This is the payoff. >From perf record -g data of ubuntu 18 boot and shutdown:
BEFORE: - 23.02% 2.82% qemu-system-aar [.] helper_lookup_tb_ptr - 20.22% helper_lookup_tb_ptr + 10.05% tb_htable_lookup - 9.13% cpu_get_tb_cpu_state 3.20% aa64_va_parameters_both 0.55% fp_exception_el - 11.66% 4.74% qemu-system-aar [.] cpu_get_tb_cpu_state - 6.96% cpu_get_tb_cpu_state 3.63% aa64_va_parameters_both 0.60% fp_exception_el 0.53% sve_exception_el AFTER: - 16.40% 3.40% qemu-system-aar [.] helper_lookup_tb_ptr - 13.03% helper_lookup_tb_ptr + 11.19% tb_htable_lookup 0.55% cpu_get_tb_cpu_state 0.98% 0.71% qemu-system-aar [.] cpu_get_tb_cpu_state 0.87% 0.24% qemu-system-aar [.] rebuild_hflags_a64 Before, helper_lookup_tb_ptr is the second hottest function in the application, consuming almost a quarter of the runtime. Within the entire execution, cpu_get_tb_cpu_state consumes about 12%. After, helper_lookup_tb_ptr has dropped to the fourth hottest function, with consumption dropping to a sixth of the runtime. Within the entire execution, cpu_get_tb_cpu_state has dropped below 1%, and the supporting function to rebuild hflags also consumes about 1%. Assertions are retained for --enable-debug-tcg. Tested-by: Alex Bennée <alex.ben...@linaro.org> Reviewed-by: Alex Bennée <alex.ben...@linaro.org> Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- v2: Retain asserts for future debugging. --- target/arm/helper.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/target/arm/helper.c b/target/arm/helper.c index c55783e540..63815fc4cf 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -11259,12 +11259,15 @@ void HELPER(rebuild_hflags_a64)(CPUARMState *env, int el) void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc, target_ulong *cs_base, uint32_t *pflags) { - uint32_t flags, pstate_for_ss; + uint32_t flags = env->hflags; + uint32_t pstate_for_ss; *cs_base = 0; - flags = rebuild_hflags_internal(env); +#ifdef CONFIG_DEBUG_TCG + assert(flags == rebuild_hflags_internal(env)); +#endif - if (is_a64(env)) { + if (FIELD_EX32(flags, TBFLAG_ANY, AARCH64_STATE)) { *pc = env->pc; if (cpu_isar_feature(aa64_bti, env_archcpu(env))) { flags = FIELD_DP32(flags, TBFLAG_A64, BTYPE, env->btype); -- 2.17.1