/bitops.h: add bitrev8 implementation"), Richard Henderson, 2021/07/26
- [PULL for-6.1 04/12] nbd/server: Mark variable unused in nbd_negotiate_meta_queries, Richard Henderson, 2021/07/26
- [PULL for-6.1 05/12] accel/tcg: Remove unused variable in cpu_exec, Richard Henderson, 2021/07/26
- [PULL for-6.1 06/12] util/selfmap: Discard mapping on error, Richard Henderson, 2021/07/26
- [PULL for-6.1 07/12] net/checksum: Remove unused variable in net_checksum_add_iov, Richard Henderson, 2021/07/26
- [PULL for-6.1 08/12] hw/audio/adlib: Remove unused variable in adlib_callback, Richard Henderson, 2021/07/26
- [PULL for-6.1 09/12] hw/ppc/spapr_events: Remove unused variable from check_exception, Richard Henderson, 2021/07/26
- [PULL for-6.1 10/12] hw/pci-hist/pnv_phb4: Fix typo in pnv_phb4_ioda_write, Richard Henderson, 2021/07/26
- [PULL for-6.1 11/12] linux-user/syscall: Remove unused variable from execve, Richard Henderson, 2021/07/26