From c8cf47a946200239826e58abc203dcaa4fdbb30c Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Sun, 25 Jul 2021 18:44:05 +0100 Subject: [PATCH] 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 Reviewed-by: Richard Henderson Message-Id: <20210725174405.24568-3-peter.maydell@linaro.org> Signed-off-by: Richard Henderson --- 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